Derivative Financial Instruments (Derivative Obligations Under Terminated Hedge Arrangements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ (281)	$ 55	$ (292)
Commodity price derivatives | Derivative gain (loss), net
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(147)	34	(292)
Interest rate derivatives | Derivative gain (loss), net
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(22)	0	0
Contingent Consideration [Member] | Interest and Other Income (Loss), Net [Member]
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(42)	(45)	0
Marketing derivatives | Derivative gain (loss), net
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ (112)	$ 21	$ 0