Arconic Inc Separation Transaction and Discontinued Operations - Carrying Amount of Major Classes of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Total Assets of Discontinued Operations
Current assets of discontinued operations	$ 0	$ 1,442
Noncurrent assets of discontinued operations	0	3,899
Total Liabilities of Discontinued Operations:
Current liabilities of discontinued operations (C)	0	1,424
Noncurrent liabilities of discontinued operations	$ 0	2,258
Discontinued Operations, Disposed of by Means Other than Sale
Total Assets of Discontinued Operations
Cash and cash equivalents		71
Receivables from customers		385
Other receivables		135
Inventories		822
Prepaid expenses and other current assets		29
Current assets of discontinued operations		1,442
Properties, plants, and equipment, net		2,834
Goodwill		426
Intangibles, net		60
Deferred income taxes		383
Other noncurrent assets		196
Noncurrent assets of discontinued operations		3,899
Total assets of discontinued operations		5,341
Total Liabilities of Discontinued Operations:
Accounts payable, trade		1,067
Accrued compensation and retirement costs		147
Taxes, including income taxes		22
Other current liabilities		188
Current liabilities of discontinued operations (C)		1,424
Accrued pension benefits		1,429
Accrued other postretirement benefits		514
Other noncurrent liabilities and deferred credits		315
Noncurrent liabilities of discontinued operations		2,258
Total liabilities of discontinued operations		$ 3,682