Income Taxes - Deferred Tax Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax valuation allowance, rollfoward
Balance at beginning of year	$ 158
Balance at end of year	149	$ 158
Deferred tax asset valuation allowance
Deferred tax valuation allowance, rollfoward
Balance at beginning of year	158	152	$ 135
Charged to Income tax expense	(9)	6	17
Balance at end of year	$ 149	$ 158	$ 152