Other Income Tax Matters - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021		Dec. 31, 2020
Income Tax Examination [Line Items]
Federal detriment		$ 4	$ 5
Federal Benefit		2	2
Federal NOL carryforward		5	161
Federal tax credit carryforwards		368	259
State NOL carryforwards		223	342
state tax credit carryforward, net of federal detirment		16	17
valuation allowances for state credit carryforwards, net of federal benefit		$ (6)	$ (8)
Federal statutory rate		21.00%	21.00%	[1]	21.00%	[1]
State income tax on pretax income, net of federal tax effect		3.50%	3.60%	[1]	3.60%	[1]
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	[1]	(14.30%)	(14.30%)		(10.30%)
Plant regulatory differences (b)	[2]	(4.50%)	(4.60%)	[1]	(5.00%)	[1]
Other tax credits, net NOL & tax credit allowances		(1.10%)	(1.00%)	[1]	(1.10%)	[1]
Other, net		0.20%	0.10%	[1]	(1.10%)	[1]
Effective income tax rate		4.80%	4.80%	[1]	7.10%	[1]
Total income tax expense		$ 37	$ 33		$ 45
Deferred tax expense excluding items below		23	63		46
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(32)	(42)		(43)
Tax expense allocated to other comprehensive income, and other		(1)	0		(1)
Total deferred tax assets		(10)	(21)		(2)
Deferred fuel costs		125	126	[1]
Operating lease liabilities		459
Bad debts		14	10	[3]
Tax credit valuation allowances		(6)	(8)	[3]
income tax expense [Member]
Income Tax Examination [Line Items]
Current federal tax expense		39	16		44
Current state tax expense		11	0		4
Current change in unrecognized tax benefit		0	(1)		(3)
Deferred federal tax benefit		(32)	(13)		(26)
Deferred state tax expense		21	31		26
Deferred change in unrecognized tax expense		1	3		2
Deferred ITCs		3	3		(2)
Total income tax expense		37	33		$ 45
Net Deferred Tax Liablility [Member]
Income Tax Examination [Line Items]
Deferred ITCs		(7)	(8)	[3]
Total deferred tax assets		(853)	(780)	[3]
Differences between book and tax bases of property		2,315	2,226	[3]
Regulatory assets		246	255	[3]
Operating lease assets		112	106	[3]
Pension expense and other employee benefits		27	23	[3]
Other		11	4	[3]
Total deferred tax liabilities		2,836	2,740	[3]
Regulatory liabilities		295	320	[3]
Tax credit carryforward		385	276	[3]
Operating lease liabilities		112	106	[3]
NOL carryforward		9	46	[3]
Other		16	14	[3]
Net deferred tax liability		1,983	1,960	[3]
Deferred Tax Assets Rate Refund		$ 21	$ 8

[1] Wind PTCs are credited to customers (reduction to revenue) and do not materially impact net income.

[2] Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred taxes are offset by corresponding revenue reductions and additional prepaid pension asset amortization.

[3] Prior periods have been reclassified to conform to current year presentation.