Derivative Assets And Liabilities Table - Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Total derivatives assets	$ 700	$ 384
Total derivatives liabilities	(1,204)	(788)
Not Designated as Hedging Instrument [Member]
Total derivatives assets	689	360
Total derivatives liabilities	(1,192)	(788)
Fair Value, Recurring [Member]
Price Risk Derivative Liabilities, at Fair Value	631	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	620	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	11	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	74	41
Total derivatives liabilities	(58)	(39)
Commodity Derivatives (Margin Deposits) [Member] | Designated as Hedging Instrument [Member]
Total derivatives assets	11	24
Total derivatives liabilities	(12)	0
Commodity Derivatives (Margin Deposits) [Member] | Not Designated as Hedging Instrument [Member]
Total derivatives assets	615	319
Total derivatives liabilities	(561)	(350)
Interest Rate Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Total derivatives assets	0	0
Total derivatives liabilities	$ (573)	$ (399)