Regulatory Assets and Liabilities, Regulatory Assets (Details) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Regulatory Assets [Line Items]
Regulatory Asset, Current		$ 23	$ 24
Regulatory Asset, Noncurrent		168	185
Environmental Remediation Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current		13	13
Regulatory Asset, Noncurrent		34	48
Pension and Retiree Medical Obligations
Regulatory Assets [Line Items]
Regulatory Asset, Current		2	2
Regulatory Asset, Noncurrent		60	62
State Commission Adjustments
Regulatory Assets [Line Items]
Regulatory Asset, Current		1	1
Regulatory Asset, Noncurrent		21	22
Recoverable Deferred Taxes on AFUDC Recorded in Plant
Regulatory Assets [Line Items]
Regulatory Asset, Current		0	0
Regulatory Asset, Noncurrent		31	26
Asset Retirement Obligation Costs
Regulatory Assets [Line Items]
Regulatory Asset, Current	[1]	0	0
Regulatory Asset, Noncurrent	[1]	21	21
Other
Regulatory Assets [Line Items]
Regulatory Asset, Current		7	8
Regulatory Asset, Noncurrent		$ 1	$ 6

[1] Includes amounts recorded for future recovery of AROs and NSP-Wisconsin’s share of nuclear decommissioning accruals.