Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Operating Revenue	[1]	$ 624	$ 698	$ 1,296	$ 363
Operating Expenses:
Fuel used in electric generation	[1]	95	143	199	280
Purchased power	[1]	25	12	38	20
Gas purchased for resale	[1]	34	44	91	121
Other operations and maintenance		93	123	183	219
Other operations and maintenance - affiliated suppliers		50	72	105	120
Impairment of assets and other charges		0	100	2	371
Depreciation and amortization		118	115	236	217
Other taxes	[1]	65	72	127	141
Total operating expenses		480	681	981	1,489
Operating income (loss)		144	17	315	(1,126)
Other income (expense), net		2	(9)	5	(14)
Interest charges, net of allowance for borrowed funds used during construction of $1, $2, $3 and $2	[1]	58	63	116	136
Income (loss) before income tax expense (benefit)		88	(55)	204	(1,276)
Income tax expense (benefit)		21	15	44	(103)
Net Income (Loss) and Other Comprehensive Income (Loss)		67	(70)	160	(1,173)
Comprehensive Income (Loss) Attributable to Noncontrolling Interest		(2)	8	3	14
Comprehensive Income (Loss) Available (Attributable) to Common Shareholder		$ 69	$ (78)	$ 157	$ (1,187)

[1] See Note 14 for amounts attributable to affiliates.