Quarterly Data - Schedule of Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales revenue, goods, net	$ 3,271	$ 3,236	$ 3,261	$ 3,192	$ 2,967	$ 3,138	$ 3,234	$ 3,055	$ 12,960	$ 12,394	$ 12,413
Net income (loss) attributable to Arconic	$ (727)	$ 119	$ 212	$ 322	$ (1,258)	$ 166	$ 135	$ 16	$ (74)	$ (941)	$ (322)
Basic
Continuing operations (in usd per share)					$ (2.98)	$ 0.11	$ 0.08	$ 0.21	$ (0.28)	$ (2.58)	$ (0.54)
Discontinued operations (in usd per share)					0.07	0.23	0.19	(0.21)	0.00	0.27	(0.39)
Net loss per share-basic (in usd per share)	$ (1.51)	$ 0.23	$ 0.44	$ 0.69	(2.91)	0.34	0.27	0.00	(0.28)	(2.31)	(0.93)
Diluted
Continuing operations (in usd per share)					(2.98)	0.11	0.08	0.21	(0.28)	(2.58)	(0.54)
Discontinued operations (in usd per share)					0.07	0.22	0.19	(0.21)	0.00	0.27	(0.39)
Net loss per share-diluted (in usd per share)	$ (1.51)	$ 0.22	$ 0.43	$ 0.65	$ (2.91)	$ 0.33	$ 0.27	$ 0.00	$ (0.28)	$ (2.31)	$ (0.93)
Goodwill impairment									$ 719	$ 0	$ 25
Tax cuts and jobs act of 2017, incomplete accounting, provisional income tax expense (benefit)	$ 272
Disposal group, contingent liability, period increase (decrease), net of tax	18
Disposal group, contingent liability, period increase (decrease)	25
Increase to allowance					$ 1,267				831	772	$ 180
Firth Rixson
Diluted
Business combination, contingent consideration arrangements, change in amount of contingent consideration, liability, net of tax									81
Contingent consideration arrangements, change in amount of contingent consideration, liability	(81)				$ (56)				81	$ 56
Engineered Products and Solutions
Diluted
Goodwill, impairment loss, net of tax	719
Goodwill impairment	$ 719								$ 719