Other Income Tax Matters - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Income Tax Examination [Line Items]
Federal detriment		$ 3	$ 4
Federal Benefit		1	2
Federal NOL carryforward		0	5
Federal tax credit carryforwards		444	368
State NOL carryforwards		0	223
state tax credit carryforward, net of federal detirment	[1]	13	16
valuation allowances for state credit carryforwards, net of federal benefit	[2]	$ (3)	$ (6)
Federal statutory rate		21.00%	21.00%		21.00%
State income tax on pretax income, net of federal tax effect		3.50%	3.50%		3.60%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	[3]	(14.50%)	(14.30%)		(14.30%)
Plant regulatory differences (b)	[4]	(5.50%)	(4.50%)		(4.60%)
Other tax credits, net NOL & tax credit allowances		(1.10%)	(1.10%)		(1.00%)
Other, net		0.60%	0.20%		0.10%
Effective income tax rate		4.00%	4.80%		4.80%
Total income tax expense		$ 29	$ 37		$ 33
Deferred tax (benefit) expense excluding items below		(89)	23		63
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(48)	(32)		(42)
Tax expense allocated to other comprehensive income and other		(1)	(1)		0
Total deferred tax assets		(178)	(10)		(21)
Operating lease liabilities		392
Adjustments to deferred income taxes for wind production tax credit cash transfers	[5]	(40)	0		0
Deferred Tax Assets, Valuation Allowance		(3)	0
income tax expense [Member]
Income Tax Examination [Line Items]
Current federal tax expense		182	39		16
Current state tax expense		28	11		0
Current change in unrecognized tax benefit		0	0		(1)
Deferred federal tax benefit		(181)	(32)		(13)
Deferred state tax expense		2	21		31
Deferred change in unrecognized tax expense		1	1		3
Deferred ITCs		3	3		(3)
Total income tax expense		29	37		$ 33
Net Deferred Tax Liablility [Member]
Income Tax Examination [Line Items]
Deferred ITCs		(10)	(7)	[6]
Total deferred tax assets		(897)	(850)	[6]
Differences between book and tax bases of property		2,326	2,315	[6]
Regulatory assets		289	243	[6]
Operating Lease Assets		95	112	[3]
Deferred Fuel Cost		51	125	[6]
Pension expense and other employee benefits		22	27	[6]
Other		8	11	[6]
Total deferred tax liabilities		2,791	2,833	[6]
Deferred Tax Assets, Tax Credit Carryforwards		457	385	[6]
Regulatory Liability		291	292	[6]
Operating lease liabilities		95	112	[6]
Bad debts		14	14	[6]
Operating Loss Carryforwards		0	9
Tax Credit Valuation Allowance		(6)	(6)	[6]
Other		32	16	[6]
Net deferred tax liability		1,894	1,983	[6]
Deferred Tax Assets Rate Refund		$ 4	$ 21	[6]

[1] State tax credit carryforwards are net of federal detriment of $3 million and $4 million as of Dec. 31, 2023 and 2022, respectively.

[2] Valuation allowances for state tax credit carryforwards were net of federal benefit of $1 million and $2 million as of Dec. 31, 2023 and 2022, respectively.

[3] Wind PTCs net of estimated transfer discount are credited to customers (reduction to revenue) and do not materially impact net income.

[4] Plant regulatory differences primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit are offset by corresponding revenue reductions.

[5] Proceeds from tax credit transfers are included in cash received (paid) for income taxes in the consolidated statement of cash flows.

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