Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 4	$ 2	$ 9	$ 26
Net discrete (benefit) expense related to changes in valuation allowance		$ 1		$ 20