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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2017	Jul. 28, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2
Trading Symbol	ARNC
Entity Registrant Name	Arconic Inc.
Entity Central Index Key	0000004281
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		441,030,999

Statement of Consolidated Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Sales (I)	$ 3,261	$ 3,234	$ 6,453	$ 6,289
Cost of goods sold (exclusive of expenses below)	2,583	2,533	5,075	4,933
Selling, general administrative, and other expenses	204	239	425	444
Research and development expenses	30	32	58	63
Provision for depreciation and amortization	137	133	270	266
Restructuring and other charges (D & E)	26	14	99	30
Operating income	281	283	526	553
Interest expense (L)	183	124	298	245
Other income, net (G)	(171)	(17)	(525)	(29)
Income from continuing operations before income taxes	269	176	753	337
Provision for income taxes	57	123	219	174
Income from continuing operations after income taxes	212	53	534	163
Income from discontinued operations after income taxes (G)		125		26
Net income	212	178	534	189
Less: Income from discontinued operations attributable to noncontrolling interests (G)		43		38
Net income attributable to Arconic	212	135	534	151
Amounts Attributable to Arconic Common Shareholders (J):
Net income	$ 194	$ 118	$ 499	$ 117
Earnings per share - basic
Continuing operations	$ 0.44	$ 0.08	$ 1.13	$ 0.30
Discontinued operations		0.19		(0.03)
Net income per share - basic	0.44	0.27	1.13	0.27
Earnings per share - diluted
Continuing operations	0.43	0.08	1.07	0.29
Discontinued operations		0.19		(0.03)
Net income per share - diluted	0.43	0.27	1.07	0.26
Dividends paid per share	$ 0.06	$ 0.09	$ 0.12	$ 0.18
Weighted Average Shares Outstanding (J):
Average shares outstanding - basic	441	438	440	438
Average shares outstanding - diluted	462	452	500	442

Statement of Consolidated Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income	$ 212	$ 178	$ 534	$ 189
Other comprehensive income (loss), net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	48	67	79	100
Foreign currency translation adjustments	99	77	166	487
Net change in unrealized gains/losses on available-for-sale securities	(101)	3	(134)	4
Net change in unrecognized gains/losses on cash flow hedges	(2)	(137)	3	(219)
Total Other comprehensive income (loss), net of tax	44	10	114	372
Comprehensive income	256	188	648	561
Arconic [Member]
Net income	212	135	534	151
Other comprehensive income (loss), net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	48	65	79	97
Foreign currency translation adjustments	99	45	166	348
Net change in unrealized gains/losses on available-for-sale securities	(101)	3	(134)	4
Net change in unrecognized gains/losses on cash flow hedges	(2)	(153)	3	(233)
Total Other comprehensive income (loss), net of tax	44	(40)	114	216
Comprehensive income	$ 256	95	$ 648	367
Noncontrolling Interests [Member]
Net income		43		38
Other comprehensive income (loss), net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits		2		3
Foreign currency translation adjustments		32		139
Net change in unrecognized gains/losses on cash flow hedges		16		14
Total Other comprehensive income (loss), net of tax		50		156
Comprehensive income		$ 93		$ 194

Consolidated Balance Sheet (unaudited) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 1,785	$ 1,863
Receivables from customers, less allowances of $8 in 2017 and $13 in 2016 (K)	1,170	974
Other receivables (G & K)	357	477
Inventories (F)	2,416	2,253
Prepaid expenses and other current assets	305	325
Total current assets	6,033	5,892
Properties, plants, and equipment	11,738	11,572
Less: accumulated depreciation and amortization	6,231	6,073
Properties, plants, and equipment, net	5,507	5,499
Goodwill	5,215	5,148
Deferred income taxes	1,080	1,234
Investment in common stock of Alcoa Corporation (G & N)	0	1,020
Other noncurrent assets	1,271	1,245
Total Assets	19,106	20,038
Current liabilities:
Short-term borrowings	48	36
Accounts payable, trade	1,667	1,744
Accrued compensation and retirement costs	363	398
Taxes, including income taxes	77	85
Accrued interest payable	124	153
Other current liabilities	379	329
Long-term debt due within one year		4
Total current liabilities	2,658	2,749
Long-term debt, less amount due within one year (L & N)	6,796	8,044
Accrued pension benefits	2,202	2,345
Accrued other postretirement benefits	822	889
Other noncurrent liabilities and deferred credits	875	870
Total liabilities	13,353	14,897
Contingencies and commitments (H)
Arconic shareholders' equity:
Preferred stock	55	55
Mandatory convertible preferred stock	3	3
Common stock	441	438
Additional capital	8,262	8,214
Accumulated deficit	(567)	(1,027)
Accumulated other comprehensive loss (C)	(2,454)	(2,568)
Total Arconic shareholders' equity	5,740	5,115
Noncontrolling interests	13	26
Total equity	5,753	5,141
Total Liabilities and Equity	$ 19,106	$ 20,038

Consolidated Balance Sheet (unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Receivables from customers, allowance	$ 8	$ 13

Statement of Consolidated Cash Flows (unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash from Operations
Net income	$ 534	$ 189
Adjustments to reconcile net income to cash from operations:
Depreciation, depletion and amortization	270	622
Deferred income taxes	27	(78)
Equity income, net of dividends		20
Restructuring and other charges	99	116
Net gain from investing activities - asset sales (G)	(515)	(28)
Net periodic pension benefit cost (M)	108	168
Stock-based compensation	48	55
Other	63	19
Changes in assets and liabilities, excluding effects of acquisitions, divestitures, and foreign currency translation adjustments:
(Increase) in receivables	(282)	(218)
(Increase) in inventories	(150)	(3)
Decrease in prepaid expenses and other current assets	30	4
(Decrease) in accounts payable, trade	(69)	(243)
(Decrease) in accrued expenses	(105)	(301)
Increase in taxes, including income taxes	121	57
Pension contributions	(163)	(147)
(Increase) in noncurrent assets	(60)	(215)
(Decrease) in noncurrent liabilities	(39)	(115)
Cash used for operations	(83)	(98)
Financing Activities
Net change in short-term borrowings (original maturities of three months or less)	9	(5)
Additions to debt (original maturities greater than three months)	512	876
Payments on debt (original maturities greater than three months) (L)	(1,333)	(882)
Proceeds from exercise of employee stock options	26	2
Dividends paid to shareholders	(88)	(114)
Distributions to noncontrolling interests	(14)	(84)
Other	(15)
Cash used for financing activities	(903)	(207)
Investing Activities
Capital expenditures	(229)	(528)
Proceeds from the sale of assets and businesses (E)	(9)	549
Additions to investments	(1)	(8)
Sales of investments (G)	888	275
Net change in restricted cash	10	7
Other (G)	245	15
Cash provided from investing activities	904	310
Effect of exchange rate changes on cash and cash equivalents	4	5
Net change in cash and cash equivalents	(78)	10
Cash and cash equivalents at beginning of year	1,863	1,919
Cash and cash equivalents at end of period	$ 1,785	$ 1,929

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 (Accumulated Deficit) [Member]	Retained Earnings (Accumulated Deficit) [Member] Preferred Class A [Member]	Retained Earnings (Accumulated Deficit) [Member] Preferred Class B [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]
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 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 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
Balance at Dec. 31, 2016	5,141			55	3	438	8,214	(1,027)				(2,568)	26
Net income	534							534
Other comprehensive income (C)	114											114
Cash dividends declared:
Common share, value	(54)							(54)
Preferred share, value		$ (1)	(34)						$ (1)	(34)
Stock-based compensation	48						48
Common stock issued: compensation plans	3					3
Distributions	(14)												(14)
Other	16							15					1
Balance at Jun. 30, 2017	5,753			55	3	441	8,262	(567)				(2,454)	13
Balance at Mar. 31, 2017	5,495			55	3	441	8,249	(768)				(2,498)	13
Net income	212							212
Other comprehensive income (C)	44											44
Cash dividends declared:
Preferred share, value			$ (18)							$ (18)
Stock-based compensation	20						20
Common stock issued: compensation plans	(7)						(7)
Other	7							7
Balance at Jun. 30, 2017	$ 5,753			$ 55	$ 3	$ 441	$ 8,262	$ (567)				$ (2,454)	$ 13

Statement of Changes in Consolidated Equity (unaudited) (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Common stock, dividends per share			$ 0.12	$ 0.06
Preferred Class A [Member]
Preferred, dividends per share	$ 0.9375	$ 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, 2017
Accounting Policies [Abstract]
Basis of Presentation	A. Basis of Presentation The interim Consolidated Financial Statements of Arconic Inc. and its subsidiaries (“Arconic” 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 2016 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 Arconic’s Annual Report on Form 10-K for the year ended December 31, 2016, which includes all disclosures required by GAAP. Certain amounts in previously issued financial statements were reclassified to conform to the current period presentation. The separation of Alcoa Inc. into two standalone, publicly-traded companies, Arconic Inc. (the new name for Alcoa Inc.) and Alcoa Corporation, became effective on November 1, 2016 (the “Separation Transaction”). The financial results of Alcoa Corporation for all periods prior to the Separation Transaction have been retrospectively reflected in the Statement of Consolidated Operations as discontinued operations and, as such, have been excluded from continuing operations and segment results for the second quarter and six months ended June 30, 2016. The cash flows, equity and comprehensive income related to Alcoa Corporation have not been segregated and are included in the Statement of Consolidated Cash Flows, Statement of Changes in Consolidated Equity and Statement of Consolidated Comprehensive Income, respectively, for the second quarter and six months ended June 30, 2016. Pursuant to the authorization provided at a special meeting of Arconic common shareholders held on October 5, 2016, shareholders approved a 1-for-3 reverse stock split of Arconic’s outstanding and authorized shares of common stock (the “Reverse Stock Split”). As a result of the Reverse Stock Split, every three shares of issued and outstanding common stock were combined into one issued and outstanding share of common stock, without any change in the par value per share. The Reverse Stock Split reduced the number of shares of common stock outstanding from approximately 1.3 billion shares to approximately 0.4 billion shares. The Company’s common stock began trading on a reverse stock split-adjusted basis on the New York Stock Exchange on October 6, 2016.

