Credit Facilities (Details) - Credit Facilities $ in Millions		12 Months Ended
		Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Line of Credit Facility [Line Items]
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Line Of Credit Facility Minimum Threshhold Percentage Of Subsidiary Assets To Consolidated Assets Required To Initiate Cross Default Provisions		15.00%
Line of Credit Facility, Minimum Amount of Indebtedness in Default to Initiate Cross Default Provisions		$ 75
Long-term Line of Credit		$ 0	$ 0
NSP Wisconsin [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio (as a percent)	[1]	48.20%	47.40%
Credit Facility	[2]	$ 150
Drawn	[3]	60
Available		$ 90
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[4]	1

[1] The credit facility has a financial covenant requiring that the debt-to-total capitalization ratio be less than or equal to 65%.

[2] This credit facility matures in September 2027.

[3] Includes outstanding commercial paper

[4] All extension requests are subject to majority bank group approval.