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Fair Value Measurements - Schedule of Investments in Debt Securities Held by Decommissioning Trust Fund (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Fair Value Measurements |  |  |  |
Purchases | $ 245 | $ 0 | $ 12,651 | $ 0
Net Proceeds | (20) | 0 | (599) | 0
Unrealized Gain (Loss) | 43 | 0 | 174 | 0
Debt securities |  |  |  |
Fair Value Measurements |  |  |  |
Purchases | 245 | 0 | 12,651 | 0
Net Proceeds | 0 | 0 | 0 | 0
Unrealized Gain (Loss) | 43 | 0 | 174 | 0
Cash and cash equivalents |  |  |  |
Fair Value Measurements |  |  |  |
Purchases | 0 | 0 | 0 | 0
Net Proceeds | (3) | 0 | (748) | 0
Unrealized Gain (Loss) | 0 | 0 | 0 | 0
Other |  |  |  |
Fair Value Measurements |  |  |  |
Purchases | 0 | 0 | 0 | 0
Net Proceeds | (17) | 0 | 149 | 0
Unrealized Gain (Loss) | $ 0 | $ 0 | $ 0 | $ 0

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