Recently Adopted and Recently Issued Accounting Guidance	6 Months Ended
	Jun. 30, 2017
Accounting Changes and Error Corrections [Abstract]
Recently Adopted and Recently Issued Accounting Guidance	B. Recently Adopted and Recently Issued Accounting Guidance Adopted In March 2016, the Financial Accounting Standards Board (“FASB”) issued changes to employee share-based payment accounting. Previously, an entity determined for each share-based payment award whether the difference between the deduction for tax purposes and the compensation cost recognized for financial reporting purposes resulted in either an excess tax benefit or a tax deficiency. Excess tax benefits were recognized in additional paid-in capital; tax deficiencies were recognized either as an offset to accumulated excess tax benefits, if any, or in the income statement. Excess tax benefits were not recognized until the deduction reduced 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 changed. Previously, excess tax benefits were 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. Additionally, for a share-based award to qualify for equity classification it previously could not be partially settled 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 became effective for Arconic on January 1, 2017. Management has concluded that the adoption of this guidance did not have a material effect 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 became effective for Arconic on January 1, 2017. Management has concluded that the adoption of this guidance did not have a material impact 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 became effective for Arconic on January 1, 2017. Management has determined that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements. In October 2016, the FASB issued changes to the accounting for Intra-Entity transactions, other than inventory. Previously, no immediate tax impact was recognized in the consolidated financial statements as a result of intra-entity transfers of assets. The previous standard precluded an entity from reflecting a tax benefit or expense from an intra-entity transfer between entities that file separate tax returns, whether or not such entities were in different tax jurisdictions, until the asset was sold to a third party or otherwise recovered. The previous standard also prohibited recognition by the buyer of a deferred tax asset for the temporary difference arising from the excess of the buyer’s tax basis over the cost to the seller. The changes require the current and deferred income tax consequences of the intra-entity transfer to be recorded when the transaction occurs. The exception to defer the tax consequences of inventory transactions is maintained. These changes became effective for Arconic on January 1, 2017. Management has determined that the adoption of this guidance did not have a material impact on the Consolidated Financial Statements. In January 2017, the FASB issued changes to the subsequent measurement of goodwill by eliminating step 2 from the goodwill impairment test, which previously required measurement of any goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. An entity will perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value without exceeding the total amount of goodwill allocated to that reporting unit. Arconic has elected to early adopt this guidance as of January 1, 2017, and will apply it on a prospective basis. Management does not anticipate that the adoption of these changes will have a material impact on the Consolidated Financial Statements. In January 2017, the FASB issued changes which narrow the definition of a business and require an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets, which would not constitute the acquisition of a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs. Arconic has elected to early adopt this guidance as of January 1, 2017, and will apply it on a prospective basis. Management does not anticipate that the adoption of these changes will have a material impact on the Consolidated Financial Statements. Issued In May 2014, the FASB issued changes to the recognition of revenue from contracts with customers. These changes created a comprehensive framework for all entities in all industries to apply in the determination of when to recognize revenue and, therefore, supersede virtually all existing revenue recognition requirements and guidance. This framework is expected to result in less complex guidance in application while providing a consistent and comparable methodology for revenue recognition. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this principle, an entity should apply the following steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract(s), (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract(s), and (v) recognize revenue when, or as, the entity satisfies a performance obligation. In August 2015, the FASB deferred the effective date of the new guidance by one year, making these changes effective for Arconic on January 1, 2018. Arconic expects to adopt the new guidance using the modified retrospective transition approach. The Company has formed a project assessment and adoption team and is currently reviewing contract terms and assessing the impact of adopting the new guidance on the Consolidated Financial Statements. Based on the Company’s initial contract assessment, it believes that revenue under certain contracts will continue to be recognized at a point in time, while revenue under other contracts, primarily within the Engineered Products and Solutions segment, may be recognized over time due to no alternative use for the product as well as an enforceable right of payment from the customer in the event of termination of the contract. The Company is continuing to assess the impact that over-time revenue recognition will have on its Consolidated Financial Statements, therefore an estimate of the impact of adopting this standard is not currently determinable. 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 Arconic on January 1, 2018. Management has determined that the potential impact of these changes on the Consolidated Financial Statements will not be material. 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 Arconic on January 1, 2019. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. An estimate of the impact of this standard is not currently determinable. In June 2016, the FASB added a new impairment model (known as the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance its estimate of expected credit losses. The CECL model applies to most debt instruments, trade receivables, lease receivables, financial guarantee contracts, and other loan commitments. The CECL model does not have a minimum threshold for recognition of impairment losses and entities will need to measure expected credit losses on assets that have a low risk of loss. These changes become effective for Arconic on January 1, 2020. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. In August 2016, the FASB issued changes to the classification of certain cash receipts and cash payments within the statement of cash flows. The guidance identifies eight specific cash flow items and the sections where they must be presented within the statement of cash flows. These changes become effective for Arconic on January 1, 2018 and early adoption is permitted. Management does not expect these changes to have a material impact on the Consolidated Financial Statements. In November 2016, the FASB issued changes to the classification of cash and cash equivalents within the cash flow statement. Restricted cash and restricted cash equivalents will be included within the cash and cash equivalents line on the cash flow statement and a reconciliation must be prepared to the statement of financial position. Transfers between restricted cash and restricted cash equivalents and cash and cash equivalents will no longer be presented as cash flow activities in the statement of cash flows and material balances of restricted cash and restricted cash equivalents must disclose information regarding the nature of the restrictions. These changes become effective for Arconic on January 1, 2018. Management has determined that the adoption of these changes will not have a material impact on the Consolidated Financial Statements. In March 2017, the FASB issued changes to shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. These changes become effective for Arconic on January 1, 2019 and early adoption is permitted. Management has determined that the adoption of these changes will not have a material impact on the Consolidated Financial Statements. In March 2017, the FASB issued changes to the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires registrants to present the service cost component of net periodic benefit cost in the same income statement line item or items as other employee compensation costs arising from services rendered during the period. In addition, only the service cost component will be eligible for asset capitalization. Registrants will present the other components of net periodic benefit cost separately from the service cost component; and, the line item or items used in the income statement to present the other components of net periodic benefit cost must be disclosed. These changes become effective for Arconic on January 1, 2018, including interim periods within those fiscal years. The new standard must be adopted retrospectively for the presentation of the service cost component and the other components of net periodic benefit cost in the income statement, and prospectively for the asset capitalization of the service cost component of net periodic benefit cost. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements. For 2017, the Company expects to record non-service related net periodic pension cost and net periodic postretirement benefit cost of approximately $150 which would be recorded separately in the Other income, net line item in the Statement of Consolidated Operations upon the adoption of this standard. Management is currently evaluating the potential impact of prospectively adopting the asset capitalization of only the service cost component. In May 2017, the FASB issued clarification to guidance on the modification accounting criteria for share-based payment awards. The new guidance requires registrants to apply modification accounting unless three specific criteria are met. The three criteria are 1) the fair value or the award is the same before and after the modification, 2) the vesting conditions are the same before and after the modification and 3) the classification as a debt or equity award is the same before and after the modification. These changes become effective for Arconic on January 1, 2018 and are to be applied prospectively to new awards granted after adoption. Management is currently evaluating the potential impact of these changes on the Consolidated Financial Statements.

Accumulated Other Comprehensive Loss

6 Months Ended

Jun. 30, 2017

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 Arconic’s shareholders and noncontrolling interests:


	Arconic						Noncontrolling Interests
	Second quarter ended June 30,						Second quarter ended June 30,
	2017			2016			2017			2016
Pension and other postretirement benefits (M)
Balance at beginning of period	$	(1,979	)	$	(3,579	)	$	—		$	(55	)
Other comprehensive income:
Unrecognized net actuarial loss and prior service cost		17			(5	)		—			1
Tax (expense) benefit		(5	)		3			—			—

Total Other comprehensive loss before reclassifications, net of tax		12			(2	)		—			1

Amortization of net actuarial loss and prior service cost⁽¹⁾		56			104			—
Tax (expense) benefit⁽²⁾		(20	)		(37	)		—			1

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		36			67			—			1

Total Other comprehensive income		48			65			—			2

Balance at end of period	$	(1,931	)	$	(3,514	)	$	—		$	(53	)

Foreign currency translation
Balance at beginning of period	$	(622	)	$	(2,109	)	$	(2	)	$	(673	)
Other comprehensive income⁽³⁾		99			45			—			32

Balance at end of period	$	(523	)	$	(2,064	)	$	(2	)	$	(641	)

Available-for-sale securities
Balance at beginning of period	$	99		$	(4	)	$	—		$	—
Other comprehensive (loss) income⁽⁴⁾		(101	)		3			—			—

Balance at end of period	$	(2	)	$	(1	)	$	—		$	—

Cash flow hedges
Balance at beginning of period	$	4		$	517		$	—		$	(5	)
Other comprehensive income (loss):
Net change from periodic revaluations		(4	)		(225	)		—			18
Tax benefit (expense)		1			66			—			(5	)

Total Other comprehensive income (loss) before reclassifications, net of tax		(3	)		(159	)		—			13

Net amount reclassified to earnings		1			7						5
Tax expense⁽²⁾		—			(1	)		—			(2	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		1			6			—			3

Total Other comprehensive income (loss)		(2	)		(153	)		—			16

Balance at end of period	$	2		$	364		$	—		$	11

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

⁽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⁾	Realized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁵⁾	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 2 through 4.


	Arconic						Noncontrolling Interests
	Six months ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Pension and other postretirement benefits (M)
Balance at beginning of period	$	(2,010	)	$	(3,611	)	$	—		$	(56	)
Other comprehensive income:
Unrecognized net actuarial loss and prior service cost		11			(64	)		—			1
Tax (expense) benefit		(4	)		26			—			—

Total Other comprehensive loss before reclassifications, net of tax		7			(38	)		—			1

Amortization of net actuarial loss and prior service cost⁽¹⁾		111			208			—			2
Tax expense⁽²⁾		(39	)		(73	)		—			—

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		72			135			—			2

Total Other comprehensive income		79			97			—			3

Balance at end of period	$	(1,931	)	$	(3,514	)	$	—		$	(53	)

Foreign currency translation
Balance at beginning of period	$	(689	)	$	(2,412	)	$	(2	)	$	(780	)
Other comprehensive income⁽³⁾		166			348			—			139

Balance at end of period	$	(523	)	$	(2,064	)	$	(2	)	$	(641	)

Available-for-sale securities
Balance at beginning of period	$	132		$	(5	)	$	—		$	—
Other comprehensive (loss) income⁽⁴⁾		(134	)		4			—			—

Balance at end of period	$	(2	)	$	(1	)	$	—		$	—

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

Total Other comprehensive income (loss) before reclassifications, net of tax		2			(239	)		—			11

Net amount reclassified to earnings		1			5						5
Tax benefit (expense)⁽²⁾		—			1			—			(2	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		1			6			—			3

Total Other comprehensive income (loss)		3			(233	)		—			14

Balance at end of period	$	2		$	364		$	—		$	11

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

⁽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⁾	Realized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁵⁾	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 2 through 4.

Restructuring and Other Charges

6 Months Ended

Jun. 30, 2017

Restructuring and Related Activities [Abstract]

Restructuring and Other Charges

D. Restructuring and Other Charges

In the second quarter of 2017, Arconic recorded Restructuring and other charges of $26 ($17 after-tax), which included $29 ($19 after-tax) for layoff costs related to cost reduction initiatives including the separation of approximately 352 employees (129 in the Engineered Products and Solutions segment, 110 in the Global Rolled Products segment, 93 in the Transportation and Construction Solutions segment, and 20 in Corporate); a net charge of $4 ($3 after-tax) for other miscellaneous items; a net benefit of $6 ($4 after-tax), for the reversal of forfeited executive stock compensation of $13, partially offset by a charge of $7 for the related severance; and a favorable benefit of $1 ($1 after-tax) for the reversal of a number of small layoff reserves related to prior periods.

In the first six months of 2017, Arconic recorded Restructuring and other charges of $99 ($86 after-tax), which included $48 ($32 after-tax) for layoff costs related to cost reduction initiatives including the separation of approximately 680 employees (243 in the Engineered Products and Solutions segment, 242 in the Global Rolled Products segment, 133 in the Transportation and Construction Solutions segment, and 62 in Corporate); a charge of $60 ($60 after-tax) related to the sale of the Fusina, Italy rolling mill; a net benefit of $6 ($4 after-tax), for the reversal of forfeited executive stock compensation of $13, partially offset by a charge of $7 for the related severance; a net benefit of $1 ($0 after-tax) for other miscellaneous items; and a favorable benefit of $2 ($2 after-tax) for the reversal of a number of small layoff reserves related to prior periods.

In the second quarter of 2016, Arconic recorded Restructuring and other charges of $14 ($9 after-tax), which included $13 ($8 after-tax) for layoff costs related to cost reduction initiatives and the separation of Alcoa Inc. (see Note G), including the separation of approximately 540 employees (300 in the Engineered Products and Solutions segment and 240 in the Transportation and Construction Solutions segment); a net charge of $7 ($4 after-tax) for other miscellaneous items; and a favorable benefit of $6 ($3 after-tax) for the reversal of a number of small layoff reserves related to prior periods.

