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Income Taxes (Tables) | 12 Months Ended
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Dec. 31, 2025
Income Tax Disclosure [Abstract] |
Schedule of Components of Income Tax Expense (Benefit) | Income tax expense on the Consolidated Statements of Operations for the years ended December 31 was as follows:
| 2025 |  | 2024 |  | 2023
| (In thousands)
Current: |  |  |  |  |
Federal | $ | 21,690 |  |  | $ | 51,899 |  |  | $ | 45,746 |
State | 8,955 |  |  | 17,767 |  |  | 18,296 |
| 30,645 |  |  | 69,666 |  |  | 64,042 |
Deferred: |  |  |  |  |
Income taxes: |  |  |  |  |
Federal | 19,032 |  |  | (1,082) |  |  | 263 |
State | 6,459 |  |  | 732 |  |  | (1,869) |
| 25,491 |  |  | (350) |  |  | (1,606) |
Total income tax expense | $ | 56,136 |  |  | $ | 69,316 |  |  | $ | 62,436 |
Schedule of Deferred Tax Assets and Liabilities | Components of deferred tax assets and deferred tax liabilities at December 31 were as follows:
| 2025 |  | 2024
| (In thousands)
Deferred tax assets: |  |  |
Deferred compensation/compensation related | $ | 20,750 |  |  | $ | 23,751 |
Asset retirement obligations | 20,506 |  |  | 15,420 |
Operating lease liabilities | 13,317 |  |  | 12,725 |
Accrued pension costs | 9,958 |  |  | 9,528 |
Capitalized inventory overheads | 9,951 |  |  | 8,359 |
Net operating loss | 3,318 |  |  | 5,528 |
Section 174 costs | — |  |  | 4,051 |
Other | 7,053 |  |  | 4,645 |
Total deferred tax assets | $ | 84,853 |  |  | $ | 84,007 |
| 2025 |  | 2024
| (In thousands)
Deferred tax liabilities: |  |  |
Basis differences on property, plant and equipment | $ | 317,809 |  |  | $ | 209,488 |
Intangible assets | 17,347 |  |  | 13,574 |
Operating lease right-of-use-assets | 13,317 |  |  | 12,725 |
Other | 21,269 |  |  | 17,419 |
Total deferred tax liabilities | 369,742 |  |  | 253,206 |
Valuation allowance | 3,028 |  |  | 5,528 |
Net deferred income tax liability | $ | (287,917) |  |  | $ | (174,727) |
Schedule of Net Deferred Income Tax Liability | The following table reconciles the change in the net deferred income tax liability from December 31, 2024, to December 31, 2025, to deferred income tax expense:
| 2025 |  | 2024
| (In thousands)
Change in net deferred income tax liability from the preceding table | $ | 113,190 |  |  | $ | 185 |
Deferred taxes established due to acquisition | (88,031) |  |  | — |
Deferred taxes associated with other comprehensive loss | 332 |  |  | (670) |
Other | — |  |  | 135 |
Deferred income tax expense for the period | $ | 25,491 |  |  | $ | (350) |
Schedule of Effective Income Tax Rate Reconciliation | Total income tax expense differs from the amount computed by applying the statutory federal income tax rate to income before taxes. The reasons for this difference were as follows:
Years ended December 31, |  | 2025 |  | 2024 |  | 2023
|  | Amount |  | % |  | Amount |  | % |  | Amount |  | %
|  | (Dollars in thousands)
Computed tax at federal statutory rate |  | $ | 44,770 |  |  | 21.0 |  |  | $ | 56,909 |  |  | 21.0 |  |  | $ | 51,515 |  |  | 21.0 |
Increases (reductions) resulting from: |  |  |  |  |  |  |  |  |  |  |  |
State income taxes, net of federal income tax* |  | 12,189 |  |  | 5.7 |  |  | 14,559 |  |  | 5.4 |  |  | 12,977 |  |  | 5.3 |
Depletion allowance |  | (2,359) |  |  | (1.1) |  |  | (2,767) |  |  | (1.0) |  |  | (2,808) |  |  | (1.1) |
Nondeductible expenses |  | 2,041 |  |  | 1.0 |  |  | 1,258 |  |  | 0.5 |  |  | 2,299 |  |  | 0.9 |
Tax credits |  | (549) |  |  | (0.3) |  |  | (720) |  |  | (0.3) |  |  | (1,722) |  |  | (0.7) |
Unrecognized tax benefits |  | 44 |  |  | — |  |  | 77 |  |  | — |  |  | 175 |  |  | 0.1 |
Total income tax expense |  | $ | 56,136 |  |  | 26.3 |  |  | $ | 69,316 |  |  | 25.6 |  |  | $ | 62,436 |  |  | 25.5 |
__________________ *State taxes in Oregon and California for 2025; and Oregon, Minnesota, and California for 2024 and 2023 constitute the majority (greater than 50%) of the tax effect within this category.
Schedule of Cash Flow Information | Cash expenditures for interest and income taxes for the years ended December 31 were as follows:
| 2025 |  | 2024 |  | 2023
| (In thousands)
Interest paid, net | $ | 78,780 |  |  | $ | 56,916 |  |  | $ | 54,925 |
Income taxes paid, net | $ | 41,765 |  |  | $ | 62,181 |  |  | $ | 76,689 |
Noncash investing and financing transactions at December 31 were as follows:
| 2025 |  | 2024 |  | 2023
| (In thousands)
Property, plant and equipment additions in accounts payable | $ | 25,840 |  |  | $ | 22,167 |  |  | $ | 12,672 |
Right-of-use assets obtained in exchange for new operating lease liabilities | $ | 15,811 |  |  | $ | 20,777 |  |  | $ | 14,967 |
Equity contribution from Centennial related to the Separation | $ | — |  |  | $ | — |  |  | $ | 64,724 |
Equity contribution to MDU Resources for asset/liability transfers related to the Separation | $ | — |  |  | $ | — |  |  | $ | (1,537) |
MDU Resources’ stock issued in connection with a business combination | $ | — |  |  | $ | — |  |  | $ | 383 |
Accrual for holdback payment related to a business combination | $ | 5,686 |  |  | $ | — |  |  | $ | — |
The following table provides cash taxes paid (net of refunds) for the year end December 31 were as follows:
Jurisdiction |  | 2025 |  | 2024
|  | (In thousands)
Federal |  | $ | 26,500 |  |  | $ | 40,736 |
Oregon |  | 6,350 |  |  | 7,229 |
Minnesota |  | 1,300 |  |  | 4,396 |
Other States/Cities |  | 7,615 |  |  | 9,820 |
Total |  | $ | 41,765 |  |  | $ | 62,181 |

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