Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									$ 2,745	$ 4,517	$ 5,189
Gains (losses) on oil, natural gas and NGL derivatives									596	5	(34)
Total oil, natural gas and NGL revenues	$ 1,259	$ 975	$ 521	$ 2,541	$ 1,926	$ 2,087	$ 2,386	$ 2,196	5,296	8,595	10,030
Marcellus
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									631	856	924
Haynesville
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									362	620	838
Eagle Ford
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									914	1,561	1,872
Brazos valley
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									514	769
Powder River Basin
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									231	478	350
Mid-Continent
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									93	233	385
Utica
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers											820
Oil
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									1,427	2,543	2,201
Gains (losses) on oil, natural gas and NGL derivatives									554	(212)	124
Oil | Marcellus
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									0	0	0
Oil | Haynesville
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									0	0	2
Oil | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									717	1,289	1,514
Oil | Brazos valley
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									485	721
Oil | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									170	369	244
Oil | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									55	164	246
Oil | Utica
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers											195
Natural gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									1,188	1,782	2,486
Gains (losses) on oil, natural gas and NGL derivatives									42	217	(147)
Natural gas | Marcellus
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									631	856	924
Natural gas | Haynesville
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									362	620	836
Natural gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									113	153	173
Natural gas | Brazos valley
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									16	32
Natural gas | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									41	77	68
Natural gas | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									25	44	84
Natural gas | Utica
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers											401
NGL
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									130	192	502
Gains (losses) on oil, natural gas and NGL derivatives									0	0	(11)
NGL | Marcellus
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									0	0	0
NGL | Haynesville
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									0	0	0
NGL | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									84	119	185
NGL | Brazos valley
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									13	16
NGL | Powder River Basin
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									20	32	38
NGL | Mid-Continent
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									13	25	55
NGL | Utica
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers											224
Oil, Natural Gas and NGL
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									3,341	4,522	5,155
Oil, Natural Gas and NGL | Oil
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									1,981	2,331	2,325
Oil, Natural Gas and NGL | Natural gas
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									1,230	1,999	2,339
Oil, Natural Gas and NGL | NGL
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									130	192	491
Marketing
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									1,799	3,619	4,390
Gains (losses) on oil, natural gas and NGL derivatives									1,869	(4)	7
Total oil, natural gas and NGL revenues										3,967	5,076
Marketing | Oil
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									1,195	2,473	2,740
Gains (losses) on oil, natural gas and NGL derivatives									1,262	0	0
Total oil, natural gas and NGL revenues										2,784	3,197
Marketing | Natural gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									494	900	1,194
Gains (losses) on oil, natural gas and NGL derivatives									497	(4)	7
Total oil, natural gas and NGL revenues										937	1,423
Marketing | NGL
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									110	246	456
Gains (losses) on oil, natural gas and NGL derivatives									110	0	0
Total oil, natural gas and NGL revenues										246	456
Other marketing revenue
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									70	352	679
Other marketing revenue | Oil
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									67	311	457
Other marketing revenue | Natural gas
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									3	41	222
Other marketing revenue | NGL
Disaggregation of Revenue [Line Items]
Total oil, natural gas and NGL revenues									$ 0	$ 0	$ 0