Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Current:
Federal	$ (6)	$ (19)
State	0	1
Total	(6)	(18)
Deferred:
Federal	61	64
State	14	9
Total	75	73
Provision (benefit) for income taxes	$ 69	$ 55