Receivables (Details) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($) agreement	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule Of Financial Receivables [Line Items]
Accounts receivable securitization arrangements | agreement				2
Deferred purchase program receivable	$ 49			$ 49		$ 12
Net cash funding received during the period				22	$ 136
Amount of cash draws under arrangement during the period				41	138
Amount of cash repayments under arrangement during the period				63	274
Accounts receivable remaining outstanding	68			68		46
Accounts receivable securitization	425			425		425
Accounts receivable securitization amount drawn	250			250		250
Customer Two
Schedule Of Financial Receivables [Line Items]
Accounts receivables sold	98	$ 58		164	$ 89
Accounts receivable remaining outstanding	92			92
Special Purpose Entity
Schedule Of Financial Receivables [Line Items]
Accounts receivables sold	71			155
Receivables, maximum allowable purchase limit				125
Financing receivables, held as collateral	$ 10			10		$ 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			$ 300	$ 400