Income Taxes - Unrecognized tax benefit (expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, beginning of period	$ 15	$ 14	$ 14
Gross increases - tax positions in current period	6	1	0
Lapse of statute of limitations	5	0	0
Balance, end of period	$ 16	$ 15	$ 14