Income Taxes - Income Tax Provision (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current
Federal	$ (3)	$ 0	$ 0
State	(6)	(26)	0
Current Income Taxes	(9)	(26)	0
Deferred
Federal	0	(297)	3
State	(10)	(8)	(13)
Deferred Income Taxes	(10)	(305)	(10)
Total Income Tax Expense (Benefit)	$ (19)	$ (331)	$ (10)