Derivative Instruments (Details 3) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Sale of Derivatives	[1],[2]	$ 256	$ 193	$ 7
Unrealized Gain (Loss) on Derivatives	[3]	275	(205)	(169)
Gain (Loss) on Derivative Instruments, Net, Pretax	[4]	531	(12)	(162)
Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Sale of Derivatives	[1],[2]	256	193	7
Unrealized Gain (Loss) on Derivatives	[3]	278	(208)	(171)
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	[3]	(3)	3	2
Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	[4],[5],[6]	816	(369)	(69)
Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	[4],[5],[6]	(282)	354	(95)
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax		$ (3)	$ 3	$ 2

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

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

[3] 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.

[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