Receivables - Additional Information (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) agreement	Dec. 31, 2019 USD ($)
Schedule Of Financial Receivables [Line Items]
Accounts receivable securitization arrangements | agreement		2
Deferred purchase price receivable		$ 12	$ 246
Net cash funding received during the period		146	0
Amount of cash draws under arrangement during the period		207	600
Amount of cash repayments under arrangement during the period		(353)	(600)
Total accounts receivable securitization arrangements		425	400
Accounts receivable securitization, amount drawn		250	350
Reduction in amount drawn		100
Customer One
Schedule Of Financial Receivables [Line Items]
Accounts receivable, sale		32
Accounts receivable sale, amount outstanding		0
Customer Two
Schedule Of Financial Receivables [Line Items]
Accounts receivable, sale		149
Accounts receivable sale, amount outstanding		50
Arconic Corporation
Schedule Of Financial Receivables [Line Items]
Deferred purchase price receivable	$ 282
Affiliated Entity
Schedule Of Financial Receivables [Line Items]
Accounts receivable, sale		165
Accounts receivable sale, amount outstanding		46	$ 0
Receivables, maximum purchase amount		125
Financing receivables, held as collateral		33
Maximum
Schedule Of Financial Receivables [Line Items]
Funding of customer receivables sold	$ 300	$ 400