Regulatory Assets and Liabilities, Regulatory Assets (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 24	$ 44
Regulatory Asset, Noncurrent		185	193
Environmental Remediation Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		13	13
Regulatory Asset, Noncurrent		48	63
Pension and Retiree Medical Obligations
Regulatory Assets [Line Items]
Regulatory Asset, Current		2	2
Regulatory Asset, Noncurrent		62	61
Deferred Fuel Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		1	23
Regulatory Asset, Noncurrent		$ 0	0
Deferred Fuel Costs | Maximum
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		1 year
State Commission Adjustments
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 1	1
Regulatory Asset, Noncurrent		22	22
Recoverable Deferred Taxes on AFUDC Recorded in Plant
Regulatory Assets [Line Items]
Regulatory Asset, Current		0	0
Regulatory Asset, Noncurrent		26	20
Asset Retirement Obligation Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current	[1]	0	0
Regulatory Asset, Noncurrent	[1]	21	18
Other
Regulatory Assets [Line Items]
Regulatory Asset, Current		7	5
Regulatory Asset, Noncurrent		$ 6	$ 9

[1] Includes amounts recorded for future recovery of AROs, less amounts recovered through NSP-Wisconsin’s share of nuclear decommissioning accruals and gains from decommissioning investments.