Derivative Instruments - Gains and Losses on Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives	$ (33)	$ 0	$ (33)	$ 0
Oil Collars and Calls | Net sales
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives	75	0	75	0
Marketing Derivatives | Net sales
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives	91	36	(119)	8
Interest Rate Swaps | Losses on interest rate swaps and warrants, net
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives	(45)	0	(45)	0
Interest Rate Swaps | Losses on interest rate swaps and warrants, net | WES Midstream
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives	(8)	0	(8)	0
Warrant | Losses on interest rate swaps and warrants, net
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives	$ 20	$ 0	$ 20	$ 0