In the first six months of 2016, Arconic recorded Restructuring and other charges of $30 ($20 after-tax), which included $30 ($19 after-tax) for layoff costs related to cost reduction initiatives and the separation of Alcoa Inc. (see Note G), including the separation of approximately 1,070 employees (800 in the Engineered Products and Solutions segment, 30 in the Global Rolled Products segment, and 240 in the Transportation and Construction Solutions segment); a net charge of $7 ($4 after-tax) for other miscellaneous items; and a net favorable benefit of $7 ($3 after-tax) for the reversal of a number of small layoff reserves related to prior periods.

Arconic 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,
	2017			2016			2017		2016
Engineered Products and Solutions	$	8		$	9		$	14	$	17
Global Rolled Products		17			—			74		2
Transportation and Construction Solutions		6			8			9		8

Segment Total		31			17			97		27
Corporate		(5	)		(3	)		2		3

Total Restructuring and other charges	$	26		$	14		$	99	$	30

As of June 30, 2017, approximately 65 of the 680 employees associated with 2017 restructuring programs, approximately 1,170 of the 1,770 employees (previously 1,800) associated with 2016 restructuring programs, and approximately 1,120 of the 1,220 employees (previously 1,240) associated with the 2015 restructuring programs were separated. The total number of employees associated with both the 2016 and 2015 restructuring programs was updated to reflect employees who, initially identified for separation, accepted other positions within Arconic, as well as natural attrition. Most of the remaining separations for the 2017 restructuring programs and all of the remaining separations for the 2016 and 2015 restructuring programs are expected to be completed by the end of 2017.

In the 2017 second quarter and six-month period, cash payments of $1 and $2, respectively, were made against layoff reserves related to 2017 restructuring programs, cash payments of $6 and $20, respectively, were made against layoff reserves related to 2016 restructuring programs, and cash payments of $1 and $4, respectively, were made against the layoff reserves related to 2015 restructuring programs.

Activity and reserve balances for restructuring charges were as follows:


	Layoff costs			Other exit costs			Total
Reserve balances at December 31, 2015	$	84		$	9		$	93
2016:
Cash payments		(73	)		(13	)		(86	)
Restructuring charges		70			27			97
Other*		(31	)		(14	)		(45	)

Reserve balances at December 31, 2016		50			9			59

2017:
Cash payments		(26	)		(5	)		(31	)
Restructuring charges		43			—			43
Other*		10			(1	)		9

Reserve balances at June 30, 2017	$	77		$	3		$	80

Other includes reversals of previously recorded restructuring charges and the effects of foreign currency translation. In 2017, Other for layoff costs includes the reclassification of a stock awards reversal of $13. In 2016, Other for other exit costs also included reclassifications of $8 in asset retirement, $2 in environmental obligations and $4 in legal obligations as these liabilities were included in Arconic’s separate reserves for asset retirement obligations, environmental remediation and legal costs.

The remaining reserves are expected to be paid in cash during the remainder of 2017, except for approximately $10 to $12, which is expected to be paid within the next year for layoffs.

Acquisitions and Divestitures	6 Months Ended
Acquisitions and Divestitures	Jun. 30, 2017
Business Combinations [Abstract]
Acquisitions and Divestitures	E. Acquisitions and Divestitures In April 2016, Arconic completed the sale of the Remmele Medical business to LISI MEDICAL for $102 in cash ($99 net of transaction costs). This business, which was part of the RTI International Metals acquisition, manufactures precision-machined metal products for customers in the minimally invasive surgical device and implantable device markets. While owned by Arconic, the operating results and assets and liabilities of this business were included in the Engineered Products and Solutions segment. Remmele Medical generated third-party sales of approximately $20 from January 1, 2016 through the divestiture date, and, at the time of the divestiture, had approximately 330 employees. This transaction is no longer subject to post-closing adjustments. In March 2017, Arconic completed the sale of its Fusina, Italy rolling mill to Slim Aluminium. While owned by Arconic, the operating results and assets and liabilities of the Fusina, Italy rolling mill were included in the Global Rolled Products segment. As part of the transaction, Arconic injected $10 of cash into the business and provided a third-party guarantee with a fair value of $5 related to Slim Aluminium’s environmental remediation. The Company recorded a loss on the sale of $60, which was recorded in Restructuring and other charges (see Note D) on the Statement of Consolidated Operations. The rolling mill generated third-party sales of approximately $37 and $72 for the six-month periods ended June 30, 2017 and 2016, respectively. At the time of the divestiture, the rolling mill had approximately 312 employees.

Inventories

6 Months Ended

Jun. 30, 2017

Inventory Disclosure [Abstract]

Inventories

F. Inventories


	June 30, 2017		December 31, 2016
Finished goods	$	652	$	625
Work-in-process		1,300		1,144
Purchased raw materials		383		408
Operating supplies		81		76

Total inventories	$	2,416	$	2,253

At June 30, 2017 and December 31, 2016, the total amount of inventories valued on a LIFO basis was $1,057 and $947, respectively. If valued on an average-cost basis, total inventories would have been $401 and $371 higher at June 30, 2017 and December 31, 2016, respectively.

Separation Transaction and Discontinued Operations

6 Months Ended

Jun. 30, 2017

Discontinued Operations and Disposal Groups [Abstract]

Separation Transaction and Discontinued Operations

G. Separation Transaction and Discontinued Operations

On November 1, 2016, Arconic completed the Separation Transaction. Alcoa Inc., which was re-named Arconic Inc., continued to own the Engineered Products and Solutions, the Global Rolled Products (except for the Warrick, IN rolling operations and the equity interest in the rolling mill at the joint venture in Saudi Arabia), and the Transportation and Construction Solutions segments. Alcoa Corporation included the Alumina and Primary Metals segments and the Warrick, IN rolling operations and equity interest in the rolling mill at the joint venture in Saudi Arabia, both of which were formerly part of Arconic’s Global Rolled Products segment. The results of operations of Alcoa Corporation for the second quarter and six months ended June 30, 2016 are presented as discontinued operations in the Statement of Consolidated Operations.

Arconic completed the Separation Transaction by distribution on November 1, 2016 of 80.1% of the outstanding common stock of Alcoa Corporation to the Company’s shareholders of record as of the close of business on October 20, 2016. Arconic retained 19.9% of the Alcoa Corporation common stock (36,311,767 shares).

In February 2017, the Company sold 23,353,000 shares of Alcoa Corporation common stock at $38.03 per share, which resulted in cash proceeds of $888 which were recorded in Sale of investments within Investing Activities in the Statement of Consolidated Cash Flows and a gain of $351, which was recorded in Other income, net in the accompanying Statement of Consolidated Operations.

In April and May 2017, the Company acquired a portion of its outstanding notes held by two investment banks (the “Investment Banks”) in exchange for cash and the Company’s remaining 12,958,767 Alcoa Corporation shares (valued at $35.91 per share) (the “Debt-for-Equity Exchange”) (See Note L). A gain of $167 on the Debt-for-Equity Exchange was recorded in Other income, net in the accompanying Statement of Consolidated Operations. The share exchange had no impact on the Statement of Consolidated Cash Flows.

The Company had recorded the retained interest as a cost method investment in Investment in common stock of Alcoa Corporation in the accompanying Consolidated Balance Sheet. The fair value of Arconic’s retained interest in Alcoa Corporation was $0 and $1,020 at June 30, 2017 and December 31, 2016, respectively. The fair value was based on the closing stock price of Alcoa Corporation as of June 30, 2017, and December 31, 2016 multiplied by the number of shares of Alcoa Corporation common stock owned by the Company at those respective dates. As of May 4, 2017, the Company no longer maintains a retained interest in Alcoa Corporation common stock.

In connection with the Separation Transaction, on October 31, 2016, Arconic and Alcoa Corporation entered into a Toll Processing and Services Agreement (the “Toll Processing Agreement”) pursuant to which Arconic provides can body stock from its Tennessee operations to Alcoa Corporation’s Warrick, Indiana rolling mill. Aluminum for the can body stock is supplied by Alcoa Corporation. The Toll Processing Agreement expires on December 31, 2018, unless sooner terminated by the parties. Tolling revenues for the second quarter and six months ended June 30, 2017 and accounts receivable at June 30, 2017 were not material to the consolidated results of operations and financial position, respectively.

As part of the Separation Transaction, Arconic had recorded a receivable in the December 2016 Consolidated Balance Sheet for the net after-tax proceeds from Alcoa Corporation’s sale of the Yadkin Hydroelectric Project. The transaction closed in the first quarter of 2017 and the Company received proceeds of $238 in the first quarter of 2017 and the remaining $5 in the second quarter of 2017. The $243 proceeds were included in Other within Investing Activities in the Statement of Consolidated Cash Flows.

The results of operations of Alcoa Corporation are presented as discontinued operations in the Statement of Consolidated Operations as summarized below:


	Second quarter ended June 30, 2016			Six months ended June 30, 2016
Sales	$	2,061		$	3,953
Cost of goods sold (exclusive of expenses below)		1,683			3,324
Selling, general administrative, and other expenses		47			102
Research and development expenses		7			18
Provision for depreciation, depletion and amortization		177			352
Restructuring and other charges		9			86
Interest expense		5			11
Other (income) expense, net		(21	)		26

Income from discontinued operations before income taxes		154			34
Provision for income taxes		29			8

Income from discontinued operations after income taxes		125			26
Less: Net income from discontinued operations attributable to noncontrolling interests		43			38

Net income (loss) from discontinued operations	$	82		$	(12	)

The cash flows related to Alcoa Corporation have not been segregated and are included in the Statement of Consolidated Cash Flows for all periods presented. The following table presents depreciation, depletion and amortization, restructuring and other charges, and purchases of property, plant and equipment of the discontinued operations related to Alcoa Corporation:


	Six months ended June 30,
	2016
Depreciation, depletion and amortization	$	352
Restructuring and other charges	$	86
Capital expenditures	$	172

