Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Aug. 10, 2018	Dec. 31, 2017
Current:
Federal	$ (19)	$ 7	$ (55)	$ 10
State	0	9	1	17
Total	(19)	16	(54)	27
Deferred:
Federal	188	(11)	312	63
State	21	19	39	36
Total	209	8	351	99
Provision (benefit) for income taxes	190	24	297	126
Provision Related To Increase In Deferred State Income Tax Rate		$ 18	38	18
Valuation Allowance, Deferred Tax Asset, Decrease Amount			31	$ 127
Income Tax Contingency [Line Items]
Tax Credit Carryforward, Valuation Allowance	105		105
Deferred Tax Liabilities, Net, Noncurrent	$ (1,648)		$ (1,648)			$ (3,147)
WPZ Merger Public Unit Exchange [Member]
Income Tax Contingency [Line Items]
Deferred Tax Liabilities, Net, Noncurrent					$ 1,829