Bilateral Credit Agreement (Details)	6 Months Ended
Jun. 30, 2022 USD ($)
Series Due June 1, 2052 \| NSP Minnesota [Member] \| Bonds [Member]
Short-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Debt Instrument, Face Amount	$ 500,000,000
Letter of Credit \| Bilateral Credit Agreement
Short-term Debt [Line Items]
Borrowing Limit	75,000,000
Amount outstanding at period end	$ 43,000,000
Letter of Credit \| Bilateral Credit Agreement \| NSP Minnesota [Member]
Short-term Debt [Line Items]
Debt Instrument, Term	1 year

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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