CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues
Revenues	$ 930	$ 758	$ 1,689	$ 1,512
Revenue from Contract with Customer, Product and Service [Extensible List]	us-gaap:OilAndGasServiceMember	us-gaap:OilAndGasServiceMember	us-gaap:OilAndGasServiceMember	us-gaap:OilAndGasServiceMember
Costs and expenses
Operating and maintenance	$ 525	$ 510	$ 1,065	$ 1,018
Cost, Product and Service [Extensible List]	us-gaap:OilAndGasServiceMember	us-gaap:OilAndGasServiceMember	us-gaap:OilAndGasServiceMember	us-gaap:OilAndGasServiceMember
Depreciation and amortization	$ 196	$ 219	$ 402	$ 436
General and administrative	45	45	88	94
Total costs and expenses	766	774	1,555	1,548
Loss on impairment	429	1	597	1
Gain (loss) on disposal of assets, net	1	(10)		(3)
Operating loss	(264)	(27)	(463)	(40)
Other income (expense), net
Interest income	4	12	13	22
Interest expense, net of amounts capitalized	(153)	(168)	(313)	(334)
Gain (loss) on retirement of debt	4	(9)	(53)	(27)
Other, net	(56)	23	(44)	31
Total other income (expense), net	(201)	(142)	(397)	(308)
Loss before income tax expense	(465)	(169)	(860)	(348)
Income tax expense	32	37	28	29
Net loss	(497)	(206)	(888)	(377)
Net income attributable to noncontrolling interest		2	1	2
Net loss attributable to controlling interest	$ (497)	$ (208)	$ (889)	$ (379)
Loss per share
Basic (in dollars per share)	$ (0.81)	$ (0.34)	$ (1.45)	$ (0.62)
Diluted (in dollars per share)	$ (0.81)	$ (0.34)	$ (1.45)	$ (0.62)
Weighted-average shares outstanding
Basic (in shares)	615	612	615	612
Diluted (in shares)	615	612	615	612