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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