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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2016	Jul. 22, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Trading Symbol	AA
Entity Registrant Name	ALCOA INC.
Entity Central Index Key	0000004281
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		1,315,374,511

Statement of Consolidated Operations (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Sales (K)	$ 5,295	$ 5,897	$ 10,242	$ 11,716
Cost of goods sold (exclusive of expenses below)	4,216	4,663	8,257	9,106
Selling, general administrative, and other expenses (P)	286	224	546	456
Research and development expenses	39	68	81	123
Provision for depreciation, depletion, and amortization	309	319	618	640
Restructuring and other charges (D)	23	217	116	394
Interest expense	129	124	256	246
Other income, net (J)	(37)		(3)	(12)
Total costs and expenses	4,965	5,615	9,871	10,953
Income before income taxes	330	282	371	763
Provision for income taxes	152	75	182	301
Net income	178	207	189	462
Less: Net income attributable to noncontrolling interests	43	67	38	127
Consolidated net income attributable to Alcoa	135	140	151	335
AMOUNTS ATTRIBUTABLE TO ALCOA COMMON SHAREHOLDERS (L):
Net income	$ 118	$ 123	$ 116	$ 300
Earnings per share:
Basic	$ 0.09	$ 0.10	$ 0.09	$ 0.25
Diluted	0.09	0.10	0.09	0.24
Dividends paid per share	$ 0.03	$ 0.03	$ 0.06	$ 0.06

Statement of Consolidated Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income	$ 178	$ 207	$ 189	$ 462
Other comprehensive (loss) income, net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	67	(1)	100	106
Foreign currency translation adjustments	77	229	487	(978)
Net change in unrealized losses/gains on available-for-sale securities	3	(2)	4
Net change in unrecognized gains/losses on cash flow hedges	(137)	430	(219)	366
Total Other comprehensive (loss) income, net of tax	10	656	372	(506)
Comprehensive income	188	863	561	(44)
Alcoa [Member]
Net income	135	140	151	335
Other comprehensive (loss) income, net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	65	(4)	97	101
Foreign currency translation adjustments	45	197	348	(760)
Net change in unrealized losses/gains on available-for-sale securities	3	(2)	4
Net change in unrecognized gains/losses on cash flow hedges	(153)	434	(233)	370
Total Other comprehensive (loss) income, net of tax	(40)	625	216	(289)
Comprehensive income	95	765	367	46
Noncontrolling Interests [Member]
Net income	43	67	38	127
Other comprehensive (loss) income, net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	2	3	3	5
Foreign currency translation adjustments	32	32	139	(218)
Net change in unrecognized gains/losses on cash flow hedges	16	(4)	14	(4)
Total Other comprehensive (loss) income, net of tax	50	31	156	(217)
Comprehensive income	$ 93	$ 98	$ 194	$ (90)

Consolidated Balance Sheet (Unaudited) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 1,929	$ 1,919
Receivables from customers, less allowances of $14 in 2016 and $13 in 2015 (M)	1,595	1,340
Other receivables (M)	494	522
Inventories (F)	3,438	3,442
Prepaid expenses and other current assets	637	730
Total current assets	8,093	7,953
Properties, plants, and equipment	34,441	33,687
Less: accumulated depreciation, depletion, and amortization	19,424	18,872
Properties, plants, and equipment, net	15,017	14,815
Goodwill (E)	5,396	5,401
Investments (G)	1,466	1,685
Deferred income taxes	2,752	2,668
Other noncurrent assets (H)	3,415	3,955
Total assets	36,139	36,477
Current liabilities:
Short-term borrowings	33	38
Accounts payable, trade	2,665	2,889
Accrued compensation and retirement costs	810	850
Taxes, including income taxes	206	239
Other current liabilities	1,000	1,174
Long-term debt due within one year	774	21
Total current liabilities	5,488	5,211
Long-term debt, less amount due within one year	8,278	8,993
Accrued pension benefits	3,122	3,298
Accrued other postretirement benefits	2,070	2,106
Other noncurrent liabilities and deferred credits	2,652	2,738
Total liabilities	21,610	22,346
CONTINGENCIES AND COMMITMENTS (I)
Alcoa shareholders' equity:
Preferred stock	55	55
Mandatory convertible preferred stock	3	3
Common stock	1,391	1,391
Additional capital	9,877	10,019
Retained earnings	8,871	8,834
Treasury stock, at cost	(2,647)	(2,825)
Accumulated other comprehensive loss (C)	(5,215)	(5,431)
Total Alcoa shareholders' equity	12,335	12,046
Noncontrolling interests	2,194	2,085
Total equity	14,529	14,131
Total liabilities and equity	$ 36,139	$ 36,477

Consolidated Balance Sheet (Unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Receivables from customers, allowance	$ 14	$ 13

Statement of Consolidated Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FROM OPERATIONS
Net income	$ 189	$ 462
Adjustments to reconcile net income to cash from operations:
Depreciation, depletion, and amortization	622	641
Deferred income taxes	(78)	(45)
Equity income, net of dividends	20	50
Restructuring and other charges (D)	116	394
Net gain from investing activities - asset sales (G & J)	(28)	(28)
Net periodic pension benefit cost (N)	168	243
Stock-based compensation	55	55
Excess tax benefits from stock-based payment arrangements		(9)
Other	19	(64)
Changes in assets and liabilities, excluding effects of acquisitions, divestitures, and foreign currency translation adjustments:
(Increase) in receivables	(218)	(200)
(Increase) in inventories	(3)	(221)
Decrease in prepaid expenses and other current assets	4	7
(Decrease) in accounts payable, trade	(243)	(130)
(Decrease) in accrued expenses	(301)	(374)
Increase in taxes, including income taxes	57	130
Pension contributions	(147)	(169)
(Increase) in noncurrent assets (I)	(215)	(352)
(Decrease) in noncurrent liabilities	(115)	(93)
CASH (USED FOR) PROVIDED FROM OPERATIONS	(98)	297
FINANCING ACTIVITIES
Net change in short-term borrowings (original maturities of three months or less)	(5)	(4)
Additions to debt (original maturities greater than three months)	876	1,027
Payments on debt (original maturities greater than three months)	(882)	(1,037)
Proceeds from exercise of employee stock options	2	26
Excess tax benefits from stock-based payment arrangements		9
Dividends paid to shareholders	(114)	(109)
Distributions to noncontrolling interests	(84)	(71)
CASH USED FOR FINANCING ACTIVITIES	(207)	(159)
INVESTING ACTIVITIES
Capital expenditures	(528)	(514)
Acquisitions, net of cash acquired (E)		(204)
Proceeds from the sale of assets and businesses (E & H)	549	59
Additions to investments	(8)	(50)
Sales of investments (G)	275	22
Net change in restricted cash	7	(9)
Other	15	11
CASH PROVIDED FROM (USED FOR) INVESTING ACTIVITIES	310	(685)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	5	(19)
Net change in cash and cash equivalents	10	(566)
Cash and cash equivalents at beginning of year	1,919	1,877
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 1,929	$ 1,311

Statement of Changes in Consolidated Equity (Unaudited) - USD ($) $ in Millions	Total	Preferred Class A [Member]	Preferred Class B [Member]	Preferred Stock [Member]	Mandatory Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Preferred Class A [Member]	Retained Earnings [Member] Preferred Class B [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2014	$ 14,794			$ 55	$ 3	$ 1,304	$ 9,284	$ 9,379			$ (3,042)	$ (4,677)	$ 2,488
Net income	462							335					127
Other comprehensive (loss) income (C)	(506)											(289)	(217)
Cash dividends declared:
Common share, value	(74)							(74)
Preferred share, value		$ (1)	$ (34)						$ (1)	$ (34)
Stock-based compensation	55						55
Common stock issued: compensation plans	16						(192)				208
Distributions	(71)												(71)
Other	(3)												(3)
Balance at Jun. 30, 2015	14,638			55	3	1,304	9,147	9,605			(2,834)	(4,966)	2,324
Balance at Mar. 31, 2015	13,843			55	3	1,304	9,124	9,520			(2,841)	(5,591)	2,269
Net income	207							140					67
Other comprehensive (loss) income (C)	656											625	31
Cash dividends declared:
Common share, value	(38)							(38)
Preferred share, value			(17)							(17)
Stock-based compensation	29						29
Common stock issued: compensation plans	1						(6)				7
Distributions	(42)												(42)
Other	(1)												(1)
Balance at Jun. 30, 2015	14,638			55	3	1,304	9,147	9,605			(2,834)	(4,966)	2,324
Balance at Dec. 31, 2015	14,131			55	3	1,391	10,019	8,834			(2,825)	(5,431)	2,085
Net income	189							151					38
Other comprehensive (loss) income (C)	372											216	156
Cash dividends declared:
Common share, value	(79)							(79)
Preferred share, value		$ (1)	(34)						$ (1)	(34)
Stock-based compensation	55						55
Common stock issued: compensation plans	(19)						(197)				178
Distributions	(84)												(84)
Other	(1)												(1)
Balance at Jun. 30, 2016	14,529			55	3	1,391	9,877	8,871			(2,647)	(5,215)	2,194
Balance at Mar. 31, 2016	14,361			55	3	1,391	9,856	8,753			(2,657)	(5,175)	2,135
Net income	178							135					43
Other comprehensive (loss) income (C)	10											(40)	50
Cash dividends declared:
Preferred share, value			$ (17)							$ (17)
Stock-based compensation	29						29
Common stock issued: compensation plans	2						(8)				10
Distributions	(34)												(34)
Balance at Jun. 30, 2016	$ 14,529			$ 55	$ 3	$ 1,391	$ 9,877	$ 8,871			$ (2,647)	$ (5,215)	$ 2,194

Statement of Changes in Consolidated Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Common stock, dividends per share		$ 0.03	$ 0.06	$ 0.06
Preferred Class A [Member]
Preferred, dividends per share		0.9375	1.875	1.875
Preferred Class B [Member]
Preferred, dividends per share	$ 6.71875	$ 6.71875	$ 13.4375	$ 13.4375

Basis of Presentation	6 Months Ended
Basis of Presentation	Jun. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	A. Basis of Presentation – The interim Consolidated Financial Statements of Alcoa Inc. and its subsidiaries (“Alcoa” or the “Company”) are unaudited. These Consolidated Financial Statements include all adjustments, consisting only of normal recurring adjustments, considered necessary by management to fairly state the Company’s results of operations, financial position, and cash flows. The results reported in these Consolidated Financial Statements are not necessarily indicative of the results that may be expected for the entire year. The 2015 year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP). This Form 10-Q report should be read in conjunction with Alcoa’s Annual Report on Form 10-K for the year ended December 31, 2015, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation (see Note B).

Recently Adopted and Recently Issued Accounting Guidance	6 Months Ended
	Jun. 30, 2016
Accounting Changes and Error Corrections [Abstract]
Recently Adopted and Recently Issued Accounting Guidance	B. Recently Adopted and Recently Issued Accounting Guidance Adopted On January 1, 2016, Alcoa adopted changes issued by the Financial Accounting Standards Board (FASB) to the presentation of extraordinary items. Such items are defined as transactions or events that are both unusual in nature and infrequent in occurrence, and, previously, were required to be presented separately in an entity’s income statement, net of income tax, after income from continuing operations. The changes eliminate the concept of an extraordinary item and, therefore, the presentation of such items is no longer required. Notwithstanding this change, an entity is still required to present and disclose a transaction or event that is both unusual in nature and infrequent in occurrence in the notes to the financial statements. The adoption of these changes had no impact on the Consolidated Financial Statements. On January 1, 2016, Alcoa adopted changes issued by the FASB to the analysis an entity must perform to determine whether it should consolidate certain types of legal entities. These changes (i) modify the evaluation of whether limited partnerships and similar legal entities are variable interest entities or voting interest entities, (ii) eliminate the presumption that a general partner should consolidate a limited partnership, (iii) affect the consolidation analysis of reporting entities that are involved with variable interest entities, particularly those that have fee arrangements and related party relationships, and (iv) provide a scope exception from consolidation guidance for reporting entities with interests in legal entities that are required to comply with or operate in accordance with requirements that are similar to those in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds. The adoption of these changes had no impact on the Consolidated Financial Statements. On January 1, 2016, Alcoa adopted changes issued by the FASB to the presentation of debt issuance costs. Previously, such costs were required to be presented as a noncurrent asset in an entity’s balance sheet and amortized into interest expense over the term of the related debt instrument. The changes require that debt issuance costs be presented in an entity’s balance sheet as a direct deduction from the carrying value of the related debt liability. The amortization of debt issuance costs remains unchanged. The FASB issued an update to these changes based on an announcement of the staff of the U.S. Securities and Exchange Commission. This update provides an exception to the FASB changes allowing debt issuance costs related to line-of-credit arrangements to continue to be presented as an asset regardless of whether there are any outstanding borrowings under such arrangement. This additional change also was adopted by Alcoa on January 1, 2016. This adoption is required on a retrospective basis; therefore, the December 31, 2015 Consolidated Balance Sheet has been updated to conform to the June 30, 2016 presentation. As a result, $51 of debt issuance costs (previously reported in Other noncurrent assets) were reclassified to the Long-term debt, less amount due within one year line item on the December 31, 2015 Consolidated Balance Sheet. Issued In January 2016, the FASB issued changes to equity investments. These changes require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. Additionally, the impairment assessment of equity investments without readily determinable fair values has been simplified by requiring a qualitative assessment to identify impairment. These changes become effective for Alcoa on January 1, 2018. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. In February 2016, the FASB issued changes to the accounting and presentation of leases. These changes require lessees to recognize a right of use asset and lease liability on the balance sheet for all leases with terms longer than 12 months. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize a right of use asset and lease liability. Additionally, when measuring assets and liabilities arising from a lease, optional payments should be included only if the lessee is reasonably certain to exercise an option to extend the lease, exercise a purchase option, or not exercise an option to terminate the lease. These changes become effective for Alcoa on January 1, 2019. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. In March 2016, the FASB issued changes to employee share-based payment accounting. Currently, an entity must determine for each share-based payment award whether the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes results in either an excess tax benefit or a tax deficiency. Excess tax benefits are recognized in additional paid-in capital; tax deficiencies are recognized either as an offset to accumulated excess tax benefits, if any, or in the income statement. Excess tax benefits are not recognized until the deduction reduces taxes payable. The changes require all excess tax benefits and tax deficiencies related to share-based payment awards to be recognized as income tax expense or benefit in the income statement. The tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. An entity also should recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. Additionally, the presentation of excess tax benefits related to share-based payment awards in the statement of cash flows is changed. Currently, excess tax benefits must be separated from other income tax cash flows and classified as a financing activity. The changes require excess tax benefits to be classified along with other income tax cash flows as an operating activity. Also, the changes require cash paid by an employer when directly withholding shares for tax-withholding purposes to be classified as a financing activity. Currently, there is no specific guidance on the classification in the statement of cash flows of cash paid by an employer to the tax authorities when directly withholding shares for tax-withholding purposes. Additionally, for a share-based award to qualify for equity classification it cannot partially settle in cash in excess of the employer’s minimum statutory withholding requirements. The changes permit equity classification of share-based awards for withholdings up to the maximum statutory tax rates in applicable jurisdictions. These changes become effective for Alcoa on January 1, 2017. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. In March 2016, the FASB issued changes eliminating the requirement for an investor to adjust an equity method investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held as a result of an increase in the level of ownership interest or degree of influence. Additionally, an entity that has an available-for-sale equity security that becomes qualified for the equity method of accounting must recognize through earnings the unrealized holding gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. These changes become effective for Alcoa on January 1, 2017. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. In March 2016, the FASB issued changes to derivative instruments designated as hedging instruments. These changes clarify that a change in the counterparty to a derivative instrument that has been designated as a hedging instrument does not, in and of itself, require dedesignation of that hedging relationship provided that all other hedge accounting criteria continue to be met. These changes become effective for Alcoa on January 1, 2017. Management does not expect these changes to have a material impact on the Consolidated Financial Statements.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=66092750

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22583-107794

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Indirect Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6515603

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22580-107794

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.10-01.(b)(6))
-URI http://asc.fasb.org/extlink&oid=27015980&loc=d3e46468-122699

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accounting Change
-URI http://asc.fasb.org/extlink&oid=6503790

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22499-107794

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Retrospective Application
-URI http://asc.fasb.org/extlink&oid=6523989

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=68064558&loc=d3e765-108305

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=68064558&loc=d3e725-108305

+ Details

Accumulated Other Comprehensive Loss

6 Months Ended

Jun. 30, 2016

Equity [Abstract]

Accumulated Other Comprehensive Loss

C. Accumulated Other Comprehensive Loss

The following table details the activity of the four components that comprise Accumulated other comprehensive loss for both Alcoa’s shareholders and noncontrolling interests:


	Alcoa						Noncontrolling Interests
	Second quarter ended June 30,						Second quarter ended June 30,
	2016			2015			2016			2015
Pension and other postretirement benefits (N)
Balance at beginning of period	$	(3,579	)	$	(3,496	)	$	(55	)	$	(62	)
Other comprehensive income (loss):
Unrecognized net actuarial loss and prior service cost/benefit		(5	)		(118	)		1			3
Tax benefit		3			39			—			—

Total Other comprehensive (loss) income before reclassifications, net of tax		(2	)		(79	)		1			3

Amortization of net actuarial loss and prior service cost/benefit⁽¹⁾		104			115			—			1
Tax (expense) benefit⁽²⁾		(37	)		(40	)		1			(1	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁸⁾		67			75			1			—

Total Other comprehensive income (loss)		65			(4	)		2			3

Balance at end of period	$	(3,514	)	$	(3,500	)	$	(53	)	$	(59	)

Foreign currency translation
Balance at beginning of period	$	(2,109	)	$	(1,803	)	$	(673	)	$	(601	)
Other comprehensive income⁽³⁾		45			197			32			32

Balance at end of period	$	(2,064	)	$	(1,606	)	$	(641	)	$	(569	)

Available-for-sale securities
Balance at beginning of period	$	(4	)	$	2		$	—		$	—
Other comprehensive income (loss)⁽⁴⁾		3			(2	)		—			—

Balance at end of period	$	(1	)	$	—		$	—		$	—

Cash flow hedges (O)
Balance at beginning of period	$	517		$	(294	)	$	(5	)	$	(2	)
Other comprehensive (loss) income:
Net change from periodic revaluations		(225	)		614			18			(5	)
Tax benefit (expense)		66			(190	)		(5	)		1

Total Other comprehensive (loss) income before reclassifications, net of tax		(159	)		424			13			(4	)

Net amount reclassified to earnings:
Aluminum contracts⁽⁵⁾		(1	)		10			—			—
Energy contracts⁽⁶⁾		—			2			—			—
Foreign exchange contracts⁽⁵⁾		—			1			—			—
Interest rate contracts⁽⁷⁾		8			1			5			—

Sub-total		7			14			5			—
Tax expense⁽²⁾		(1	)		(4	)		(2	)		—

Total amount reclassified from Accumulated other comprehensive income (loss), net of tax⁽⁸⁾		6			10			3			—

Total Other comprehensive (loss) income		(153	)		434			16			(4	)

Balance at end of period	$	364		$	140		$	11		$	(6	)


	Alcoa						Noncontrolling Interests
	Six months ended June 30,						Six months ended June 30,
	2016			2015			2016			2015
Pension and other postretirement benefits (N)
Balance at beginning of period	$	(3,611	)	$	(3,601	)	$	(56	)	$	(64	)
Other comprehensive income:
Unrecognized net actuarial loss and prior service cost/benefit		(64	)		(76	)		1			3
Tax benefit		26			28			—			—

Total Other comprehensive (loss) income before reclassifications, net of tax		(38	)		(48	)		1			3

Amortization of net actuarial loss and prior service cost/benefit⁽¹⁾		208			229			2			4
Tax expense⁽²⁾		(73	)		(80	)		—			(2	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁸⁾		135			149			2			2

Total Other comprehensive income		97			101			3			5

Balance at end of period	$	(3,514	)	$	(3,500	)	$	(53	)	$	(59	)

Foreign currency translation
Balance at beginning of period	$	(2,412	)	$	(846	)	$	(780	)	$	(351	)
Other comprehensive income (loss)⁽³⁾		348			(760	)		139			(218	)

Balance at end of period	$	(2,064	)	$	(1,606	)	$	(641	)	$	(569	)

Available-for-sale securities
Balance at beginning of period	$	(5	)	$	—		$	—		$	—
Other comprehensive income⁽⁴⁾		4			—			—			—

Balance at end of period	$	(1	)	$	—		$	—		$	—

Cash flow hedges (O)
Balance at beginning of period	$	597		$	(230	)	$	(3	)	$	(2	)
Other comprehensive (loss) income:
Net change from periodic revaluations		(342	)		504			15			(5	)
Tax benefit (expense)		103			(156	)		(4	)		1

Total Other comprehensive (loss) income before reclassifications, net of tax		(239	)		348			11			(4	)

Net amount reclassified to earnings:
Aluminum contracts⁽⁵⁾		(6	)		23			—			—
Energy contracts⁽⁶⁾		1			4			—			—
Foreign exchange contracts⁽⁵⁾		1			1			—			—
Interest rate contracts⁽⁷⁾		8			1			5			—
Nickel contracts⁽⁶⁾		1			—			—			—

Sub-total		5			29			5			—
Tax benefit (expense)⁽²⁾		1			(7	)		(2	)		—

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁸⁾		6			22			3			—

Total Other comprehensive (loss) income		(233	)		370			14			(4	)

Balance at end of period	$	364		$	140		$	11		$	(6	)

⁽¹⁾	These amounts were included in the computation of net periodic benefit cost for pension and other postretirement benefits (see Note N).

⁽²⁾	These amounts were included in Provision for income taxes on the accompanying Statement of Consolidated Operations.

