Segment and Geographic Area Information - Schedule of Segment Operating Profit to Consolidated Net Income (Loss) Income Attributable to Arconic (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total segment operating profit		$ 2,015,000,000	$ 1,586,000,000	$ 1,689,000,000
Impairment of goodwill		0	0	719,000,000
Restructuring and other charges		(620,000,000)	(9,000,000)	(165,000,000)
Operating income		1,035,000,000	1,325,000,000	480,000,000
Interest expense	$ (24,000,000)	(338,000,000)	(378,000,000)	(496,000,000)
Other (expense) income, net		(122,000,000)	(79,000,000)	486,000,000
Income before income taxes		575,000,000	868,000,000	470,000,000
Segment Reconciling Item
Segment Reporting Information [Line Items]
Impairment of goodwill		0	0	(719,000,000)
Restructuring and other charges		(620,000,000)	(9,000,000)	(165,000,000)
Corporate expense		(360,000,000)	(252,000,000)	(325,000,000)
Operating income		1,035,000,000	1,325,000,000	480,000,000
Interest expense		(338,000,000)	(378,000,000)	(496,000,000)
Other (expense) income, net		(122,000,000)	(79,000,000)	486,000,000
Income before income taxes		$ 575,000,000	$ 868,000,000	$ 470,000,000