Derivative and Hedging Activities - Oil, Natural Gas and NGL Revenues Table (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Losses on undesignated oil, natural gas and NGL derivatives	$ (301)	$ (117)
Revenues	2,196	2,524	[1]
Oil, natural gas and NGL sales
Derivative [Line Items]
Losses on terminated cash flow hedges	(10)	(10)
Oil, natural gas and NGL sales | Commodity contract | Not designated as hedging instrument
Derivative [Line Items]
Losses on undesignated oil, natural gas and NGL derivatives	(291)	(107)
Oil, natural gas and NGL
Derivative [Line Items]
Oil, natural gas and NGL revenues	1,230	1,360
Revenues	$ 929	$ 1,243	[1]

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