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INVESTMENTS - SUMMARY OF INVESTMENTS WITH UNREALIZED LOSSES BY INVESTMENT CATEGORY (Details) - USD ($) $ in Millions | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Fair value |  |
Less than 12 months | $ 597.9 | $ 1,169.9
12 months or greater | 10,076.8 | 10,886.4
Total | 10,674.7 | 12,056.3
Unrealized losses |  |
Less than 12 months | (3.4) | (24.5)
12 months or greater | (1,099.3) | (1,365.0)
Total | (1,102.7) | (1,389.5)
Corporate securities |  |
Fair value |  |
Less than 12 months | 134.4 | 332.0
12 months or greater | 5,074.8 | 5,199.0
Total | 5,209.2 | 5,531.0
Unrealized losses |  |
Less than 12 months | (0.7) | (5.3)
12 months or greater | (562.6) | (640.6)
Total | (563.3) | (645.9)
United States Treasury securities and obligations of United States government corporations and agencies |  |
Fair value |  |
Less than 12 months | 0.0 | 126.7
12 months or greater | 157.6 | 34.5
Total | 157.6 | 161.2
Unrealized losses |  |
Less than 12 months | 0.0 | (10.2)
12 months or greater | (11.6) | (3.1)
Total | (11.6) | (13.3)
States and political subdivisions |  |
Fair value |  |
Less than 12 months | 43.9 | 236.9
12 months or greater | 1,175.2 | 990.0
Total | 1,219.1 | 1,226.9
Unrealized losses |  |
Less than 12 months | (0.4) | (3.8)
12 months or greater | (183.2) | (181.2)
Total | (183.6) | (185.0)
Foreign governments |  |
Fair value |  |
Less than 12 months | 1.3 | 6.2
12 months or greater | 16.3 | 21.1
Total | 17.6 | 27.3
Unrealized losses |  |
Less than 12 months | 0.0 | 0.0
12 months or greater | (2.0) | (2.3)
Total | (2.0) | (2.3)
Asset-backed securities |  |
Fair value |  |
Less than 12 months | 61.4 | 46.9
12 months or greater | 860.5 | 1,066.8
Total | 921.9 | 1,113.7
Unrealized losses |  |
Less than 12 months | (0.6) | (0.8)
12 months or greater | (55.9) | (106.0)
Total | (56.5) | (106.8)
Agency residential mortgage-backed securities |  |
Fair value |  |
Less than 12 months | 9.3 | 73.4
12 months or greater | 3.2 | 7.1
Total | 12.5 | 80.5
Unrealized losses |  |
Less than 12 months | 0.0 | (0.4)
12 months or greater | 0.0 | (0.1)
Total | 0.0 | (0.5)
Non-agency residential mortgage-backed securities |  |
Fair value |  |
Less than 12 months | 23.8 | 69.0
12 months or greater | 935.2 | 1,062.9
Total | 959.0 | 1,131.9
Unrealized losses |  |
Less than 12 months | (0.2) | (1.3)
12 months or greater | (104.0) | (151.4)
Total | (104.2) | (152.7)
Collateralized loan obligations |  |
Fair value |  |
Less than 12 months | 237.0 | 75.0
12 months or greater | 115.1 | 590.9
Total | 352.1 | 665.9
Unrealized losses |  |
Less than 12 months | (1.2) | (0.3)
12 months or greater | (4.3) | (12.7)
Total | (5.5) | (13.0)
Commercial mortgage-backed securities |  |
Fair value |  |
Less than 12 months | 86.8 | 203.8
12 months or greater | 1,738.9 | 1,914.1
Total | 1,825.7 | 2,117.9
Unrealized losses |  |
Less than 12 months | (0.3) | (2.4)
12 months or greater | (175.7) | (267.6)
Total | $ (176.0) | $ (270.0)

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