Dividend and Other Capital-Related Restrictions (Details) $ in Millions	Dec. 31, 2024 USD ($)
Dividend and Other Capital-Related Restrictions [Abstract]
Minimum calendar year average equity to total capitalization ratio authorized by state commission	52.50%	[1]
Equity to total capitalization ratio	52.70%	[1]
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 12
Total Capitalization	$ 2,922

[1] NSP-Wisconsin cannot pay annual dividends in excess of forecasted levels if its average equity-to-total capitalization ratio falls below the commission authorized level.