⁽³⁾	In all periods presented, there were no tax impacts related to rate changes and no amounts were reclassified to earnings.

⁽⁴⁾	In all periods presented, unrealized and realized gains and losses related to these securities were immaterial. Realized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁵⁾	These amounts were included in Sales on the accompanying Statement of Consolidated Operations.

⁽⁶⁾	These amounts were included in Cost of goods sold on the accompanying Statement of Consolidated Operations.

⁽⁷⁾

For Alcoa, $7 of the amount in both the second quarter ended and six months ended as of June 30, 2016 was included in Other income, net on the accompanying Statement of Consolidated Operations. The remaining amount in both the second quarter ended and six months ended as of June 30, 2016 and the entire amount in both the second quarter ended and six months ended as of June 30, 2015 were included in Interest expense on the accompanying Statement of Consolidated Operations. For Noncontrolling interests, the amount in both the second quarter ended and six months ended as of June 30, 2016 was included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁸⁾	A positive amount indicates a corresponding charge to earnings and a negative amount indicates a corresponding benefit to earnings. These amounts were reflected on the accompanying Statement of Consolidated Operations in the line items indicated in footnotes 1 through 7.

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e681-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

Restructuring and Other Charges

6 Months Ended

Jun. 30, 2016

Restructuring and Related Activities [Abstract]

Restructuring and Other Charges

D. Restructuring and Other Charges – In the second quarter and six-month period of 2016, Alcoa recorded Restructuring and other charges of $23 ($16 after-tax and noncontrolling interest) and $116 ($77 after-tax and noncontrolling interest), respectively.

Restructuring and other charges in the 2016 second quarter included $15 ($11 after-tax and noncontrolling interest) for layoff costs related to cost reduction initiatives and the planned separation of Alcoa (see Note P), including the separation of approximately 540 employees (300 in the Engineered Products and Solutions segment and 240 in the Transportation and Construction Solutions segment); $8 ($6 after-tax and noncontrolling interest) for additional net costs related to decisions made in the fourth quarter of 2015 to permanently close and demolish the Warrick (Indiana) smelter and to curtail the Wenatchee (Washington) smelter and Point Comfort (Texas) refinery (see below); a net charge of $8 ($4 after-tax and noncontrolling interest) for other miscellaneous items; and $8 ($5 after-tax and noncontrolling interest) for the reversal of a number of small layoff reserves related to prior periods.

In the 2016 six-month period, Restructuring and other charges included $86 ($56 after-tax and noncontrolling interest) for additional net costs related to decisions made in the fourth quarter of 2015 to permanently close and demolish the Warrick (Indiana) smelter and to curtail the Wenatchee (Washington) smelter and Point Comfort (Texas) refinery (see below); $34 ($25 after-tax and noncontrolling interest) for layoff costs related to cost reduction initiatives and the planned separation of Alcoa (see Note P), including the separation of approximately 1,100 employees (800 in the Engineered Products and Solutions segment, 240 in the Transportation and Construction Solutions segment, and 30 each in the Primary Metals and Global Rolled Products segments); a net charge of $8 ($4 after-tax and noncontrolling interest) for other miscellaneous items; and $12 ($8 after-tax and noncontrolling interest) for the reversal of a number of small layoff reserves related to prior periods.

In the 2016 six-month period, costs related to the closure and curtailment actions included accelerated depreciation of $70 related to the Warrick smelter as it continued to operate during the 2016 first quarter; $20 ($1 in the 2016 second quarter) for the reversal of severance costs initially recorded in the 2015 fourth quarter; and $36 ($9 in the 2016 second quarter) in other costs. Additionally in the 2016 six-month period, remaining inventories, mostly operating supplies and raw materials, were written down to their net realizable value, resulting in a charge of $5 ($3 after-tax and noncontrolling interest) ($2 ($1 after-tax and noncontrolling interest) in the 2016 second quarter), which was recorded in Cost of goods sold on the accompanying Statement of Consolidated Operations. The other costs of $36 ($9 in the 2016 second quarter) represent $27 ($10 in the 2016 second quarter) for contract termination, $7 in asset retirement obligations for the rehabilitation of a coal mine related to the Warrick smelter, and $2 ($(1) in the 2016 second quarter) in other related costs. Additional charges may be recognized in future periods related to these actions.

In the second quarter and six-month period of 2015, Alcoa recorded Restructuring and other charges of $217 ($141 after-tax and noncontrolling interest) and $394 ($299 after-tax and noncontrolling interest), respectively.

Restructuring and other charges in the 2015 second quarter included $179 ($115 after-tax and noncontrolling interest) for exit costs related to decisions to permanently shut down and demolish a smelter and a power station (see below); $18 ($10 after-tax and noncontrolling interest) for the separation of approximately 120 employees (Alumina segment) and other charges related to the decisions to temporarily curtail both a portion of the capacity (443,000 metric-tons-per-year) at the refinery in Suriname and the remaining capacity (74,000 metric-tons-per-year) at the São Luís smelter in Brazil; $16 ($13 after-tax and noncontrolling interest) for layoff costs, including the separation of approximately 390 employees (210 in the Engineered Products and Solutions segment, 150 in the Primary Metals segment, and 30 in the Global Rolled Products segment); $10 ($7 after-tax and noncontrolling interest) related to post-closing adjustments associated with two December 2014 divestitures; a net credit of $5 ($3 after-tax and noncontrolling interest) for other miscellaneous items; and $1 ($1 after-tax and noncontrolling interest) for the reversal of a few layoff reserves related to prior periods.

In the 2015 six-month period, Restructuring and other charges included the aforementioned $179 ($115 after-tax and noncontrolling interest); $159 ($149 after-tax and noncontrolling interest) related to the March 2015 divestiture of a rolling mill in Russia and post-closing adjustments associated with three December 2014 divestitures; $38 ($23 after-tax and noncontrolling interest) for the separation of approximately 800 employees (680 in the Primary Metals segment and 120 in the Alumina segment), supplier contract-related costs, and other charges associated with the aforementioned decisions to temporarily curtail certain capacity at the São Luís smelter and the refinery in Suriname; $29 ($21 after-tax and noncontrolling interest) for layoff costs, including the separation of approximately 600 employees (290 in the Engineered Products and Solutions segment, 150 in the Primary Metals segment, 60 in the Global Rolled Products segment, 50 in the Transportation and Construction Solutions segment, and 50 in Corporate); a net credit of $3 ($2 after-tax and noncontrolling interest) for other miscellaneous items; and $8 ($7 after-tax and noncontrolling interest) for the reversal of a number of small layoff reserves related to prior periods.

In the second quarter of 2015, management approved the permanent shutdown and demolition of the Poços de Caldas smelter (capacity of 96,000 metric-tons-per-year) in Brazil and the Anglesea power station (includes the closure of a related coal mine) in Australia. The entire capacity at Poços de Caldas has been temporarily idled since May 2014 and the Anglesea power station was shut down at the end of August 2015. Demolition and remediation activities related to the Poços de Caldas smelter and the Anglesea power station began in late 2015 and are expected to be completed by the end of 2026 and 2020, respectively.

The decision on the Poços de Caldas smelter was due to management’s conclusion that the smelter was no longer competitive as a result of challenging global market conditions for primary aluminum, which led to the initial curtailment, that have not dissipated and higher costs. For the Anglesea power station, the decision was made because a sale process did not result in a sale and there would be imminent operating costs and financial constraints related to this site in the remainder of 2015 and beyond, including significant costs to source coal from available resources, necessary maintenance costs, and a depressed outlook for forward electricity prices. The Anglesea power station previously supplied approximately 40 percent of the power needs for the Point Henry smelter, which was closed in August 2014.

In the 2015 second quarter and six-month period, costs related to the shutdown actions included asset impairments of $86, representing the write-off of the remaining book value of all related properties, plants, and equipment; $11 for the layoff of approximately 100 employees (Primary Metals segment); and $82 in other exit costs. Additionally in the 2015 second quarter and six-month period, remaining inventories, mostly operating supplies and raw materials, were written down to their net realizable value, resulting in a charge of $4 ($2 after-tax and noncontrolling interest), which was recorded in Cost of goods sold on the accompanying Statement of Consolidated Operations. The other exit costs of $82 represent $45 in asset retirement obligations and $29 in environmental remediation, both of which were triggered by the decisions to permanently shut down and demolish the aforementioned structures in Brazil and Australia (includes the rehabilitation of a related coal mine), and $8 in supplier and customer contract-related costs.

Alcoa does not include Restructuring and other charges in the results of its reportable segments. The pretax impact of allocating such charges to segment results would have been as follows:


	Second quarter ended June 30,					Six months ended June 30,
	2016			2015		2016			2015
Alumina	$	(1	)	$	10	$	4		$	17
Primary Metals		10			173		88			198
Global Rolled Products		—			1		2			136
Engineered Products and Solutions		9			8		17			11
Transportation and Construction Solutions		8			1		8			3

Segment total		26			193		119			365
Corporate		(3	)		24		(3	)		29

Total restructuring and other charges	$	23		$	217	$	116		$	394

As of June 30, 2016, approximately 730 of the 1,100 employees associated with 2016 restructuring programs, approximately 3,800 of the 5,000 employees (previously 5,200) associated with 2015 restructuring programs, and approximately 2,600 of the 2,700 employees (previously 2,870) associated with 2014 restructuring programs were separated. The total number of employees associated with both 2015 and 2014 restructuring programs was updated to reflect employees, who were initially identified for separation, accepting other positions within Alcoa and natural attrition. Most of the remaining separations for the 2016 restructuring programs and all of the remaining separations for the 2015 and 2014 restructuring programs are expected to be completed by the end of 2016.

In the 2016 second quarter and six-month period, cash payments of $9 and $11, respectively, were made against layoff reserves related to 2016 restructuring programs, $30 and $92, respectively, were made against layoff reserves related to 2015 restructuring programs, and $1 and $3, respectively, were made against layoff reserves related to 2014 restructuring programs.

Activity and reserve balances for restructuring charges were as follows:


	Layoff costs			Other exit costs			Total
Reserve balances at December 31, 2014	$	98		$	34		$	132

2015:
Cash payments		(111	)		(12	)		(123	)
Restructuring charges		299			233			532
Other*		(60	)		(231	)		(291	)

Reserve balances at December 31, 2015		226			24			250

2016:
Cash payments		(107	)		(22	)		(129	)
Restructuring charges		34			41			75
Other*		(31	)		1			(30	)

Reserve balances at June 30, 2016	$	122		$	44		$	166

Other includes reversals of previously recorded restructuring charges and the effects of foreign currency translation. In the 2016 six-month period, Other for layoff costs also included a reclassification of $1 in pension benefits costs, as this obligation was included in Alcoa’s separate liability for pension benefits obligations (see Note N). Additionally in the 2016 six-month period, Other for other exit costs also included a reclassification of $7 in asset retirement obligations, as this liability was included in Alcoa’s separate reserve for asset retirement obligations. In 2015, Other for layoff costs also included a reclassification of $35 in pension and other postretirement benefits costs, as these obligations were included in Alcoa’s separate liability for pension and other postretirement benefits obligations. Additionally in 2015, Other for other exit costs also included a reclassification of the following restructuring charges: $76 in asset retirement and $86 in environmental obligations, as these liabilities were included in Alcoa’s separate reserves for asset retirement obligations and environmental remediation.

The remaining reserves are expected to be paid in cash during the remainder of 2016, with the exception of approximately $25 to $30, which is expected to be paid over the next several years for ongoing site remediation work and special layoff benefit payments.

Acquisitions and Divestitures	6 Months Ended
Acquisitions and Divestitures	Jun. 30, 2016
Business Combinations [Abstract]
Acquisitions and Divestitures	E. Acquisitions and Divestitures – In April 2016, Alcoa completed the sale of the Remmele Medical business to LISI MEDICAL for $102 in cash ($99 net of transaction costs), which was included in Proceeds from the sale of assets and businesses on the accompanying Statement of Consolidated Cash Flows. This business, which was part of the RTI International Metals (RTI) acquisition (see below), manufactures precision-machined metal products for customers in the minimally invasive surgical device and implantable device markets. No gain was recorded on this transaction as the excess of the proceeds over the carrying value of the net assets of this business was reflected as a purchase price adjustment (decrease to goodwill of $44) to the preliminary allocation of the purchase price related to Alcoa’s acquisition of RTI. While owned by Alcoa, the operating results and assets and liabilities of this business were included in the Engineered Products and Solutions segment. This business generated sales of approximately $20 from January 1, 2016 through the divestiture date, April 29, 2016, and, at the time of the divestiture, had approximately 330 employees. This transaction is subject to certain post-closing adjustments as defined in the sale agreement. In July 2016, Alcoa’s wholly-owned subsidiary, Alcoa Power Generating Inc., reached an agreement to sell its 215-megawatt Yadkin Hydroelectric Project (Yadkin) to ISQ Hydro Aggregator LLC. Yadkin encompasses four hydroelectric power developments (reservoirs, dams and powerhouses), known as High Rock, Tuckertown, Narrows and Falls, situated along a 38-mile stretch of the Yadkin River through the central part of North Carolina. This transaction is expected to close in the second half of 2016, subject to customary federal and state regulatory approvals. The power generated by Yadkin is primarily sold into the open market. Yadkin generated sales of approximately $20 in 2015, and had approximately 35 employees as of June 30, 2016. The carrying value of the net assets to be sold was $128 and $127 as of June 30, 2016 and December 31, 2015, respectively, which consist mostly of properties, plants, and equipment. In March 2015, Alcoa completed the acquisition of an aerospace structural castings company, TITAL, for $204 (€188) in cash (an additional $1 (€1) was paid in September 2015 to settle working capital in accordance with the purchase agreement). TITAL, a privately held company with approximately 650 employees based in Germany, produces aluminum and titanium investment casting products for the aerospace and defense markets. The purpose of this acquisition is to capture increasing demand for advanced jet engine components made of titanium, establish titanium-casting capabilities in Europe, and expand existing aluminum casting capacity. The assets, including the associated goodwill, and liabilities of this business were included within Alcoa’s Engineered Products and Solutions segment since the date of acquisition. Based on the preliminary allocation of the purchase price, goodwill of $118 was recorded for this transaction. In the first quarter of 2016, the allocation of the purchase price was finalized, based, in part, on the completion of a third-party valuation of certain assets acquired, resulting in a $1 reduction of the initial goodwill amount. None of the $117 in goodwill is deductible for income tax purposes and no other intangible assets were identified. This transaction is no longer subject to post-closing adjustments. In July 2015, Alcoa completed the acquisition of RTI, a global supplier of titanium and specialty metal products and services for the commercial aerospace, defense, energy, and medical device markets, for $870 in Alcoa common stock. The preliminary allocation of the purchase price resulted in total assets of $1,752, including $240 in goodwill and $73 in intangibles, $822 in total liabilities, and $60 in additional capital. In the 2016 six-month period, Alcoa updated the estimated beginning balances of certain assets acquired, including a decrease to each of properties, plants, and equipment of $110, inventories of $48, and intangible assets of $33 and an increase to goodwill of $54. These changes were based, in part, on management’s review of information from a preliminary third-party valuation and the sale of the medical device business (see above). The current allocation of the purchase price, which will be finalized in the third quarter of 2016, is subject to change upon further review by management.

Inventories

6 Months Ended

Jun. 30, 2016

Inventory Disclosure [Abstract]

Inventories

F. Inventories


	June 30, 2016		December 31, 2015
Finished goods	$	827	$	811
Work-in-process		1,344		1,272
Bauxite and alumina		416		445
Purchased raw materials		650		720
Operating supplies		201		194

	$	3,438	$	3,442

At June 30, 2016 and December 31, 2015, the total amount of inventories valued on a LIFO basis was $1,335 and $1,373, respectively. If valued on an average-cost basis, total inventories would have been $567 and $559 higher at June 30, 2016 and December 31, 2015, respectively.

Investments

6 Months Ended

Jun. 30, 2016

Investments Schedule [Abstract]

Investments

G. Investments – A summary of unaudited financial information for Alcoa’s equity investments is as follows (amounts represent 100% of investee financial information):


	Second quarter ended June 30,					Six months ended June 30,
	2016		2015			2016		2015
Sales	$	904	$	971		$	1,796	$	1,857
Cost of goods sold		679		862			1,360		1,557
Net income (loss)		14		(45	)		29		(86	)

In April 2016, Alcoa’s majority-owned subsidiary, Alcoa of Australia Limited (AofA), sold its 20% interest in a consortium, DBP, the owner and operator of the Dampier to Bunbury Natural Gas Pipeline (DBNGP) in Western Australia, to the only other member of the consortium, DUET Group. AofA received $145 (A$192) in cash, which was included in Sales of investments on the accompanying Statement of Consolidated Cash Flows, and recorded a gain of $27 (A$35) ($11 (A$15) after-tax and noncontrolling interest) in Other income, net on the accompanying Statement of Consolidated Operations. Prior to this transaction, AofA’s 20% interest was previously classified as an equity investment on Alcoa’s Consolidated Balance Sheet. As part of the transaction, AofA will maintain its current access to approximately 30% of the DBNGP transmission capacity for gas supply to its three alumina refineries in Western Australia. AofA is part of Alcoa World Alumina and Chemicals (AWAC), an unincorporated joint venture that consists of a group of companies, which are owned 60% by Alcoa and 40% by Alumina Limited of Australia.

In the 2016 six-month period, Alcoa sold various exchange-traded fixed income and equity securities held by its captive insurance company for $130, which was included in Sales of investments on the accompanying Statement of Consolidated Cash Flows, and recorded a loss of $3 ($2 after-tax) in Other income, net on the accompanying Statement of Consolidated Operations. Previously, these securities were classified as available-for-sale investments on Alcoa’s Consolidated Balance Sheet and were carried at fair value with unrealized gains and losses recognized in other comprehensive income. As of June 30, 2016 and December 31, 2015, the carrying value of available-for-sale-securities was $68 and $193, respectively, which was included in Investments on the accompanying Consolidated Balance Sheet.

H. Other Noncurrent Assets – In the first quarter of 2016, Alcoa received $234 in proceeds from the redemption of certain company-owned life insurance policies. In the second quarter of 2016, Alcoa liquidated additional company-owned life insurance policies for $223 in cash. Both of these amounts were included in Proceeds from the sale of assets and businesses on the accompanying Statement of Consolidated Cash Flows. As the cash received was equivalent to the cash surrender value of these policies, no gain or loss was recognized on the sales of these policies. As of June 30, 2016 and December 31, 2015, the cash surrender value of life insurance policies was $26 and $492, respectively, which was included in Other noncurrent assets on the accompanying Consolidated Balance Sheet.

Other Noncurrent Assets	6 Months Ended
Other Noncurrent Assets	Jun. 30, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Noncurrent Assets	H. Other Noncurrent Assets – In the first quarter of 2016, Alcoa received $234 in proceeds from the redemption of certain company-owned life insurance policies. In the second quarter of 2016, Alcoa liquidated additional company-owned life insurance policies for $223 in cash. Both of these amounts were included in Proceeds from the sale of assets and businesses on the accompanying Statement of Consolidated Cash Flows. As the cash received was equivalent to the cash surrender value of these policies, no gain or loss was recognized on the sales of these policies. As of June 30, 2016 and December 31, 2015, the cash surrender value of life insurance policies was $26 and $492, respectively, which was included in Other noncurrent assets on the accompanying Consolidated Balance Sheet.

