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Regulatory Matters (Tables) | 6 Months Ended
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Jun. 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 June 30, 2024 and December 31, 2023 and the period we expect to recover or refund such amounts:
| Period of |  | June 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 |  |  | $ | 86,057 |  |  | $ | 154 |  |  | $ | 86,134 |
Alternative Revenue Program Riders 2 | Up to 2 years |  | 3,548 |  |  | 95 |  |  | 3,719 |  |  | 158 |
Deferred Income Taxes | Asset lives |  | — |  |  | 7,187 |  |  | — |  |  | 6,940 |
Fuel Clause Adjustments 1 | Up to 1 year |  | 1,663 |  |  | — |  |  | 7,294 |  |  | — |
Derivative Instruments 1 | Up to 2 years |  | 1,516 |  |  | 462 |  |  | 4,210 |  |  | — |
Other 1 | Various |  | 1,291 |  |  | 1,804 |  |  | 750 |  |  | 2,483 |
Total Regulatory Assets |  |  | $ | 8,172 |  |  | $ | 95,605 |  |  | $ | 16,127 |  |  | $ | 95,715 |
Regulatory Liabilities |  |  |  |  |  |  |  |  |
Deferred Income Taxes | Asset lives |  | $ | — |  |  | $ | 133,412 |  |  | $ | — |  |  | $ | 136,022 |
Plant Removal Obligations | Asset lives |  | — |  |  | 117,499 |  |  | — |  |  | 117,030 |
Fuel Clause Adjustments | Up to 1 year |  | 24,055 |  |  | — |  |  | 11,350 |  |  | — |
Alternative Revenue Program Riders | Up to 1 year |  | 13,879 |  |  | — |  |  | 6,885 |  |  | — |
North Dakota PTC Refunds | Asset lives |  | — |  |  | 14,612 |  |  | — |  |  | 12,011 |
Pension and Other Postretirement Benefit Plans | Various |  | 6,138 |  |  | 8,894 |  |  | 6,138 |  |  | 11,307 |
Other | Various |  | 1,111 |  |  | 651 |  |  | 1,035 |  |  | 177 |
Total Regulatory Liabilities |  |  | $ | 45,183 |  |  | $ | 275,068 |  |  | $ | 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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