Receivables (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) agreement	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule Of Financial Receivables [Line Items]
Accounts receivable securitization arrangements | agreement	2
Deferred purchase program receivable	$ 68		$ 12
Net cash funding received during the period	26	$ 52
Amount of cash draws under arrangement during the period	18	98
Amount of cash repayments under arrangement during the period	44	150
Accounts receivable remaining outstanding	65		46
Accounts receivable securitization	425		425
Accounts receivable securitization amount drawn	243		250
Reduction in accounts receivable from securitization	7
Customer One
Schedule Of Financial Receivables [Line Items]
Accounts receivables sold	7	14
Accounts receivable remaining outstanding	7
Customer Two
Schedule Of Financial Receivables [Line Items]
Accounts receivables sold	59	17
Accounts receivable remaining outstanding	57
Special Purpose Entity
Schedule Of Financial Receivables [Line Items]
Accounts receivables sold	84
Receivables, maximum allowable purchase limit	125
Financing receivables, held as collateral	16		$ 33
Arconic Corporation
Schedule Of Financial Receivables [Line Items]
Deferred purchase program receivable		282
Maximum
Schedule Of Financial Receivables [Line Items]
Funding of customer receivables sold, maximum	$ 400	$ 300