Income Taxes - Reconciliation of the Beginning and Ending Balances of the Total Amounts of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, including related interest and penalties	$ 10	$ 12	$ 17	$ 15
Increases in tax positions for current years	2	2	0
Increases in tax positions for prior years	0	2	8
Lapse in statute of limitations	(4)	(3)	(6)
Settlements with tax authorities	$ 0	$ (6)	$ 0