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Investments - Debt Securities, Available-for-Sale (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Available-for-Sale |  |
Cost | $ 0.0 | $ 405.4
Unrealized gains | 0.0 | 0.0
Unrealized losses | 0.0 | (0.1)
Fair value | 0.0 | 405.3
Trading |  |
Cost | 24.6 | 17.9
Unrealized gains | 0.0 | 0.0
Unrealized losses | (0.3) | (0.1)
Fair value | $ 24.3 | $ 17.8

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