Derivative and Hedging Activities - Oil, Natural Gas and NGL Revenues (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018
Derivative [Line Items]
Gains (losses) on undesignated 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 sales
Derivative [Line Items]
Losses on terminated cash flow hedges	(8)	(7)		(18)	(17)
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	283	(244)		(8)	(351)
Oil, natural gas and NGL
Derivative [Line Items]
Oil, natural gas and NGL revenues	1,179	1,233		2,409	2,593
Revenues	$ 1,454	$ 982	[1]	$ 2,383	$ 2,225	[1]

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