Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,003	$ 1,331		$ 3,412	$ 3,924
Gains (losses) on oil, natural gas and NGL derivatives	167	(132)		141	(500)
Revenues	2,087	2,424	[1]	6,669	7,237	[1]
Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	1,170	1,199	[1]	3,553	3,424	[1]
Marketing
Disaggregation of Revenue [Line Items]
Revenues	805	1,030		2,773	3,182
Gains (losses) on oil, natural gas and NGL derivatives	0			(3)
Revenues	889	1,219	[1]	3,038	3,738	[1]
Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	84	189		268	556
Marcellus
Disaggregation of Revenue [Line Items]
Revenues	158	184		656	646
Haynesville
Disaggregation of Revenue [Line Items]
Revenues	129	195		494	605
Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	336	493		1,168	1,411
Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	209			548
Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	118	108		355	243
Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	53	85		191	301
Utica
Disaggregation of Revenue [Line Items]
Revenues		266			718
Oil
Disaggregation of Revenue [Line Items]
Revenues	613	594		1,879	1,698
Gains (losses) on oil, natural gas and NGL derivatives	124	(100)		(49)	(388)
Oil | Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	737	494		1,830	1,310
Oil | Marketing
Disaggregation of Revenue [Line Items]
Revenues	603	707		1,830	2,125
Gains (losses) on oil, natural gas and NGL derivatives	0			0
Revenues	683	826		2,060	2,506
Oil | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	80	119		230	381
Oil | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	0	0		0	0
Oil | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	0	0		0	2
Oil | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	282	399		962	1,148
Oil | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	194			513
Oil | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	97	78		273	173
Oil | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	40	58		131	196
Oil | Utica
Disaggregation of Revenue [Line Items]
Revenues		59			179
Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	353	578		1,383	1,822
Gains (losses) on oil, natural gas and NGL derivatives	43	(18)		190	(85)
Natural Gas | Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	396	560		1,573	1,737
Natural Gas | Marketing
Disaggregation of Revenue [Line Items]
Revenues	165	211		741	733
Gains (losses) on oil, natural gas and NGL derivatives	0			(3)
Revenues	169	281		776	908
Natural Gas | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	4	70		38	175
Natural Gas | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	158	184		656	646
Natural Gas | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	129	195		494	603
Natural Gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	32	36		117	120
Natural Gas | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	10			23
Natural Gas | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	16	17		59	40
Natural Gas | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	8	15		34	63
Natural Gas | Utica
Disaggregation of Revenue [Line Items]
Revenues		131			350
NGL
Disaggregation of Revenue [Line Items]
Revenues	37	159		150	404
Gains (losses) on oil, natural gas and NGL derivatives	0	(14)		0	(27)
NGL | Oil, natural gas and NGL revenue
Disaggregation of Revenue [Line Items]
Revenues	37	145		150	377
NGL | Marketing
Disaggregation of Revenue [Line Items]
Revenues	37	112		202	324
Gains (losses) on oil, natural gas and NGL derivatives	0			0
Revenues	37	112		202	324
NGL | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	0	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	22	58		89	143
NGL | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	5			12
NGL | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	5	13		23	30
NGL | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	$ 5	12		$ 26	42
NGL | Utica
Disaggregation of Revenue [Line Items]
Revenues		$ 76			$ 189

[1] Financial information for 2018 has been recast to reflect the retrospective application of the successful efforts method of accounting. See Note 1.