Segment and Geographic Area Information - Schedule of Segment Operating Profit to Consolidated Net Income (Loss) Income Attributable to Arconic (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total segment operating profit	$ 626	$ 579	$ 775
Interest expense	(381)	(338)	(377)
Other (expense) income, net	(74)	(31)	30
Income before income taxes	171	210	428
Total segment sales
Segment Reporting Information [Line Items]
Total segment operating profit	890	1,390	1,105
Restructuring and other charges
Segment Reporting Information [Line Items]
Total segment operating profit	(182)	(582)	(163)
Corporate expense
Segment Reporting Information [Line Items]
Total segment operating profit	$ (82)	$ (229)	$ (167)