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Regulatory Matters (Tables) | 9 Months Ended
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Sep. 30, 2024
Regulatory Assets and Liabilities Disclosure [Abstract] |
Schedule of Regulatory Assets and Liabilities | The following presents our current and long-term regulatory assets and liabilities as of September 30, 2024 and December 31, 2023 and the period we expect to recover or refund such amounts:
| Period of |  | September 30, 2024 |  | December 31, 2023
(in thousands) | Recovery/Refund |  | Current |  | Long-Term |  | Current |  | Long-Term
Regulatory Assets |  |  |  |  |  |  |  |  |
Pension and Other Postretirement Benefit Plans 1 | Various |  | $ | 154 |  |  | $ | 86,020 |  |  | $ | 154 |  |  | $ | 86,134 |
Alternative Revenue Program Riders 2 | Up to 2 years |  | 4,145 |  |  | 145 |  |  | 3,719 |  |  | 158 |
Deferred Income Taxes | Asset lives |  | — |  |  | 7,217 |  |  | — |  |  | 6,940 |
Fuel Clause Adjustments 1 | Up to 1 year |  | — |  |  | — |  |  | 7,294 |  |  | — |
Derivative Instruments 1 | Up to 2 years |  | 2,116 |  |  | 686 |  |  | 4,210 |  |  | — |
Other 1 | Various |  | 1,445 |  |  | 1,469 |  |  | 750 |  |  | 2,483 |
Total Regulatory Assets |  |  | $ | 7,860 |  |  | $ | 95,537 |  |  | $ | 16,127 |  |  | $ | 95,715 |
Regulatory Liabilities |  |  |  |  |  |  |  |  |
Deferred Income Taxes | Asset lives |  | $ | — |  |  | $ | 131,584 |  |  | $ | — |  |  | $ | 136,022 |
Plant Removal Obligations | Asset lives |  | — |  |  | 125,681 |  |  | — |  |  | 117,030 |
Fuel Clause Adjustments | Up to 1 year |  | 18,808 |  |  | — |  |  | 11,350 |  |  | — |
Alternative Revenue Program Riders | Up to 1 year |  | 17,594 |  |  | — |  |  | 6,885 |  |  | — |
North Dakota PTC Refunds | Asset lives |  | — |  |  | 17,115 |  |  | — |  |  | 12,011 |
Pension and Other Postretirement Benefit Plans | Various |  | 6,138 |  |  | 7,737 |  |  | 6,138 |  |  | 11,307 |
Other | Various |  | 1,145 |  |  | 880 |  |  | 1,035 |  |  | 177 |
Total Regulatory Liabilities |  |  | $ | 43,685 |  |  | $ | 282,997 |  |  | $ | 25,408 |  |  | $ | 276,547 |
1 Costs subject to recovery without a rate of return. |  |  |  |  |  |  |  |  |
2 Amounts eligible for recovery includes an incentive or rate of return. |  |  |  |  |  |  |  |

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