Contingencies and Commitments	6 Months Ended
Contingencies and Commitments	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	H. Contingencies and Commitments Contingencies Environmental Matters Arconic 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. Arconic’s remediation reserve balance was $301 at June 30, 2017 and $308 at December 31, 2016 (of which $42 and $48, respectively, was classified as a current liability), and reflects the most probable costs to remediate identified environmental conditions for which costs can be reasonably estimated. Payments related to remediation expenses applied against the reserve were $5 and $7 in the second quarter and six months ended June 30, 2017, respectively. This amount includes expenditures currently mandated, as well as those not required by any regulatory authority or third party. Included in annual operating expenses are the recurring costs of managing hazardous substances and environmental programs. These costs are estimated to be approximately 1% or less of cost of goods sold. The following discussion provides details regarding the current status of certain significant reserves related to current or former Arconic sites. Massena West, NY—Arconic has an ongoing remediation project related to the Grasse River, which is adjacent to Arconic’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 in a Record of Decision 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, 2017 and December 31, 2016, the reserve balance associated with this matter was $224 and $228, respectively. Arconic is in the planning and design phase, which is expected to be completed in 2017. Following that, 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. Tax Pursuant to the Tax Matters Agreement entered into between Arconic and Alcoa Corporation in connection with the Separation Transaction, Arconic shares responsibility with Alcoa Corporation, and Alcoa Corporation has agreed to partially indemnify Arconic, with respect to the following matter. As previously reported, 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, Arconic filed an appeal of this second assessment in Spain’s Central Tax Administrative Court, which was denied in January 2015. Arconic filed another appeal of this second assessment in Spain’s National Court in March 2015. The combined assessments, remeasured for a tax rate change enacted in November 2014, total $283 (€248), including interest. On January 16, 2017, Spain’s National Court issued a decision in favor of the Company related to the assessment received in September 2010. The Spanish Tax Administration did not file an appeal within the applicable period. A further decision is expected on the application of this ruling to the overall assessment. Spain’s National Court has not yet rendered a decision related to the assessment received in July 2013. 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, which would be shared between Arconic and Alcoa Corporation as provided for in the Tax Matters Agreement related to the Separation Transaction. 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. Reynobond PE Regulatory investigations are being conducted in connection with the fatal Grenfell Tower fire in London, UK on June 13, 2017. A French subsidiary of Arconic, Arconic Architectural Products SAS (AAP SAS), supplied a product, Reynobond PE, to its customer, a cladding system fabricator, which used the product as one component of the overall cladding system on Grenfell Tower. The fabricator supplied its portion of the cladding system to the façade installer, who then completed and installed the system under the direction of the general contractor. Neither Arconic nor AAP SAS was involved in the design or installation of the system used at the Tower, nor did it have a role in any other aspect of the building’s refurbishment or original design. In July 2017, three purported class action complaints were filed against Arconic and certain officers, directors and/or other parties, alleging that, in light of the Grenfell Tower fire, certain Company filings with the Securities and Exchange Commission contained false and misleading disclosures and omissions in violation of the federal securities laws. While the Company believes that these cases are without merit and intends to challenge them vigorously, there can be no assurances regarding the ultimate resolution of these matters. Given the preliminary nature of these matters and the uncertainty of litigation, the Company cannot reasonably estimate at this time the likelihood of an unfavorable outcome or the possible loss or range of losses in the event of an unfavorable outcome. Other In addition to the matters discussed above, various other lawsuits, claims, and proceedings have been or may be instituted or asserted against Arconic, 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 currently be determined because of the considerable uncertainties that exist. Therefore, it is possible that the Company’s liquidity or results of operations in a 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 results of operations, financial position or cash flows of the Company. Commitments Guarantees At June 30, 2017, Arconic had outstanding bank guarantees related to tax matters, outstanding debt, workers’ compensation, environmental obligations, energy contracts, and customs duties, among others. The total amount committed under these guarantees, which expire at various dates between 2017 and 2026, was $46 at June 30, 2017. Pursuant to the Separation and Distribution Agreement between Arconic and Alcoa Corporation, Arconic was required to provide maximum potential future payment guarantees for Alcoa Corporation issued on behalf of a third party of $314 and $354 at June 30, 2017 and December 31, 2016. These guarantees expire at various times between 2017 and 2024, and relate to project financing for Alcoa Corporation’s aluminum complex in Saudi Arabia. Furthermore, Arconic was required to provide guarantees up to an estimated present value amount of $1,600 related to two long-term supply agreements for energy for Alcoa Corporation facilities. In accordance with the Separation and Distribution Agreement, Arconic is only liable for these guaranteed amounts in the event of an Alcoa Corporation payment default. In December 2016, Arconic entered into a one-year claims purchase agreement with a bank covering claims up to $245 related to the Saudi Arabian aluminum complex and two long-term energy supply agreements. Most of the premium related to this claims purchase agreement is being paid by Alcoa Corporation. At June 30, 2017 and December 31, 2016, the combined fair value of the three required guarantees was $36 and $35, respectively, which was included in Other noncurrent liabilities and deferred credits on the accompanying Consolidated Balance Sheet. Arconic was also required to provide guarantees of $50 related to two Alcoa Corporation energy supply contracts. These guarantees expired in March 2017. Additionally, Arconic was required to provide guarantees of $53 related to certain Alcoa Corporation environmental liabilities. Notification of a change in guarantor to Alcoa Corporation was made to the appropriate environmental agencies and as such, Arconic no longer provides these guarantees. Letters of Credit Arconic has outstanding letters of credit, primarily related to workers’ compensation and environmental obligations. The total amount committed under these letters of credit, which automatically renew or expire at various dates, primarily in 2017, was $133 at June 30, 2017. Pursuant to the Separation and Distribution Agreement, Arconic was required to retain letters of credit of $61 that had previously been provided related to both Arconic and Alcoa Corporation workers’ compensation claims which occurred prior to November 1, 2016. Alcoa Corporation’s workers’ compensation claims and letter of credit fees paid by Arconic are being billed to and are being fully reimbursed by Alcoa Corporation. Additionally, Arconic was required to provide letters of credit totaling $103 for certain Alcoa Corporation equipment leases and energy contracts. The entire $103 of outstanding letters of credit were cancelled in 2017 when Alcoa Corporation issued its own letters of credit to cover these obligations. Surety Bonds Arconic has outstanding surety bonds, primarily related to tax matters, contract performance, workers’ compensation, environmental-related matters, and customs duties. The total amount committed under these surety bonds, which expire at various dates, primarily in 2017, was $127 at June 30, 2017. Pursuant to the Separation and Distribution Agreement, Arconic was required to provide surety bonds related to Alcoa Corporation workers’ compensation claims which occurred prior to November 1, 2016 and, as a result, Arconic has $25 in outstanding surety bonds relating to these liabilities. Alcoa Corporation workers’ compensation claims and surety bond fees paid by Arconic are being billed to and are being fully reimbursed by Alcoa Corporation.

Segment Information

6 Months Ended

Jun. 30, 2017

Segment Reporting [Abstract]

Segment Information

I. Segment Information

Arconic is a producer of multi-material products including sheet, plate, precision castings, forgings, rolled rings, extrusions, wheels and fasteners. Arconic’s products are used worldwide in transportation (including aerospace, automotive, truck, trailer, rail, and shipping), packaging, building and construction, oil and gas, defense, and industrial applications. Arconic’s segments are organized by product on a worldwide basis. In the first quarter of 2017, the Company changed its primary measure of segment performance from After-tax operating income (ATOI) to Adjusted earnings before interest, tax, depreciation and amortization (“Adjusted EBITDA”). Segment performance under Arconic’s management reporting system is evaluated based on a number of factors; however, the primary measure of performance is Adjusted EBITDA. Arconic’s definition of Adjusted EBITDA is net margin plus an add-back for depreciation and amortization and special items. Net margin is equivalent to Sales minus the following items: Cost of goods sold; Selling, general administrative, and other expenses; Research and development expenses; and Provision for depreciation and amortization. The Adjusted EBITDA presented may not be comparable to similarly titled measures of other companies.

Items required to reconcile Combined segment adjusted EBITDA to Net income attributable to Arconic include: the Provision for depreciation and amortization; Restructuring and other charges; the impact of LIFO inventory accounting; metal price lag (the timing difference created when the average price of metal sold differs from the average cost of the metal when purchased by the respective segment - generally, when the price of metal increases, metal price lag is favorable, and when the price of metal decreases, metal price lag is unfavorable); corporate expense (general administrative and selling expenses of operating the corporate headquarters and other global administrative facilities and corporate research and development expenses); other items, including intersegment profit eliminations; Other income, net; Interest expense; Income tax expense; and the results of discontinued operations. Prior period information has been recast to conform to current year presentation.

The operating results of Arconic’s reportable segments were as follows:


	Engineered Products and Solutions		Global Rolled Products		Transportation and Construction Solutions		Combined Segment
Second quarter ended June 30, 2017
Sales:
Third-party sales	$	1,484	$	1,268	$	501	$	3,253
Intersegment sales		—		37		—		37

Total sales	$	1,484	$	1,305	$	501	$	3,290

Profit and loss:
Depreciation and amortization		66		51		12		129
Adjusted EBITDA		310		164		82		556

Second quarter ended June 30, 2016
Sales:
Third-party sales	$	1,465	$	1,316	$	467	$	3,248
Intersegment sales		—		29		—		29

Total sales	$	1,465	$	1,345	$	467	$	3,277

Profit and loss:
Depreciation and amortization		62		50		12		124
Adjusted EBITDA		329		163		76		568


	Engineered Products and Solutions		Global Rolled Products		Transportation and Construction Solutions		Combined Segment
Six months ended June 30, 2017
Sales:
Third-party sales	$	2,969	$	2,517	$	950	$	6,436
Intersegment sales		—		71		—		71

Total sales	$	2,969	$	2,588	$	950	$	6,507

Profit and loss:
Depreciation and amortization		130		101		24		255
Adjusted EBITDA		616		335		154		1,105

Six months ended June 30, 2016
Sales:
Third-party sales	$	2,914	$	2,500	$	896	$	6,310
Intersegment sales		—		58		—		58

Total sales	$	2,914	$	2,558	$	896	$	6,368

Profit and loss:
Depreciation and amortization		127		100		23		250
Adjusted EBITDA		634		318		140		1,092

The following table reconciles Combined segment adjusted EBITDA to Net income attributable to Arconic:


	Second quarter ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Combined segment adjusted EBITDA	$	556		$	568		$	1,105		$	1,092
Unallocated amounts:
Depreciation and amortization		(137	)		(133	)		(270	)		(266	)
Restructuring and other charges		(26	)		(14	)		(99	)		(30	)
Impact of LIFO		(11	)		(13	)		(30	)		(25	)
Metal price lag		19			6			41			6
Corporate expense		(91	)		(115	)		(182	)		(191	)
Other		(29	)		(16	)		(39	)		(33	)

Operating income	$	281		$	283		$	526		$	553
Other income, net		171			17			525			29
Interest expense		(183	)		(124	)		(298	)		(245	)

Income from continuing operations before income taxes	$	269		$	176		$	753		$	337
Income taxes		(57	)		(123	)		(219	)		(174	)
Discontinued operations		—			82			—			(12	)

Net income attributable to Arconic	$	212		$	135		$	534		$	151

Earnings Per Share

6 Months Ended

Jun. 30, 2017

Earnings Per Share [Abstract]

Earnings Per Share

J. 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 number of shares and per share amounts for all periods presented below have been updated to reflect the Reverse Stock Split (see Note A).

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


	Second quarter ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Income from continuing operations after income taxes	$	212		$	53		$	534		$	163
Less: Preferred stock dividends declared		(18	)		(17	)		(35	)		(35	)

Income from continuing operations available to Arconic common shareholders		194			36			499			128
Income (loss) from discontinued operations after income taxes and noncontrolling interests		—			82			—			(12	)

Net income available to Arconic common shareholders - basic		194			118			499			116
Add: Interest expense related to convertible notes		2			2			4			—
Add: Dividends related to mandatory convertible preferred stock		—			—			34			—

Net income available to Arconic common shareholders - diluted	$	196		$	120		$	537		$	116

Average shares outstanding - basic		441			438			440			438
Effect of dilutive securities:
Stock options		2			1			2			—
Stock and performance awards		5			4			5			4
Mandatory convertible preferred stock		—			—			39			—
Convertible notes		14			9			14			—

Average shares outstanding - diluted		462			452			500			442

The following shares were excluded from the calculation of Average shares outstanding – diluted as their effect was anti-dilutive.


	Second quarter ended June 30,				Six months ended June 30,
	2017		2016		2017		2016
Mandatory convertible preferred stock		39		26		—		26
Convertible notes		—		—		—		9

Additionally, options to purchase 7 million shares of common stock at a weighted average exercise price of $28.85 and options to purchase 8 million shares of common stock at a weighted average exercise price of $38.18 were outstanding as of June 30, 2017 and 2016, respectively, but were not included in the computation of diluted EPS because their effect was anti-dilutive as the exercise price of the options was greater than the average market price of Arconic’s common stock.