Contingencies and Commitments	6 Months Ended
Contingencies and Commitments	Jun. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	I. Contingencies and Commitments Contingencies Litigation On June 5, 2015, Alcoa World Alumina LLC (“AWA”) and St. Croix Alumina, L.L.C. (“SCA”) filed a complaint in Delaware Chancery Court for a declaratory judgment and injunctive relief to resolve a dispute between Alcoa and Glencore Ltd. (“Glencore”) with respect to claimed obligations under a 1995 asset purchase agreement between Alcoa and Glencore. The dispute arose from Glencore’s demand that Alcoa indemnify it for liabilities it may have to pay to Lockheed Martin (“Lockheed”) related to the St. Croix alumina refinery. Lockheed had earlier filed suit against Glencore in federal court in New York seeking indemnity for liabilities it had incurred and would incur to the U.S. Virgin Islands to remediate certain properties at the refinery property and claimed that Glencore was required by an earlier, 1989 purchase agreement to indemnify it. Glencore had demanded that Alcoa indemnify and defend it in the Lockheed case and threatened to claim against Alcoa in the New York action despite exclusive jurisdiction for resolution of disputes under the 1995 purchase agreement being in Delaware. After Glencore conceded that it was not seeking to add Alcoa to the New York action, AWA and SCA dismissed their complaint in the Chancery Court case and on August 6, 2015 filed a complaint for declaratory judgment in Delaware Superior Court. AWA and SCA filed a motion for judgment on the pleadings on September 16, 2015. Glencore answered AWA’s and SCA’s complaint and asserted counterclaims on August 27, 2015, and on October 2, 2015 filed its own motion for judgment on the pleadings. Argument on the parties’ motions was held by the court on December 7, 2015, and by order dated February 8, 2016, the court granted Alcoa’s motion and denied Glencore’s motion, resulting in Alcoa not being liable to indemnify Glencore for the Lockheed action. The decision also leaves for pretrial discovery and possible summary judgment or trial Glencore’s claims for costs and fees it incurred in defending and settling an earlier Superfund action brought against Glencore by the Government of the Virgin Islands. On February 17, 2016, Glencore filed notice of its application for interlocutory appeal of the February 8, 2016 ruling. AWA and SCA filed an opposition to that application on February 29, 2016. On March 10, 2016, the court denied Glencore’s motion for interlocutory appeal and on the same day entered judgment on claims other than Glencore’s claims for costs and fees it incurred in defending and settling the earlier Superfund action brought against Glencore by the Government of the Virgin Islands. On March 29, 2016, Glencore filed a withdrawal of its notice of interlocutory appeal, and on April 6, 2016, Glencore filed an appeal of the court’s March 10, 2016 judgment to the Delaware Supreme Court. At this time, the Company is unable to reasonably predict the ultimate outcome for this matter. Before 2002, Alcoa purchased power in Italy in the regulated energy market and received a drawback of a portion of the price of power under a special tariff in an amount calculated in accordance with a published resolution of the Italian Energy Authority, Energy Authority Resolution n. 204/1999 (“204/1999”). In 2001, the Energy Authority published another resolution, which clarified that the drawback would be calculated in the same manner, and in the same amount, in either the regulated or unregulated market. At the beginning of 2002, Alcoa left the regulated energy market to purchase energy in the unregulated market. Subsequently, in 2004, the Energy Authority introduced regulation no. 148/2004 which set forth a different method for calculating the special tariff that would result in a different drawback for the regulated and unregulated markets. Alcoa challenged the new regulation in the Administrative Court of Milan and received a favorable judgment in 2006. Following this ruling, Alcoa continued to receive the power price drawback in accordance with the original calculation method, through 2009, when the European Commission declared all such special tariffs to be impermissible “state aid.” In 2010, the Energy Authority appealed the 2006 ruling to the Consiglio di Stato (final court of appeal). On December 2, 2011, the Consiglio di Stato ruled in favor of the Energy Authority and against Alcoa, thus presenting the opportunity for the energy regulators to seek reimbursement from Alcoa of an amount equal to the difference between the actual drawback amounts received over the relevant time period, and the drawback as it would have been calculated in accordance with regulation 148/2004. On February 23, 2012, Alcoa filed its appeal of the decision of the Consiglio di Stato (this appeal was subsequently withdrawn in March 2013). On March 26, 2012, Alcoa received a letter from the agency (Cassa Conguaglio per il Settore Eletrico (CCSE)) responsible for making and collecting payments on behalf of the Energy Authority demanding payment in the amount of approximately $110 (€85), including interest. By letter dated April 5, 2012, Alcoa informed CCSE that it disputes the payment demand of CCSE since (i) CCSE was not authorized by the Consiglio di Stato decisions to seek payment of any amount, (ii) the decision of the Consiglio di Stato has been appealed (see above), and (iii) in any event, no interest should be payable. On April 29, 2012, Law No. 44 of 2012 (“44/2012”) came into effect, changing the method to calculate the drawback. On February 21, 2013, Alcoa received a revised request letter from CCSE demanding Alcoa’s subsidiary, Alcoa Trasformazioni S.r.l., make a payment in the amount of $97 (€76), including interest, which reflects a revised calculation methodology by CCSE and represents the high end of the range of reasonably possible loss associated with this matter of $0 to $97 (€76). Alcoa rejected that demand and formally challenged it through an appeal before the Administrative Court on April 5, 2013. The Administrative Court scheduled a hearing for December 19, 2013, which was subsequently postponed until April 17, 2014, and further postponed until June 19, 2014. On that date, the Administrative Court listened to Alcoa’s oral argument, and on September 2, 2014, rendered its decision. The Administrative Court declared the payment request of CCSE and the Energy Authority to Alcoa to be unsubstantiated based on the 148/2004 resolution with respect to the January 19, 2007 through November 19, 2009 timeframe. On December 18, 2014, the CCSE and the Energy Authority appealed the Administrative Court’s September 2, 2014 decision; however, a date for the hearing has not been scheduled. As a result of the conclusion of the European Commission Matter on January 26, 2016 (see Note N in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015), management modified its outlook with respect to a portion of the pending legal proceedings related to this matter. As such, a charge of $37 (€34) was recorded in Restructuring and other charges for the year ended December 31, 2015 to establish a partial reserve for this matter. At this time, the Company is unable to reasonably predict the ultimate outcome for this matter. Environmental Matters Alcoa participates in environmental assessments and cleanups at more than 100 locations. These include owned or operating facilities and adjoining properties, previously owned or operating facilities and adjoining properties, and waste sites, including Superfund (Comprehensive Environmental Response, Compensation and Liability Act (CERCLA)) sites. A liability is recorded for environmental remediation when a cleanup program becomes probable and the costs can be reasonably estimated. As assessments and cleanups proceed, the liability is adjusted based on progress made in determining the extent of remedial actions and related costs. The liability can change substantially due to factors such as the nature and extent of contamination, changes in remedial requirements, and technological changes, among others. Alcoa’s remediation reserve balance was $606 and $604 at June 30, 2016 and December 31, 2015 (of which $49 and $50 was classified as a current liability), respectively, and reflects the most probable costs to remediate identified environmental conditions for which costs can be reasonably estimated. In the 2016 second quarter and six-month period, the remediation reserve was increased by $6 and $13, respectively. The change in both periods was due to a net charge associated with a number of sites and was recorded in Cost of goods sold on the accompanying Statement of Consolidated Operations. Payments related to remediation expenses applied against the reserve were $14 and $25 in the 2016 second quarter and six-month period, respectively. These amounts include expenditures currently mandated, as well as those not required by any regulatory authority or third party. In the 2016 second quarter and six-month period, the change in the reserve also reflects an increase of $6 and $11, respectively, due to the effects of foreign currency translation and an increase of $3 related to the acquisition of RTI International Metals (see Note E). Included in annual operating expenses are the recurring costs of managing hazardous substances and environmental programs. These costs are estimated to be approximately 2% of cost of goods sold. The following discussion provides details regarding the current status of certain significant reserves related to current or former Alcoa sites. Massena West, NY—Alcoa has an ongoing remediation project related to the Grasse River, which is adjacent to Alcoa’s Massena plant site. Many years ago, it was determined that sediments and fish in the river contain varying levels of polychlorinated biphenyls (PCBs). The project, which was selected by the U.S. Environmental Protection Agency (EPA) in a Record of Decision (ROD) issued in April 2013, is aimed at capping PCB contaminated sediments with concentration in excess of one part per million in the main channel of the river and dredging PCB contaminated sediments in the near-shore areas where total PCBs exceed one part per million. At June 30, 2016 and December 31, 2015, the reserve balance associated with this matter was $232 and $234, respectively. Alcoa is in the planning and design phase, which is expected to be completed in 2017. Subsequently in 2017, the actual remediation fieldwork is expected to commence and take approximately four years. The majority of the project funding is expected to be spent between 2017 and 2021. Sherwin, TX—In connection with the sale of the Sherwin alumina refinery, which was required to be divested as part of the Reynolds merger in 2000, Alcoa agreed to retain responsibility for the remediation of the then existing environmental conditions, as well as a pro rata share of the final closure of the active bauxite residue waste disposal areas (known as the Copano facility). Alcoa’s share of the closure costs is proportional to the total period of operation of the active waste disposal areas. At June 30, 2016 and December 31, 2015, the reserve balance associated with Sherwin was $30. Approximately half of the project funding is expected to be spent through 2019. The remainder is not expected to be spent in the foreseeable future as it is dependent upon the operating life of the active waste disposal areas. East St. Louis, IL—Alcoa has an ongoing remediation project related to an area used for the disposal of bauxite residue from former alumina refining operations. The project, which was selected by the EPA in a ROD issued in July 2012, is aimed at implementing a soil cover over the affected area. On November 1, 2013, the U.S. Department of Justice lodged a consent decree on behalf of the EPA for Alcoa to conduct the work outlined in the ROD. This consent decree was entered as final in February 2014 by the U.S. Department of Justice. As a result, Alcoa began construction in March 2014; the field work on this project was completed at the end of June 2016. Alcoa is now in the documentation and final reporting stage with the EPA, which will continue into 2017 when this matter will transition into a long-term inspection and monitoring program (Alcoa has a second project in East St. Louis that is separate from the matter presented herein on which Alcoa is expecting an EPA decision at some point in the remainder of 2016 – any resulting liability is not expected to be material). At June 30, 2016 and December 31, 2015, the reserve balance associated with this matter was $6 and $8, respectively. Fusina and Portovesme, Italy—In 1996, Alcoa acquired the Fusina smelter and rolling operations and the Portovesme smelter, both of which are owned by Alcoa’s subsidiary Alcoa Trasformazioni S.r.l. (“Trasformazioni”), from Alumix, an entity owned by the Italian Government. At the time of the acquisition, Alumix indemnified Alcoa for pre-existing environmental contamination at the sites. In 2004, the Italian Ministry of Environment and Protection of Land and Sea (MOE) issued orders to Trasformazioni and Alumix for the development of a clean-up plan related to soil contamination in excess of allowable limits under legislative decree and to institute emergency actions and pay natural resource damages. Trasformazioni appealed the orders and filed suit against Alumix, among others, seeking indemnification for these liabilities under the provisions of the acquisition agreement. In 2009, Ligestra S.r.l. (“Ligestra”), Alumix’s successor, and Trasformazioni agreed to a stay of the court proceedings while investigations were conducted and negotiations advanced towards a possible settlement. In December 2009, Trasformazioni and Ligestra reached an initial agreement for settlement of the liabilities related to Fusina while negotiations continued related to Portovesme (see below). The agreement outlined an allocation of payments to the MOE for emergency action and natural resource damages and the scope and costs for a proposed soil remediation project, which was formally presented to the MOE in mid-2010. The agreement was contingent upon final acceptance of the remediation project by the MOE. As a result of entering into this agreement, Alcoa increased the reserve by $12 in 2009 for Fusina. Based on comments received from the MOE and local and regional environmental authorities, Trasformazioni submitted a revised remediation plan in the first half of 2012; however, such revisions did not require any change to the existing reserve. In October 2013, the MOE approved the project submitted by Alcoa, resulting in no adjustment to the reserve. In January 2014, in anticipation of Alcoa reaching a final administrative agreement with the MOE, Alcoa and Ligestra entered into a final agreement related to Fusina for allocation of payments to the MOE for emergency action and natural resource damages and the costs for the approved soil remediation project. The agreement resulted in Ligestra assuming 50% to 80% of all payments and remediation costs. On February 27, 2014, Alcoa and the MOE reached a final administrative agreement for conduct of work. The agreement includes both a soil and groundwater remediation project estimated to cost $33 (€24) and requires payments of $25 (€18) to the MOE for emergency action and natural resource damages. The remediation projects are slated to begin as soon as Alcoa receives final approval from the Ministry of Infrastructure. Based on the final agreement with Ligestra, Alcoa’s share of all costs and payments is $17 (€12), of which $9 (€6) related to the damages will be paid annually over a 10-year period, which began in April 2014, and was previously fully reserved. Separately, in 2009, due to additional information derived from the site investigations conducted at Portovesme, Alcoa increased the reserve by $3. In November 2011, Trasformazioni and Ligestra reached an agreement for settlement of the liabilities related to Portovesme, similar to the one for Fusina. A proposed soil remediation project for Portovesme was formally presented to the MOE in June 2012. Neither the agreement with Ligestra nor the proposal to the MOE resulted in a change to the reserve for Portovesme. In November 2013, the MOE rejected the proposed soil remediation project and requested a revised project be submitted. In May 2014, Trasformazioni and Ligestra submitted a revised soil remediation project that addressed certain stakeholders’ concerns. Alcoa increased the reserve by $3 in 2014 to reflect the estimated higher costs associated with the revised soil remediation project, as well as current operating and maintenance costs of the Portovesme site. In October 2014, the MOE required a further revised project be submitted to reflect the removal of a larger volume of contaminated soil than what had been proposed, as well as design changes for the cap related to the remaining contaminated soil left in place and the expansion of an emergency containment groundwater pump and treatment system that was previously installed. Trasformazioni and Ligestra submitted the further revised soil remediation project in February 2015. As a result, Alcoa increased the reserve by $7 in March 2015 to reflect the increase in the estimated costs of the project. In October 2015, Alcoa received a final ministerial decree approving the February 2015 revised soil remediation project. Work on the soil remediation project commenced in the second quarter of 2016 and is expected to be completed in 2019. Alcoa and Ligestra are now working on a final groundwater remediation project, which will be submitted to the MOE for review during the second half of 2016. The ultimate outcome of this matter may result in a change to the existing reserve for Portovesme. Baie Comeau, Quebec, Canada—In August 2012, Alcoa presented an analysis of remediation alternatives to the Quebec Ministry of Sustainable Development, Environment, Wildlife and Parks (MDDEP), in response to a previous request, related to known PCBs and polycyclic aromatic hydrocarbons (PAHs) contained in sediments of the Anse du Moulin bay. As such, Alcoa increased the reserve for Baie Comeau by $25 in 2012 to reflect the estimated cost of Alcoa’s recommended alternative, consisting of both dredging and capping of the contaminated sediments. In July 2013, Alcoa submitted the Environmental Impact Assessment for the project to the MDDEP. The MDDEP notified Alcoa that the project as it was submitted was approved and a final ministerial decree was issued in July 2015. As a result, no further adjustment to the reserve was required in 2015. The decree provides final approval for the project and allows Alcoa to start work on the final project design, which is expected to be completed in the second half of 2016 with construction on the project expected to begin in 2017. Completion of the final project design and bidding of the project may result in additional liability in a future period. Mosjøen, Norway—In September 2012, Alcoa presented an analysis of remediation alternatives to the Norwegian Environmental Agency (NEA) (formerly the Norwegian Climate and Pollution Agency, or “Klif”), in response to a previous request, related to known PAHs in the sediments located in the harbor and extending out into the fjord. As such, Alcoa increased the reserve for Mosjøen by $20 in 2012 to reflect the estimated cost of the baseline alternative for dredging of the contaminated sediments. A proposed project reflecting this alternative was formally presented to the NEA in June 2014, and was resubmitted in late 2014 to reflect changes by the NEA. The revised proposal did not result in a change to the reserve for Mosjøen. In April 2015, the NEA notified Alcoa that the revised project was approved and required submission of the final project design before issuing a final order. Alcoa completed and submitted the final project design, which identified a need to stabilize the related wharf structure to allow for the sediment dredging in the harbor. As a result, Alcoa increased the reserve for Mosjøen by $11 in June 2015 to reflect the estimated cost of the wharf stabilization. Also in June 2015, the NEA issued a final order approving the project as well as the final project design. In September 2015, Alcoa increased the reserve by $1 to reflect the potential need (based on prior experience with similar projects) to perform additional dredging if the results of sampling, which is required by the order, don’t achieve the required cleanup levels. Project construction commenced in the first quarter of 2016 and is expected to be completed by the end of 2017. Tax In September 2010, following a corporate income tax audit covering the 2003 through 2005 tax years, an assessment was received as a result of Spain’s tax authorities disallowing certain interest deductions claimed by a Spanish consolidated tax group owned by the Company. An appeal of this assessment in Spain’s Central Tax Administrative Court by the Company was denied in October 2013. In December 2013, the Company filed an appeal of the assessment in Spain’s National Court. Additionally, following a corporate income tax audit of the same Spanish tax group for the 2006 through 2009 tax years, Spain’s tax authorities issued an assessment in July 2013 similarly disallowing certain interest deductions. In August 2013, the Company filed an appeal of this second assessment in Spain’s Central Tax Administrative Court, which was denied in January 2015. The Company filed an appeal of this second assessment in Spain’s National Court in March 2015. At June 30, 2016, the combined assessments total $269 (€243), including interest. The Company believes it has meritorious arguments to support its tax position and intends to vigorously litigate the assessments through Spain’s court system. However, in the event the Company is unsuccessful, a portion of the assessments may be offset with existing net operating losses available to the Spanish consolidated tax group. Additionally, it is possible that the Company may receive similar assessments for tax years subsequent to 2009. At this time, the Company is unable to reasonably predict an outcome for this matter. In March 2013, Alcoa’s subsidiary, Alcoa World Alumina Brasil (AWAB), was notified by the Brazilian Federal Revenue Office (RFB) that approximately $110 (R$220) of value added tax credits previously claimed are being disallowed and a penalty of 50% assessed. Of this amount, AWAB received $41 (R$82) in cash in May 2012. The value added tax credits were claimed by AWAB for both fixed assets and export sales related to the Juruti bauxite mine and São Luís refinery expansion. The RFB has disallowed credits they allege belong to the consortium in which AWAB owns an interest and should not have been claimed by AWAB. Credits have also been disallowed as a result of challenges to apportionment methods used, questions about the use of the credits, and an alleged lack of documented proof. AWAB presented defense of its claim to the RFB on April 8, 2013. If AWAB is successful in this administrative process, the RFB would have no further recourse. If unsuccessful in this process, AWAB has the option to litigate at a judicial level. Separately from AWAB’s administrative appeal, in June 2015, new tax law was enacted repealing the provisions in the tax code that were the basis for the RFB assessing a 50% penalty in this matter. As such, the estimated range of reasonably possible loss is $0 to $32 (R$103), whereby the maximum end of the range represents the portion of the disallowed credits applicable to the export sales and excludes the 50% penalty. Additionally, the estimated range of disallowed credits related to AWAB’s fixed assets is $0 to $36 (R$117), which would increase the net carrying value of AWAB’s fixed assets if ultimately disallowed. It is management’s opinion that the allegations have no basis; however, at this time, management is unable to reasonably predict an outcome for this matter. Between 2000 and 2002, Alcoa Alumínio (Alumínio) sold approximately 2,000 metric tons of metal per month from its Poços de Caldas facility, located in the State of Minas Gerais (the “State”), to Alfio, a customer also located in the State. Sales in the State were exempted from value-added tax (VAT) requirements. Alfio subsequently sold metal to customers outside of the State, but did not pay the required VAT on those transactions. In July 2002, Alumínio received an assessment from State auditors on the theory that Alumínio should be jointly and severally liable with Alfio for the unpaid VAT. In June 2003, the administrative tribunal found Alumínio liable, and Alumínio filed a judicial case in the State in February 2004 contesting the finding. In May 2005, the Court of First Instance found Alumínio solely liable, and a panel of a State appeals court confirmed this finding in April 2006. Alumínio filed a special appeal to the Superior Tribunal of Justice (STJ) in Brasilia (the federal capital of Brazil) later in 2006. In 2011, the STJ (through one of its judges) reversed the judgment of the lower courts, finding that Alumínio should neither be solely nor jointly and severally liable with Alfio for the VAT, which ruling was then appealed by the State. In August 2012, the STJ agreed to have the case reheard before a five-judge panel. A decision from this panel is pending, but additional appeals are likely. At June 30, 2016, the assessment totaled $43 (R$139), including penalties and interest. While the Company believes it has meritorious defenses, the Company is unable to reasonably predict an outcome. Other In connection with the sale in 2001 of Reynolds Metals Company’s (“Reynolds,” a subsidiary of Alcoa), alumina refinery in Gregory, Texas, Reynolds assigned an Energy Services Agreement (“ESA”) with Gregory Power Partners (“Gregory Power”) for purchase of steam and electricity by the refinery. On January 11, 2016, Sherwin Alumina Company, LLC (“Sherwin”), the current owner of the refinery, and one of its affiliate entities, filed bankruptcy petitions in Corpus Christi, Texas for reorganization under Chapter 11 of the Bankruptcy Code. On January 26, 2016, Gregory Power delivered notice to Reynolds that Sherwin’s bankruptcy filing constitutes a breach of the ESA; on January 29, 2016, Reynolds responded that the filing does not constitute a breach. Sherwin has indicated that it may cease operations if an acceptable, modified ESA cannot be achieved and it is not able to continue its bauxite supply agreement with a subsidiary of Noranda Aluminum Holding Corporation. If Sherwin is unable to confirm a revised plan of reorganization to continue operation of the refinery, Reynolds may face claims under the ESA or for environmental remediation at the refinery and associated properties. This matter is neither estimable nor probable; therefore, at this time, the Company is unable to reasonably predict the ultimate outcome. In addition to the matters discussed above, various other lawsuits, claims, and proceedings have been or may be instituted or asserted against Alcoa, including those pertaining to environmental, product liability, safety and health, and tax matters. While the amounts claimed in these other matters may be substantial, the ultimate liability cannot now be determined because of the considerable uncertainties that exist. Therefore, it is possible that the Company’s liquidity or results of operations in a particular period could be materially affected by one or more of these other matters. However, based on facts currently available, management believes that the disposition of these other matters that are pending or asserted will not have a material adverse effect, individually or in the aggregate, on the financial position of the Company. Commitments Investments Alcoa has an investment in a joint venture for the development, construction, ownership, and operation of an integrated aluminum complex (bauxite mine, alumina refinery, aluminum smelter, and rolling mill) in Saudi Arabia. The joint venture is owned 74.9% by the Saudi Arabian Mining Company (known as “Ma’aden”) and 25.1% by Alcoa and consists of three separate companies as follows: one each for the mine and refinery, the smelter, and the rolling mill. Alcoa accounts for its investment in the joint venture under the equity method. Capital investment in the project is expected to total approximately $10,800 (SAR 40.5 billion) and has been funded through a combination of equity contributions by the joint venture partners and project financing by the joint venture, which has been guaranteed by both partners (see below). Both the equity contributions and the guarantees of the project financing are based on the joint venture’s partners’ ownership interests. Originally, it was estimated that Alcoa’s total equity investment in the joint venture would be approximately $1,100, of which Alcoa has contributed $982, including $1 in the 2016 six-month period. Based on changes to both the project’s capital investment and equity and debt structure from the initial plans, the estimated $1,100 equity contribution may be reduced. As of June 30, 2016 and December 31, 2015, the carrying value of Alcoa’s investment in this project was $883 and $928, respectively. The smelting and rolling mill companies have project financing totaling $4,227 (reflects principal repayments made through June 30, 2016), of which $1,061 represents Alcoa’s share (the equivalent of Alcoa’s 25.1% interest in the smelting and rolling mill companies). In conjunction with the financings, Alcoa issued guarantees on behalf of the smelting and rolling mill companies to the lenders in the event that such companies default on their debt service requirements through 2017 and 2020 for the smelting company and 2018 and 2021 for the rolling mill company (Ma’aden issued similar guarantees for its 74.9% interest). Alcoa’s guarantees for the smelting and rolling mill companies cover total debt service requirements of $142 in principal and up to a maximum of approximately $30 in interest per year (based on projected interest rates). At June 30, 2016 and December 31, 2015, the combined fair value of the guarantees was $4 and $7, respectively, which was included in Other noncurrent liabilities and deferred credits on the accompanying Consolidated Balance Sheet. The mining and refining company has project financing totaling $2,232, of which $560 represents AWAC’s 25.1% interest in the mining and refining company. In conjunction with the financings, Alcoa, on behalf of AWAC, issued guarantees to the lenders in the event that the mining and refining company defaults on its debt service requirements through 2019 and 2024 (Ma’aden issued similar guarantees for its 74.9% interest). Alcoa’s guarantees for the mining and refining company cover total debt service requirements of $120 in principal and up to a maximum of approximately $30 in interest per year (based on projected interest rates). At both June 30, 2016 and December 31, 2015, the combined fair value of the guarantees was $3, which was included in Other noncurrent liabilities and deferred credits on the accompanying Consolidated Balance Sheet. In the event Alcoa would be required to make payments under the guarantees, 40% of such amount would be contributed to Alcoa by Alumina Limited, consistent with its ownership interest in AWAC. In 2004, AofA acquired a 20% interest in a consortium, which subsequently purchased the Dampier to Bunbury Natural Gas Pipeline (DBNGP) in Western Australia, in exchange for an initial cash investment of $17 (A$24). The investment in the DBNGP, which was classified as an equity investment, was made in order to secure a competitively priced long-term supply of natural gas to AofA’s refineries in Western Australia. AofA made additional contributions of $141 (A$176) for its share of the pipeline capacity expansion and other operational purposes of the consortium through September 2011. In late 2011, the consortium initiated a three-year equity call plan to improve its capitalization structure. This plan required AofA to contribute $39 (A$40), all of which was made through December 2014. Following the completion of the three-year equity call plan in December 2014, the consortium initiated a new equity call plan to further improve its capitalization structure. This plan required AofA to contribute $30 (A$36) through mid-2016, of which $20 (A$27) was made through March 31, 2016, including $3 (A$5) in the 2016 first quarter. In April 2016, AofA sold its interest in the consortium (see Note G), effectively terminating its remaining obligation to make contributions under the current equity call plan. As part of the sale transaction, AofA will maintain its current access to approximately 30% of the DBNGP transmission capacity for gas supply to its three alumina refineries in Western Australia under an existing agreement to purchase gas transmission services from the DBNGP. At June 30, 2016, AofA has an asset of $275 (A$372) representing prepayments made under the agreement for future gas transmission services. On April 8, 2015, AofA secured a new 12-year gas supply agreement to power its three alumina refineries in Western Australia beginning in July 2020. This agreement was conditional on the completion of a third-party acquisition of the related energy assets from the then-current owner, which occurred in June 2015. The terms of AofA’s gas supply agreement required a prepayment of $500 to be made in two installments. The first installment of $300 was made at the time of the completion of the third-party acquisition in June 2015 and the second installment of $200 was made in April 2016. Both of these amounts were included in (Increase) in noncurrent assets on the accompanying Statement of Consolidated Cash Flows in the respective periods. At June 30, 2016 and December 31, 2015, Alcoa has an asset of $484 (A$654) and $288 (A$395), respectively, representing the respective prepayments made under this agreement, which were included in Other noncurrent assets on the accompanying Consolidated Balance Sheet.

