Segment Information - Schedule of Combined Segment Adjusted EBITDA to Net Income Attributable to Arconic (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total segment operating profit	$ 432	$ 454	$ 832	$ 905
Restructuring and other charges	(15)	(26)	(22)	(99)
Operating income	324	320	657	603
Interest expense	(89)	(183)	(203)	(298)
Other (expense) income, net	(41)	132	(61)	448
Income before income taxes	194	269	393	753
Segment Reconciling Items
Segment Reporting Information [Line Items]
Restructuring and other charges	(15)	(26)	(22)	(99)
Corporate expense	(93)	(108)	(153)	(203)
Operating income	324	320	657	603
Interest expense	(89)	(183)	(203)	(298)
Other (expense) income, net	(41)	132	(61)	448
Income before income taxes	$ 194	$ 269	$ 393	$ 753

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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