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INVESTMENTS - SUMMARY OF INVESTMENTS WITH UNREALIZED LOSSES BY INVESTMENT CATEGORY (Details) - USD ($) $ in Millions | Mar. 31, 2026 | Dec. 31, 2025
--- | --- | ---
Fair value |  |
Less than 12 months | $ 4,728.1 | $ 1,864.0
12 months or greater | 5,045.5 | 5,964.9
Total | 9,773.6 | 7,828.9
Unrealized losses |  |
Less than 12 months | (99.3) | (58.5)
12 months or greater | (827.8) | (836.7)
Total | (927.1) | (895.2)
Corporate securities |  |
Fair value |  |
Less than 12 months | 2,103.4 | 734.9
12 months or greater | 1,866.3 | 2,645.8
Total | 3,969.7 | 3,380.7
Unrealized losses |  |
Less than 12 months | (75.5) | (44.3)
12 months or greater | (411.6) | (426.7)
Total | (487.1) | (471.0)
United States Treasury securities and obligations of United States government corporations and agencies |  |
Fair value |  |
Less than 12 months | 18.9 | 0.4
12 months or greater | 153.3 | 153.9
Total | 172.2 | 154.3
Unrealized losses |  |
Less than 12 months | (0.2) | 0.0
12 months or greater | (32.3) | (30.2)
Total | (32.5) | (30.2)
States and political subdivisions |  |
Fair value |  |
Less than 12 months | 261.4 | 275.6
12 months or greater | 846.8 | 806.0
Total | 1,108.2 | 1,081.6
Unrealized losses |  |
Less than 12 months | (9.9) | (8.5)
12 months or greater | (136.5) | (127.6)
Total | (146.4) | (136.1)
Foreign governments |  |
Fair value |  |
Less than 12 months | 8.1 | 3.1
12 months or greater | 17.4 | 24.3
Total | 25.5 | 27.4
Unrealized losses |  |
Less than 12 months | (0.2) | 0.0
12 months or greater | (3.2) | (2.7)
Total | (3.4) | (2.7)
Asset-backed securities |  |
Fair value |  |
Less than 12 months | 618.0 | 187.8
12 months or greater | 441.5 | 487.7
Total | 1,059.5 | 675.5
Unrealized losses |  |
Less than 12 months | (5.1) | (1.8)
12 months or greater | (45.5) | (44.9)
Total | (50.6) | (46.7)
Agency residential mortgage-backed securities |  |
Fair value |  |
Less than 12 months | 100.6 | 59.8
12 months or greater | 13.7 | 13.8
Total | 114.3 | 73.6
Unrealized losses |  |
Less than 12 months | (0.6) | 0.0
12 months or greater | (0.3) | (0.2)
Total | (0.9) | (0.2)
Non-agency residential mortgage-backed securities |  |
Fair value |  |
Less than 12 months | 239.5 | 131.4
12 months or greater | 624.8 | 703.3
Total | 864.3 | 834.7
Unrealized losses |  |
Less than 12 months | (1.7) | (0.9)
12 months or greater | (83.9) | (90.0)
Total | (85.6) | (90.9)
Collateralized loan obligations |  |
Fair value |  |
Less than 12 months | 772.4 | 227.3
12 months or greater | 72.9 | 62.9
Total | 845.3 | 290.2
Unrealized losses |  |
Less than 12 months | (2.4) | (0.9)
12 months or greater | (1.8) | (1.8)
Total | (4.2) | (2.7)
Commercial mortgage-backed securities |  |
Fair value |  |
Less than 12 months | 605.8 | 243.7
12 months or greater | 1,008.8 | 1,067.2
Total | 1,614.6 | 1,310.9
Unrealized losses |  |
Less than 12 months | (3.7) | (2.1)
12 months or greater | (112.7) | (112.6)
Total | $ (116.4) | $ (114.7)

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