Other Income, Net

6 Months Ended

Jun. 30, 2016

Other Income and Expenses [Abstract]

Other Income, Net

J. Other Income, Net


	Second quarter ended June 30,						Six months ended June 30,
	2016			2015			2016			2015
Equity loss	$	15		$	24		$	37		$	44
Interest income		(5	)		(4	)		(9	)		(7	)
Foreign currency (gains) losses, net		(9	)		6			6			(10	)
Net gain from asset sales		(30	)		(28	)		(28	)		(28	)
Net loss on mark-to-market derivative contracts (O)		8			7			9			3
Other, net		(16	)		(5	)		(18	)		(14	)

	$	(37	)	$	—		$	(3	)	$	(12	)

In the 2016 second quarter and six-month period, Net gain from assets sales included a $27 gain related to the sale of an equity interest in a natural gas pipeline in Australia (see Note G). In the 2015 second quarter and six-month period, Net gain from assets sales included a $29 gain related to the sale of land around the Lake Charles, LA anode facility.

Segment Information

6 Months Ended

Jun. 30, 2016

Segment Reporting [Abstract]

Segment Information

K. Segment Information – The operating results of Alcoa’s reportable segments were as follows (differences between segment totals and consolidated totals are in Corporate):


	Alumina			Primary Metals			Global Rolled Products			Engineered Products and Solutions		Transportation and Construction Solutions		Total
Second quarter ended June 30, 2016
Sales:
Third-party sales	$	694		$	1,119		$	1,550		$	1,465	$	467	$	5,295
Intersegment sales		300			473			29			—		—		802

Total sales	$	994		$	1,592		$	1,579		$	1,465	$	467	$	6,097

Profit and loss:
Equity loss	$	(7	)	$	—		$	(10	)	$	—	$	—	$	(17	)
Depreciation, depletion, and amortization		66			101			55			62		12		296
Income taxes		40			—			28			87		18		173
After-tax operating income (ATOI)		109			41			68			180		46		444
Second quarter ended June 30, 2015
Sales:
Third-party sales	$	924		$	1,534		$	1,668		$	1,279	$	492	$	5,897
Intersegment sales		431			562			34			—		—		1,027

Total sales	$	1,355		$	2,096		$	1,702		$	1,279	$	492	$	6,924

Profit and loss:
Equity loss	$	(11	)	$	(5	)	$	(7	)	$	—	$	—	$	(23	)
Depreciation, depletion, and amortization		77			109			56			54		11		307
Income taxes		87			6			25			81		17		216
ATOI		215			67			76			165		44		567


	Alumina			Primary Metals			Global Rolled Products			Engineered Products and Solutions		Transportation and Construction Solutions		Total
Six months ended June 30, 2016
Sales:
Third-party sales	$	1,239		$	2,242		$	2,947		$	2,914	$	896	$	10,238
Intersegment sales		592			948			58			—		—		1,598

Total sales	$	1,831		$	3,190		$	3,005		$	2,914	$	896	$	11,836

Profit and loss:
Equity (loss) income	$	(21	)	$	4		$	(21	)	$	—	$	—	$	(38	)
Depreciation, depletion, and amortization		129			203			111			127		23		593
Income taxes		45			(16	)		62			165		32		288
ATOI		117			55			136			342		85		735
Six months ended June 30, 2015
Sales:
Third-party sales	$	1,811		$	3,106		$	3,289		$	2,536	$	963	$	11,705
Intersegment sales		932			1,254			70			—		—		2,256

Total sales	$	2,743		$	4,360		$	3,359		$	2,536	$	963	$	13,961

Profit and loss:
Equity loss	$	(18	)	$	(8	)	$	(16	)	$	—	$	—	$	(42	)
Depreciation, depletion, and amortization		157			218			112			105		21		613
Income taxes		179			63			61			157		31		491
ATOI		436			254			130			321		82		1,223

The following table reconciles total segment ATOI to consolidated net income attributable to Alcoa:


	Second quarter ended June 30,						Six months ended June 30,
	2016			2015			2016			2015
Total segment ATOI	$	444		$	567		$	735		$	1,223
Unallocated amounts (net of tax):
Impact of LIFO		(10	)		36			(6	)		43
Metal price lag		7			(39	)		8			(62	)
Interest expense		(84	)		(80	)		(167	)		(160	)
Noncontrolling interests		(43	)		(67	)		(38	)		(127	)
Corporate expense		(77	)		(65	)		(132	)		(127	)
Restructuring and other charges		(15	)		(159	)		(76	)		(320	)
Other		(87	)		(53	)		(173	)		(135	)

Consolidated net income attributable to Alcoa	$	135		$	140		$	151		$	335

Items required to reconcile total segment ATOI to consolidated net income attributable to Alcoa include: the impact of LIFO inventory accounting; metal price lag; interest expense; noncontrolling interests; corporate expense (general administrative and selling expenses of operating the corporate headquarters and other global administrative facilities, along with depreciation and amortization on corporate-owned assets); restructuring and other charges; and other items, including intersegment profit eliminations, differences between tax rates applicable to the segments and the consolidated effective tax rate, and other nonoperating items such as foreign currency transaction gains/losses and interest income.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ Details

Earnings Per Share

6 Months Ended

Jun. 30, 2016

Earnings Per Share [Abstract]

Earnings Per Share

L. Earnings Per Share – Basic earnings per share (EPS) amounts are computed by dividing earnings, after the deduction of preferred stock dividends declared, by the average number of common shares outstanding. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive share equivalents outstanding.

The information used to compute basic and diluted EPS attributable to Alcoa common shareholders was as follows (shares in millions):


	Second quarter ended June 30,				Six months ended June 30,
	2016		2015		2016		2015
Net income attributable to Alcoa	$	135	$	140	$	151	$	335
Less: preferred stock dividends declared		17		17		35		35

Net income available to Alcoa common shareholders – basic		118		123		116		300
Add: interest expense related to convertible notes		2		—		—		—
Add: dividends related to mandatory convertible preferred stock		—		—		—		—

Net income available to Alcoa common shareholders – diluted	$	120	$	123	$	116	$	300

Average shares outstanding – basic		1,315		1,222		1,314		1,222
Effect of dilutive securities:
Stock options		2		4		1		5
Stock and performance awards		11		11		11		11
Convertible notes		28		—		—		—
Mandatory convertible preferred stock		—		—		—		—

Average shares outstanding – diluted		1,356		1,237		1,326		1,238

In all periods presented, 77 million share equivalents related to mandatory convertible preferred stock were not included in the computation of diluted EPS because their effect was anti-dilutive. Additionally, in the 2016 six-month period, 28 million share equivalents related to convertible notes were not included in the computation of diluted EPS because their effect was anti-dilutive

Options to purchase 25 million and 13 million shares of common stock at a weighted average exercise price of $12.73 and $14.78 per share were outstanding as of June 30, 2016 and 2015, respectively, but were not included in the computation of diluted EPS because they were anti-dilutive, as the exercise prices of the options were greater than the average market price of Alcoa’s common stock.

Receivables	6 Months Ended
Receivables	Jun. 30, 2016
Transfers and Servicing [Abstract]
Receivables	M. Receivables – Alcoa has an arrangement with three financial institutions to sell certain customer receivables without recourse on a revolving basis. The sale of such receivables is completed through the use of a bankruptcy remote special purpose entity, which is a consolidated subsidiary of Alcoa. This arrangement provides for minimum funding of $200 up to a maximum of $500 for receivables sold. The initial sale of receivables in March 2012 resulted in the setup of a deferred purchase price of $254. Alcoa has received net cash funding of $350 ($1,508 in draws and $1,158 in repayments) since the program’s inception, including $100 ($200 in draws and $100 in repayments) in the 2016 six-month period. As of June 30, 2016 and December 31, 2015, the deferred purchase price receivable was $197 and $249, respectively, which was included in Other receivables on the accompanying Consolidated Balance Sheet. The deferred purchase price receivable is reduced as collections of the underlying receivables occur; however, as this is a revolving program, the sale of new receivables will result in an increase in the deferred purchase price receivable. The net change in the deferred purchase price receivable was reflected in the (Increase) in receivables line item on the accompanying Statement of Consolidated Cash Flows. This activity is reflected as an operating cash flow because the related customer receivables are the result of an operating activity with an insignificant, short-term interest rate risk. The gross amount of receivables sold and total cash collected under this program since its inception was $27,521 and $26,974, respectively. Alcoa services the customer receivables for the financial institutions at market rates; therefore, no servicing asset or liability was recorded.

- Definition

The entire disclosure for a transferor's continuing involvement in financial assets that it has transferred in a securitization or asset-backed financing arrangement, the nature of any restrictions on assets reported by an entity in its statement of financial position that relate to a transferred financial asset (including the carrying amounts of such assets), how servicing assets and servicing liabilities are reported, and (for securitization or asset-backed financing arrangements accounted for as sales) when a transferor has continuing involvement with the transferred financial assets and transfers of financial assets accounted for as secured borrowings, how the transfer of financial assets affects an entity's financial position, financial performance, and cash flows.

+ References + Details

Pension and Other Postretirement Benefits

6 Months Ended

Jun. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Pension and Other Postretirement Benefits

N. Pension and Other Postretirement Benefits – The components of net periodic benefit cost were as follows:


	Second quarter ended June 30,						Six months ended June 30,
Pension benefits	2016			2015			2016			2015
Service cost	$	41		$	44		$	81		$	88
Interest cost		122			145			244			289
Expected return on plan assets		(186	)		(189	)		(371	)		(377	)
Recognized net actuarial loss		102			117			204			235
Amortization of prior service cost		4			4			8			8
Settlements*		2			—			2			1
Special termination benefits*		—			10			1			12

Net periodic benefit cost	$	85		$	131		$	169		$	256

*	Except for Settlements of $2 in both the second quarter and six months ended June 30, 2016, these amounts were recorded in Restructuring and other charges on the accompanying Statement of Consolidated Operations (see Note D).


	Second quarter ended June 30,						Six months ended June 30,
Other postretirement benefits	2016			2015			2016			2015
Service cost	$	4		$	4		$	7		$	7
Interest cost		19			23			37			46
Recognized net actuarial loss		5			5			11			9
Amortization of prior service benefit		(7	)		(10	)		(13	)		(19	)
Curtailments*		—			(1	)		—			(1	)
Special termination benefits*		—			1			—			1

Net periodic benefit cost	$	21		$	22		$	42		$	43

*	These amounts were recorded in Restructuring and other charges on the accompanying Statement of Consolidated Operations (see Note D).

In conjunction with the annual measurement of the funded status of Alcoa’s pension and other postretirement benefit plans at December 31, 2015, management elected to change the manner in which the interest cost component of net periodic benefit cost is determined in 2016 and beyond. Previously, the interest cost component was determined by multiplying the single equivalent rate and the aggregate discounted cash flows of the plans’ projected benefit obligations. Under the new methodology, the interest cost component is determined by aggregating the product of the discounted cash flows of the plans’ projected benefit obligations for each year and an individual spot rate (referred to as the “spot rate” approach). In the 2016 second quarter and six-month period, this change resulted in a lower interest cost component of net periodic benefit cost under the new methodology compared to the previous methodology of $24 and $48, respectively, for pension plans and $4 and $8, respectively, for other postretirement benefit plans. Management believes this new methodology, which represents a change in an accounting estimate, is a better measure of the interest cost as each year’s cash flows are specifically linked to the interest rates of bond payments in the same respective year.

Derivatives and Other Financial Instruments

6 Months Ended

Jun. 30, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivatives and Other Financial Instruments

O. Derivatives and Other Financial Instruments

Fair Value

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value hierarchy distinguishes between (i) market participant assumptions developed based on market data obtained from independent sources (observable inputs) and (ii) an entity’s own assumptions about market participant assumptions developed based on the best information available in the circumstances (unobservable inputs). The fair value hierarchy consists of three broad levels, which gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The three levels of the fair value hierarchy are described below:

•

Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities.

•

Level 2 - Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly, including quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in markets that are not active; inputs other than quoted prices that are observable for the asset or liability (e.g., interest rates); and inputs that are derived principally from or corroborated by observable market data by correlation or other means.

•

Level 3 - Inputs that are both significant to the fair value measurement and unobservable.

Derivatives

Alcoa is exposed to certain risks relating to its ongoing business operations, including financial, market, political, and economic risks. The following discussion provides information regarding Alcoa’s exposure to the risks of changing commodity prices, interest rates, and foreign currency exchange rates.

Alcoa’s commodity and derivative activities are subject to the management, direction, and control of the Strategic Risk Management Committee (SRMC), which is composed of the chief executive officer, the chief financial officer, and other officers and employees that the chief executive officer selects. The SRMC meets on a periodic basis to review derivative positions and strategy and reports to Alcoa’s Board of Directors on the scope of its activities.

The aluminum, energy, interest rate, and foreign exchange contracts are held for purposes other than trading. They are used primarily to mitigate uncertainty and volatility, and to cover underlying exposures. Alcoa is not involved in trading activities for energy, weather derivatives, or other nonexchange commodity trading activities.

A number of Alcoa’s aluminum, energy, and foreign exchange contracts are classified as Level 1 and an interest rate contract is classified as Level 2 under the fair value hierarchy. These energy, foreign exchange, and interest rate contracts are not material to Alcoa’s Consolidated Financial Statements for all periods presented.

For the aluminum contracts classified as Level 1, the total fair value of derivatives recorded as assets and liabilities was $6 and $11, respectively, at June 30, 2016 and $8 and $58, respectively, at December 31, 2015. These contracts were entered into to either hedge forecasted sales or purchases of aluminum in order to manage the associated aluminum price risk. Certain of these contracts are designated as hedging instruments, either fair value or cash flow, and the remaining are not designated as such. Combined, Alcoa recognized a net gain of $1 and $3 in the 2016 second quarter and six-month period, respectively, and a net gain of $15 and $41 in the 2015 second quarter and six-month period, respectively, in Sales on the accompanying Statement of Consolidated Operations related to these aluminum contracts.

In addition to the Level 1 and 2 derivative instruments described above, Alcoa has ten derivative instruments classified as Level 3 under the fair value hierarchy. These instruments are composed of eight embedded aluminum derivatives, an energy contract, and an embedded credit derivative, all of which relate to energy supply contracts associated with nine smelters and three refineries. Five of the embedded aluminum derivatives and the energy contract were designated as cash flow hedging instruments and three of the embedded aluminum derivatives and the embedded credit derivative were not designated as hedging instruments.

The following section describes the valuation methodologies used by Alcoa to measure its Level 3 derivative instruments at fair value. Derivative instruments classified as Level 3 in the fair value hierarchy represent those in which management has used at least one significant unobservable input in the valuation model. Alcoa uses a discounted cash flow model to fair value all Level 3 derivative instruments. Where appropriate, the description below includes the key inputs to those models and any significant assumptions. These valuation models are reviewed and tested at least on an annual basis.

Inputs in the valuation models for Level 3 derivative instruments are composed of the following: (i) quoted market prices (e.g., aluminum prices on the 10-year London Metal Exchange (LME) forward curve and energy prices), (ii) significant other observable inputs (e.g., information concerning time premiums and volatilities for certain option type embedded derivatives and regional premiums for aluminum contracts), and (iii) unobservable inputs (e.g., aluminum and energy prices beyond those quoted in the market). For periods beyond the term of quoted market prices for aluminum, Alcoa estimates the price of aluminum by extrapolating the 10-year LME forward curve. Additionally, for periods beyond the term of quoted market prices for energy, management has developed a forward curve based on independent consultant market research. Where appropriate, valuations are adjusted for various factors such as liquidity, bid/offer spreads, and credit considerations. Such adjustments are generally based on available market evidence (Level 2). In the absence of such evidence, management’s best estimate is used (Level 3). If a significant input that is unobservable in one period becomes observable in a subsequent period, the related asset or liability would be transferred to the appropriate classification (Level 1 or 2) in the period of such change (there were no such transfers in the periods presented).

Alcoa has two power contracts, each of which contain an embedded derivative that indexes the price of power to the LME price of aluminum. Additionally, Alcoa has three power contracts, each of which contain an embedded derivative that indexes the price of power to the LME price of aluminum plus the Midwest premium. The embedded derivatives in these five power contracts are primarily valued using observable market prices; however, due to the length of the contracts, the valuation models also require management to estimate the long-term price of aluminum based upon an extrapolation of the 10-year LME forward curve and/or 5-year Midwest premium curve. Significant increases or decreases in the actual LME price beyond 10 years and/or the Midwest premium beyond 5 years would result in a higher or lower fair value measurement. An increase in actual LME price and/or the Midwest premium over the inputs used in the valuation models will result in a higher cost of power and a corresponding decrease to the derivative asset or increase to the derivative liability. The embedded derivatives have been designated as cash flow hedges of forward sales of aluminum. Unrealized gains and losses were included in Other comprehensive (loss) income on the accompanying Consolidated Balance Sheet while realized gains and losses were included in Sales on the accompanying Statement of Consolidated Operations.

Also, Alcoa has a power contract (expires in September 2016 – see below) separate from above that contains an LME-linked embedded derivative. The embedded derivative is valued using the probability and interrelationship of future LME prices, Australian dollar to U.S. dollar exchange rates, and the U.S. consumer price index. Significant increases or decreases in the LME price would result in a higher or lower fair value measurement. An increase in actual LME price over the inputs used in the valuation model will result in a higher cost of power and a corresponding decrease to the derivative asset. This embedded derivative did not qualify for hedge accounting treatment. Unrealized gains and losses from the embedded derivative were included in Other income, net on the accompanying Statement of Consolidated Operations while realized gains and losses were included in Cost of goods sold on the accompanying Statement of Consolidated Operations as electricity purchases were made under the contract. At the time this derivative asset was recognized, an equivalent amount was recognized as a deferred credit in Other noncurrent liabilities and deferred credits on the accompanying Consolidated Balance Sheet. This deferred credit is recognized in Other income, net on the accompanying Statement of Consolidated Operations as power is received over the life of the contract.

