Segment Information - Schedule of Segment ATOI to Consolidated Net Income Attributable to Arconic (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Total segment ATOI	$ 395	$ 410	$ 1,130	$ 1,633
Metal price lag	4	(48)	12	(110)
Interest expense	(133)	(123)	(389)	(369)
Noncontrolling interests	(20)	(62)	(58)	(189)
Consolidated net income attributable to Arconic	166	44	317	379
Other [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	1	50	(5)	93
Interest expense	(86)	(80)	(253)	(240)
Noncontrolling interests	(20)	(62)	(58)	(189)
Corporate expense	(77)	(72)	(209)	(199)
Restructuring and other charges	(13)	(48)	(89)	(368)
Other	$ (38)	$ (106)	$ (211)	$ (241)