v3.26.1
Debt
 6 Months Ended
Jun. 30, 2026
Debt Disclosure [Abstract]  
Debt Debt
Certain debt instruments of the Company and its subsidiaries contain restrictive and financial covenants and cross-default provisions. In order to borrow under the respective debt agreements, the Company and its subsidiaries must be in compliance with the applicable covenants and certain other conditions. The Company and its subsidiaries were in compliance with applicable covenants at June 30, 2026. In the event the Company or its subsidiaries do not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued.
Credit facilities
Montana-Dakota's commercial paper program is supported by a revolving credit agreement. While the amount of commercial paper outstanding does not reduce available capacity under the revolving credit agreement, Montana-Dakota does not issue commercial paper in an aggregate amount exceeding the available capacity under the credit agreement. The Company's borrowings under the commercial paper program and revolving credit agreements are classified as long-term debt as they are intended to be refinanced on a long-term basis through continued borrowings. All of the credit agreements contain customary covenants and provisions, including covenants not to permit, as of the end of any fiscal quarter, the ratio of funded debt to total capitalization (determined on a consolidated basis) to be greater than 65 percent. Other covenants include restrictions on the sale of certain assets, limitations on indebtedness and the making of certain investments.
The following table summarizes the outstanding revolving credit facilities of the Company and its subsidiaries:

CompanyDebt-to-Total Capitalization Ratio at June 30, 2026Provisions for Increased Borrowings, up to a maximum of:Facility
Limit		Amount Outstanding at June 30, 2026Amount Outstanding at June 30, 2025Amount Outstanding at December 31, 2025Letters of Credit at June 30, 2026Expiration
Date
(In millions)
Montana-Dakota Utilities Co.51 %$250.0 $200.0 $82.0 $43.3 $132.0 $— 12/11/30
Cascade Natural Gas Corporation49 %$225.0 $175.0 $108.3 $14.0 $96.5 $2.2 12/11/30
Intermountain Gas Company53 %$225.0 $175.0 $77.9 $86.8 $67.3 $— 12/11/30
MDU Resources Group, Inc.47 %$250.0 $200.0 $45.0 $— $32.9 $1.0 12/11/30
Long-term Debt Outstanding
Long-term debt outstanding was as follows:
Weighted
Average
Interest
Rate at
June 30, 2026
June 30, 2026June 30, 2025December 31, 2025
(In thousands)
Senior Notes due on dates ranging from July 15, 2026 to June 15, 20624.83 %$2,110,000 $1,947,000 $2,010,000 
Credit agreements due on December 11, 20305.27 %231,150 100,800 196,700 
Term Loan Agreements due on dates ranging from January 31, 2027 to March 31, 20394.04 %126,900 61,600 310,900 
Commercial paper supported by revolving credit agreement4.06 %82,000 43,300 132,000 
Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 20297.32 %35,000 35,000 35,000 
Other notes due on November 30, 20386.00 %321 338 329 
Less unamortized debt issuance costs8,214 6,103 8,074 
Total long-term debt2,577,157 2,181,935 2,676,855 
Less current maturities4,700 136,700 144,700 
Net long-term debt$2,572,457 $2,045,235 $2,532,155 

Montana-Dakota On October 28, 2025, Montana-Dakota entered into a NPA to issue $250.0 million of senior notes, with maturity dates of October 28, 2035, October 28, 2040, and February 2, 2056, at a weighted average interest rate of 5.96 percent. On October 28, 2025, Montana-Dakota issued $150.0 million in senior notes under the NPA with the remaining $100.0 million issued on February 2, 2026. The agreement contains customary covenants and provisions, including a covenant of Montana-Dakota not to permit, at any time, the ratio of total debt to capitalization to be greater than 65 percent. Other covenants include a minimum interest coverage ratio and restrictions on the sale of certain assets.

On December 30, 2025, Montana-Dakota entered into a $250.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of January 29, 2027. In February 2026 and March 2026, Montana-Dakota paid down $100.0 million and $80.0 million of the outstanding balance under the term loan agreement, respectively. The agreement contains customary covenants and provisions, including a covenant of Montana-Dakota not to permit, at any time, the ratio of total debt to capitalization to be greater than 65 percent. The covenants also include certain restrictions on the sale of certain assets, loans, and investments.

On June 16, 2026, Montana-Dakota entered into a NPA to issue $225.0 million of senior notes, with a maturity date of August 18, 2057, at an interest rate of 6.17 percent. The $225.0 million is expected to be issued August 18, 2026. The agreement contains customary covenants and provisions, including a covenant of Montana-Dakota not to permit, at any time, the ratio of total debt to capitalization to be greater than 65 percent. Other covenants include a minimum interest coverage ratio and restrictions on the sale of certain assets.

WBI Energy Transmission On January 15, 2026, WBI Energy Transmission extended its $350.0 million uncommitted note purchase and private shelf agreement from December 22, 2025 to December 22, 2028, unless either party terminates such issuance right. WBI Energy Transmission had $235.0 million of notes outstanding at June 30, 2026, which reduced the remaining capacity under this uncommitted private shelf agreement to $115.0 million. The principal amount and interest rate of any series of shelf notes will be determined at the applicable time of issuance and purchase.
WBI Energy Transmission's ratio of total debt to total capitalization at June 30, 2026 was 39 percent.