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Fair Value Measurements - Schedule of Costs and Fair Values of Investments in Debt Securities Held in Decommissioning Trust Fund (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Cost |  |
Less than 5 years | $ 23,359 | $ 10,708
5 years to 10 years | 0 | 0
Due after 10 years | 0 | 0
Total | 23,359 | 10,708
Estimated Fair Value |  |
Less than 5 years | 23,478 | 10,653
5 years to 10 years | 0 | 0
Due after 10 years | 0 | 0
Total | $ 23,478 | $ 10,653

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