Derivative and Hedging Activities - Oil, Natural Gas and NGL Revenues (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Gains (losses) on undesignated 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 sales
Derivative [Line Items]
Losses on terminated cash flow hedges	(8)	(8)		(26)	(25)
Oil, natural gas and NGL sales | Commodity contract | Not designated as hedging instrument
Derivative [Line Items]
Gains (losses) on undesignated oil, natural gas and NGL derivatives	175	(124)		167	(475)
Oil, natural gas and NGL
Derivative [Line Items]
Oil, natural gas and NGL revenues	1,003	1,331		3,412	3,924
Revenues	$ 1,170	$ 1,199	[1]	$ 3,553	$ 3,424	[1]

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