Receivables	6 Months Ended
Receivables	Jun. 30, 2017
Transfers and Servicing [Abstract]
Receivables	K. Receivables Arconic 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 using a bankruptcy remote special purpose entity, which is a consolidated subsidiary of Arconic. This arrangement provides for minimum funding of $200 up to a maximum of $400 for receivables sold. On March 30, 2012, Arconic initially sold $304 of customer receivables in exchange for $50 cash and $254 of deferred purchase program under the arrangement. Arconic has received additional net cash funding of $300 ($2,058 in draws and $1,758 in repayments) since the program’s inception, including net cash draws totaling $0 ($300 in draws and $300 in repayments) in the six months ended June 30, 2017. As of June 30, 2017, and December 31, 2016, the deferred purchase program receivable was $222 and $83, respectively, which was included in Other receivables on the accompanying Consolidated Balance Sheet. The deferred purchase program 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 program receivable. The net change in the deferred purchase program 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 $32,629 and $32,057, respectively. Arconic services the customer receivables for the financial institutions at market rates; therefore, no servicing asset or liability was recorded.

Debt

6 Months Ended

Jun. 30, 2017

Debt Disclosure [Abstract]

Debt

L. Debt


	June 30, 2017			December 31, 2016
6.50% Bonds, due 2018	$	—		$	250
6.75% Notes, due 2018		—			750
5.72% Notes, due 2019		500			750
1.63% Convertible Notes, due 2019*		403			403
6.150% Notes, due 2020		1,000			1,000
5.40% Notes due 2021		1,250			1,250
5.87% Notes, due 2022		627			627
5.125% Notes, due 2024		1,250			1,250
5.90% Notes, due 2027		625			625
6.75% Bonds, due 2028		300			300
5.95% Notes, due 2037		625			625
Iowa Finance Authority Loan, due 2042		250			250
Other**		(34	)		(32	)

Total debt		6,796			8,048
Less: amount due within one year		—			4

Total long-term debt	$	6,796		$	8,044

*	Amount was assumed in conjunction with the July 2015 acquisition of RTI International Metals, Inc.

Includes various financing arrangements related to subsidiaries, unamortized debt discounts related to outstanding notes and bonds listed in the table above, an equity option related to the convertible notes due in 2019, adjustments to the carrying value of long-term debt related to an interest rate swap contract accounted for as a fair value hedge, and unamortized debt issuance costs.

Public Debt – In April 2017, the Company announced three separate cash tender offers by the Investment Banks for the purchase of the Company’s 6.50% Bonds due 2018 (the “6.50% Bonds”), 6.75% Notes due 2018 (the “6.75% Notes”), and 5.72% Notes due 2019 (the “5.72% Notes”), up to a maximum purchase amount of $1,000 aggregate principal amount of notes, subject to certain conditions.

The Investment Banks purchased notes totaling $805 aggregate principal amount, including $150 aggregate principal amount of 6.50% Bonds, $405 aggregate principal amount of 6.75% Notes, and $250 aggregate principal amount of $5.72% Notes.

The Company agreed to acquire the notes from the Investment Banks for $409 in cash plus its remaining investment in Alcoa Corporation common stock (12,958,767 shares valued at $35.91 per share) for total consideration of $874 including accrued and unpaid interest. The Company recorded a charge of $58 ($27 in cash) primarily for the premium for the early redemption of the notes, a benefit of $8 for the proceeds of a related interest rate swap agreement, and a charge of $2 for legal fees associated with the transaction in Interest expense, and recorded a gain of $167 in Other income, net on the Debt-for-Equity Exchange.

On June 19, 2017, the Company completed the early redemption of its remaining outstanding 6.50% Bonds, with aggregate principal amount of $100, and its remaining outstanding 6.75% Notes, with aggregate principal amount of $345, for $479 in cash including accrued and unpaid interest. As a result of the early redemption of the 6.50% Bonds and 6.75% Notes, the Company recorded a charge of $24 in Interest expense for the premium paid for the early redemption of these notes in excess of their carrying value.

Pension and Other Postretirement Benefits

6 Months Ended

Jun. 30, 2017

Retirement Benefits [Abstract]

Pension and Other Postretirement Benefits

M. 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,
	2017			2016			2017			2016
Pension benefits
Service cost	$	22		$	41		$	45		$	81
Interest cost		58			122			116			244
Expected return on plan assets		(83	)		(186	)		(166	)		(371	)
Recognized net actuarial loss		55			102			110			204
Amortization of prior service cost (benefits)		2			4			3			8
Settlements		—			2			—			2
Special termination benefits		—			—			—			1

Net periodic benefit cost*	$	54		$	85		$	108		$	169
Discontinued operations		—			40			—			73

Net amount recognized in Statement of Consolidated Operations	$	54		$	45		$	108		$	96


	Second quarter ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Other postretirement benefits
Service cost	$	2		$	4		$	4		$	7
Interest cost		7			19			15			37
Recognized net actuarial loss		1			5			2			11
Amortization of prior service cost (benefits)		(2	)		(7	)		(4	)		(13	)
Special termination benefits		—			—			—			—


	Second quarter ended				Six months ended
	June 30,				June 30,
	2017		2016		2017		2016
Pension benefits
Net periodic benefit cost*	$	8	$	21	$	17	$	42
Discontinued operations		—		13		—		25

Net amount recognized in Statement of Consolidated Operations	$	8	$	8	$	17	$	17

*	Components of Net periodic benefit cost were included within Cost of goods sold, Selling, general administrative, and other expenses, Research and development expenses and Restructuring and other charges in the Statement of Consolidated Operations.

In conjunction with the Separation Transaction, the Pension Benefit Guaranty Corporation approved management’s plan to separate the Alcoa Inc. pension plans between Arconic Inc. and Alcoa Corporation. The plan stipulates that Arconic will make cash contributions over a period of 30 months to its two largest pension plans. Payments are expected to be made in three increments of no less than $50 each ($150 total) over this 30-month period. The first payment of $50 was made on April 18, 2017.

Financial Instruments

6 Months Ended

Jun. 30, 2017

Investments, All Other Investments [Abstract]

Financial Instruments

N. 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.

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


	June 30, 2017				December 31, 2016
	Carrying		Fair		Carrying		Fair
	value		value		value		value
Cash and cash equivalents	$	1,785		1,785	$	1,863	$	1,863
Restricted cash		5		5		15		15
Derivatives - current asset		19		19		14		14
Noncurrent receivables		20		20		21		21
Derivatives - noncurrent asset		12		12		10		10
Available-for-sale securities		104		104		102		102
Investment in common stock of Alcoa Corporation		—		—		1,020		1,020
Short-term borrowings		48		48		36		36
Derivatives - current liability		14		14		5		5
Long-term debt due within one year		—		—		4		4
Derivatives - noncurrent liability		9		9		3		3
Contingent payment related to an acquisition		80		80		78		78
Long-term debt, less amount due within one year		6,796		7,249		8,044		8,519

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

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

Derivatives. The fair value of derivative contracts classified as Level 1 was based on identical unrestricted assets and liabilities. The fair value of derivative contracts classified as Level 2 was based on inputs other than quoted prices that are observable for the asset or liability (e.g. interest rates).

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.

Investment in common stock of Alcoa Corporation. The fair value was based on the closing stock price of Alcoa Corporation on the New York Stock Exchange at June 30, 2017 and December 31, 2016 multiplied by the number of shares of Alcoa Corporation common stock owned by Arconic at those dates. This investment was classified in Level 1 of the fair value hierarchy. The Company disposed of its remaining investment in Alcoa Corporation common stock in the second quarter of 2017.

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 Arconic 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.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	O. Subsequent Events Management evaluated all activity of Arconic 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, with the exception of the events disclosed below. In July 2017, three purported class action complaints were filed against Arconic and other defendants. See Note H for further information on these matters.

Accumulated Other Comprehensive Loss (Tables)

6 Months Ended

Jun. 30, 2017

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 Arconic’s shareholders and noncontrolling interests:


	Arconic						Noncontrolling Interests
	Second quarter ended June 30,						Second quarter ended June 30,
	2017			2016			2017			2016
Pension and other postretirement benefits (M)
Balance at beginning of period	$	(1,979	)	$	(3,579	)	$	—		$	(55	)
Other comprehensive income:
Unrecognized net actuarial loss and prior service cost		17			(5	)		—			1
Tax (expense) benefit		(5	)		3			—			—

Total Other comprehensive loss before reclassifications, net of tax		12			(2	)		—			1

Amortization of net actuarial loss and prior service cost⁽¹⁾		56			104			—
Tax (expense) benefit⁽²⁾		(20	)		(37	)		—			1

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		36			67			—			1

Total Other comprehensive income		48			65			—			2

Balance at end of period	$	(1,931	)	$	(3,514	)	$	—		$	(53	)

Foreign currency translation
Balance at beginning of period	$	(622	)	$	(2,109	)	$	(2	)	$	(673	)
Other comprehensive income⁽³⁾		99			45			—			32

Balance at end of period	$	(523	)	$	(2,064	)	$	(2	)	$	(641	)

Available-for-sale securities
Balance at beginning of period	$	99		$	(4	)	$	—		$	—
Other comprehensive (loss) income⁽⁴⁾		(101	)		3			—			—

Balance at end of period	$	(2	)	$	(1	)	$	—		$	—

Cash flow hedges
Balance at beginning of period	$	4		$	517		$	—		$	(5	)
Other comprehensive income (loss):
Net change from periodic revaluations		(4	)		(225	)		—			18
Tax benefit (expense)		1			66			—			(5	)

Total Other comprehensive income (loss) before reclassifications, net of tax		(3	)		(159	)		—			13

Net amount reclassified to earnings		1			7						5
Tax expense⁽²⁾		—			(1	)		—			(2	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		1			6			—			3

Total Other comprehensive income (loss)		(2	)		(153	)		—			16

Balance at end of period	$	2		$	364		$	—		$	11

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

⁽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⁾	Realized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁵⁾	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 2 through 4.


	Arconic						Noncontrolling Interests
	Six months ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Pension and other postretirement benefits (M)
Balance at beginning of period	$	(2,010	)	$	(3,611	)	$	—		$	(56	)
Other comprehensive income:
Unrecognized net actuarial loss and prior service cost		11			(64	)		—			1
Tax (expense) benefit		(4	)		26			—			—

Total Other comprehensive loss before reclassifications, net of tax		7			(38	)		—			1

Amortization of net actuarial loss and prior service cost⁽¹⁾		111			208			—			2
Tax expense⁽²⁾		(39	)		(73	)		—			—

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		72			135			—			2

Total Other comprehensive income		79			97			—			3

Balance at end of period	$	(1,931	)	$	(3,514	)	$	—		$	(53	)

Foreign currency translation
Balance at beginning of period	$	(689	)	$	(2,412	)	$	(2	)	$	(780	)
Other comprehensive income⁽³⁾		166			348			—			139

Balance at end of period	$	(523	)	$	(2,064	)	$	(2	)	$	(641	)

Available-for-sale securities
Balance at beginning of period	$	132		$	(5	)	$	—		$	—
Other comprehensive (loss) income⁽⁴⁾		(134	)		4			—			—

Balance at end of period	$	(2	)	$	(1	)	$	—		$	—

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

Total Other comprehensive income (loss) before reclassifications, net of tax		2			(239	)		—			11

Net amount reclassified to earnings		1			5						5
Tax benefit (expense)⁽²⁾		—			1			—			(2	)

Total amount reclassified from Accumulated other comprehensive loss, net of tax⁽⁵⁾		1			6			—			3

Total Other comprehensive income (loss)		3			(233	)		—			14

Balance at end of period	$	2		$	364		$	—		$	11

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

⁽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⁾	Realized gains and losses were included in Other income, net on the accompanying Statement of Consolidated Operations.

