Revenue - Disaggregated Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 672	$ 1,003	$ 2,006	$ 3,412
Gains (losses) on oil, natural gas and NGL derivatives	(161)	167	573	141
Revenues	975	2,087	4,037	6,669
Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	511	1,170	2,579	3,553
Marketing
Disaggregation of Revenue [Line Items]
Revenues		805	1,344	2,773
Gains (losses) on oil, natural gas and NGL derivatives				(3)
Revenues	448	889	1,412	3,038
Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues		84	68	268
Marcellus
Disaggregation of Revenue [Line Items]
Revenues	137	158	445	657
Haynesville
Disaggregation of Revenue [Line Items]
Revenues	92	129	245	494
Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	241	336	675	1,167
Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	133	209	394	548
Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	47	118	175	355
Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	22	53	72	191
Oil
Disaggregation of Revenue [Line Items]
Revenues	366	613	1,091	1,879
Gains (losses) on oil, natural gas and NGL derivatives	(2)	124	689	(49)
Oil | Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	364	737	1,780	1,830
Oil | Marketing
Disaggregation of Revenue [Line Items]
Revenues		603	930	1,830
Gains (losses) on oil, natural gas and NGL derivatives				0
Revenues	301	683	997	2,060
Oil | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues		80	67	230
Oil | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Oil | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Oil | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	189	282	539	962
Oil | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	127	194	375	513
Oil | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	36	97	133	273
Oil | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	14	40	44	131
Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	270	353	824	1,384
Gains (losses) on oil, natural gas and NGL derivatives	(159)	43	(116)	190
Natural Gas | Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	111	396	708	1,574
Natural Gas | Marketing
Disaggregation of Revenue [Line Items]
Revenues		165	338	741
Gains (losses) on oil, natural gas and NGL derivatives				(3)
Revenues	116	169	339	776
Natural Gas | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues		4	1	38
Natural Gas | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	137	158	445	657
Natural Gas | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	92	129	245	494
Natural Gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	26	32	77	117
Natural Gas | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	3	10	10	23
Natural Gas | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	7	16	28	59
Natural Gas | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	5	8	19	34
NGL
Disaggregation of Revenue [Line Items]
Revenues	36	37	91	149
Gains (losses) on oil, natural gas and NGL derivatives	0	0	0	0
NGL | Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	36	37	91	149
NGL | Marketing
Disaggregation of Revenue [Line Items]
Revenues		37	76	202
Gains (losses) on oil, natural gas and NGL derivatives				0
Revenues	31	37	76	202
NGL | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues		0	0	0
NGL | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
NGL | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
NGL | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	26	22	59	88
NGL | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	3	5	9	12
NGL | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	4	5	14	23
NGL | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	$ 3	$ 5	$ 9	$ 26