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v3.25.3

Investments - Fair Value and Gross Unrealized Losses (Details) $ in Millions | Sep. 30, 2025 USD ($) | Sep. 30, 2025 security | Sep. 30, 2025 | Sep. 30, 2025 position | Dec. 31, 2024 USD ($) | Dec. 31, 2024 security | Dec. 31, 2024 | Dec. 31, 2024 position
--- | --- | --- | --- | --- | --- | --- | --- | ---
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Number of positions with a gross unrealized loss, 12 Months or Less (security) | security |  | 427 |  |  |  | 665 |  |
Number of positions with a gross unrealized loss, more than 12 months (security) |  | 1,708 |  | 1,708 |  | 1,862 |  | 1,862
Number of positions with a gross unrealized loss, Total (security) | security |  | 2,135 |  |  |  | 2,527 |  |
Fair value as a percentage of total fixed maturities and equity securities fair value, 12 Months or Less (percent) |  |  | 10.30% |  |  |  | 15.80% |
Fair value as a percentage of total fixed maturities and equity securities fair value, more than 12 months (percent) |  |  | 44.30% |  |  |  | 51.10% |
Fair value as a percentage of total fixed maturities and equity securities fair value, Total (percent) |  |  | 54.60% |  |  |  | 66.90% |
Fixed maturity securities |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | $ 585.5 |  |  |  | $ 849.1 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 2,509.5 |  |  |  | 2,751.7 |  |  |
Fixed maturity securities, Fair Value, Total | 3,095.0 |  |  |  | 3,600.8 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 12.5 |  |  |  | 19.2 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 382.7 |  |  |  | 483.8 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | 395.2 |  |  |  | 503.0 |  |  |
Mortgage-backed securities |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | 43.8 |  |  |  | 208.3 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 244.3 |  |  |  | 419.3 |  |  |
Fixed maturity securities, Fair Value, Total | 288.1 |  |  |  | 627.6 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 0.4 |  |  |  | 3.1 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 39.2 |  |  |  | 71.7 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | 39.6 |  |  |  | 74.8 |  |  |
Other |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | 10.7 |  |  |  | 77.1 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 285.6 |  |  |  | 274.6 |  |  |
Fixed maturity securities, Fair Value, Total | 296.3 |  |  |  | 351.7 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 0.2 |  |  |  | 1.5 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 56.4 |  |  |  | 67.6 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | 56.6 |  |  |  | 69.1 |  |  |
Municipal bonds |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | 190.3 |  |  |  | 193.5 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 616.2 |  |  |  | 632.0 |  |  |
Fixed maturity securities, Fair Value, Total | 806.5 |  |  |  | 825.5 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 4.9 |  |  |  | 3.4 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 83.1 |  |  |  | 102.4 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | 88.0 |  |  |  | 105.8 |  |  |
Foreign government bonds |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | 0.0 |  |  |  | 1.5 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 12.0 |  |  |  | 11.7 |  |  |
Fixed maturity securities, Fair Value, Total | 12.0 |  |  |  | 13.2 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 0.0 |  |  |  | 0.0 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 0.6 |  |  |  | 0.9 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | 0.6 |  |  |  | 0.9 |  |  |
Corporate bonds |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | 162.9 |  |  |  | 235.4 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 954.6 |  |  |  | 1,075.8 |  |  |
Fixed maturity securities, Fair Value, Total | 1,117.5 |  |  |  | 1,311.2 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 5.9 |  |  |  | 10.3 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 175.7 |  |  |  | 219.8 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | 181.6 |  |  |  | 230.1 |  |  |
Other asset-backed securities |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value |  |  |  |  |  |  |  |
Fixed maturity securities, Fair Value, 12 Months or Less | 177.8 |  |  |  | 133.3 |  |  |
Fixed maturity securities, Fair Value, More than 12 Months | 396.8 |  |  |  | 338.3 |  |  |
Fixed maturity securities, Fair Value, Total | 574.6 |  |  |  | 471.6 |  |  |
Fixed maturity securities, Gross Unrealized Losses |  |  |  |  |  |  |  |
Fixed maturity securities, Gross Unrealized Losses, 12 Months or Less | 1.1 |  |  |  | 0.9 |  |  |
Fixed maturity securities, Gross Unrealized Losses, More than 12 Months | 27.7 |  |  |  | 21.4 |  |  |
Fixed maturity securities, Gross Unrealized Losses, Total | $ 28.8 |  |  |  | $ 22.3 |  |  |

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