⁽⁵⁾	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 2 through 4.

Restructuring and Other Charges (Tables)

6 Months Ended

Jun. 30, 2017

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,
	2017			2016			2017		2016
Engineered Products and Solutions	$	8		$	9		$	14	$	17
Global Rolled Products		17			—			74		2
Transportation and Construction Solutions		6			8			9		8

Segment Total		31			17			97		27
Corporate		(5	)		(3	)		2		3

Total Restructuring and other charges	$	26		$	14		$	99	$	30

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, 2015	$	84		$	9		$	93
2016:
Cash payments		(73	)		(13	)		(86	)
Restructuring charges		70			27			97
Other*		(31	)		(14	)		(45	)

Reserve balances at December 31, 2016		50			9			59

2017:
Cash payments		(26	)		(5	)		(31	)
Restructuring charges		43			—			43
Other*		10			(1	)		9

Reserve balances at June 30, 2017	$	77		$	3		$	80

Inventories (Tables)

6 Months Ended

Jun. 30, 2017

Inventory Disclosure [Abstract]

Schedule of Inventory Components


	June 30, 2017		December 31, 2016
Finished goods	$	652	$	625
Work-in-process		1,300		1,144
Purchased raw materials		383		408
Operating supplies		81		76

Total inventories	$	2,416	$	2,253

Separation Transaction and Discontinued Operations (Tables)

6 Months Ended

Jun. 30, 2017

Alcoa Corporation [Member]

Summary of Discontinued Operations in Financial Statements

The results of operations of Alcoa Corporation are presented as discontinued operations in the Statement of Consolidated Operations as summarized below:


	Second quarter ended June 30, 2016			Six months ended June 30, 2016
Sales	$	2,061		$	3,953
Cost of goods sold (exclusive of expenses below)		1,683			3,324
Selling, general administrative, and other expenses		47			102
Research and development expenses		7			18
Provision for depreciation, depletion and amortization		177			352
Restructuring and other charges		9			86
Interest expense		5			11
Other (income) expense, net		(21	)		26

Income from discontinued operations before income taxes		154			34
Provision for income taxes		29			8

Income from discontinued operations after income taxes		125			26
Less: Net income from discontinued operations attributable to noncontrolling interests		43			38

Net income (loss) from discontinued operations	$	82		$	(12	)


	Six months ended June 30,
	2016
Depreciation, depletion and amortization	$	352
Restructuring and other charges	$	86
Capital expenditures	$	172

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721533-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721665-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1474-107760

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721683-107760

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=84176398&loc=SL51724579-110230

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5C
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721675-107760

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721663-107760

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2941-110230

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721659-107760

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5A
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721671-107760

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5D
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721677-107760

+ Details

Segment Information (Tables)

6 Months Ended

Jun. 30, 2017

Segment Reporting [Abstract]

Schedule of Operating Results of Arconic's Reportable Segments

The operating results of Arconic’s reportable segments were as follows:


	Engineered Products and Solutions		Global Rolled Products		Transportation and Construction Solutions		Combined Segment
Second quarter ended June 30, 2017
Sales:
Third-party sales	$	1,484	$	1,268	$	501	$	3,253
Intersegment sales		—		37		—		37

Total sales	$	1,484	$	1,305	$	501	$	3,290

Profit and loss:
Depreciation and amortization		66		51		12		129
Adjusted EBITDA		310		164		82		556

Second quarter ended June 30, 2016
Sales:
Third-party sales	$	1,465	$	1,316	$	467	$	3,248
Intersegment sales		—		29		—		29

Total sales	$	1,465	$	1,345	$	467	$	3,277

Profit and loss:
Depreciation and amortization		62		50		12		124
Adjusted EBITDA		329		163		76		568


	Engineered Products and Solutions		Global Rolled Products		Transportation and Construction Solutions		Combined Segment
Six months ended June 30, 2017
Sales:
Third-party sales	$	2,969	$	2,517	$	950	$	6,436
Intersegment sales		—		71		—		71

Total sales	$	2,969	$	2,588	$	950	$	6,507

Profit and loss:
Depreciation and amortization		130		101		24		255
Adjusted EBITDA		616		335		154		1,105

Six months ended June 30, 2016
Sales:
Third-party sales	$	2,914	$	2,500	$	896	$	6,310
Intersegment sales		—		58		—		58

Total sales	$	2,914	$	2,558	$	896	$	6,368

Profit and loss:
Depreciation and amortization		127		100		23		250
Adjusted EBITDA		634		318		140		1,092

Schedule of Combined Segment Adjusted EBITDA to Net Income Attributable to Arconic

The following table reconciles Combined segment adjusted EBITDA to Net income attributable to Arconic:


	Second quarter ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Combined segment adjusted EBITDA	$	556		$	568		$	1,105		$	1,092
Unallocated amounts:
Depreciation and amortization		(137	)		(133	)		(270	)		(266	)
Restructuring and other charges		(26	)		(14	)		(99	)		(30	)
Impact of LIFO		(11	)		(13	)		(30	)		(25	)
Metal price lag		19			6			41			6
Corporate expense		(91	)		(115	)		(182	)		(191	)
Other		(29	)		(16	)		(39	)		(33	)

Operating income	$	281		$	283		$	526		$	553
Other income, net		171			17			525			29
Interest expense		(183	)		(124	)		(298	)		(245	)

Income from continuing operations before income taxes	$	269		$	176		$	753		$	337
Income taxes		(57	)		(123	)		(219	)		(174	)
Discontinued operations		—			82			—			(12	)

Net income attributable to Arconic	$	212		$	135		$	534		$	151

Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2017

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 Arconic common shareholders was as follows (shares in millions):


	Second quarter ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Income from continuing operations after income taxes	$	212		$	53		$	534		$	163
Less: Preferred stock dividends declared		(18	)		(17	)		(35	)		(35	)

Income from continuing operations available to Arconic common shareholders		194			36			499			128
Income (loss) from discontinued operations after income taxes and noncontrolling interests		—			82			—			(12	)

Net income available to Arconic common shareholders - basic		194			118			499			116
Add: Interest expense related to convertible notes		2			2			4			—
Add: Dividends related to mandatory convertible preferred stock		—			—			34			—

Net income available to Arconic common shareholders - diluted	$	196		$	120		$	537		$	116

Average shares outstanding - basic		441			438			440			438
Effect of dilutive securities:
Stock options		2			1			2			—
Stock and performance awards		5			4			5			4
Mandatory convertible preferred stock		—			—			39			—
Convertible notes		14			9			14			—

Average shares outstanding - diluted		462			452			500			442

Schedule of Anti Dilutive Securities Excluded From Computation of Average Shares Outstanding

The following shares were excluded from the calculation of Average shares outstanding – diluted as their effect was anti-dilutive.


	Second quarter ended June 30,				Six months ended June 30,
	2017		2016		2017		2016
Mandatory convertible preferred stock		39		26		—		26
Convertible notes		—		—		—		9

Debt (Tables)

6 Months Ended

Jun. 30, 2017

Debt Disclosure [Abstract]

Schedule of Long-Term Debt


	June 30, 2017			December 31, 2016
6.50% Bonds, due 2018	$	—		$	250
6.75% Notes, due 2018		—			750
5.72% Notes, due 2019		500			750
1.63% Convertible Notes, due 2019*		403			403
6.150% Notes, due 2020		1,000			1,000
5.40% Notes due 2021		1,250			1,250
5.87% Notes, due 2022		627			627
5.125% Notes, due 2024		1,250			1,250
5.90% Notes, due 2027		625			625
6.75% Bonds, due 2028		300			300
5.95% Notes, due 2037		625			625
Iowa Finance Authority Loan, due 2042		250			250
Other**		(34	)		(32	)

Total debt		6,796			8,048
Less: amount due within one year		—			4

Total long-term debt	$	6,796		$	8,044

*	Amount was assumed in conjunction with the July 2015 acquisition of RTI International Metals, Inc.

Pension and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2017

Retirement Benefits [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,
	2017			2016			2017			2016
Pension benefits
Service cost	$	22		$	41		$	45		$	81
Interest cost		58			122			116			244
Expected return on plan assets		(83	)		(186	)		(166	)		(371	)
Recognized net actuarial loss		55			102			110			204
Amortization of prior service cost (benefits)		2			4			3			8
Settlements		—			2			—			2
Special termination benefits		—			—			—			1

Net periodic benefit cost*	$	54		$	85		$	108		$	169
Discontinued operations		—			40			—			73

Net amount recognized in Statement of Consolidated Operations	$	54		$	45		$	108		$	96


	Second quarter ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Other postretirement benefits
Service cost	$	2		$	4		$	4		$	7
Interest cost		7			19			15			37
Recognized net actuarial loss		1			5			2			11
Amortization of prior service cost (benefits)		(2	)		(7	)		(4	)		(13	)
Special termination benefits		—			—			—			—


	Second quarter ended				Six months ended
	June 30,				June 30,
	2017		2016		2017		2016
Pension benefits
Net periodic benefit cost*	$	8	$	21	$	17	$	42
Discontinued operations		—		13		—		25

Net amount recognized in Statement of Consolidated Operations	$	8	$	8	$	17	$	17

*	Components of Net periodic benefit cost were included within Cost of goods sold, Selling, general administrative, and other expenses, Research and development expenses and Restructuring and other charges in the Statement of Consolidated Operations.

Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2017

Investments, All Other Investments [Abstract]

Schedule of Carrying Values and Fair Values of Financial Instruments

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


	June 30, 2017				December 31, 2016
	Carrying		Fair		Carrying		Fair
	value		value		value		value
Cash and cash equivalents	$	1,785		1,785	$	1,863	$	1,863
Restricted cash		5		5		15		15
Derivatives - current asset		19		19		14		14
Noncurrent receivables		20		20		21		21
Derivatives - noncurrent asset		12		12		10		10
Available-for-sale securities		104		104		102		102
Investment in common stock of Alcoa Corporation		—		—		1,020		1,020
Short-term borrowings		48		48		36		36
Derivatives - current liability		14		14		5		5
Long-term debt due within one year		—		—		4		4
Derivatives - noncurrent liability		9		9		3		3
Contingent payment related to an acquisition		80		80		78		78
Long-term debt, less amount due within one year		6,796		7,249		8,044		8,519

Basis of Presentation - Additional Information (Detail) - Common Stock [Member] shares in Billions	Oct. 05, 2016 shares	Oct. 04, 2016 shares
Basis Of Presentation [Line Items]
Reverse stock split ratio	0.33
Common stock share outstanding	0.4	1.3

Recently Adopted and Recently Issued Accounting Guidance - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Non-service related net periodic pension cost	$ 150
Net periodic postretirement benefit cost	108	$ 168
Postretirement Benefit Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net periodic postretirement benefit cost	$ 150