Additionally, Alcoa has a natural gas supply contract, which has an LME-linked ceiling. This embedded derivative is valued using probabilities of future LME aluminum prices and the price of Brent crude oil (priced on Platts), including the interrelationships between the two commodities subject to the ceiling. Any change in the interrelationship would result in a higher or lower fair value measurement. An LME ceiling was embedded into the contract price to protect against an increase in the price of oil without a corresponding increase in the price of LME. An increase in oil prices with no similar increase in the LME price would limit the increase of the price paid for natural gas. This embedded derivative did not qualify for hedge accounting treatment. Unrealized gains and losses from the embedded derivative were included in Other income, net on the accompanying Statement of Consolidated Operations while realized gains and losses were included in Cost of goods sold on the accompanying Statement of Consolidated Operations as gas purchases were made under the contract.

In the second quarter of 2016, Alcoa and the related counterparty elected to modify the pricing of an existing power contract for a smelter in the United States. This amendment contains an embedded derivative that now indexes the price of power to the LME price of aluminum plus the Midwest premium. The embedded derivative is valued using the interrelationship of future metal prices (LME base plus Midwest premium) and the amount of megawatt hours of energy needed to produce the forecasted metric tons of aluminum at the smelter. Significant increases or decreases in the metal price would result in a higher or lower fair value measurement. An increase in actual metal price over the inputs used in the valuation model will result in a higher cost of power and a corresponding increase to the derivative liability. Management elected not to qualify the embedded derivative for hedge accounting treatment. Unrealized gains and losses from the embedded derivative will be included in Other income, net on the accompanying Statement of Consolidated Operations while realized gains and losses will be included in Cost of goods sold on the accompanying Statement of Consolidated Operations as electricity purchases are made under the contract. At the time this derivative liability was recognized, an equivalent amount was recognized as a deferred charge in Other noncurrent assets on the accompanying Consolidated Balance Sheet. This deferred charge will be recognized in Other income, net on the accompanying Statement of Consolidated Operations as power is received over the life of the contract.

Furthermore, Alcoa has a power contract, which contains an embedded derivative that indexes the difference between the long-term debt ratings of Alcoa and the counterparty from any of the three major credit rating agencies. Management uses market prices, historical relationships, and forecast services to determine fair value. Significant increases or decreases in any of these inputs would result in a lower or higher fair value measurement. A wider credit spread between Alcoa and the counterparty would result in a higher cost of power and a corresponding increase in the derivative liability. This embedded derivative did not qualify for hedge accounting treatment. Unrealized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations while realized gains and losses were included in Cost of goods sold on the accompanying Statement of Consolidated Operations as electricity purchases were made under the contract.

Finally, Alcoa has a derivative contract that will hedge the anticipated power requirements at one of its smelters once the existing power contract expires in September 2016 (see above). Beyond the term where market information is available, management has developed a forward curve, for valuation purposes, based on independent consultant market research. Significant increases or decreases in the power market may result in a higher or lower fair value measurement. Lower prices in the power market would cause a decrease in the derivative asset. The derivative contract has been designated as a cash flow hedge of future purchases of electricity. Unrealized gains and losses on this contract were recorded in Other comprehensive (loss) income on the accompanying Consolidated Balance Sheet. Once the designated hedge period begins in September 2016, realized gains and losses will be recorded in Cost of goods sold as electricity purchases are made under the power contract.

The following table presents quantitative information related to the significant unobservable inputs described above for Level 3 derivative contracts:


	Fair value at June 30, 2016*		Unobservable input	Range ($ in full amounts)
Assets:
Embedded aluminum derivatives	$	718	Price of aluminum beyond forward curve	Aluminum: $2,093 per metric ton in 2026 to $2,245 per metric ton in 2029 (two contracts) and $2,540 per metric ton in 2036 (one contract) Midwest premium: $0.0775 per pound in 2021 to $0.0775 per pound in 2029 (two contracts) and 2036 (one contract)
Embedded aluminum derivative		23	Interrelationship of future aluminum prices, foreign currency exchange rates, and the U.S. consumer price index (CPI)	Aluminum: $1,631 per metric ton in July 2016 to $1,637 per metric ton in September 2016 Foreign currency: A$1 = $0.74 in 2016 (July through September) CPI: 1982 base year of 100 and 236 in 2016 (July through September)
Embedded aluminum derivative		4	Interrelationship of LME price to overall energy price	Aluminum: $1,614 per metric ton in 2016 to $1,755 per metric ton in 2019
Embedded aluminum derivative		—	Interrelationship of future aluminum and oil prices	Aluminum: $1,631 per metric ton in 2016 to $1,710 per metric ton in 2018 Oil: $49 per barrel in 2016 to $55 per barrel in 2018
Energy contract		40	Price of electricity beyond forward curve	Electricity: $48 per megawatt hour in 2019 to $116 per megawatt hour in 2036
Liabilities:
Embedded aluminum derivative		196	Price of aluminum beyond forward curve	Aluminum: $2,093 per metric ton in 2026 to $2,137 per metric ton in 2027
Embedded aluminum derivative		32	Interrelationship of LME price to the amount of megawatt hours of energy needed to produce the forecasted metric tons of aluminum	Aluminum: $1,631 per metric ton in 2016 to $1,729 per metric ton in 2019 Midwest premium: $0.0725 per pound in 2016 to $0.0775 per pound in 2019 Electricity: rate at 2 million megawatt hours per year
Embedded credit derivative		33	Credit spread between Alcoa and counterparty	3.45% to 3.81% (3.63% median)

The fair value of the energy contract reflected as an asset in this table is lower by $9 compared to the respective amount reflected in the Level 3 tables presented below. This is due to the fact that this contract is in a liability position for the current portion but is in an asset position for the noncurrent portion, and is reflected as such on the accompanying Consolidated Balance Sheet. However, this derivative is reflected as a net asset in the above table for purposes of presenting the assumptions utilized to measure the fair value of the derivative instrument in its entirety.

The fair values of Level 3 derivative instruments recorded as assets and liabilities in the accompanying Consolidated Balance Sheet were as follows:


	June 30, 2016		December 31, 2015
Asset Derivatives
Derivatives designated as hedging instruments:
Prepaid expenses and other current assets:
Embedded aluminum derivatives	$	51	$	72
Other noncurrent assets:
Embedded aluminum derivatives		671		994
Energy contract		49		2

Total derivatives designated as hedging instruments	$	771	$	1,068

Derivatives not designated as hedging instruments:
Prepaid expenses and other current assets:
Embedded aluminum derivatives	$	23	$	69

Total derivatives not designated as hedging instruments	$	23	$	69

Total Asset Derivatives	$	794	$	1,137

Liability Derivatives
Derivatives designated as hedging instruments:
Other current liabilities:
Embedded aluminum derivative	$	14	$	9
Energy contract		9		4
Other noncurrent liabilities and deferred credits:
Embedded aluminum derivative		182		160

Total derivatives designated as hedging instruments	$	205	$	173

Derivatives not designated as hedging instruments:
Other current liabilities:
Embedded aluminum derivative	$	8	$	—
Embedded credit derivative		5		6
Other noncurrent liabilities and deferred credits:
Embedded aluminum derivative		24		—
Embedded credit derivative		28		29

Total derivatives not designated as hedging instruments	$	65	$	35

Total Liability Derivatives	$	270	$	208

The following tables present a reconciliation of activity for Level 3 derivative contracts:


	Assets					Liabilities
Second quarter ended June 30, 2016	Embedded aluminum derivatives			Energy contract		Embedded aluminum derivative			Embedded credit derivative			Energy contract
Opening balance – April 1, 2016	$	988		$	6	$	161		$	33		$	11
Total gains or losses (realized and unrealized) included in:
Sales		(3	)		—		(3	)		—			—
Cost of goods sold		(30	)		—		—			(2	)		—
Other income, net		(4	)		—		—			2			—
Other comprehensive loss		(215	)		37		38			—			(8	)
Purchases, sales, issuances, and settlements*		—			—		32			—			—
Transfers into and/or out of Level 3*		—			—		—			—			—
Other		9			6		—			—			6

Closing balance – June 30, 2016	$	745		$	49	$	228		$	33		$	9

Change in unrealized gains or losses included in earnings for derivative contracts held at June 30, 2016:
Sales	$	—		$	—	$	—		$	—		$	—
Cost of goods sold		—			—		—			—			—
Other income, net		(4	)		—		—			2			—

In the 2016 second quarter, there was an issuance of a new embedded derivative contained in an amendment to an existing power contract. There were no purchases, sales or settlements of Level 3 derivative instruments. Additionally, there were no transfers of derivative instruments into or out of Level 3.


	Assets					Liabilities
Six months ended June 30, 2016	Embedded aluminum derivatives			Energy contract		Embedded aluminum derivative			Embedded credit derivative			Energy contract
Opening balance – January 1, 2016	$	1,135		$	2	$	169		$	35		$	4
Total gains or losses (realized and unrealized) included in:
Sales		(10	)		—		(5	)		—			—
Cost of goods sold		(61	)		—		—			(3	)		—
Other income, net		(8	)		2		—			1			(1	)
Other comprehensive income		(336	)		39		32			—			—
Purchases, sales, issuances, and settlements*		—			—		32			—			—
Transfers into and/or out of Level 3*		—			—		—			—			—
Other		25			6		—			—			6

Closing balance – June 30, 2016	$	745		$	49	$	228		$	33		$	9

Change in unrealized gains or losses included in earnings for derivative contracts held at June 30, 2016:
Sales	$	—		$	—	$	—		$	—		$	—
Cost of goods sold		—			—		—			—			—
Other income, net		(8	)		2		—			1			(1	)

In the 2016 six-month period, there was an issuance of a new embedded derivative contained in an amendment to an existing power contract. There were no purchases, sales or settlements of Level 3 derivative instruments. Additionally, there were no transfers of derivative instruments into or out of Level 3.

Derivatives Designated As Hedging Instruments – Cash Flow Hedges

For derivative instruments that are designated and qualify as cash flow hedges, the effective portion of unrealized gains or losses on the derivative is reported as a component of other comprehensive income (OCI). Realized gains or losses on the derivative are reclassified from OCI into earnings in the same period or periods during which the hedged transaction impacts earnings. Gains and losses on the derivative representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized directly in earnings immediately.

Alcoa has five Level 3 embedded aluminum derivatives and one Level 3 energy contract that have been designated as cash flow hedges as follows.

Embedded aluminum derivatives. Alcoa has entered into energy supply contracts that contain pricing provisions related to the LME aluminum price. The LME-linked pricing features are considered embedded derivatives. Five of these embedded derivatives have been designated as cash flow hedges of forward sales of aluminum. At June 30, 2016 and December 31, 2015, these embedded aluminum derivatives hedge forecasted aluminum sales of 3,261 kmt and 3,307 kmt, respectively.

Alcoa recognized a net unrealized loss of $253 and $368 in the 2016 second quarter and six-month period, respectively, and a net unrealized gain of $616 and $518 in the 2015 second quarter and six-month period, respectively, in Other comprehensive (loss) income related to these five derivative instruments. Additionally, Alcoa reclassified a realized gain of less than $1 and $5 in the 2016 second quarter and six-month period, respectively, and a realized loss of $12 and $24 in the 2015 second quarter and six-month period, respectively, from Accumulated other comprehensive loss to Sales. Assuming market rates remain constant with the rates at June 30, 2016, a realized gain of $25 is expected to be recognized in Sales over the next 12 months.

Also, Alcoa recognized a gain of less than $1 in the 2016 six-month period (no such gain was recognized in the 2016 second quarter) and a gain of less than $1 and $1 in the 2015 second quarter and six-month period, respectively, in Other income, net related to the amount excluded from the assessment of hedge effectiveness. There was no ineffectiveness related to these five derivative instruments in the 2016 second quarter and six-month period and the 2015 second quarter and six-month period.

Energy contract. Alcoa has a derivative contract that will hedge the anticipated power requirements at one of its smelters once the existing power contract expires in September 2016. At June 30, 2016 and December 31, 2015, this energy contract hedges forecasted electricity purchases of 59,409,328 megawatt hours. Alcoa recognized an unrealized gain of $45 and $39 in the 2016 second quarter and six-month period, respectively, and an unrealized loss of $17 and $11 in the 2015 second quarter and six-month period, respectively, in Other comprehensive (loss) income. Additionally, Alcoa recognized a gain of $3 in Other income, net related to hedge ineffectiveness in the 2016 six-month period. There was no ineffectiveness related to the energy contract in the 2016 second quarter and the 2015 second quarter and six-month period.

Derivatives Not Designated As Hedging Instruments

Alcoa has three Level 3 embedded aluminum derivatives and one Level 3 embedded credit derivative that do not qualify for hedge accounting treatment. As such, gains and losses related to the changes in fair value of these instruments are recorded directly in earnings. In the second quarter of 2016 and 2015, Alcoa recognized a loss of $6 and $5, respectively, in Other income, net, of which a loss of $4 and $2, respectively, related to the embedded aluminum derivatives and a loss of $2 and $3, respectively, related to the embedded credit derivative. In the six-month period of 2016 and 2015, Alcoa recognized a loss of $9 and $2, respectively, in Other income, net, of which a loss of $8 and $1, respectively, related to the embedded aluminum derivatives and a loss of $1 and $1, respectively, related to the embedded credit derivative.

Material Limitations

The disclosures with respect to commodity prices, interest rates, and foreign currency exchange risk do not take into account the underlying commitments or anticipated transactions. If the underlying items were included in the analysis, the gains or losses on the futures contracts may be offset. Actual results will be determined by a number of factors that are not under Alcoa’s control and could vary significantly from those factors disclosed.

Alcoa is exposed to credit loss in the event of nonperformance by counterparties on the above instruments, as well as credit or performance risk with respect to its hedged customers’ commitments. Although nonperformance is possible, Alcoa does not anticipate nonperformance by any of these parties. Contracts are with creditworthy counterparties and are further supported by cash, treasury bills, or irrevocable letters of credit issued by carefully chosen banks. In addition, various master netting arrangements are in place with counterparties to facilitate settlement of gains and losses on these contracts.

Other Financial Instruments

The carrying values and fair values of Alcoa’s other financial instruments were as follows:


	June 30, 2016				December 31, 2015
	Carrying value		Fair value		Carrying value		Fair value
Cash and cash equivalents	$	1,929	$	1,929	$	1,919	$	1,919
Restricted cash		30		30		37		37
Noncurrent receivables		19		19		17		17
Available-for-sale securities		68		68		193		193
Short-term borrowings		33		33		38		38
Commercial paper		—		—		—		—
Long-term debt due within one year		774		791		21		21
Contingent payment related to an acquisition		132		132		130		130
Long-term debt, less amount due within one year		8,278		8,670		8,993		8,922

The following methods were used to estimate the fair values of other financial instruments:

Cash and cash equivalents, Restricted cash, Short-term borrowings, and Commercial paper. The carrying amounts approximate fair value because of the short maturity of the instruments. The fair value amounts for Cash and cash equivalents, Restricted cash, and Commercial paper were classified in Level 1, and Short-term borrowings were classified in Level 2.

Noncurrent receivables. The fair value of noncurrent receivables was based on anticipated cash flows, which approximates carrying value, and was classified in Level 2 of the fair value hierarchy.

Available-for-sale securities. The fair value of such securities was based on quoted market prices. These financial instruments consist of exchange-traded fixed income and equity securities, which are carried at fair value and were classified in Level 1 of the fair value hierarchy.

Contingent payment related to an acquisition. The fair value was based on the net present value of expected future cash flows and was classified in Level 3 of the fair value hierarchy.

Long-term debt due within one year and Long-term debt, less amount due within one year. The fair value was based on quoted market prices for public debt and on interest rates that are currently available to Alcoa for issuance of debt with similar terms and maturities for non-public debt. The fair value amounts for all Long-term debt were classified in Level 2 of the fair value hierarchy.

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6441202&loc=d3e80720-113993

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5579245-113959

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624258-113959

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
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-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5708775-113959

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5708773-113959

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5580258-113959

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 17: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(n))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Proposed Separation Transaction	6 Months Ended
Proposed Separation Transaction	Jun. 30, 2016
Text Block [Abstract]
Proposed Separation Transaction	P. Proposed Separation Transaction – On September 28, 2015, Alcoa announced that its Board of Directors preliminarily approved a plan to separate into two standalone, publicly-traded companies. One company will be named Alcoa Corporation and will include the Alumina and Primary Metals segments and the Warrick, IN rolling operations and the equity interest in the rolling mill at the joint venture in Saudi Arabia, both of which are currently part of the Global Rolled Products segment. Alcoa, which will be re-named Arconic Inc., will continue to own the Global Rolled Products (except for the aforementioned rolling operations to be included in the future Alcoa Corporation company), Engineered Products and Solutions, and Transportation and Construction Solutions segments. Alcoa is targeting to complete the separation in the second half of 2016. The transaction is subject to a number of conditions, including, but not limited to, final approval by Alcoa’s Board of Directors; receipt of a private letter ruling from the Internal Revenue Service regarding certain U.S. federal income tax matters relating to the transaction; receipt of an opinion of legal counsel with respect to the tax-free nature of the transaction for U.S. federal income tax purposes; and the effectiveness of a Form 10 registration statement, which was filed with the U.S. Securities and Exchange Commission on June 29, 2016. Upon completion of the separation, Alcoa shareholders will own all of the outstanding shares of the future Arconic Inc. company, and each Alcoa shareholder as of the separation record date will own a pro rata share of the outstanding shares of the future Alcoa Corporation company to be distributed (up to 19.9% of such shares may be retained by the future Arconic Inc. company). Alcoa may, at any time and for any reason until the proposed transaction is complete, abandon the separation plan or modify or change its terms. In the 2016 second quarter and six-month period, Alcoa recognized $45 ($37 after-tax) and $63 ($54 after-tax), respectively, in Selling, general administrative, and other expenses on the accompanying Statement of Consolidated Operations for costs related to the proposed separation transaction.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	Q. Subsequent Events – Management evaluated all activity of Alcoa and concluded that no subsequent events have occurred that would require recognition in the Consolidated Financial Statements or disclosure in the Notes to the Consolidated Financial Statements, except as described below. On July 21, 2016, Alcoa’s Board of Directors authorized both a reverse stock split of the Company’s common stock at a ratio of one-for-three and a proportionate reduction in the number of authorized shares of Alcoa’s common stock from 1.8 billion to 600 million. Alcoa will hold a special shareholder meeting on October 5, 2016 to seek approval of the reverse stock split and authorized share count reduction, both of which require an affirmative vote of a majority of votes cast by the shareholders entitled to vote. Alcoa is not planning to issue fractional shares as a result of the reverse stock split; therefore, cash payments in lieu of such fractional shares would be made to shareholders, as applicable. The reverse stock split would not change the proportionate equity interests or voting rights of holders of Alcoa’s common stock, subject to the treatment of fractional shares. As of July 22, 2016, 1,315,374,511 shares of Alcoa’s common stock were outstanding.

Accumulated Other Comprehensive Loss (Tables)

6 Months Ended

Jun. 30, 2016

Equity [Abstract]

Summary of Changes in Accumulated Other Comprehensive (Loss) by Component

The following table details the activity of the four components that comprise Accumulated other comprehensive loss for both Alcoa’s shareholders and noncontrolling interests:


	Alcoa						Noncontrolling Interests
	Second quarter ended June 30,						Second quarter ended June 30,
	2016			2015			2016			2015
Pension and other postretirement benefits (N)
Balance at beginning of period	$	(3,579	)	$	(3,496	)	$	(55	)	$	(62	)
Other comprehensive income (loss):
Unrecognized net actuarial loss and prior service cost/benefit		(5	)		(118	)		1			3
Tax benefit		3			39			—			—

Total Other comprehensive (loss) income before reclassifications, net of tax		(2	)		(79	)		1			3

Amortization of net actuarial loss and prior service cost/benefit⁽¹⁾		104			115			—			1
Tax (expense) benefit⁽²⁾		(37	)		(40	)		1			(1	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁸⁾		67			75			1			—

Total Other comprehensive income (loss)		65			(4	)		2			3

Balance at end of period	$	(3,514	)	$	(3,500	)	$	(53	)	$	(59	)

Foreign currency translation
Balance at beginning of period	$	(2,109	)	$	(1,803	)	$	(673	)	$	(601	)
Other comprehensive income⁽³⁾		45			197			32			32

Balance at end of period	$	(2,064	)	$	(1,606	)	$	(641	)	$	(569	)

Available-for-sale securities
Balance at beginning of period	$	(4	)	$	2		$	—		$	—
Other comprehensive income (loss)⁽⁴⁾		3			(2	)		—			—

Balance at end of period	$	(1	)	$	—		$	—		$	—

Cash flow hedges (O)
Balance at beginning of period	$	517		$	(294	)	$	(5	)	$	(2	)
Other comprehensive (loss) income:
Net change from periodic revaluations		(225	)		614			18			(5	)
Tax benefit (expense)		66			(190	)		(5	)		1

Total Other comprehensive (loss) income before reclassifications, net of tax		(159	)		424			13			(4	)

Net amount reclassified to earnings:
Aluminum contracts⁽⁵⁾		(1	)		10			—			—
Energy contracts⁽⁶⁾		—			2			—			—
Foreign exchange contracts⁽⁵⁾		—			1			—			—
Interest rate contracts⁽⁷⁾		8			1			5			—

Sub-total		7			14			5			—
Tax expense⁽²⁾		(1	)		(4	)		(2	)		—

Total amount reclassified from Accumulated other comprehensive income (loss), net of tax⁽⁸⁾		6			10			3			—

Total Other comprehensive (loss) income		(153	)		434			16			(4	)

Balance at end of period	$	364		$	140		$	11		$	(6	)


	Alcoa						Noncontrolling Interests
	Six months ended June 30,						Six months ended June 30,
	2016			2015			2016			2015
Pension and other postretirement benefits (N)
Balance at beginning of period	$	(3,611	)	$	(3,601	)	$	(56	)	$	(64	)
Other comprehensive income:
Unrecognized net actuarial loss and prior service cost/benefit		(64	)		(76	)		1			3
Tax benefit		26			28			—			—

Total Other comprehensive (loss) income before reclassifications, net of tax		(38	)		(48	)		1			3

Amortization of net actuarial loss and prior service cost/benefit⁽¹⁾		208			229			2			4
Tax expense⁽²⁾		(73	)		(80	)		—			(2	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁸⁾		135			149			2			2

Total Other comprehensive income		97			101			3			5

Balance at end of period	$	(3,514	)	$	(3,500	)	$	(53	)	$	(59	)

Foreign currency translation
Balance at beginning of period	$	(2,412	)	$	(846	)	$	(780	)	$	(351	)
Other comprehensive income (loss)⁽³⁾		348			(760	)		139			(218	)

Balance at end of period	$	(2,064	)	$	(1,606	)	$	(641	)	$	(569	)

Available-for-sale securities
Balance at beginning of period	$	(5	)	$	—		$	—		$	—
Other comprehensive income⁽⁴⁾		4			—			—			—

Balance at end of period	$	(1	)	$	—		$	—		$	—

Cash flow hedges (O)
Balance at beginning of period	$	597		$	(230	)	$	(3	)	$	(2	)
Other comprehensive (loss) income:
Net change from periodic revaluations		(342	)		504			15			(5	)
Tax benefit (expense)		103			(156	)		(4	)		1

Total Other comprehensive (loss) income before reclassifications, net of tax		(239	)		348			11			(4	)

Net amount reclassified to earnings:
Aluminum contracts⁽⁵⁾		(6	)		23			—			—
Energy contracts⁽⁶⁾		1			4			—			—
Foreign exchange contracts⁽⁵⁾		1			1			—			—
Interest rate contracts⁽⁷⁾		8			1			5			—
Nickel contracts⁽⁶⁾		1			—			—			—

Sub-total		5			29			5			—
Tax benefit (expense)⁽²⁾		1			(7	)		(2	)		—

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁸⁾		6			22			3			—

Total Other comprehensive (loss) income		(233	)		370			14			(4	)

Balance at end of period	$	364		$	140		$	11		$	(6	)

⁽¹⁾	These amounts were included in the computation of net periodic benefit cost for pension and other postretirement benefits (see Note N).

