Income Taxes Other Income Tax Matters (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021		Dec. 31, 2020
Income Tax [Line Items]
Federal NOL carryforward		$ 20	$ 20	$ 765
Federal tax credit carryforwards		1,593	1,593	1,172
State NOL carryforwards		1,022	1,022	1,648
Valuation allowances for state NOL carryforwards		(3)	(3)	(3)
state tax credit carryforward, net of federal detirment	[1]	85	85	89
valuation allowances for state credit carryforwards, net of federal benefit	[2]	(62)	(62)	(64)
Federal detriment		$ 23	$ 23	$ 24
Federal statutory rate			21.00%	21.00%	[3]	21.00%	[3]
State income tax on pretax income, net of federal tax effect			4.90%	5.00%	[3]	4.90%	[3]
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	[4]		(27.40%)	(23.40%)	[3]	(15.70%)	[3]
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[5]		(5.50%)	(6.20%)	[3]	(7.60%)	[3]
Other tax credits, net NOL & tax credit allowances			(1.30%)	(1.10%)	[3]	(1.20%)	[3]
NOL Carryback		0.00%		0.00%	[3]	(0.90%)	[3]
Other, net			(0.10%)	0.10%	[3]	(0.90%)	[3]
Effective income tax rate			(8.40%)	(4.60%)	[3]	(0.40%)	[3]
Total income tax benefit			$ (135)	$ (70)		$ (6)
Deferred tax (benefit) expense excluding items below			(138)	148		237
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities			8	(221)		(247)
Income Tax Expense (Benefit), Intraperiod Tax Allocation			(10)	(6)		2
Deferred tax benefit		$ (140)	(140)			(8)
Deferred fuel costs		222	222	262	[6]
Regulatory liabilities		1,255	1,255
Total deferred tax assets				79
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Federal Benefit		16	16	17
income tax expense
Income Tax [Line Items]
Current federal tax expense (benefit)			1	15		(13)
Current state tax expense (benefit)			3	(2)		2
Current change in unrecognized tax expense			5	1		18
Deferred federal tax benefit			(239)	(183)		(89)
Deferred state tax expense			96	99		91
Deferred change in unrecognized tax expense (benefit)			3	5		(10)
Deferred ITCs			(4)	(5)		(5)
Total income tax benefit			(135)	(70)		$ (6)
Net Deferred Tax Liablility [Member]
Income Tax [Line Items]
Federal tax credit carryforwards		325	325	351	[6]
Deferred ITCs			14	15	[6]
Differences between book and tax bases of property			6,442	6,231	[6]
Regulatory assets		508	508	560	[6]
Operating lease assets		325	325	351	[6]
Pension expense		159	159	175	[6]
Other		92	92	88	[6]
Total deferred tax liabilities		7,748	7,748	7,667	[6]
Tax credit carryforward		1,679	1,679	1,261	[6]
Regulatory liabilities		742	742	742	[6]
Other employee benefits		102	102	119	[6]
NOL carryforward		(57)	(57)	(247)	[6]
NOL and tax credit valuation allowances		(62)	(62)	(64)	[6]
Other		135	135	102	[6]
Total deferred tax assets		2,992	2,992	2,773	[6]
Net deferred tax liability		$ 4,756	$ 4,756	$ 4,894	[6]

[1] State tax credit carryforwards are net of federal detriment of $23 million and $24 million as of Dec. 31, 2022 and 2021.

[2] Valuation allowances for state tax credit carryforwards were net of federal benefit of $16 million and $17 million as of Dec. 31, 2022 and 2021.

[3] Prior period amounts have been restated to conform with current year presentation.

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

[5] 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

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