Derivatives - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) on commodity derivatives	$ 47,000,000	$ (70,000,000)	$ (28,000,000)	$ (324,000,000)
Commodity
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) on commodity derivatives	33,000,000	19,000,000	(69,000,000)	(69,000,000)
Net gain (loss) on settlements, net	14,000,000	(89,000,000)	41,000,000	(255,000,000)
Interest Rate
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount					$ 0
Deferred loss related to interest rate swaps	1,000,000
Operating Segments | United States E&P
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) on commodity derivatives	14,000,000	$ (89,000,000)	41,000,000	$ (255,000,000)
Cash Flow Hedging | Interest Rate
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	$ 160,000,000		$ 160,000,000