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Selected Balance Sheet Information: Accounts Receivable (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024 | Dec. 31, 2023
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Selected Balance Sheet Information [Abstract] |  |  |  |
Billed Accounts Receivable | $ 173.7 | $ 201.5 |  |
Unbilled Revenue | 79.8 | 151.8 |  |
Less: Allowance for Credit Losses | (2.1) | (2.1) | $ (1.4) | $ (2.2)
Account Receivable, net | $ 251.4 | $ 351.2 |  |

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