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Investments - Net Investment Gains (Losses) by Transaction Type (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract] |  |  |  |
Credit loss impairments | $ (0.5) | $ 0.0 | $ (0.5) | $ (0.5)
Intent-to-sell impairments | (0.2) | (0.6) | (0.2) | (6.7)
Total impairments | (0.7) | (0.6) | (0.7) | (7.2)
Sales and other, net | 0.1 | (3.5) | (3.2) | (25.2)
Change in fair value - equity securities | 5.2 | (1.4) | 5.7 | 5.3
Change in fair value and gains (losses) realized on settlements - derivatives | (0.8) | (2.9) | (1.7) | (2.6)
Net investment gains (losses) | $ 3.8 | $ (8.4) | $ 0.1 | $ (29.7)

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- Definition Other than Temporary Impairment Losses, Investments, Portion Recognized In Earnings, Change In Intent + References No definition available. + Details
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