Derivatives - Gains and Losses on Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Losses on interest rate swaps and Berkshire warrants, net	$ (76)	$ 0	$ (661)	$ 0
Oil Collars and Calls | Net sales
Derivative Instruments, Gain (Loss) [Line Items]
Losses on interest rate swaps and Berkshire warrants, net	5	0	957	0
Marketing Derivatives | Net sales
Derivative Instruments, Gain (Loss) [Line Items]
Losses on interest rate swaps and Berkshire warrants, net	(392)	683	18	1,248
Interest Rate Swaps | Gains (losses) on interest rate swaps and warrants, net
Derivative Instruments, Gain (Loss) [Line Items]
Losses on interest rate swaps and Berkshire warrants, net	3	0	(666)	0
Warrant | Gains (losses) on interest rate swaps and warrants, net
Derivative Instruments, Gain (Loss) [Line Items]
Losses on interest rate swaps and Berkshire warrants, net	$ (79)	$ 0	$ 5	$ 0