Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Current:
Federal	$ 3	$ 0
State	6	0
Total	9	0
Deferred:
Federal	15	(5)
State	13	7
Total	28	2
Provision (benefit) for income taxes	37	$ 2
Valuation Allowance, Deferred Tax Asset, Decrease Amount	$ 127