Derivatives - Gains and Losses on Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on interest rate swaps and Berkshire warrants, net	$ 88	$ (33)	$ (573)	$ (33)
Collars and Call Options | Net sales
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on interest rate swaps and Berkshire warrants, net	110	75	1,067	75
Marketing Derivatives | Net sales
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on interest rate swaps and Berkshire warrants, net	(18)	91	0	(119)
Interest Rate Swaps | Gains (losses) on interest rate swaps and warrants, net
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on interest rate swaps and Berkshire warrants, net	88	(53)	(577)	(53)
Warrant | Gains (losses) on interest rate swaps and warrants, net
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on interest rate swaps and Berkshire warrants, net	$ 0	$ 20	$ 5	$ 20