Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Operating Revenue	[1]	$ 755	$ 795	$ 2,051	$ 1,158
Operating Expenses:
Fuel used in electric generation	[1]	135	167	334	447
Purchased power	[1]	25	15	63	35
Gas purchased for resale	[1]	33	37	124	158
Other operations and maintenance		93	90	276	309
Other operations and maintenance - affiliated suppliers		49	54	154	174
Impairment of assets and other charges		63	0	65	371
Depreciation and amortization		118	116	354	333
Other taxes	[1]	59	55	186	196
Total operating expenses		575	534	1,556	2,023
Operating income (loss)		180	261	495	(865)
Other income (expense), net		(2)	(13)	3	(27)
Interest charges, net of allowance for borrowed funds used during construction of $2, $2, $5 and $4(1)	[1]	57	66	173	202
Income (loss) before income tax expense (benefit)		121	182	325	(1,094)
Income tax expense (benefit)		15	40	59	(63)
Net Income (Loss)		106	142	266	(1,031)
Other Comprehensive Income:
Deferred cost of employee benefit plans, net of tax of $-, $-, $-, $-		0	1	0	1
Total Comprehensive Income (Loss)		106	143	266	(1,030)
Comprehensive Income Attributable to Noncontrolling Interest		5	0	8	14
Comprehensive Income (Loss) Available (Attributable) to Common Shareholder		$ 101	$ 143	$ 258	$ (1,044)

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