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Investments - Net Realized Gains (Losses), Including Impairment, Recognized in the Consolidated Statements of Operations (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2026 | Mar. 31, 2025
Net realized (losses) gains on investments related to sales and other and fair value changes to equity securities: |  |
Total net realized losses on investments related to sales and other and fair value changes to equity securities | $ (15.6) | $ (13.0)
Net realized losses related to impairments: |  |
Total net realized losses related to impairments | (5.6) | (3.0)
Total net realized losses on investments and fair value changes to equity securities | (21.2) | (16.0)
Equity securities, realized gain | 0.1 | 2.5
Equity investment, impairment loss | 0.0 | 3.0
Fixed maturity securities |  |
Net realized (losses) gains on investments related to sales and other and fair value changes to equity securities: |  |
Total net realized losses on investments related to sales and other and fair value changes to equity securities | (13.0) | (17.0)
Net realized losses related to impairments: |  |
Total net realized losses related to impairments | (2.5) | 0.0
Equity securities |  |
Net realized (losses) gains on investments related to sales and other and fair value changes to equity securities: |  |
Total net realized losses on investments related to sales and other and fair value changes to equity securities | (2.7) | 2.8
Commercial mortgage loans on real estate |  |
Net realized (losses) gains on investments related to sales and other and fair value changes to equity securities: |  |
Total net realized losses on investments related to sales and other and fair value changes to equity securities | 0.3 | 1.4
Other investments |  |
Net realized (losses) gains on investments related to sales and other and fair value changes to equity securities: |  |
Total net realized losses on investments related to sales and other and fair value changes to equity securities | (0.2) | (0.2)
Net realized losses related to impairments: |  |
Total net realized losses related to impairments | $ (3.1) | $ (3.0)

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