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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension and other postretirement benefits
Total Other comprehensive income	$ 48	$ 67	$ 79	$ 100
Foreign currency translation
Other comprehensive income	99	77	166	487
Available-for-sale securities
Other comprehensive (loss) income	(101)	3	(134)	4
Cash flow hedges
Total Other comprehensive income (loss)	(2)	(137)	3	(219)
Arconic [Member]
Pension and other postretirement benefits
Balance at beginning of period	(1,979)	(3,579)	(2,010)	(3,611)
Unrecognized net actuarial loss and prior service cost	17	(5)	11	(64)
Tax (expense) benefit	(5)	3	(4)	26
Total Other comprehensive loss before reclassifications, net of tax	12	(2)	7	(38)
Amortization of net actuarial loss and prior service cost	56	104	111	208
Tax (expense) benefit	(20)	(37)	(39)	(73)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	36	67	72	135
Total Other comprehensive income	48	65	79	97
Balance at end of period	(1,931)	(3,514)	(1,931)	(3,514)
Foreign currency translation
Balance at beginning of period	(622)	(2,109)	(689)	(2,412)
Other comprehensive income	99	45	166	348
Balance at end of period	(523)	(2,064)	(523)	(2,064)
Available-for-sale securities
Balance at beginning of period	99	(4)	132	(5)
Other comprehensive (loss) income	(101)	3	(134)	4
Balance at end of period	(2)	(1)	(2)	(1)
Cash flow hedges
Balance at beginning of period	4	517	(1)	597
Net change from periodic revaluations	(4)	(225)	4	(342)
Tax (expense) benefit	1	66	(2)	103
Total Other comprehensive income (loss) before reclassifications, net of tax	(3)	(159)	2	(239)
Net amount reclassified to earnings	1	7	1	5
Tax benefit (expense)		(1)		1
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1	6	1	6
Total Other comprehensive income (loss)	(2)	(153)	3	(233)
Balance at end of period	2	364	2	364
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period		(55)		(56)
Unrecognized net actuarial loss and prior service cost		1		1
Total Other comprehensive loss before reclassifications, net of tax		1		1
Amortization of net actuarial loss and prior service cost				2
Tax (expense) benefit		1
Total amount reclassified from Accumulated other comprehensive loss, net of tax		1		2
Total Other comprehensive income		2		3
Balance at end of period		(53)		(53)
Foreign currency translation
Balance at beginning of period	(2)	(673)	(2)	(780)
Other comprehensive income		32		139
Balance at end of period	$ (2)	(641)	$ (2)	(641)
Cash flow hedges
Balance at beginning of period		(5)		(3)
Net change from periodic revaluations		18		15
Tax (expense) benefit		(5)		(4)
Total Other comprehensive income (loss) before reclassifications, net of tax		13		11
Net amount reclassified to earnings		5		5
Tax benefit (expense)		(2)		(2)
Total amount reclassified from Accumulated other comprehensive loss, net of tax		3		3
Total Other comprehensive income (loss)		16		14
Balance at end of period		$ 11		$ 11

Restructuring and Other Charges - Additional Information (Detail)		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 Employees	Jun. 30, 2017 USD ($) Employees Positions	Jun. 30, 2016 USD ($) Positions	Jun. 30, 2017 USD ($) Employees Positions	Jun. 30, 2016 USD ($) Positions	Dec. 31, 2016 USD ($) Employees
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 26,000,000	$ 14,000,000	$ 99,000,000	$ 30,000,000
Restructuring and other charges after tax and noncontrolling interest		$ 17,000,000	$ 9,000,000	$ 86,000,000	$ 20,000,000
Number of employees associated with layoff costs \| Positions		352	540	680	1,070
Reversal of forfeited executive stock compensation		$ 13,000,000		$ 13,000,000
Severance charges		7,000,000		7,000,000
Cash payments made against the layoff reserves				31,000,000		$ 86,000,000
Minimum amount of cash payments expected to be paid beyond the end of the current annual period				10,000,000
Maximum amount of cash payments expected to be paid beyond the end of the current annual period				12,000,000
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ (5,000,000)	$ (3,000,000)	$ 2,000,000	$ 3,000,000
Number of employees associated with layoff costs \| Positions		20		62
Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs \| Positions		129	300	243	800
Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs \| Positions		110		242	30
Transportation and Construction Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs \| Positions		93	240	133	240
Fusina Italy [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				$ 60,000,000
Restructuring and other charges after tax and noncontrolling interest				60,000,000
Restructuring Programs Layoffs 2015 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 29,000,000	$ 13,000,000	48,000,000	$ 30,000,000
Restructuring and other charges after tax and noncontrolling interest		$ 19,000,000	8,000,000	$ 32,000,000	19,000,000
Number of employees associated with layoff costs \| Employees				1,220		1,240
Approximate number of employees already laid off \| Employees	1,120	1,120		1,120
Cash payments made against the layoff reserves		$ 1,000,000		$ 4,000,000
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		4,000,000	7,000,000	1,000,000	7,000,000
Restructuring and other charges after tax and noncontrolling interest		3,000,000	4,000,000	0	4,000,000
Other Adjustments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		1,000,000	6,000,000	2,000,000	7,000,000
Restructuring and other charges after tax and noncontrolling interest		$ 1,000,000	$ 3,000,000	$ 2,000,000	$ 3,000,000
Restructuring Programs Layoffs 2017 [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs \| Employees	680
Approximate number of employees already laid off \| Employees	65	65		65
Cash payments made against the layoff reserves		$ 1,000,000		$ 2,000,000
Restructuring Programs Layoffs 2016 [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs \| Employees	1,770					1,800
Approximate number of employees already laid off \| Employees	1,170	1,170		1,170
Cash payments made against the layoff reserves		$ 6,000,000		$ 20,000,000
Reversal of Forfeited Executive Stock Compensation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		6,000,000		6,000,000
Restructuring and other charges after tax and noncontrolling interest		$ 4,000,000		$ 4,000,000

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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 26	$ 14	$ 99	$ 30
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	31	17	97	27
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(5)	(3)	2	3
Engineered Products and Solutions [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	8	9	14	17
Global Rolled Products [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	17		74	2
Transportation and Construction Solutions [Member] \| Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 6	$ 8	$ 9	$ 8

Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	$ 59	$ 93
Cash payments	(31)	(86)
Restructuring charges	43	97
Other	9	(45)
Restructuring reserve ending balance	80	59
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	50	84
Cash payments	(26)	(73)
Restructuring charges	43	70
Other	10	(31)
Restructuring reserve ending balance	77	50
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	9	9
Cash payments	(5)	(13)
Restructuring charges		27
Other	(1)	(14)
Restructuring reserve ending balance	$ 3	$ 9

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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 26	$ 14	$ 99	$ 30
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Asset retirement obligations					$ 8
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					2
Legal Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 4
Stock awards reversal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 13

Acquisitions and Divestitures - Additional Information (Detail) $ in Millions	1 Months Ended		3 Months Ended		4 Months Ended	6 Months Ended
	Mar. 31, 2017 USD ($)	Apr. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($) Employees	Jun. 30, 2017 USD ($) Employees	Jun. 30, 2016 USD ($)
Business Acquisition [Line Items]
Third-party sale generated in last annual period prior to divestiture			$ 3,261	$ 3,234		$ 6,453	$ 6,289
LISI MEDICAL [Member]
Business Acquisition [Line Items]
Cash received on sale of operations		$ 102
Sale of Remmele Medical business, net of transaction costs		$ 99
Slim Aluminium [Member]
Business Acquisition [Line Items]
Third-party sale generated in last annual period prior to divestiture						$ 37	$ 72
Number of employees \| Employees						312
Cash expense related to sale of rolling mill	$ 10
Third party guarantee with a fair value related to environmental remediation	$ 5
Slim Aluminium [Member] \| Restructuring and Other Charges [Member]
Business Acquisition [Line Items]
Loss on sale of rolling mill						$ 60
RTI [Member]
Business Acquisition [Line Items]
Third-party sale generated in last annual period prior to divestiture					$ 20
Number of employees \| Employees					330

Inventories - Schedule of Inventory Components (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Finished goods	$ 652	$ 625
Work-in-process	1,300	1,144
Purchased raw materials	383	408
Operating supplies	81	76
Total inventories	$ 2,416	$ 2,253

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Inventories valued on a LIFO basis	$ 1,057	$ 947
Total inventories valued on an average-cost basis	$ 401	$ 371

Separation Transaction and Discontinued Operations - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended			3 Months Ended		6 Months Ended
	Nov. 01, 2016	May 31, 2017	Apr. 30, 2017	Feb. 28, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock sold				23,353,000			12,958,767
Common stock sold per share				$ 38.03	$ 35.91		$ 35.91
Cash proceeds sale of common stock				$ 888
Pre-tax gain on sale of common stock				$ 351			$ 167
Investment in common stock of Alcoa Corporation					$ 0		0	$ 1,020
Investment Banks [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock sold		12,958,767	12,958,767
Common stock sold per share		$ 35.91	$ 35.91
Pre-tax gain on sale of common stock		$ 167	$ 167
Yadkin [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets					$ 5	$ 238	$ 243
Alcoa Corporation [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock outstanding percentage	80.10%
Number of common stock retained							36,311,767
Percentage of common stock retained							19.90%

Separation Transaction and Discontinued Operations - Summary of Discontinued Operations in Statement of Consolidated Operations (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations after income taxes	$ 125	$ 26
Less: Net income from discontinued operations attributable to noncontrolling interests	43	38
Net income (loss) from discontinued operations	82	(12)
Alcoa Corporation [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales	2,061	3,953
Cost of goods sold (exclusive of expenses below)	1,683	3,324
Selling, general administrative, and other expenses	47	102
Research and development expenses	7	18
Provision for depreciation, depletion and amortization	177	352
Restructuring and other charges	9	86
Interest expense	5	11
Other (income) expense, net	(21)	26
Income from discontinued operations before income taxes	154	34
Provision for income taxes	29	8
Income from discontinued operations after income taxes	125	26
Less: Net income from discontinued operations attributable to noncontrolling interests	43	38
Net income (loss) from discontinued operations	$ 82	$ (12)

Separation Transaction and Discontinued Operations - Summary of Discontinued Operations in Statement of Consolidated Cash Flows (Detail) - Alcoa Corporation [Member] $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation, depletion and amortization	$ 352
Restructuring and other charges	86
Capital expenditures	$ 172

Contingencies and Commitments - Additional Information - 1 (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Number of cleanup locations		More than 100
Remediation reserve balance	$ 301	$ 301	$ 308
Remediation reserve balance, classified as a current liability	42	42	48
Payments related to remediation expenses applied against the reserve	5	$ 7
Actual remediation fieldwork period		4 years
Maximum [Member]
Loss Contingencies [Line Items]
Majority of the project funding period		2021
Minimum [Member]
Loss Contingencies [Line Items]
Majority of the project funding period		2017
Massena West, NY [Member]
Loss Contingencies [Line Items]
Remediation reserve balance	$ 224	$ 224	$ 228
Recurring Costs of Managing Hazardous Substances and Environmental Programs [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Percentage of cost of goods sold		1.00%

Contingencies and Commitments - Additional Information - 2 (Detail) € in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 EUR (€)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Total combined assessments	$ 283	€ 248
Guarantees of third party related to project financing	46
Letters of credit, total amount committed	$ 133
Letters of credit, expiration date	2017
Total amount committed under outstanding surety bonds	$ 127
Surety bonds, expiration date	2017
Other Noncurrent Liabilities and Deferred Credits [Member]
Loss Contingencies [Line Items]
Combined fair value of guarantees	$ 36			$ 35
Separation Agreement [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	314			354
Total amount committed under outstanding surety bonds	25
Supply Agreement [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	1,600
Purchase Agreement [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing				$ 245
Alcoa Corporation Energy Supply Contracts Guarantee [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing			$ 50
Alcoa Corporation Environmental Liabilities Guarantee [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	53
Alcoa Corporation Workers Compensation Claims [Member]
Loss Contingencies [Line Items]
Letters of credit, total amount committed	61
Alcoa Corporation Equipment Leases And Energy Contracts [Member]
Loss Contingencies [Line Items]
Letters of credit, total amount committed	$ 103
Minimum [Member] \| Separation Agreement [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2017
Minimum [Member] \| Outstanding bank guarantees [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2017
Maximum [Member] \| Separation Agreement [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2024
Maximum [Member] \| Outstanding bank guarantees [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2026

