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Investments - Carrying Amount of Equity Method Limited Partnership Interests (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | $ 1,137.8 | $ 1,121.3
Commercial mortgage loan funds |  |
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | 593.2 | 596.0
Real estate equity funds |  |
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | 146.5 | 144.7
Private equity funds |  |
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | 112.5 | 102.2
Infrastructure equity funds |  |
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | 83.6 | 81.7
Infrastructure debt funds |  |
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | 66.5 | 69.0
Other funds |  |
Schedule of Equity Method Investments [Line Items] |  |
Limited partnership interests | $ 135.5 | $ 127.7

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