Segment Information - Schedule of Operating Results of Arconic's Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3,209	$ 3,541
Segment operating profit	508	448
Operating Segments
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,209	3,540
Total sales including intersegment sales	3,244	3,592
Segment operating profit	508	448
Restructuring and other charges (credits)	16	29
Provision for depreciation and amortization	122	130
Capital expenditures	58	156
Intersegment sales
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(35)	(52)
Engineered Products and Forgings
Segment Reporting Information [Line Items]
Segment operating profit	339	313
Restructuring and other charges (credits)	34	18
Provision for depreciation and amortization	65	71
Capital expenditures	36	117
Engineered Products and Forgings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,631	1,756
Total sales including intersegment sales	1,631	1,756
Engineered Products and Forgings | Intersegment sales
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Global Rolled Products
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,578	1,784
Segment operating profit	169	135
Restructuring and other charges (credits)	(18)	11
Provision for depreciation and amortization	57	59
Capital expenditures	22	39
Global Rolled Products | Operating Segments
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,578	1,784
Total sales including intersegment sales	1,613	1,836
Global Rolled Products | Intersegment sales
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ (35)	$ (52)