Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Current:
Federal	$ 7	$ 0	$ 10	$ 0
State	9	1	17	1
Foreign	0	0	0	(1)
Total	16	1	27	0
Deferred:
Federal	(11)	8	63	(49)
State	19	71	36	60
Foreign	0	(11)	0	(85)
Total	8	68	99	(74)
Provision (benefit) for income taxes	24	69	126	(74)
Provision Related To Increase In Deferred State Income Tax Rate	$ 18	$ 43	18	$ 43
Valuation Allowance, Deferred Tax Asset, Decrease Amount			$ 127