Segment Information - Schedule of Operating Results of Arconic's Reportable Segments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total sales	$ 3,261	$ 3,234	$ 6,453	$ 6,289
Depreciation and amortization	129	124	255	250
Adjusted EBITDA	556	568	1,105	1,092
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	3,290	3,277	6,507	6,368
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	37	29	71	58
Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	3,253	3,248	6,436	6,310
Engineered Products and Solutions [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	66	62	130	127
Adjusted EBITDA	310	329	616	634
Engineered Products and Solutions [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	1,484	1,465	2,969	2,914
Engineered Products and Solutions [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,484	1,465	2,969	2,914
Global Rolled Products [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	51	50	101	100
Adjusted EBITDA	164	163	335	318
Global Rolled Products [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	1,305	1,345	2,588	2,558
Global Rolled Products [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	37	29	71	58
Global Rolled Products [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,268	1,316	2,517	2,500
Transportation and Construction Solutions [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	12	12	24	23
Adjusted EBITDA	82	76	154	140
Transportation and Construction Solutions [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	501	467	950	896
Transportation and Construction Solutions [Member] \| Third-Party Sales [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	$ 501	$ 467	$ 950	$ 896

Segment Information - Schedule of Combined Segment Adjusted EBITDA to Net Income Attributable to Arconic (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jun. 19, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Combined segment adjusted EBITDA		$ 556	$ 568	$ 1,105	$ 1,092
Depreciation and amortization		(137)	(133)	(270)	(266)
Restructuring and other charges		(26)	(14)	(99)	(30)
Operating income		281	283	526	553
Other income, net		171	17	525	29
Interest expense	$ (24)	(183)	(124)	(298)	(245)
Income from continuing operations before income taxes		269	176	753	337
Income taxes		(57)	(123)	(219)	(174)
Discontinued operations			82		(12)
Net income attributable to Arconic		212	135	534	151
Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		(137)	(133)	(270)	(266)
Restructuring and other charges		(26)	(14)	(99)	(30)
Impact of LIFO		(11)	(13)	(30)	(25)
Metal price lag		19	6	41	6
Corporate expense		(91)	(115)	(182)	(191)
Other		(29)	(16)	(39)	(33)
Operating income		281	283	526	553
Other income, net		171	17	525	29
Interest expense		(183)	(124)	(298)	(245)
Income from continuing operations before income taxes		269	176	753	337
Income taxes		$ (57)	(123)	$ (219)	(174)
Discontinued operations			$ 82		$ (12)

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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Income from continuing operations after income taxes	$ 212	$ 53	$ 534	$ 163
Less: Preferred stock dividends declared	(18)	(17)	(35)	(35)
Income from continuing operations available to Arconic common shareholders	194	36	499	128
Income (loss) from discontinued operations after income taxes and noncontrolling interests		82		(12)
Net income available to Arconic common shareholders - basic	194	118	499	117
Add: Interest expense related to convertible notes	2	2	4
Add: Dividends related to mandatory convertible preferred stock			34
Net income available to Arconic common shareholders - diluted	$ 196	$ 120	$ 537	$ 116
Average shares outstanding - basic	441	438	440	438
Stock options	2	1	2
Stock and performance awards	5	4	5	4
Mandatory convertible preferred stock			39
Convertible notes	14	9	14
Average shares outstanding - diluted	462	452	500	442

Earnings Per Share - Schedule of Anti Dilutive Securities Excluded From Computation of Average Shares Outstanding (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016
Mandatory Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities	39	26	26
Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities			9

Earnings Per Share - Additional Information (Detail) - $ / shares shares in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Equity Unit Purchase Agreements [Member]
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities	7	8
Stock Options [Member]
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average exercise price of options	$ 28.85	$ 38.18

Receivables - Additional Information (Detail)		6 Months Ended	12 Months Ended
Receivables - Additional Information (Detail)	Mar. 30, 2012 USD ($)	Jun. 30, 2017 USD ($) Agreement	Dec. 31, 2016 USD ($)
Schedule Of Financial Receivables [Line Items]
Number of arrangement with different financial institution to sell customer receivables \| Agreement		3
Sale of customer receivables	$ 304,000,000
Cash received for receivables	50,000,000
Deferred purchase program receivable	$ 254,000,000	$ 222,000,000	$ 83,000,000
Net cash funding received since inception		300,000,000
Amount of cash draws under arrangement since inception		2,058,000,000
Amount of cash repayments under arrangement since inception		1,758,000,000
Net cash funding received during the period		0
Amount of cash draws under arrangement during the period		300,000,000
Amount of cash repayments under arrangement during the period		300,000,000
Accounts receivables		32,629,000,000
Cash collections of other receivables		32,057,000,000
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		$ 400,000,000

Debt - Schedule of Long-Term Debt (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt	$ 6,796	$ 8,048
Less: amount due within one year		4
Long-term debt, excluding amount due within one year	6,796	8,044
Long-term debt	6,796	8,048
6.50% Bonds, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt		250
Long-term debt		250
6.75% Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt		750
Long-term debt		750
5.72% Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt	500	750
Long-term debt	500	750
1.63% Convertible Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt	403	403
Long-term debt	403	403
6.150% Notes, Due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	1,000	1,000
Long-term debt	1,000	1,000
5.40% Notes, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt	1,250	1,250
Long-term debt	1,250	1,250
5.87% Notes, Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	627	627
Long-term debt	627	627
5.125% Notes, Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	1,250	1,250
Long-term debt	1,250	1,250
5.90% Notes, Due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	625	625
Long-term debt	625	625
6.75% Bonds, Due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	300	300
Long-term debt	300	300
5.95% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	625	625
Long-term debt	625	625
Iowa Finance Authority Loan, Due 2042 [Member]
Debt Instrument [Line Items]
Long-term debt	250	250
Long-term debt	250	250
Other [Member]
Debt Instrument [Line Items]
Long-term debt	34	32
Long-term debt	$ 34	$ 32

Debt - Schedule of Long-Term Debt (Parenthetical) (Detail)	6 Months Ended
	Jun. 30, 2017
6.50% Bonds, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	6.50%
Debt instrument, maturity date	2018
6.75% Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	6.75%
Debt instrument, maturity date	2018
5.72% Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	5.72%
Debt instrument, maturity date	2019
1.63% Convertible Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	1.63%
Debt instrument, maturity date	2019
6.150% Notes, Due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	6.15%
Debt instrument, maturity date	2020
5.40% Notes, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	5.40%
Debt instrument, maturity date	2021
5.87% Notes, Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	5.87%
Debt instrument, maturity date	2022
5.125% Notes, Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	5.125%
Debt instrument, maturity date	2024
5.90% Notes, Due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	5.90%
Debt instrument, maturity date	2027
6.75% Bonds, Due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	6.75%
Debt instrument, maturity date	2028
5.95% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate	5.95%
Debt instrument, maturity date	2037
Iowa Finance Authority Loan, Due 2042 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	2042

Debt - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended			3 Months Ended		6 Months Ended
	Jun. 19, 2017	May 31, 2017	Apr. 30, 2017	Feb. 28, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Debt Instrument [Line Items]
Repayment of debt							$ 409
Common stock sold				23,353,000			12,958,767
Common stock sold per share				$ 38.03	$ 35.91		$ 35.91
Pre-tax gain on sale of common stock				$ 351			$ 167
Consideration amount including accrued and unpaid interest					$ 874		874
Interest expense							58
Interest paid							27
Legal fees							2
Interest expense for premium paid for early redemption of notes in excess of carrying value	$ 24				$ 183	$ 124	$ 298	$ 245
6.50% Bonds, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate					6.50%		6.50%
Debt instrument, maturity date							2018
6.50% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	100
6.75% Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate					6.75%		6.75%
Debt instrument, maturity date							2018
6.75% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	345
Redemption amount	$ 479
5.72% Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate					5.72%		5.72%
Debt instrument, maturity date							2019
Investment Banks [Member]
Debt Instrument [Line Items]
Long-term debt					$ 805		$ 805
Common stock sold		12,958,767	12,958,767
Common stock sold per share		$ 35.91	$ 35.91
Pre-tax gain on sale of common stock		$ 167	$ 167
Investment Banks [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long-term debt			$ 1,000
Investment Banks [Member] \| 6.50% Bonds, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate			6.50%		6.50%		6.50%
Debt instrument, maturity date			2018
Long-term debt					$ 150		$ 150
Investment Banks [Member] \| 6.75% Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate			6.75%		6.75%		6.75%
Debt instrument, maturity date			2018
Long-term debt					$ 405		$ 405
Investment Banks [Member] \| 5.72% Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate			5.72%		5.72%		5.72%
Debt instrument, maturity date			2019
Long-term debt					$ 250		$ 250
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Proceeds from interest rate swap agreement							$ 8

Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			$ 108	$ 168
Net periodic benefit costs continuing and discontinued
Net periodic benefit cost			108	168
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 22	$ 41	45	81
Interest cost	58	122	116	244
Expected return on plan assets	(83)	(186)	(166)	(371)
Recognized net actuarial loss	55	102	110	204
Amortization of prior service cost (benefits)	2	4	3	8
Settlements		2		2
Special termination benefits				1
Net periodic benefit cost	54	85	108	169
Net periodic benefit costs continuing and discontinued
Discontinued operations		40		73
Net amount recognized in Statement of Consolidated Operations	54	45	108	96
Net periodic benefit cost	54	85	108	169
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	4	4	7
Interest cost	7	19	15	37
Recognized net actuarial loss	1	5	2	11
Amortization of prior service cost (benefits)	(2)	(7)	(4)	(13)
Net periodic benefit cost	8	21	17	42
Net periodic benefit costs continuing and discontinued
Discontinued operations		13		25
Net amount recognized in Statement of Consolidated Operations	8	8	17	17
Net periodic benefit cost	$ 8	$ 21	$ 17	$ 42

Pension and Other Postretirement Benefits - Additional Information (Detail)		6 Months Ended
	Apr. 18, 2017 USD ($)	Jun. 30, 2017 USD ($) Installments
Retirement Benefits [Abstract]
Cash contribution term to pension plan		30 months
Number of installments \| Installments		3,000,000
Minimum required cash contribution to pension plan		$ 50,000,000
Aggregate cash cash contribution to pension plan		$ 150,000,000
First payment to pension plan	$ 50,000,000

Financial Instruments - Schedule of Carrying Values and Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Carrying Value [Member]
Derivative [Line Items]
Cash and cash equivalents	$ 1,785	$ 1,863
Restricted cash	5	15
Derivatives - current asset	19	14
Noncurrent receivables	20	21
Derivatives - noncurrent asset	12	10
Available-for-sale securities	104	102
Investment in common stock of Alcoa Corporation		1,020
Short-term borrowings	48	36
Derivatives - current liability	14	5
Long-term debt due within one year		4
Derivatives - noncurrent liability	9	3
Contingent payment related to an acquisition	80	78
Long-term debt, less amount due within one year	6,796	8,044
Fair Value [Member]
Derivative [Line Items]
Cash and cash equivalents	1,785	1,863
Restricted cash	5	15
Derivatives - current asset	19	14
Noncurrent receivables	20	21
Derivatives - noncurrent asset	12	10
Available-for-sale securities	104	102
Investment in common stock of Alcoa Corporation		1,020
Short-term borrowings	48	36
Derivatives - current liability	14	5
Long-term debt due within one year		4
Derivatives - noncurrent liability	9	3
Contingent payment related to an acquisition	80	78
Long-term debt, less amount due within one year	$ 7,249	$ 8,519