Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,179	$ 1,233		$ 2,409	$ 2,593
Gains (losses) on oil, natural gas and NGL derivatives	275	(251)		(26)	(368)
Revenues	2,386	2,289	[1]	4,582	4,813	[1]
Oil, natural gas and NGL
Disaggregation of Revenue [Line Items]
Revenues	1,454	982	[1]	2,383	2,225	[1]
Marketing
Disaggregation of Revenue [Line Items]
Revenues	824	1,069		1,967	2,158
Gains (losses) on oil, natural gas and NGL derivatives	(1)			(3)
Revenues	916	1,273	[1]	2,149	2,519	[1]
Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	93	204		185	361
Marcellus
Disaggregation of Revenue [Line Items]
Revenues	198	169		500	462
Haynesville
Disaggregation of Revenue [Line Items]
Revenues	164	199		365	411
Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	406	478		831	919
Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	213			340
Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	128	72		237	135
Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	70	89		136	215
Utica
Disaggregation of Revenue [Line Items]
Revenues		226			451
Oil
Disaggregation of Revenue [Line Items]
Revenues	700	567		1,266	1,104
Gains (losses) on oil, natural gas and NGL derivatives	86	(202)		(173)	(288)
Oil | Oil, natural gas and NGL
Disaggregation of Revenue [Line Items]
Revenues	786	365		1,093	816
Oil | Marketing
Disaggregation of Revenue [Line Items]
Revenues	614	732		1,227	1,418
Gains (losses) on oil, natural gas and NGL derivatives	0			0
Revenues	692	877		1,377	1,680
Oil | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	78	145		150	262
Oil | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	0	0		0	0
Oil | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	0	1		0	2
Oil | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	349	390		680	750
Oil | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	199			320
Oil | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	102	52		176	95
Oil | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	50	62		90	138
Oil | Utica
Disaggregation of Revenue [Line Items]
Revenues		62			119
Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	436	538		1,031	1,244
Gains (losses) on oil, natural gas and NGL derivatives	189	(35)		147	(67)
Natural Gas | Oil, natural gas and NGL
Disaggregation of Revenue [Line Items]
Revenues	625	503		1,178	1,177
Natural Gas | Marketing
Disaggregation of Revenue [Line Items]
Revenues	162	235		575	528
Gains (losses) on oil, natural gas and NGL derivatives	(1)			(3)
Revenues	176	294		607	627
Natural Gas | Other marketing revenue
Disaggregation of Revenue [Line Items]
Revenues	15	59		35	99
Natural Gas | Marcellus
Disaggregation of Revenue [Line Items]
Revenues	198	169		500	462
Natural Gas | Haynesville
Disaggregation of Revenue [Line Items]
Revenues	164	198		365	409
Natural Gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues	37	42		85	84
Natural Gas | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	9			13
Natural Gas | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	18	11		43	23
Natural Gas | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	10	15		25	47
Natural Gas | Utica
Disaggregation of Revenue [Line Items]
Revenues		103			219
NGL
Disaggregation of Revenue [Line Items]
Revenues	43	128		112	245
Gains (losses) on oil, natural gas and NGL derivatives	0	(14)		0	(13)
NGL | Oil, natural gas and NGL
Disaggregation of Revenue [Line Items]
Revenues	43	114		112	232
NGL | Marketing
Disaggregation of Revenue [Line Items]
Revenues	48	102		165	212
Gains (losses) on oil, natural gas and NGL derivatives	0			0
Revenues	48	102		165	212
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	20	46		66	85
NGL | Brazos Valley
Disaggregation of Revenue [Line Items]
Revenues	5			7
NGL | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenues	8	9		18	17
NGL | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenues	$ 10	12		$ 21	30
NGL | Utica
Disaggregation of Revenue [Line Items]
Revenues		$ 61			$ 113

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