Arconic Inc. Separation Transaction and Discontinued Operations - Summary of Results of Discontinued Operations (Details) - Discontinued Operations, Disposed of by Means Other than Sale - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Sales	$ 0	$ 1,874	$ 1,576	$ 3,662
Cost of goods sold	0	1,603	1,292	3,129
Selling, general administrative, research and development and other expenses	4	85	106	160
Provision for depreciation and amortization	0	61	59	122
Restructuring and other charges	0	27	(18)	(5)
Interest expense	0	0	7	0
Other expense, net	0	24	42	43
Income (loss) from discontinued operations	(4)	74	88	213
Provision for income taxes	8	59	38	97
Income (loss) from discontinued operations after income taxes	$ (12)	$ 15	$ 50	$ 116