Borrowings and Other Financing Instruments Dividend and Other Capital-Related Restrictions (Details) $ in Millions	Dec. 31, 2022 USD ($)
NSP Minnesota
Debt Instrument [Line Items]
Equity to total capitalization ratio, low end of range (in hundredths)	47.20%
Equity to total capitalization ratio, high end of range (in hundredths)	57.60%
Equity to total capitalization ratio	52.30%
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 1,446
Capitalization, Short term debt, long term debt and equity	14,984
Maximum total capitalization	16,140
Maximum additional short term debt authorized for issuance	$ 2,400	[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%
Equity to total capitalization ratio	52.80%
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 11	[2]
Capitalization, Short term debt, long term debt and equity	2,280	[2]
Maximum additional long term debt authorized for issuance	50
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)	54.30%	[3]
Unrestricted Retained Earnings Per State Regulatory Commissions Dividend Restrictions	$ 540	[4]
Capitalization, Short term debt, long term debt and equity	7,094,000	[4]
Maximum additional long term debt authorized for issuance	0
Maximum additional short term debt authorized for issuance	600
PSCo
Debt Instrument [Line Items]
Maximum additional long term debt authorized for issuance	1,300
Maximum additional short term debt authorized for issuance	$ 800

[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.