Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Operating Revenue	[1]	$ 672	$ (335)
Operating Expenses:
Fuel used in electric generation	[1]	104	137
Purchased power	[1]	13	8
Gas purchased for resale	[1]	57	77
Other operations and maintenance		90	96
Other operations and maintenance - affiliated suppliers		55	48
Impairment of assets and other charges		2	271
Depreciation and amortization		118	102
Other taxes	[1]	62	69
Total operating expenses		501	808
Operating income (loss)		171	(1,143)
Other income (expense), net		3	(5)
Interest charges, net of allowance for borrowed funds used during construction of $2 and $-(1)	[1]	58	73
Income (loss) before income tax expense (benefit)		116	(1,221)
Income tax expense (benefit)		23	(118)
Net Income (Loss) and Other Comprehensive Income (Loss)		93	(1,103)
Comprehensive Income Attributable to Noncontrolling Interest		5	6
Comprehensive Income (Loss) Available (Attributable) to Common Shareholder		$ 88	$ (1,109)

[1] See Note 12 for amounts attributable to affiliates.