Income Taxes - Deferred Income Tax Valuation Allowance Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets Valuation Allowance [Roll Forward]
Beginning balance of deferred income tax valuation allowance	$ 119	$ 119	$ 126
Charges against goodwill	2	1	0
Decreases	(26)	(1)	(7)
Ending balance of deferred income tax valuation allowance	$ 95	$ 119	$ 119