Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Operating Revenue	[1]	$ 744	$ 672
Operating Expenses:
Fuel used in electric generation	[1]	132	104
Purchased power	[1]	16	13
Gas purchased for resale	[1]	81	57
Other operations and maintenance		99	90
Other operations and maintenance - affiliated suppliers		53	55
Impairment of assets and other charges		60	2
Depreciation and amortization		121	118
Other taxes	[1]	65	62
Total operating expenses		627	501
Operating income		117	171
Other income, net		6	3
Interest charges, net of allowance for borrowed funds used during construction of $1 and $2(1)	[1]	55	58
Income before income tax expense		68	116
Income tax expense		13	23
Net Income and Other Comprehensive Income		55	93
Comprehensive Income Attributable to Noncontrolling Interest		4	5
Comprehensive Income Available to Common Shareholder		$ 51	$ 88

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