Borrowings and Other Financing Instruments Dividend and Other Capital-Related Restrictions (Details) $ in Millions	Dec. 31, 2024 USD ($)
NSP Minnesota
Debt Instrument [Line Items]
Equity to total capitalization ratio, low end of range (in hundredths)	47.60%
Equity to total capitalization ratio, high end of range (in hundredths)	58.20%
Equity to total capitalization ratio	53.00%
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 1,809
Capitalization, Short term debt, long term debt and equity	17,490
Maximum total capitalization	17,800
Maximum additional short term debt authorized for issuance	$ 2,670	[1]
Maximum percentage of short term debt to total capitalization (in hundredths)	15.00%
NSP-Wisconsin
Debt Instrument [Line Items]
Minimum calendar year average equity to total capitalization ratio authorized by state commission	52.50%	[2]
Equity to total capitalization ratio	52.70%	[2]
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 12
Capitalization, Short term debt, long term debt and equity	2,922
Maximum additional long term debt authorized for issuance	225
Maximum additional short term debt authorized for issuance	$ 150
SPS
Debt Instrument [Line Items]
Equity to total capitalization ratio (excluding short-term debt), low end of range (in hundredths)	45.00%	[3]
Equity to total capitalization ratio (excluding short-term debt), high end of range (in hundredths)	55.00%	[3]
Equity to total capitalization ratio (excluding short-term debt) (in hundredths)	54.40%	[3]
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 592	[4]
Capitalization, Short term debt, long term debt and equity	7,789	[4]
Maximum additional long term debt authorized for issuance	150
Maximum additional short term debt authorized for issuance	700
PSCo
Debt Instrument [Line Items]
Maximum additional long term debt authorized for issuance	1,300
Maximum additional short term debt authorized for issuance	$ 1,200

[1] NSP-Minnesota has authorization to issue long-term securities provided the equity-to-total capitalization remains within the required range, and to issue short-term debt provided it does not exceed 15% of total capitalization.

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

[3] Excludes short-term debt.

[4] May not pay a dividend that would cause a loss of its investment grade bond rating.