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)