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Other Investments - Schedule of Changes in Other Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Other Investments [Roll Forward] |  |  |  |
Balance, beginning of period | $ 530.3 | $ 457.0 | $ 480.9 | $ 421.6
Purchases and commitments | 13.6 | 16.0 | 78.1 | 62.0
Sales and distributions | (20.4) | (20.5) | (47.1) | (49.4)
Net realized and unrealized gains | 9.3 | 5.4 | 20.9 | 23.7
Balance, end of period | 532.8 | 457.9 | 532.8 | 457.9
Equity Securities Without Readily Determinable Fair Value [Roll Forward] |  |  |  |
Balance, beginning of period | 50.4 | 50.4 | 50.4 | 50.4
Purchases and commitments | 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 | 479.9 | 406.6 | 430.5 | 371.2
Purchases and commitments | 13.6 | 16.0 | 78.1 | 62.0
Sales and distributions | (20.4) | (20.5) | (47.1) | (49.4)
Net realized and unrealized gains | 9.3 | 5.4 | 20.9 | 23.7
Balance, end of period | $ 482.4 | $ 407.5 | $ 482.4 | $ 407.5

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