Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Unrecognized Tax Benefits
Unrecognized tax benefits at beginning of year	$ 7	$ 4
Increases as a result of tax positions taken during the current period	1	3
Decreases as a result of tax positions taken during a prior period	(1)	0
Total unrecognized tax benefits at end of year	$ 7	$ 7