Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total operating revenues	$ 592	$ 990
Depreciation, depletion and amortization expense	113	112
Impairments	1,479	0
Operating income (loss)	(1,490)	213
Interest expense	19	14
Gain (loss) on derivative	339	(32)
Gain on early extinguishment of debt	28	0
Other income, net	1	1
Provision (benefit) from income taxes	406	(426)
Assets	5,275	6,446	$ 6,717
Capital investments	237	325
Restructuring charges	10	3
Cash and cash equivalents	5		5
Property, plant and equipment	3,916		5,267
Unamortized debt expense	17		19
Right-of-use asset	152		$ 159
Change in accrued expenditures	8	66
Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	300	493
E&P
Segment Reporting Information [Line Items]
Total operating revenues	353	551
Depreciation, depletion and amortization expense	111	110
Impairments	1,479
Operating income (loss)	(1,486)	210
Interest expense	19	14
Gain (loss) on derivative	339	(32)
Gain on early extinguishment of debt	0
Other income, net	1	1
Provision (benefit) from income taxes	406	(426)
Assets	4,900	5,562
Capital investments	237	325
Restructuring charges	10	3
E&P | Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	(9)	(9)
Marketing
Segment Reporting Information [Line Items]
Total operating revenues	239	439
Depreciation, depletion and amortization expense	2	2
Impairments	0
Operating income (loss)	(4)	3
Interest expense	0	0
Gain (loss) on derivative	0	0
Gain on early extinguishment of debt	0
Other income, net	0	0
Provision (benefit) from income taxes	0	0
Assets	214	342
Capital investments	0	0
Marketing | Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	309	502
Other
Segment Reporting Information [Line Items]
Total operating revenues	0	0
Depreciation, depletion and amortization expense	0	0
Impairments	0
Operating income (loss)	0	0
Interest expense	0	0
Gain (loss) on derivative	0	0
Gain on early extinguishment of debt	28
Other income, net	0	0
Provision (benefit) from income taxes	0	0
Assets	161	542
Capital investments	0	0
Cash and cash equivalents	5	366
Income tax receivable	32	68
Property, plant and equipment	23	56
Unamortized debt expense	10	10
Prepayments	9	10
Non-qualified retirement plan	5	7
Right-of-use asset	77	25
Other | Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	$ 0	$ 0