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Other Investments - Schedule of Changes in Other Investments (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Other Investments [Roll Forward] |  |
Balance, beginning of period | $ 421.6 | $ 375.2
Net realized and unrealized gains | 34.2 | 1.7
Additions and commitments | 82.5 | 104.3
Sales and distributions | (57.4) | (59.6)
Balance, end of period | 480.9 | 421.6
Without Readily Determinable Fair Values |  |
Balance, beginning of period | 50.4 | 50.4
Net realized and unrealized gains | 0.0 | 0.0
Additions and commitments | 0.0 | 0.0
Sales and distributions | 0.0 | 0.0
Balance, end of period | 50.4 | 50.4
Fair Value Measured at NAV |  |
Other Investments [Roll Forward] |  |
Balance, beginning of period | 371.2 | 324.8
Net realized and unrealized gains | 34.2 | 1.7
Additions and commitments | 82.5 | 104.3
Sales and distributions | (57.4) | (59.6)
Balance, end of period | $ 430.5 | $ 371.2

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