⁽²⁾	These amounts were included in Provision for income taxes on the accompanying Statement of Consolidated Operations.

⁽³⁾	In all periods presented, there were no tax impacts related to rate changes and no amounts were reclassified to earnings.

⁽⁴⁾	In all periods presented, unrealized and realized gains and losses related to these securities were immaterial. Realized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁵⁾	These amounts were included in Sales on the accompanying Statement of Consolidated Operations.

⁽⁶⁾	These amounts were included in Cost of goods sold on the accompanying Statement of Consolidated Operations.

⁽⁷⁾

⁽⁸⁾	A positive amount indicates a corresponding charge to earnings and a negative amount indicates a corresponding benefit to earnings. These amounts were reflected on the accompanying Statement of Consolidated Operations in the line items indicated in footnotes 1 through 7.

Restructuring and Other Charges (Tables)

6 Months Ended

Jun. 30, 2016

Restructuring and Related Activities [Abstract]

Schedule of Restructuring and Other Charges by Reportable Segments, Pretax

The pretax impact of allocating such charges to segment results would have been as follows:


	Second quarter ended June 30,					Six months ended June 30,
	2016			2015		2016			2015
Alumina	$	(1	)	$	10	$	4		$	17
Primary Metals		10			173		88			198
Global Rolled Products		—			1		2			136
Engineered Products and Solutions		9			8		17			11
Transportation and Construction Solutions		8			1		8			3

Segment total		26			193		119			365
Corporate		(3	)		24		(3	)		29

Total restructuring and other charges	$	23		$	217	$	116		$	394

Activity and Reserve Balances for Restructuring Charges

Activity and reserve balances for restructuring charges were as follows:


	Layoff costs			Other exit costs			Total
Reserve balances at December 31, 2014	$	98		$	34		$	132

2015:
Cash payments		(111	)		(12	)		(123	)
Restructuring charges		299			233			532
Other*		(60	)		(231	)		(291	)

Reserve balances at December 31, 2015		226			24			250

2016:
Cash payments		(107	)		(22	)		(129	)
Restructuring charges		34			41			75
Other*		(31	)		1			(30	)

Reserve balances at June 30, 2016	$	122		$	44		$	166

Inventories (Tables)

6 Months Ended

Jun. 30, 2016

Inventory Disclosure [Abstract]

Schedule of Inventory Components


	June 30, 2016		December 31, 2015
Finished goods	$	827	$	811
Work-in-process		1,344		1,272
Bauxite and alumina		416		445
Purchased raw materials		650		720
Operating supplies		201		194

	$	3,438	$	3,442

Investments (Tables)

6 Months Ended

Jun. 30, 2016

Investments Schedule [Abstract]

Summary of Unaudited Financial Information for Alcoa's Equity Investments

A summary of unaudited financial information for Alcoa’s equity investments is as follows (amounts represent 100% of investee financial information):


	Second quarter ended June 30,					Six months ended June 30,
	2016		2015			2016		2015
Sales	$	904	$	971		$	1,796	$	1,857
Cost of goods sold		679		862			1,360		1,557
Net income (loss)		14		(45	)		29		(86	)

Other Income, Net (Tables)

6 Months Ended

Jun. 30, 2016

Other Income and Expenses [Abstract]

Schedule of Other Income, Net


	Second quarter ended June 30,						Six months ended June 30,
	2016			2015			2016			2015
Equity loss	$	15		$	24		$	37		$	44
Interest income		(5	)		(4	)		(9	)		(7	)
Foreign currency (gains) losses, net		(9	)		6			6			(10	)
Net gain from asset sales		(30	)		(28	)		(28	)		(28	)
Net loss on mark-to-market derivative contracts (O)		8			7			9			3
Other, net		(16	)		(5	)		(18	)		(14	)

	$	(37	)	$	—		$	(3	)	$	(12	)

Segment Information (Tables)

6 Months Ended

Jun. 30, 2016

Segment Reporting [Abstract]

Schedule of Operating Results of Alcoa's Reportable Segments

The operating results of Alcoa’s reportable segments were as follows (differences between segment totals and consolidated totals are in Corporate):


	Alumina			Primary Metals			Global Rolled Products			Engineered Products and Solutions		Transportation and Construction Solutions		Total
Second quarter ended June 30, 2016
Sales:
Third-party sales	$	694		$	1,119		$	1,550		$	1,465	$	467	$	5,295
Intersegment sales		300			473			29			—		—		802

Total sales	$	994		$	1,592		$	1,579		$	1,465	$	467	$	6,097

Profit and loss:
Equity loss	$	(7	)	$	—		$	(10	)	$	—	$	—	$	(17	)
Depreciation, depletion, and amortization		66			101			55			62		12		296
Income taxes		40			—			28			87		18		173
After-tax operating income (ATOI)		109			41			68			180		46		444
Second quarter ended June 30, 2015
Sales:
Third-party sales	$	924		$	1,534		$	1,668		$	1,279	$	492	$	5,897
Intersegment sales		431			562			34			—		—		1,027

Total sales	$	1,355		$	2,096		$	1,702		$	1,279	$	492	$	6,924

Profit and loss:
Equity loss	$	(11	)	$	(5	)	$	(7	)	$	—	$	—	$	(23	)
Depreciation, depletion, and amortization		77			109			56			54		11		307
Income taxes		87			6			25			81		17		216
ATOI		215			67			76			165		44		567


	Alumina			Primary Metals			Global Rolled Products			Engineered Products and Solutions		Transportation and Construction Solutions		Total
Six months ended June 30, 2016
Sales:
Third-party sales	$	1,239		$	2,242		$	2,947		$	2,914	$	896	$	10,238
Intersegment sales		592			948			58			—		—		1,598

Total sales	$	1,831		$	3,190		$	3,005		$	2,914	$	896	$	11,836

Profit and loss:
Equity (loss) income	$	(21	)	$	4		$	(21	)	$	—	$	—	$	(38	)
Depreciation, depletion, and amortization		129			203			111			127		23		593
Income taxes		45			(16	)		62			165		32		288
ATOI		117			55			136			342		85		735
Six months ended June 30, 2015
Sales:
Third-party sales	$	1,811		$	3,106		$	3,289		$	2,536	$	963	$	11,705
Intersegment sales		932			1,254			70			—		—		2,256

Total sales	$	2,743		$	4,360		$	3,359		$	2,536	$	963	$	13,961

Profit and loss:
Equity loss	$	(18	)	$	(8	)	$	(16	)	$	—	$	—	$	(42	)
Depreciation, depletion, and amortization		157			218			112			105		21		613
Income taxes		179			63			61			157		31		491
ATOI		436			254			130			321		82		1,223

Schedule of Segment ATOI to Consolidated Net Income Attributable to Alcoa

The following table reconciles total segment ATOI to consolidated net income attributable to Alcoa:


	Second quarter ended June 30,						Six months ended June 30,
	2016			2015			2016			2015
Total segment ATOI	$	444		$	567		$	735		$	1,223
Unallocated amounts (net of tax):
Impact of LIFO		(10	)		36			(6	)		43
Metal price lag		7			(39	)		8			(62	)
Interest expense		(84	)		(80	)		(167	)		(160	)
Noncontrolling interests		(43	)		(67	)		(38	)		(127	)
Corporate expense		(77	)		(65	)		(132	)		(127	)
Restructuring and other charges		(15	)		(159	)		(76	)		(320	)
Other		(87	)		(53	)		(173	)		(135	)

Consolidated net income attributable to Alcoa	$	135		$	140		$	151		$	335

Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2016

Earnings Per Share [Abstract]

Reconciliation of Information Used to Compute Basic and Diluted EPS

The information used to compute basic and diluted EPS attributable to Alcoa common shareholders was as follows (shares in millions):


	Second quarter ended June 30,				Six months ended June 30,
	2016		2015		2016		2015
Net income attributable to Alcoa	$	135	$	140	$	151	$	335
Less: preferred stock dividends declared		17		17		35		35

Net income available to Alcoa common shareholders – basic		118		123		116		300
Add: interest expense related to convertible notes		2		—		—		—
Add: dividends related to mandatory convertible preferred stock		—		—		—		—

Net income available to Alcoa common shareholders – diluted	$	120	$	123	$	116	$	300

Average shares outstanding – basic		1,315		1,222		1,314		1,222
Effect of dilutive securities:
Stock options		2		4		1		5
Stock and performance awards		11		11		11		11
Convertible notes		28		—		—		—
Mandatory convertible preferred stock		—		—		—		—

Average shares outstanding – diluted		1,356		1,237		1,326		1,238

Pension and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Cost

The components of net periodic benefit cost were as follows:


	Second quarter ended June 30,						Six months ended June 30,
Pension benefits	2016			2015			2016			2015
Service cost	$	41		$	44		$	81		$	88
Interest cost		122			145			244			289
Expected return on plan assets		(186	)		(189	)		(371	)		(377	)
Recognized net actuarial loss		102			117			204			235
Amortization of prior service cost		4			4			8			8
Settlements*		2			—			2			1
Special termination benefits*		—			10			1			12

Net periodic benefit cost	$	85		$	131		$	169		$	256

*	Except for Settlements of $2 in both the second quarter and six months ended June 30, 2016, these amounts were recorded in Restructuring and other charges on the accompanying Statement of Consolidated Operations (see Note D).


	Second quarter ended June 30,						Six months ended June 30,
Other postretirement benefits	2016			2015			2016			2015
Service cost	$	4		$	4		$	7		$	7
Interest cost		19			23			37			46
Recognized net actuarial loss		5			5			11			9
Amortization of prior service benefit		(7	)		(10	)		(13	)		(19	)
Curtailments*		—			(1	)		—			(1	)
Special termination benefits*		—			1			—			1

Net periodic benefit cost	$	21		$	22		$	42		$	43

*	These amounts were recorded in Restructuring and other charges on the accompanying Statement of Consolidated Operations (see Note D).

Derivatives and Other Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Quantitative Information for Level 3 Derivative Contracts

The following table presents quantitative information related to the significant unobservable inputs described above for Level 3 derivative contracts:


	Fair value at June 30, 2016*		Unobservable input	Range ($ in full amounts)
Assets:
Embedded aluminum derivatives	$	718	Price of aluminum beyond forward curve	Aluminum: $2,093 per metric ton in 2026 to $2,245 per metric ton in 2029 (two contracts) and $2,540 per metric ton in 2036 (one contract) Midwest premium: $0.0775 per pound in 2021 to $0.0775 per pound in 2029 (two contracts) and 2036 (one contract)
Embedded aluminum derivative		23	Interrelationship of future aluminum prices, foreign currency exchange rates, and the U.S. consumer price index (CPI)	Aluminum: $1,631 per metric ton in July 2016 to $1,637 per metric ton in September 2016 Foreign currency: A$1 = $0.74 in 2016 (July through September) CPI: 1982 base year of 100 and 236 in 2016 (July through September)
Embedded aluminum derivative		4	Interrelationship of LME price to overall energy price	Aluminum: $1,614 per metric ton in 2016 to $1,755 per metric ton in 2019
Embedded aluminum derivative		—	Interrelationship of future aluminum and oil prices	Aluminum: $1,631 per metric ton in 2016 to $1,710 per metric ton in 2018 Oil: $49 per barrel in 2016 to $55 per barrel in 2018
Energy contract		40	Price of electricity beyond forward curve	Electricity: $48 per megawatt hour in 2019 to $116 per megawatt hour in 2036
Liabilities:
Embedded aluminum derivative		196	Price of aluminum beyond forward curve	Aluminum: $2,093 per metric ton in 2026 to $2,137 per metric ton in 2027
Embedded aluminum derivative		32	Interrelationship of LME price to the amount of megawatt hours of energy needed to produce the forecasted metric tons of aluminum	Aluminum: $1,631 per metric ton in 2016 to $1,729 per metric ton in 2019 Midwest premium: $0.0725 per pound in 2016 to $0.0775 per pound in 2019 Electricity: rate at 2 million megawatt hours per year
Embedded credit derivative		33	Credit spread between Alcoa and counterparty	3.45% to 3.81% (3.63% median)

Schedule of Fair Values of Level 3 Derivative Instruments Recorded as Assets and Liabilities

The fair values of Level 3 derivative instruments recorded as assets and liabilities in the accompanying Consolidated Balance Sheet were as follows:


	June 30, 2016		December 31, 2015
Asset Derivatives
Derivatives designated as hedging instruments:
Prepaid expenses and other current assets:
Embedded aluminum derivatives	$	51	$	72
Other noncurrent assets:
Embedded aluminum derivatives		671		994
Energy contract		49		2

Total derivatives designated as hedging instruments	$	771	$	1,068

Derivatives not designated as hedging instruments:
Prepaid expenses and other current assets:
Embedded aluminum derivatives	$	23	$	69

Total derivatives not designated as hedging instruments	$	23	$	69

Total Asset Derivatives	$	794	$	1,137

Liability Derivatives
Derivatives designated as hedging instruments:
Other current liabilities:
Embedded aluminum derivative	$	14	$	9
Energy contract		9		4
Other noncurrent liabilities and deferred credits:
Embedded aluminum derivative		182		160

Total derivatives designated as hedging instruments	$	205	$	173

Derivatives not designated as hedging instruments:
Other current liabilities:
Embedded aluminum derivative	$	8	$	—
Embedded credit derivative		5		6
Other noncurrent liabilities and deferred credits:
Embedded aluminum derivative		24		—
Embedded credit derivative		28		29

Total derivatives not designated as hedging instruments	$	65	$	35

Total Liability Derivatives	$	270	$	208

Schedule of Reconciliation of Activity for Derivative Contracts

The following tables present a reconciliation of activity for Level 3 derivative contracts:


	Assets					Liabilities
Second quarter ended June 30, 2016	Embedded aluminum derivatives			Energy contract		Embedded aluminum derivative			Embedded credit derivative			Energy contract
Opening balance – April 1, 2016	$	988		$	6	$	161		$	33		$	11
Total gains or losses (realized and unrealized) included in:
Sales		(3	)		—		(3	)		—			—
Cost of goods sold		(30	)		—		—			(2	)		—
Other income, net		(4	)		—		—			2			—
Other comprehensive loss		(215	)		37		38			—			(8	)
Purchases, sales, issuances, and settlements*		—			—		32			—			—
Transfers into and/or out of Level 3*		—			—		—			—			—
Other		9			6		—			—			6

Closing balance – June 30, 2016	$	745		$	49	$	228		$	33		$	9

Change in unrealized gains or losses included in earnings for derivative contracts held at June 30, 2016:
Sales	$	—		$	—	$	—		$	—		$	—
Cost of goods sold		—			—		—			—			—
Other income, net		(4	)		—		—			2			—

Schedule of Carrying Values and Fair Values of Other Financial Instruments

The carrying values and fair values of Alcoa’s other financial instruments were as follows:


	June 30, 2016				December 31, 2015
	Carrying value		Fair value		Carrying value		Fair value
Cash and cash equivalents	$	1,929	$	1,929	$	1,919	$	1,919
Restricted cash		30		30		37		37
Noncurrent receivables		19		19		17		17
Available-for-sale securities		68		68		193		193
Short-term borrowings		33		33		38		38
Commercial paper		—		—		—		—
Long-term debt due within one year		774		791		21		21
Contingent payment related to an acquisition		132		132		130		130
Long-term debt, less amount due within one year		8,278		8,670		8,993		8,922

Recently Adopted and Recently Issued Accounting Guidance - Additional Information (Detail) $ in Millions	Jan. 01, 2016 USD ($)
Accounting Changes and Error Corrections [Abstract]
Change due to recent accounting guidance	$ 51

- Definition

Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

+ References + Details

Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension and other postretirement benefits
Total Other comprehensive income	$ 67	$ (1)	$ 100	$ 106
Foreign currency translation
Other comprehensive income	77	229	487	(978)
Available-for-sale securities
Other comprehensive income	3	(2)	4
Cash flow hedges
Total Other comprehensive (loss) income	(137)	430	(219)	366
Energy Contracts [Member]
Cash flow hedges
Total Other comprehensive (loss) income before reclassifications, net of tax	45	(17)	39	(11)
Alcoa [Member]
Pension and other postretirement benefits
Balance at beginning of period	(3,579)	(3,496)	(3,611)	(3,601)
Unrecognized net actuarial loss and prior service cost/benefit	(5)	(118)	(64)	(76)
Tax benefit	3	39	26	28
Total Other comprehensive (loss) income before reclassifications, net of tax	(2)	(79)	(38)	(48)
Amortization of net actuarial loss and prior service cost/benefit	104	115	208	229
Tax (expense) benefit	(37)	(40)	(73)	(80)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	67	75	135	149
Total Other comprehensive income	65	(4)	97	101
Balance at end of period	(3,514)	(3,500)	(3,514)	(3,500)
Foreign currency translation
Balance at beginning of period	(2,109)	(1,803)	(2,412)	(846)
Other comprehensive income	45	197	348	(760)
Balance at end of period	(2,064)	(1,606)	(2,064)	(1,606)
Available-for-sale securities
Balance at beginning of period	(4)	2	(5)
Other comprehensive income	3	(2)	4
Balance at end of period	(1)		(1)
Cash flow hedges
Balance at beginning of period	517	(294)	597	(230)
Net change from periodic revaluations	(225)	614	(342)	504
Tax benefit (expense)	66	(190)	103	(156)
Total Other comprehensive (loss) income before reclassifications, net of tax	(159)	424	(239)	348
Net amount reclassified to earnings	7	14	(5)	29
Tax benefit (expense)	(1)	(4)	1	(7)
Total amount reclassified from Accumulated other comprehensive income (loss), net of tax	6	10	6	22
Total Other comprehensive (loss) income	(153)	434	(233)	370
Balance at end of period	364	140	364	140
Alcoa [Member] \| Aluminum Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings	(1)	10	(6)	23
Alcoa [Member] \| Energy Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings		2	1	4
Alcoa [Member] \| Foreign Exchange Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings		1	1	1
Alcoa [Member] \| Interest Rate Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings	8	1	8	1
Alcoa [Member] \| Nickel Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings			1
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period	(55)	(62)	(56)	(64)
Unrecognized net actuarial loss and prior service cost/benefit	1	3	1	3
Total Other comprehensive (loss) income before reclassifications, net of tax	1	3	1	3
Amortization of net actuarial loss and prior service cost/benefit		1	2	4
Tax (expense) benefit	1	(1)		(2)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1		2	2
Total Other comprehensive income	2	3	3	5
Balance at end of period	(53)	(59)	(53)	(59)
Foreign currency translation
Balance at beginning of period	(673)	(601)	(780)	(351)
Other comprehensive income	32	32	139	(218)
Balance at end of period	(641)	(569)	(641)	(569)
Cash flow hedges
Balance at beginning of period	(5)	(2)	(3)	(2)
Net change from periodic revaluations	18	(5)	15	(5)
Tax benefit (expense)	(5)	1	(4)	1
Total Other comprehensive (loss) income before reclassifications, net of tax	13	(4)	11	(4)
Net amount reclassified to earnings	5		5
Tax benefit (expense)	(2)		(2)
Total amount reclassified from Accumulated other comprehensive income (loss), net of tax	3		3
Total Other comprehensive (loss) income	16	(4)	14	(4)
Balance at end of period	11	$ (6)	11	$ (6)
Noncontrolling Interests [Member] \| Interest Rate Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings	$ 5		$ 5

Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Interest Rate Contracts [Member] \| Other Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings	$ 7	$ 7

Restructuring and Other Charges - Additional Information (Detail)		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 Employees	Jun. 30, 2016 USD ($) Employees	Jun. 30, 2015 USD ($) Employees t	Jun. 30, 2016 USD ($) Employees	Jun. 30, 2015 USD ($) Employees	Dec. 31, 2015 USD ($) Employees
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 23,000,000	$ 217,000,000	$ 116,000,000	$ 394,000,000
Restructuring and other charges after tax and noncontrolling interest		16,000,000	141,000,000	77,000,000	299,000,000
Other costs				30,000,000		$ 291,000,000
Inventory write down					4,000,000
Inventory write down after tax and noncontrolling interests					2,000,000
Minimum amount of cash payments expected to be paid beyond the end of the current annual period				25,000,000
Maximum amount of cash payments expected to be paid beyond the end of the current annual period				30,000,000
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		(3,000,000)	$ 24,000,000	(3,000,000)	29,000,000
Warrick Smelter, Wenatchee Smelter and Point Comfort [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		8,000,000		86,000,000
Restructuring and other charges after tax and noncontrolling interest		6,000,000		56,000,000
Warrick, IN Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Other costs		9,000,000		36,000,000
Inventory write down		2,000,000		5,000,000
Inventory write down after tax and noncontrolling interests		1,000,000		3,000,000
Other related costs		1,000,000		$ 2,000,000
Suriname [Member]
Restructuring Cost and Reserve [Line Items]
Capacity of lines under review \| t			443,000
Suriname [Member] \| Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees			120
Rolling Mill in Russia [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					179,000,000
Restructuring and other charges after tax and noncontrolling interest					115,000,000
Sao Luis Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					38,000,000
Restructuring and other charges after tax and noncontrolling interest					$ 23,000,000
Number of positions \| Employees					800
Sao Luis Smelter [Member] \| Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees					680
Sao Luis Smelter [Member] \| Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees					120
Pocos de Caldas Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Capacity closure \| t			96,000
Point Henry Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Percentage of power supply				40.00%
Asset Retirement Obligation Costs [Member] \| Warrick, IN Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Other costs				$ 7,000,000
Restructuring And Related Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		15,000,000
Restructuring and other charges after tax and noncontrolling interest		11,000,000
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		8,000,000	$ 5,000,000	8,000,000	$ 3,000,000
Restructuring and other charges after tax and noncontrolling interest		4,000,000	3,000,000	4,000,000	2,000,000
Other Adjustments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		8,000,000	1,000,000	12,000,000	8,000,000
Restructuring and other charges after tax and noncontrolling interest		$ 5,000,000	1,000,000	8,000,000	7,000,000
Restructuring Programs Layoffs 2015 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				34,000,000
Restructuring and other charges after tax and noncontrolling interest				$ 25,000,000
Number of positions \| Employees	5,000	540		1,100		5,200
Approximate number of employees already laid off \| Employees	3,800	3,800		3,800
Cash payments made against the layoff reserves		$ 30,000,000		$ 92,000,000
Restructuring Programs Layoffs 2015 [Member] \| Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees		300		800
Restructuring Programs Layoffs 2015 [Member] \| Transportation and Construction Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees		240		240
Restructuring Programs Layoffs 2015 [Member] \| Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees				30
Asset Impairment and Accelerated Depreciation [Member] \| Warrick, IN Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				$ 70,000,000
Severance costs		$ 1,000,000		20,000,000
Other costs		9,000,000		36,000,000
Contract Termination [Member] \| Warrick, IN Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Other costs		$ 10,000,000		27,000,000
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			179,000,000		82,000,000
Restructuring and other charges after tax and noncontrolling interest			115,000,000
Other costs				$ (1,000,000)		$ 231,000,000
Restructuring Programs Layoffs 2014 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			16,000,000		29,000,000
Restructuring and other charges after tax and noncontrolling interest			$ 13,000,000		$ 21,000,000
Number of positions \| Employees	2,700		390		600	2,870
Capacity of lines under review \| t			74,000
Approximate number of employees already laid off \| Employees	2,600	2,600		2,600
Cash payments made against the layoff reserves		$ 1,000,000		$ 3,000,000
Restructuring Programs Layoffs 2014 [Member] \| Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees					50
Restructuring Programs Layoffs 2014 [Member] \| Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees			210		290
Restructuring Programs Layoffs 2014 [Member] \| Transportation and Construction Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees					50
Restructuring Programs Layoffs 2014 [Member] \| Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees			150		150
Restructuring Programs Layoffs 2014 [Member] \| Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees			30		60
Restructuring Programs Layoffs 2014 [Member] \| Suriname [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 18,000,000
Restructuring and other charges after tax and noncontrolling interest			10,000,000
Post Closing Adjustments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			10,000,000
Restructuring and other charges after tax and noncontrolling interest			$ 7,000,000
Divested Businesses [Member] \| Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 159,000,000
Restructuring and other charges after tax and noncontrolling interest					149,000,000
Shutdown and Curtailment Actions [Member]
Restructuring Cost and Reserve [Line Items]
Asset impairment charges					$ 86,000,000
Number of employees associated with layoff costs \| Employees					100
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 11,000,000
Other costs				31,000,000		$ 60,000,000
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				$ 7,000,000	45,000,000	76,000,000
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					29,000,000	$ 86,000,000
Supplier and Customer Contract [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 8,000,000
Restructuring Programs Layoffs 2016 [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions \| Employees	1,100
Approximate number of employees already laid off \| Employees	730	730		730
Cash payments made against the layoff reserves		$ 9,000,000		$ 11,000,000

Restructuring and Other Charges - Schedule of Restructuring and Other Charges by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 23	$ 217	$ 116	$ 394
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	26	193	119	365
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(3)	24	(3)	29
Alumina [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(1)	10	4	17
Primary Metals [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	10	173	88	198
Global Rolled Products [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		1	2	136
Engineered Products and Solutions [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	9	8	17	11
Transportation and Construction Solutions [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 8	$ 1	$ 8	$ 3

Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	$ 250	$ 132
Cash payments	(129)	(123)
Restructuring charges	75	532
Other	(30)	(291)
Restructuring reserve ending balance	166	250
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	226	98
Cash payments	(107)	(111)
Restructuring charges	34	299
Other	(31)	(60)
Restructuring reserve ending balance	122	226
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	24	34
Cash payments	(22)	(12)
Restructuring charges	41	233
Other	1	(231)
Restructuring reserve ending balance	$ 44	$ 24

Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost			$ 30		$ 291
Restructuring and other charges	$ 23	$ 217	116	$ 394
Pension And Other Postretirement Benefits Costs Charged To Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost					35
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			7	45	76
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				$ 29	$ 86
Pension Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost			1
Restructuring and other charges	$ 2		$ 2

Acquisitions and Divestitures - 2015 Acquisitions - Additional Information (Detail) € in Millions			1 Months Ended		3 Months Ended			4 Months Ended	6 Months Ended		12 Months Ended
	Jul. 29, 2016 HydroelectricPowerDevelopments	Apr. 30, 2016 USD ($)	Mar. 31, 2015 USD ($) Employees	Mar. 31, 2015 EUR (€) Employees	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)	Apr. 29, 2016 USD ($) Employees	Jun. 30, 2016 USD ($) Employees	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Mar. 31, 2015 EUR (€)
Business Acquisition [Line Items]
Gain from sale of Remmele Medical business		$ 0
Sale generated in last annual period prior to divestiture					$ 5,295,000,000		$ 5,897,000,000		$ 10,242,000,000	$ 11,716,000,000
Number of employees \| Employees									35
Sale generated by Yadkin											$ 20,000,000
Carrying value of net assets to be sold					128,000,000				$ 128,000,000		127,000,000
Goodwill					5,396,000,000				5,396,000,000		$ 5,401,000,000
Income tax expense					152,000,000		$ 75,000,000		182,000,000	$ 301,000,000
Subsequent Event [Member]
Business Acquisition [Line Items]
No of hydroelectric power developments held by Yadkin \| HydroelectricPowerDevelopments	4
Goodwill [Member]
Business Acquisition [Line Items]
Increase (decrease) intangible assets		(44,000,000)
LISI MEDICAL [Member]
Business Acquisition [Line Items]
Cash received on sale of operations		102,000,000
Sale of Remmele Medical business, net of transaction costs		$ 99,000,000
TITAL [Member]
Business Acquisition [Line Items]
Number of employees \| Employees			650	650
Cash paid for business acquisition			$ 204,000,000	€ 188
Business acquisition transaction cost			1,000,000										€ 1
Goodwill			$ 118,000,000		117,000,000				117,000,000
Income tax expense									0
Other intangible assets					$ 0				0
TITAL [Member] \| Goodwill [Member]
Business Acquisition [Line Items]
Increase (decrease) intangible assets						$ 1,000,000
RTI [Member]
Business Acquisition [Line Items]
Sale generated in last annual period prior to divestiture								$ 20,000,000
Number of employees \| Employees								330
Goodwill												$ 240,000,000
Common stock conversion transaction value												870,000,000
Total assets												1,752,000,000
Intangibles												73,000,000
Total liabilities												822,000,000
Additional capital												$ 60,000,000
Decrease in properties, plants, and equipment									110,000,000
Decrease in inventories									48,000,000
RTI [Member] \| Goodwill [Member]
Business Acquisition [Line Items]
Increase (decrease) intangible assets									54,000,000
RTI [Member] \| Intangible Assets [Member]
Business Acquisition [Line Items]
Increase (decrease) intangible assets									$ 33,000,000

Inventories - Schedule of Inventory Components (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Finished goods	$ 827	$ 811
Work-in-process	1,344	1,272
Bauxite and alumina	416	445
Purchased raw materials	650	720
Operating supplies	201	194
Inventories, total	$ 3,438	$ 3,442

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Inventories valued on a LIFO basis	$ 1,335	$ 1,373
Total inventories valued on an average-cost basis	$ 567	$ 559

Investments - Summary of Unaudited Financial Information for Alcoa's Equity Investments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Investments Schedule [Abstract]
Sales	$ 904	$ 971	$ 1,796	$ 1,857
Cost of goods sold	679	862	1,360	1,557
Net income (loss)	$ 14	$ (45)	$ 29	$ (86)

Investments - Additional Information (Detail) $ in Millions, $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended			12 Months Ended
	Apr. 30, 2016 USD ($) Refinery	Apr. 30, 2016 AUD ($) Refinery	Jun. 30, 2016 USD ($)	Jun. 30, 2016 AUD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2016 AUD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2004	Dec. 31, 2015 USD ($)
Schedule of Equity Method Investments [Line Items]
Gain after tax and noncontrolling interest			$ 11	$ 15	$ 27	$ 35
Number of alumina refineries to be powered under supplied agreement \| Refinery	3	3
Sales of investments					275		$ 22
Carrying value of available-for-sale-securities			128		$ 128				$ 127
Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture	60.00%	60.00%			25.10%	25.10%
Alumina Limited of Australia [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture	40.00%	40.00%
AofA [Member] \| Dampier to Bunbury Natural Gas Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Investment percentage in DBP to be sold	20.00%	20.00%
Amount to be received by sale of investment percentage in DBP	$ 145	$ 192
Percentage of access to be maintained in DBNGP transmission capacity for gas supply	30.00%	30.00%						20.00%
Exchange Traded Fixed Income and Equity Securities [Member]
Schedule of Equity Method Investments [Line Items]
Sales of investments					$ 130
Loss on sale of investment					3
Loss on sale of investment, after tax					2
Carrying value of available-for-sale-securities			$ 68		$ 68				$ 193

Other Noncurrent Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Other Non Current Assets [Abstract]
Proceeds from sale of company-owned life insurance policies	$ 223,000,000	$ 234,000,000
Gain or loss recognized on sale of company-owned life insurance policies			$ 0
Cash surrender value of life insurance	$ 26,000,000		$ 26,000,000	$ 492,000,000

Contingencies and Commitments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)	Feb. 21, 2013 USD ($)	Feb. 21, 2013 EUR (€)	Mar. 26, 2012 USD ($)	Mar. 26, 2012 EUR (€)
Loss Contingencies [Line Items]
Management estimate for maximum exposure from class action					$ 110,000,000	€ 85,000,000
Partial reserve	$ 37,000,000	€ 34,000,000
Alcoa Trasformazioni [Member]
Loss Contingencies [Line Items]
Management estimate for maximum exposure from class action			$ 97,000,000	€ 76,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Provision for contract losses			0
Maximum [Member]
Loss Contingencies [Line Items]
Provision for contract losses			$ 97,000,000	€ 76,000,000

Contingencies and Commitments - Additional Information - 1 (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Sep. 30, 2015	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Number of cleanup locations			More than 100
Remediation reserve balance		$ 606	$ 606	$ 604
Remediation reserve balance, classified as a current liability		49	49	50
Increase in remediation reserve	$ 1	6	13
Payments related to remediation expenses applied against the reserve		14	25
Increase (Decrease) in reserves due to effects of foreign currency translation		6	11
Increase (Decrease) in reserves due to effects of Acquisition			$ 3
Actual remediation fieldwork period			4 years
Guarantee debt service expiration year			2019
Minimum [Member]
Loss Contingencies [Line Items]
Majority of the project funding period			2017
Maximum [Member]
Loss Contingencies [Line Items]
Majority of the project funding period			2021
Massena West, NY [Member]
Loss Contingencies [Line Items]
Remediation reserve balance		232	$ 232	234
Sherwin, TX site [Member]
Loss Contingencies [Line Items]
Remediation reserve balance		30	30	30
Expected portion of funding through 2019		15	15
East St. Louis, IL Site [Member]
Loss Contingencies [Line Items]
Remediation reserve balance		$ 6	$ 6	$ 8
Recurring Costs of Managing Hazardous Substances and Environmental Programs [Member]
Loss Contingencies [Line Items]
Percentage of cost of goods sold			2.00%

Contingencies and Commitments - Additional Information - 2 (Detail) € in Millions, R$ in Millions, $ in Millions, ر.س in Billions						1 Months Ended								3 Months Ended			6 Months Ended			12 Months Ended							36 Months Ended	93 Months Ended
	Apr. 08, 2015 USD ($) Installment Refinery	Feb. 27, 2014 USD ($)	Feb. 27, 2014 EUR (€)	Apr. 08, 2013 USD ($)	Apr. 08, 2013 BRL (R$)	Apr. 30, 2016 Refinery	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jan. 31, 2014	Oct. 31, 2013 USD ($)	Mar. 31, 2013 USD ($)	May 31, 2012 USD ($)	May 31, 2012 BRL (R$)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2016 AUD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2016 SAR (ر.س)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 AUD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2004 USD ($)	Dec. 31, 2004 AUD ($)	Dec. 31, 2002 t	Sep. 30, 2011 USD ($)	Sep. 30, 2011 AUD ($)	Jun. 30, 2016 EUR (€)	Jun. 30, 2016 BRL (R$)	Jun. 30, 2016 AUD ($)	Dec. 31, 2015 AUD ($)	Apr. 08, 2013 BRL (R$)	Mar. 31, 2013 BRL (R$)
Loss Contingencies [Line Items]
Increase in remediation reserve								$ 1,000,000						$ 6,000,000			$ 13,000,000
Revised project cost submitted to reflect the removal of a larger volume of contaminated soil							$ 7,000,000
Total combined assessments														269,000,000			269,000,000													€ 243
Number of alumina refineries to be powered under supplied agreement \| Refinery						3
State and Local Jurisdiction [Member]
Loss Contingencies [Line Items]
Total combined assessments														43,000,000			43,000,000														R$ 139
Maaden Alcoa Joint Venture [Member]
Loss Contingencies [Line Items]
Required plan contributions																	10,800,000,000	ر.س 40.5
Capital investment																	1,000,000
Equity investments														883,000,000			883,000,000			$ 928,000,000
Maaden Alcoa Joint Venture [Member] \| Alcoa [Member]
Loss Contingencies [Line Items]
Required plan contributions																	1,100,000,000
Capital investment																	$ 982,000,000
Ma'aden Joint Venture [Member]
Loss Contingencies [Line Items]
Ownership interest in joint venture																	74.90%	74.90%
Alcoa Joint Venture [Member]
Loss Contingencies [Line Items]
Ownership interest in joint venture						60.00%											25.10%	25.10%
Project financing Investment														1,061			$ 1,061
Maaden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member]
Loss Contingencies [Line Items]
Project financing Investment														4,227,000,000			4,227,000,000
Maaden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member] \| Other Noncurrent Liabilities and Deferred Credits [Member]
Loss Contingencies [Line Items]
Guarantee issued on behalf of smelting and rolling mill companies														4,000,000			4,000,000			7,000,000
Maaden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member] \| Financial Guarantee [Member]
Loss Contingencies [Line Items]
Debt service requirements, principal																	142,000,000
Debt service requirements, interest maximum																	30,000,000
Maaden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member] \| Alcoa [Member]
Loss Contingencies [Line Items]
Project financing Investment														142,000,000			142,000,000
Maaden Alcoa Joint Venture Mine And Refinery Company [Member] \| Other Noncurrent Liabilities and Deferred Credits [Member]
Loss Contingencies [Line Items]
Guarantee issued on behalf of smelting and rolling mill companies														3,000,000			3,000,000			$ 3,000,000
Maaden Alcoa Joint Venture Mine And Refinery Company [Member] \| Financial Guarantee [Member]
Loss Contingencies [Line Items]
Debt service requirements, principal																	120,000,000
Debt service requirements, interest maximum																	30,000,000
Maaden Alcoa Joint Venture Mine And Refinery Company [Member] \| AWAC [Member]
Loss Contingencies [Line Items]
Project financing Investment														560,000,000			560,000,000
Maaden Alcoa Joint Venture Mine And Refinery Company [Member] \| Alcoa [Member]
Loss Contingencies [Line Items]
Project financing Investment														2,232,000,000			$ 2,232,000,000
Alumina Limited [Member]
Loss Contingencies [Line Items]
Percentage of amount required to be contributed in the event Alcoa would be required to make payments under the guarantees																	40.00%	40.00%
Ligestra [Member]
Loss Contingencies [Line Items]
Costs and payments		$ 17,000,000	€ 12
Costs and payments related to damages		9,000,000	6
Payment period																	10 years	10 years
Ligestra [Member] \| Minimum [Member]
Loss Contingencies [Line Items]
Percentage of payments and remediation costs									50.00%
Ligestra [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Percentage of payments and remediation costs									80.00%
Italian Ministry of Environment and Protection of Land and Sea[Member]
Loss Contingencies [Line Items]
Soil remediation project, estimated cost		33,000,000	24
Payments for emergency action and natural resource damages		$ 25,000,000	€ 18
Alcoa World Alumina Brasil [Member]
Loss Contingencies [Line Items]
Disallowed tax credits											$ 110,000,000																								R$ 220
Percentage of penalty of the gross disallowed amount				50.00%	50.00%						50.00%
Value added tax receivable												$ 41,000,000	R$ 82
Estimated range of reasonably possible loss, minimum \| R$					R$ 103
Alcoa World Alumina Brasil [Member] \| Minimum [Member]
Loss Contingencies [Line Items]
Estimated range of reasonably possible loss, minimum				$ 0
Alcoa World Alumina Brasil [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Estimated range of reasonably possible loss, minimum				32,000,000
Alcoa World Alumina Brasil [Member] \| Fixed Assets [Member]
Loss Contingencies [Line Items]
Disallowed tax credits \| R$																																		R$ 117
Alcoa World Alumina Brasil [Member] \| Fixed Assets [Member] \| Minimum [Member]
Loss Contingencies [Line Items]
Disallowed tax credits				0
Alcoa World Alumina Brasil [Member] \| Fixed Assets [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Disallowed tax credits				$ 36,000,000
Alcoa Aluminio [Member]
Loss Contingencies [Line Items]
Metal sold per month \| t																											2,000
Majority-Owned Subsidiary \| AofA [Member] \| Service Agreements [Member]
Loss Contingencies [Line Items]
Gas supply agreement period																				12 years
Number of alumina refineries to be powered under supplied agreement \| Refinery	3
Number of installments \| Installment	2
Gas supply agreement prepayment amount	$ 500,000,000
Majority-Owned Subsidiary \| AofA [Member] \| Service Agreements [Member] \| First Installment [Member]
Loss Contingencies [Line Items]
Gas supply agreement prepayment amount	300,000,000
Asset included in other noncurrent assets														484,000,000			$ 484,000,000			$ 288,000,000												$ 654	$ 395
Majority-Owned Subsidiary \| AofA [Member] \| Service Agreements [Member] \| Second Installment [Member]
Loss Contingencies [Line Items]
Gas supply agreement prepayment amount	$ 200,000,000
Fusina [Member]
Loss Contingencies [Line Items]
Increase in remediation reserve										$ 0														$ 12,000,000
Portovesme [Member]
Loss Contingencies [Line Items]
Increase in remediation reserve																					$ 3,000,000			$ 3,000,000
Baie Comeau Smelter [Member]
Loss Contingencies [Line Items]
Increase in remediation reserve																							$ 25,000,000
Mosjoen [Member]
Loss Contingencies [Line Items]
Increase in remediation reserve																			$ 11,000,000				$ 20,000,000
Dampier to Bunbury Natural Gas Pipeline [Member]
Loss Contingencies [Line Items]
Capital investment																									$ 17,000,000	$ 24
Dampier to Bunbury Natural Gas Pipeline [Member] \| AofA [Member]
Loss Contingencies [Line Items]
Capital investment																												$ 141,000,000	$ 176
Investment percentage						30.00%																			20.00%	20.00%
Prepayments made under the agreement for future gas transmission services														$ 275,000,000			$ 275,000,000															$ 372
Dampier to Bunbury Natural Gas Pipeline [Member] \| Three-Year Equity Call Plan [Member]
Loss Contingencies [Line Items]
Required plan contributions																					39,000,000	$ 40
Dampier to Bunbury Natural Gas Pipeline [Member] \| New Equity Call Plan [Member]
Loss Contingencies [Line Items]
Required plan contributions															$ 3,000,000	$ 5					$ 30,000,000	$ 36
Capital investment															$ 20,000,000	$ 27

