Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income tax benefit	$ 0	$ 3	$ 26	$ (1)
Net discrete (benefit) expense related to changes in valuation allowance	$ 2	$ 1	$ 17	$ 6