Derivative Assets And Liabilities Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Total derivatives assets	$ 147	$ 384
Total derivatives liabilities	(726)	(788)
Designated as Hedging Instrument [Member] | Commodity derivatives (margin deposits)
Total derivatives assets	32	24
Total derivatives liabilities	(52)	0
Not Designated as Hedging Instrument [Member]
Total derivatives assets	115	360
Total derivatives liabilities	(674)	(788)
Not Designated as Hedging Instrument [Member] | Commodity derivatives (margin deposits)
Total derivatives assets	68	319
Total derivatives liabilities	(107)	(350)
Not Designated as Hedging Instrument [Member] | Commodity derivatives
Total derivatives assets	47	41
Total derivatives liabilities	(45)	(39)
Not Designated as Hedging Instrument [Member] | Interest rate derivatives
Total derivatives assets	0	0
Total derivatives liabilities	$ (522)	$ (399)