Other Income, Net - Schedule of Other Income, Net (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other Income and Expenses [Abstract]
Equity loss	$ 15	$ 24	$ 37	$ 44
Interest income	(5)	(4)	(9)	(7)
Foreign currency (gains) losses, net	(9)	6	6	(10)
Net gain from asset sales	(30)	(28)	(28)	(28)
Net loss on mark-to-market derivative contracts (O)	8	7	9	3
Other, net	(16)	$ (5)	(18)	(14)
Other (income) expenses, net	$ (37)		$ (3)	$ (12)

Other Income, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other Non operating Income Expense [Line Items]
Net loss (gain) from asset sales	$ 30	$ 28	$ 28	$ 28
Disposal of Equity Interests [Member]
Other Non operating Income Expense [Line Items]
Net loss (gain) from asset sales	$ 27		$ 27
Disposal of Land [Member]
Other Non operating Income Expense [Line Items]
Net loss (gain) from asset sales		$ 29		$ 29

Segment Information - Schedule of Operating Results of Alcoa's Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Equity (loss) income		$ (23)	$ (38)	$ (42)
Total sales	$ 5,295	5,897	10,242	11,716
Depreciation, depletion, and amortization	296	307	593	613
Income taxes	173	216	288	491
After-tax operating income (ATOI)	444	567	735	1,223
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	6,097	6,924	11,836	13,961
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	802	1,027	1,598	2,256
Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	5,295	5,897	10,238	11,705
Alumina [Member]
Segment Reporting Information [Line Items]
Equity (loss) income		(11)	(21)	(18)
Depreciation, depletion, and amortization	66	77	129	157
Income taxes	40	87	45	179
After-tax operating income (ATOI)	109	215	117	436
Alumina [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	994	1,355	1,831	2,743
Alumina [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	300	431	592	932
Alumina [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	694	924	1,239	1,811
Primary Metals [Member]
Segment Reporting Information [Line Items]
Equity (loss) income		(5)	4	(8)
Depreciation, depletion, and amortization	101	109	203	218
Income taxes		6	(16)	63
After-tax operating income (ATOI)	41	67	55	254
Primary Metals [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	1,592	2,096	3,190	4,360
Primary Metals [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	473	562	948	1,254
Primary Metals [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,119	1,534	2,242	3,106
Global Rolled Products [Member]
Segment Reporting Information [Line Items]
Equity (loss) income		(7)	(21)	(16)
Depreciation, depletion, and amortization	55	56	111	112
Income taxes	28	25	62	61
After-tax operating income (ATOI)	68	76	136	130
Global Rolled Products [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	1,579	1,702	3,005	3,359
Global Rolled Products [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	29	34	58	70
Global Rolled Products [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,550	1,668	2,947	3,289
Engineered Products and Solutions [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion, and amortization	62	54	127	105
Income taxes	87	81	165	157
After-tax operating income (ATOI)	180	165	342	321
Engineered Products and Solutions [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	1,465	1,279	2,914	2,536
Engineered Products and Solutions [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,465	1,279	2,914	2,536
Transportation and Construction Solutions [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion, and amortization	12	11	23	21
Income taxes	18	17	32	31
After-tax operating income (ATOI)	46	44	85	82
Transportation and Construction Solutions [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	467	492	896	963
Transportation and Construction Solutions [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	$ 467	$ 492	$ 896	$ 963

Segment Information - Schedule of Segment ATOI to Consolidated Net Income Attributable to Alcoa (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Total segment ATOI	$ 444	$ 567	$ 735	$ 1,223
Metal price lag	7	(39)	8	(62)
Interest expense	(129)	(124)	(256)	(246)
Noncontrolling interests	(43)	(67)	(38)	(127)
Consolidated net income attributable to Alcoa	135	140	151	335
Other [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	(10)	36	(6)	43
Interest expense	(84)	(80)	(167)	(160)
Noncontrolling interests	(43)	(67)	(38)	(127)
Corporate expense	(77)	(65)	(132)	(127)
Restructuring and other charges	(15)	(159)	(76)	(320)
Other	$ (87)	$ (53)	$ (173)	$ (135)

Earnings Per Share - Reconciliation of Information Used to Compute Basic and Diluted EPS (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income attributable to Alcoa	$ 135	$ 140	$ 151	$ 335
Less: preferred stock dividends declared	17	17	35	35
Net income available to Alcoa common shareholders - basic	118	123	116	300
Add: interest expense related to convertible notes	2
Add: dividends related to mandatory convertible preferred stock	0	0	0	0
Net income available to Alcoa common shareholders - diluted	$ 120	$ 123	$ 116	$ 300
Average shares outstanding - basic	1,315	1,222	1,314	1,222
Stock options	2	4	1	5
Stock and performance awards	11	11	11	11
Convertible notes	28
Mandatory convertible preferred stock	0	0	0	0
Average shares outstanding - diluted	1,356	1,237	1,326	1,238

Earnings Per Share - Additional Information (Detail) - $ / shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Mandatory Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities	77	77	77	77
Equity Unit Purchase Agreements [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities			25	13
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average exercise price of options			$ 12.73	$ 14.78
Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities			28

Receivables - Additional Information (Detail)		6 Months Ended	12 Months Ended
Receivables - Additional Information (Detail)	Mar. 30, 2012 USD ($)	Jun. 30, 2016 USD ($) Agreement	Dec. 31, 2015 USD ($)
Schedule Of Financial Receivables [Line Items]
Number of arrangement with different financial institution to sell customer receivables \| Agreement		3
Deferred purchase price receivable	$ 254,000,000	$ 197,000,000	$ 249,000,000
Net cash funding received		100,000,000
Amount of cash draws under arrangement		200,000,000
Amount of cash repayments under arrangement		100,000,000
Accounts receivables		27,521,000,000
Cash collections of other receivables		26,974,000,000
Minimum [Member]
Schedule Of Financial Receivables [Line Items]
Funding of customer receivables sold		200,000,000
Maximum [Member]
Schedule Of Financial Receivables [Line Items]
Funding of customer receivables sold		500,000,000
Predecessor [Member]
Schedule Of Financial Receivables [Line Items]
Net cash funding received		350,000,000
Amount of cash draws under arrangement		1,508,000,000
Amount of cash repayments under arrangement		$ 1,158,000,000

Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 41	$ 44	$ 81	$ 88
Interest cost	122	145	244	289
Expected return on plan assets	(186)	(189)	(371)	(377)
Recognized net actuarial loss	102	117	204	235
Amortization of prior service benefit	4	4	8	8
Settlements	2		2	1
Special termination benefits		10	1	12
Net periodic benefit cost	85	131	169	256
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4	7	7
Interest cost	19	23	37	46
Recognized net actuarial loss	5	5	11	9
Amortization of prior service benefit	(7)	(10)	(13)	(19)
Special termination benefits		1		1
Net periodic benefit cost	$ 21	22	$ 42	43
Curtailments		$ (1)		$ (1)

Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Restructuring and other charges	$ 23	$ 217	$ 116	$ 394
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Restructuring and other charges	$ 2		$ 2

Pension and Other Postretirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in interest cost component of net periodic benefit cost determination	$ 24	$ 48
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in interest cost component of net periodic benefit cost determination	$ 4	$ 8

Derivatives and Other Financial Instruments - Additional Information (Detail) t in Thousands	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2016 USD ($) Derivative	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) MWh Derivative Agency t	Mar. 31, 2016	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) MWh t
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other derivative contracts estimated term of quoted market prices, in years				10 years
Number of credit rating agencies \| Agency			3
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	10		10
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of derivatives recorded as assets	$ 6,000,000		$ 6,000,000			$ 8,000,000
Fair value of derivatives recorded as liabilities	11,000,000		11,000,000			$ 58,000,000
Net gain (loss) of derivative instruments	1,000,000	$ 15,000,000	3,000,000		$ 41,000,000
Derivatives Not Designated as Hedging Instruments [Member] \| Other Expenses (Income), Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain (loss) of derivative instruments	(6,000,000)	(5,000,000)	(9,000,000)		(2,000,000)
Embedded Aluminum Derivative [Member] \| Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recognized an unrealized gain (loss)	(253,000,000)	616,000,000	(368,000,000)		518,000,000
Realized gain (loss) on derivatives	$ 1,000,000	(12,000,000)	$ 5,000,000		(24,000,000)
Embedded Aluminum Derivative [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	8		8
Embedded Aluminum Derivative [Member] \| Level 3 [Member] \| Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	9		9
Embedded Aluminum Derivative [Member] \| Derivatives Designated as Hedging Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aluminum forecast sales \| t			3,261			3,307
Embedded Aluminum Derivative [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain (loss) expected to be recognized into earnings over the next 12 months			$ 25,000,000
Derivative instruments ineffectiveness	$ 0	0	0		0
Embedded Aluminum Derivative [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedging [Member] \| Other Expenses (Income), Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other expenses (income), net	0	1,000,000	1,000,000		1,000,000
Embedded Aluminum Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain (loss) of derivative instruments	$ (4,000,000)	(2,000,000)	$ (8,000,000)		(1,000,000)
Embedded Aluminum Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	3		3
Energy Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recognized an unrealized gain (loss)	$ 45,000,000	(17,000,000)	$ 39,000,000		(11,000,000)
Energy Contracts [Member] \| Level 3 [Member] \| Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	3		3
Energy Contracts [Member] \| Derivatives Designated as Hedging Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments ineffectiveness	$ 0	0	$ 3,000,000		0
Forecasted energy purchases in megawatt hours \| MWh			59,409,328			59,409,328
Embedded Credit Derivative [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	5		5
Embedded Credit Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain (loss) of derivative instruments	$ (2,000,000)	$ (3,000,000)	$ (1,000,000)		$ (1,000,000)
Embedded Credit Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of derivative instruments \| Derivative	0		0

Derivatives and Other Financial Instruments - Schedule of Quantitative Information for Level 3 Derivative Contracts (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($) MWh Index $ / MWh $ / Metric_Ton $ / lb $ / AUD $ / Barrels	Dec. 31, 2015 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets, Fair value \| $	$ 794	$ 1,137
Embedded Aluminum Derivative [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets, Fair value \| $	718
Derivative Liabilities, Fair value \| $	$ 196
Embedded Aluminum Derivative [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	2,093
Maturity year of future aluminum price	2026
Embedded Aluminum Derivative [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	2,137
Maturity year of future aluminum price	2027
Embedded Aluminum Derivative [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Average Price [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	2,093
Maturity year of future aluminum price	2026
Embedded Aluminum Derivative [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Midwest Premium \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Midwest Premium \| $ / lb	0.0775
Foreign currency exchange rate expected year	2021
Embedded Aluminum Derivative [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Midwest Premium \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Midwest Premium \| $ / lb	0.0775
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets, Fair value \| $	$ 23
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] \| Average Price [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,631
Maturity year of future aluminum price	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,637
Maturity year of future aluminum price	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] \| Estimated Foreign Currency Exchange Rate [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency exchange rate \| $ / AUD	0.74
Foreign currency exchange rate expected year	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum Prices, Foreign Currency Exchange Rates, and U.S. Consumer Price Index [Member] \| Consumer Price Index [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Consumer price index base year	1982
Consumer price index base \| Index	100
Expected consumer price index \| Index	236
Expected consumer price index, Year	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of LME Price to Overall Energy Price [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets, Fair value \| $	$ 4
Embedded Aluminum Derivative [Member] \| Interrelationship of LME Price to Overall Energy Price [Member] \| Average Price [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,614
Maturity year of future aluminum price	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of LME Price to Overall Energy Price [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,755
Maturity year of future aluminum price	2019
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum and Oil Prices [Member] \| Average Price [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,631
Maturity year of future aluminum price	2016
Expected future oil prices \| $ / Barrels	49
Maturity year of future oil price	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of Future Aluminum and Oil Prices [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,710
Maturity year of future aluminum price	2018
Expected future oil prices \| $ / Barrels	55
Maturity year of future oil price	2018
Embedded Aluminum Derivative [Member] \| Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Liabilities, Fair value \| $	$ 32
Megawatt hours per year \| MWh	2,000,000
Embedded Aluminum Derivative [Member] \| Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] \| Average Price [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,631
Maturity year of future aluminum price	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	1,729
Maturity year of future aluminum price	2019
Embedded Aluminum Derivative [Member] \| Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] \| Midwest Premium \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Midwest Premium \| $ / lb	0.0725
Foreign currency exchange rate expected year	2016
Embedded Aluminum Derivative [Member] \| Interrelationship of London Metal Exchange Price to Amount Of Megawatt Hours of Energy Needed to Produce Forecasted Metric Tons of Aluminum [Member] \| Midwest Premium \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Midwest Premium \| $ / lb	0.0775
Foreign currency exchange rate expected year	2019
Embedded Aluminum Derivative [Member] \| Two Contracts [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	2,245
Maturity year of future aluminum price	2029
Embedded Aluminum Derivative [Member] \| Two Contracts [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Midwest Premium \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency exchange rate expected year	2029
Embedded Aluminum Derivative [Member] \| One Contract [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Expected future aluminum prices	2,540
Maturity year of future aluminum price	2036
Embedded Aluminum Derivative [Member] \| One Contract [Member] \| Price of Aluminum beyond Forward Curve [Member] \| Midwest Premium \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency exchange rate expected year	2036
Energy Contracts [Member] \| Price of Electricity beyond Forward Curve [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Assets, Fair value \| $	$ 40
Energy Contracts [Member] \| Price of Electricity beyond Forward Curve [Member] \| Average Price [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Price of electricity beyond forward curve \| $ / MWh	48
Maturity date of electricity beyond forward curve	2019
Energy Contracts [Member] \| Price of Electricity beyond Forward Curve [Member] \| Average Price [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Price of electricity beyond forward curve \| $ / MWh	116
Maturity date of electricity beyond forward curve	2036
Embedded Credit Derivative [Member] \| Credit Spread between Alcoa and Counterparty [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Liabilities, Fair value \| $	$ 33
Embedded Credit Derivative [Member] \| Credit Spread between Alcoa and Counterparty [Member] \| Credit Spread [Member] \| Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Percentage of credit spread	3.63%
Embedded Credit Derivative [Member] \| Credit Spread between Alcoa and Counterparty [Member] \| Credit Spread [Member] \| Level 3 [Member] \| Minimum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Percentage of credit spread	3.45%
Embedded Credit Derivative [Member] \| Credit Spread between Alcoa and Counterparty [Member] \| Credit Spread [Member] \| Level 3 [Member] \| Maximum [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Percentage of credit spread	3.81%

Derivatives and Other Financial Instruments - Schedule of Fair Values of Level 3 Derivative Instruments Recorded as Assets and Liabilities (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	$ 794	$ 1,137
Fair value liability derivatives	270	208
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	771	1,068
Fair value liability derivatives	205	173
Derivatives Designated as Hedging Instruments [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	51	72
Derivatives Designated as Hedging Instruments [Member] \| Other Noncurrent Assets [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	671	994
Derivatives Designated as Hedging Instruments [Member] \| Other Noncurrent Assets [Member] \| Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	49	2
Derivatives Designated as Hedging Instruments [Member] \| Other Current Liabilities [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	14	9
Derivatives Designated as Hedging Instruments [Member] \| Other Current Liabilities [Member] \| Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	9	4
Derivatives Designated as Hedging Instruments [Member] \| Other Noncurrent Liabilities and Deferred Credits [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	182	160
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	23	69
Fair value liability derivatives	65	35
Derivatives Not Designated as Hedging Instruments [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	23	69
Derivatives Not Designated as Hedging Instruments [Member] \| Other Current Liabilities [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	8
Derivatives Not Designated as Hedging Instruments [Member] \| Other Current Liabilities [Member] \| Embedded Credit Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	5	6
Derivatives Not Designated as Hedging Instruments [Member] \| Other Noncurrent Liabilities and Deferred Credits [Member] \| Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	24
Derivatives Not Designated as Hedging Instruments [Member] \| Other Noncurrent Liabilities and Deferred Credits [Member] \| Embedded Credit Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	$ 28	$ 29

Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets, Purchases, sales, issuances, and settlements	$ 0	$ 0
Embedded Aluminum Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets, Beginning balance	988,000,000	1,135,000,000
Fair value measurement, Assets, Sales	(3,000,000)	(10,000,000)
Fair value measurement, Assets, Cost of goods sold	(30,000,000)	(61,000,000)
Fair value measurement, Assets, Other income, net	(4,000,000)	(8,000,000)
Fair value measurement, Assets, Other comprehensive income	(215,000,000)	(336,000,000)
Fair value measurement, Assets, Transfers into and/or out of Level 3	0	0
Fair value measurement, Assets, Other	9,000,000
Fair value measurement, Assets, Other		25,000,000
Fair value measurement, Assets, Ending balance	745,000,000	745,000,000
Fair value measurement, Assets, Sales	0	0
Fair value measurement, Assets, Cost of goods sold	0	0
Fair value measurement, Assets, Other income , net	(4,000,000)	(8,000,000)
Fair value measurement, Liabilities, Beginning balance	161,000,000	169,000,000
Fair value measurement, Liabilities, Sales	(3,000,000)	(5,000,000)
Fair value measurement, Liabilities, Other comprehensive income	38,000,000	32,000,000
Fair value measurement, Liabilities, Purchases, sales, issuances, and settlements	32,000,000	32,000,000
Fair value measurement, Liabilities, Transfers into and/or out of Level 3	0	0
Fair value measurement, Liabilities, Ending balance	228,000,000	228,000,000
Fair value measurement, Liabilities, Sales	0	0
Fair value measurement, Liabilities, Cost of goods sold	0	0
Embedded Credit Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Liabilities, Beginning balance	33,000,000	35,000,000
Fair value measurement, Liabilities, Cost of goods sold	(2,000,000)	(3,000,000)
Fair value measurement, Liabilities, Other income, net	2,000,000	1,000,000
Fair value measurement, Liabilities, Transfers into and/or out of Level 3	0	0
Fair value measurement, Liabilities, Ending balance	33,000,000	33,000,000
Fair value measurement, Liabilities, Sales	0	0
Fair value measurement, Liabilities, Cost of goods sold	0	0
Fair value measurement, Liabilities, Other income, net	2,000,000	1,000,000
Energy Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets, Beginning balance	6,000,000	2,000,000
Fair value measurement, Assets, Other income, net		2,000,000
Fair value measurement, Assets, Other comprehensive income	37,000,000	39,000,000
Fair value measurement, Assets, Transfers into and/or out of Level 3	0	0
Fair value measurement, Assets, Other	6,000,000
Fair value measurement, Assets, Other		6,000,000
Fair value measurement, Assets, Ending balance	49,000,000	49,000,000
Fair value measurement, Assets, Sales	0	0
Fair value measurement, Assets, Cost of goods sold	0	0
Fair value measurement, Assets, Other income , net		2,000,000
Fair value measurement, Liabilities, Beginning balance	11,000,000	4,000,000
Fair value measurement, Liabilities, Other income, net		(1,000,000)
Fair value measurement, Liabilities, Other comprehensive income	(8,000,000)
Fair value measurement, Liabilities, Transfers into and/or out of Level 3	0	0
Fair value measurement, Liabilities, Other	6,000,000
Fair value measurement, Liabilities, Other		6,000,000
Fair value measurement, Liabilities, Ending balance	9,000,000	9,000,000
Fair value measurement, Liabilities, Sales	0	0
Fair value measurement, Liabilities, Cost of goods sold	$ 0	0
Fair value measurement, Liabilities, Other income, net		$ (1,000,000)

Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Parenthetical) (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Fair value measurement, Assets, Purchases, sales and settlements	$ 0	$ 0

Derivatives and Other Financial Instruments - Schedule of Carrying Values and Fair Values of Other Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Carrying Value [Member]
Derivative [Line Items]
Cash and cash equivalents	$ 1,929	$ 1,919
Restricted cash	30	37
Noncurrent receivables	19	17
Available-for-sale securities	68	193
Short-term borrowings	33	38
Commercial paper	0	0
Long-term debt due within one year	774	21
Contingent payment related to an acquisition	132	130
Long-term debt, less amount due within one year	8,278	8,993
Fair Value [Member]
Derivative [Line Items]
Cash and cash equivalents	1,929	1,919
Restricted cash	30	37
Noncurrent receivables	19	17
Available-for-sale securities	68	193
Short-term borrowings	33	38
Commercial paper	0	0
Long-term debt due within one year	791	21
Contingent payment related to an acquisition	132	130
Long-term debt, less amount due within one year	$ 8,670	$ 8,922

Proposed Separation Transaction - Additional Information (Detail) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)
Arconic Inc [Member]
Proposed Separation Transaction [Line Items]
Percentage of shares retained	19.90%	19.90%
Selling, General Administrative, and Other Expenses [Member]
Proposed Separation Transaction [Line Items]
Costs related to proposed transaction, pre-tax	$ 45	$ 63
Costs related to proposed transaction, after-tax	$ 37	$ 54

Subsequent Events - Additional Information (Detail) - shares	6 Months Ended
	Jun. 30, 2016	Jul. 22, 2016	Jul. 21, 2016	Jul. 20, 2016
Subsequent Event [Line Items]
Reverse stock split description	On July 21, 2016, Alcoa’s Board of Directors authorized both a reverse stock split of the Company’s common stock at a ratio of one-for-three.
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of authorized shares of Alcoa's common stock			600,000,000	1,800,000,000
Common stock share outstanding		1,315,374,511