Derivative Assets And Liabilities Table - Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Total derivatives assets	$ 455	$ 384
Total derivatives liabilities	(1,043)	(788)
Not Designated as Hedging Instrument [Member]
Total derivatives assets	437	360
Total derivatives liabilities	(1,021)	(788)
Fair Value, Recurring [Member]
Price Risk Derivative Liabilities, at Fair Value	466	389
Forward Physical Swaps [Member] | Fair Value, Recurring [Member] | Commodity Derivatives - Natural Gas [Member]
Price Risk Derivative Liabilities, at Fair Value	1
Level 1 | Fair Value, Recurring [Member]
Price Risk Derivative Liabilities, at Fair Value	443	383
Level 1 | Forward Physical Swaps [Member] | Fair Value, Recurring [Member] | Commodity Derivatives - Natural Gas [Member]
Price Risk Derivative Liabilities, at Fair Value	0
Level 2 | Fair Value, Recurring [Member]
Price Risk Derivative Liabilities, at Fair Value	23	6
Level 2 | Forward Physical Swaps [Member] | Fair Value, Recurring [Member] | Commodity Derivatives - Natural Gas [Member]
Price Risk Derivative Liabilities, at Fair Value	1
Commodity Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Total derivatives assets	67	41
Total derivatives liabilities	(77)	(39)
Commodity Derivatives (Margin Deposits) [Member] | Designated as Hedging Instrument [Member]
Total derivatives assets	18	24
Total derivatives liabilities	(22)	0
Commodity Derivatives (Margin Deposits) [Member] | Not Designated as Hedging Instrument [Member]
Total derivatives assets	370	319
Total derivatives liabilities	(367)	(350)
Interest Rate Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Total derivatives assets	0	0
Total derivatives liabilities	$ (577)	$ (399)