Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Current:
Federal	$ 0	$ 0	$ 3	$ 0
State	2	0	8	0
Foreign	0	(1)	0	(1)
Total	2	(1)	11	(1)
Deferred:
Federal	59	(52)	74	(57)
State	4	(18)	17	(11)
Foreign	0	(74)	0	(74)
Total	63	(144)	91	(142)
Provision (benefit) for income taxes	$ 65	$ (145)	102	(143)
Valuation Allowance, Deferred Tax Asset, Decrease Amount			$ 127
Canadian Operations [Member]
Income Tax Contingency [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down				$ 341