Financing Activities	6 Months Ended
Jun. 30, 2026
Financing Activities [Abstract]
Financing Activities	(6) Financing Activities We exercised a five-year renewal option on a default supply procurement agreement, which we have recorded as a finance lease on our Condensed Consolidated Balance Sheets. As a result, the finance lease term was extended and will mature on June 30, 2031. On April 9, 2026, we amended our existing NorthWestern Energy Group Term Loan Credit Agreement (NWE Group Term Loan) to extend the maturity date from April 10, 2026 to December 31, 2026. In May 2026, we repaid $50.0 million of this NWE Group Term Loan. On April 28, 2026, NWE Public Service priced $150.0 million aggregate principal amount of South Dakota First Mortgage Bonds at a fixed interest rate of 5.51 percent maturing on June 15, 2036. We completed the issuance and sale of these bonds on June 15, 2026. Proceeds were utilized to redeem NWE Public Service's $60.0 million of 2.80 percent South Dakota First Mortgage Bonds due on June 15, 2026, to repay outstanding borrowings under our credit facility, and for general utility purposes. On May 27, 2026, NW Corp entered into a $225.0 million secured Term Loan Credit Agreement (NW Corp Term Loan) with a maturity date of November 26, 2027. NW Corp's obligations under the NW Corp Term Loan are secured by $225.0 million of Montana First Mortgage Bonds issued to the administrative agent of the term loan facility. Borrowings may be made at a variable interest rate equal to the Secured Overnight Financing Rate plus an applicable margin as provided in the NW Corp Term Loan. Proceeds were used to repay a portion of NW Corp's outstanding revolving credit facility borrowings. The NW Corp Term Loan provides for prepayment of the principal and interest; however, amounts prepaid may not be reborrowed. The NW Corp Term Loan requires NW Corp to maintain a consolidated indebtedness to total capitalization ratio of 65 percent or less. It also contains covenants which, among other things, limit our ability to engage in any consolidation or merger (except for our pending merger with Black Hills) or otherwise liquidate or dissolve, dispose of property, and restricts certain affiliate transactions.

On April 9, 2026, we amended our existing NorthWestern Energy Group Term Loan Credit Agreement (NWE Group Term Loan) to extend the maturity date from April 10, 2026 to December 31, 2026. In May 2026, we repaid $50.0 million of this NWE Group Term Loan.

On April 28, 2026, NWE Public Service priced $150.0 million aggregate principal amount of South Dakota First Mortgage Bonds at a fixed interest rate of 5.51 percent maturing on June 15, 2036. We completed the issuance and sale of these bonds on June 15, 2026. Proceeds were utilized to redeem NWE Public Service's $60.0 million of 2.80 percent South Dakota First Mortgage Bonds due on June 15, 2026, to repay outstanding borrowings under our credit facility, and for general utility purposes.

On May 27, 2026, NW Corp entered into a $225.0 million secured Term Loan Credit Agreement (NW Corp Term Loan) with a maturity date of November 26, 2027. NW Corp's obligations under the NW Corp Term Loan are secured by $225.0 million of Montana First Mortgage Bonds issued to the administrative agent of the term loan facility. Borrowings may be made at a variable interest rate equal to the Secured Overnight Financing Rate plus an applicable margin as provided in the NW Corp Term Loan. Proceeds were used to repay a portion of NW Corp's outstanding revolving credit facility borrowings. The NW Corp Term Loan provides for prepayment of the principal and interest; however, amounts prepaid may not be reborrowed. The NW Corp Term Loan requires NW Corp to maintain a consolidated indebtedness to total capitalization ratio of 65 percent or less. It also contains covenants which, among other things, limit our ability to engage in any consolidation or merger (except for our pending merger with Black Hills) or otherwise liquidate or dissolve, dispose of property, and restricts certain affiliate transactions.