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Investments - Schedule of Changes in Other Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Other Investments [Roll Forward] |  |  |  |
Balance, beginning of period | $ 566.1 | $ 530.3 | $ 539.0 | $ 480.9
Purchases and commitments funded | 19.6 | 13.6 | 68.5 | 78.1
Sales and distributions | (25.4) | (20.4) | (67.3) | (47.1)
Net realized and unrealized gains | 13.9 | 9.3 | 34.0 | 20.9
Balance, end of period | 574.2 | 532.8 | 574.2 | 532.8
Equity Securities Without Readily Determinable Fair Value [Roll Forward] |  |  |  |
Balance, beginning of period | 50.4 | 50.4 | 50.4 | 50.4
Purchases and commitments funded | 0.0 | 0.0 | 0.0 | 0.0
Sales and distributions | 0.0 | 0.0 | 0.0 | 0.0
Net realized and unrealized gains | 0.0 | 0.0 | 0.0 | 0.0
Balance, end of period | 50.4 | 50.4 | 50.4 | 50.4
Fair Value Measured at NAV |  |  |  |
Other Investments [Roll Forward] |  |  |  |
Balance, beginning of period | 515.7 | 479.9 | 488.6 | 430.5
Purchases and commitments funded | 19.6 | 13.6 | 68.5 | 78.1
Sales and distributions | (25.4) | (20.4) | (67.3) | (47.1)
Net realized and unrealized gains | 13.9 | 9.3 | 34.0 | 20.9
Balance, end of period | $ 523.8 | $ 482.4 | $ 523.8 | $ 482.4

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