Derivative Instruments (Details 4) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary of Derivative Instruments by Risk Exposure [Abstract]
Gain (Loss) on Derivative Instruments, Net, Pretax	[1]	$ 39	$ 244	$ 213	$ 400
Gain (Loss) on Sale of Derivatives	[2],[3]	18	58	15	169
Mark-to-market gain (loss)	[4]	21	186	198	231
Sales [Member]
Summary of Derivative Instruments by Risk Exposure [Abstract]
Gain (Loss) on Derivative Instruments, Net, Pretax	[1],[5],[6]	34	541	541	578
Cost of Sales [Member]
Summary of Derivative Instruments by Risk Exposure [Abstract]
Gain (Loss) on Derivative Instruments, Net, Pretax	[1],[5],[6]	37	(296)	(272)	(176)
Interest Expense [Member]
Summary of Derivative Instruments by Risk Exposure [Abstract]
Gain (Loss) on Derivative Instruments, Net, Pretax	[1]	(32)	(1)	(56)	(2)
Interest rate hedging instruments
Summary of Derivative Instruments by Risk Exposure [Abstract]
Gain (Loss) on Sale of Derivatives	[2],[3],[7]	(18)	0	(18)	0
Mark-to-market gain (loss)	[4]	(14)	(1)	(38)	(2)
Energy Related Derivative
Summary of Derivative Instruments by Risk Exposure [Abstract]
Gain (Loss) on Sale of Derivatives	[2],[3]	36	58	33	169
Mark-to-market gain (loss)	[4]	$ 35	$ 187	$ 236	$ 233

[1] In addition to changes in market value on derivatives not designated as hedges, changes in mark-to-market gain (loss) also includes adjustments to reflect changes in credit default risk exposure.

[2] Does not include the realized value associated with derivative instruments that settle through physical delivery.

[3] Includes amortization of acquisition date fair value of financial derivative activity related to the acquisition of Champion Energy and Calpine Solutions.

[4] In addition to changes in market value on derivatives not designated as hedges, changes in mark-to-market gain (loss) also includes adjustments to reflect changes in credit default risk exposure.

[5] Does not include the realized value associated with derivative instruments that settle through physical delivery.

[6] Includes amortization of acquisition date fair value of financial derivative activity related to the acquisition of Champion Energy and Calpine Solutions.

[7] Includes costs associated with the termination of de-designated interest rate hedging instruments recorded to interest expense related to our Steamboat project debt that was repaid in June 2020.