Accounts Receivable - Schedule of Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable
Other	$ 37	$ 1
Total accounts receivable	425	553
Less: allowance for credit losses	(61)	(39)	$ (41)	$ (47)
Accounts receivable, less allowance	364	514
Earned and unbilled receivables
Accounts receivable
Total accounts receivable	63	81
Trade and purchased receivables
Accounts receivable
Total accounts receivable	$ 325	$ 471