Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Aug. 10, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Current:
Federal		$ (10)	$ (19)	$ (25)	$ (55)
State		0	0	0	1
Foreign		1	0	1	0
Total		(9)	(19)	(24)	(54)
Deferred:
Federal		73	188	225	312
State		13	21	43	39
Total		86	209	268	351
Provision (benefit) for income taxes		$ 77	190	$ 244	297
Provision Related To Increase In Deferred State Income Tax Rate					38
Income Tax Contingency [Line Items]
Tax Credit Carryforward, Valuation Allowance			$ 105		105
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount					$ (31)
WPZ Merger Agreement [Member]
Income Tax Contingency [Line Items]
Increase (Decrease) in Deferred Income Taxes	$ (1,829)