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Property and Casualty Insurance Reserves - Short-duration Insurance Contracts, Claims Development (Details) $ in Millions | Dec. 31, 2024 USD ($) claim | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
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Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | $ 2,399.4 |  |  |  |
Specialty Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 7,775.6 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 6,364.6 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | 38.7 |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | 1,449.7 |  |  |  |
Specialty Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 3,833.7 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 3,804.5 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | (2.8) |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | 26.4 |  |  |  |
Commercial Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 1,496.3 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 833.6 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | 9.7 |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | 672.4 |  |  |  |
Commercial Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 328.0 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 310.8 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | (0.1) |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | 17.1 |  |  |  |
Preferred Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 710.1 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 555.0 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | 4.5 |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | 159.6 |  |  |  |
Preferred Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 444.6 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 445.8 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | 0.0 |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | (1.2) |  |  |  |
Homeowners Insurance |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 657.2 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | 618.4 |  |  |  |
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance | 0.8 |  |  |  |
Loss and Allocated LAE Reserves, Net of Reinsurance | 39.6 |  |  |  |
2020 | Specialty Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 1,417.8 | $ 1,415.9 | $ 1,407.8 | $ 1,406.4 | $ 1,401.2
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 20.1 |  |  |  |
Cumulative Number of Reported Claims | claim | 476,106 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 1,381.3 | 1,350.0 | 1,287.8 | 1,107.6 | 555.2
2020 | Specialty Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 659.7 | 659.0 | 659.5 | 659.5 | 650.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (0.1) |  |  |  |
Cumulative Number of Reported Claims | claim | 296,478 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 659.4 | 658.8 | 659.7 | 663.8 | 585.5
2020 | Commercial Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 159.7 | 155.6 | 154.0 | 152.0 | 140.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 4.1 |  |  |  |
Cumulative Number of Reported Claims | claim | 19,662 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 144.5 | 129.7 | 111.7 | 87.6 | 37.0
2020 | Commercial Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 32.3 | 32.1 | 32.1 | 32.2 | 31.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.1 |  |  |  |
Cumulative Number of Reported Claims | claim | 11,041 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 32.1 | 32.0 | 32.0 | 31.9 | 26.2
2020 | Preferred Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 158.4 | 158.8 | 151.8 | 153.6 | 148.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 1.3 |  |  |  |
Cumulative Number of Reported Claims | claim | 24,701 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 149.8 | 141.4 | 117.7 | 92.8 | 44.4
2020 | Preferred Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 97.5 | 97.5 | 97.9 | 98.0 | 96.1
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.0 |  |  |  |
Cumulative Number of Reported Claims | claim | 47,591 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 97.5 | 97.5 | 97.6 | 98.4 | 90.9
2020 | Homeowners Insurance |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 141.8 | 141.2 | 144.6 | 149.8 | 157.0
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.2 |  |  |  |
Cumulative Number of Reported Claims | claim | 14,102 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 140.8 | 139.8 | 137.4 | 130.8 | $ 94.6
2021 | Specialty Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 1,861.0 | 1,844.2 | 1,824.7 | 1,856.9 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 52.8 |  |  |  |
Cumulative Number of Reported Claims | claim | 586,566 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 1,767.5 | 1,680.8 | 1,429.4 | 657.1 |
2021 | Specialty Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 967.4 | 967.2 | 967.5 | 958.0 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (0.1) |  |  |  |
Cumulative Number of Reported Claims | claim | 361,993 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 967.2 | 968.3 | 977.5 | 890.1 |
2021 | Commercial Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 250.4 | 240.4 | 228.6 | 225.6 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 13.9 |  |  |  |
Cumulative Number of Reported Claims | claim | 27,486 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 208.3 | 168.6 | 128.0 | 50.8 |
2021 | Commercial Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 51.8 | 51.6 | 51.9 | 52.4 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.3 |  |  |  |
Cumulative Number of Reported Claims | claim | 17,703 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 51.5 | 51.4 | 51.9 | 43.3 |
2021 | Preferred Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 182.0 | 180.6 | 179.8 | 176.9 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 3.7 |  |  |  |
Cumulative Number of Reported Claims | claim | 27,243 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 161.9 | 144.1 | 106.1 | 50.3 |
2021 | Preferred Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 117.1 | 117.1 | 117.9 | 118.5 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.0 |  |  |  |
Cumulative Number of Reported Claims | claim | 53,490 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 117.1 | 117.2 | 118.1 | 113.1 |
2021 | Homeowners Insurance |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 144.3 | 143.9 | 149.8 | 149.9 |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.5 |  |  |  |
Cumulative Number of Reported Claims | claim | 13,555 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 141.3 | 139.7 | 132.6 | $ 100.6 |
2022 | Specialty Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 1,880.7 | 1,848.7 | 1,765.9 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 98.0 |  |  |  |
Cumulative Number of Reported Claims | claim | 475,177 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 1,700.4 | 1,463.3 | 738.2 |  |
2022 | Specialty Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 990.0 | 989.5 | 993.5 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (1.7) |  |  |  |
Cumulative Number of Reported Claims | claim | 309,091 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 990.5 | 997.8 | 921.9 |  |
2022 | Commercial Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 317.9 | 309.1 | 305.1 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 34.8 |  |  |  |
Cumulative Number of Reported Claims | claim | 32,476 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 222.1 | 159.0 | 72.2 |  |
2022 | Commercial Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 74.8 | 74.7 | 74.5 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.5 |  |  |  |
Cumulative Number of Reported Claims | claim | 21,567 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 74.2 | 74.6 | 66.8 |  |
2022 | Preferred Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 173.5 | 172.4 | 165.0 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 8.6 |  |  |  |
Cumulative Number of Reported Claims | claim | 24,246 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 139.1 | 111.0 | 55.0 |  |
2022 | Preferred Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 113.6 | 113.5 | 110.9 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (0.2) |  |  |  |
Cumulative Number of Reported Claims | claim | 48,160 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 113.7 | 114.6 | 108.7 |  |
2022 | Homeowners Insurance |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 155.2 | 152.7 | 142.7 |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 1.1 |  |  |  |
Cumulative Number of Reported Claims | claim | 11,526 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 149.3 | 141.2 | $ 97.0 |  |
2023 | Specialty Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 1,391.7 | 1,448.7 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 150.5 |  |  |  |
Cumulative Number of Reported Claims | claim | 304,878 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 1,092.8 | 580.4 |  |  |
2023 | Specialty Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 715.8 | 722.6 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (5.9) |  |  |  |
Cumulative Number of Reported Claims | claim | 206,366 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 720.7 | 699.2 |  |  |
2023 | Commercial Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 361.7 | 379.9 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 87.1 |  |  |  |
Cumulative Number of Reported Claims | claim | 35,327 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 189.6 | 87.5 |  |  |
2023 | Commercial Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 87.5 | 90.0 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 0.2 |  |  |  |
Cumulative Number of Reported Claims | claim | 20,202 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 86.9 | 80.6 |  |  |
2023 | Preferred Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 137.5 | 135.0 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 17.6 |  |  |  |
Cumulative Number of Reported Claims | claim | 16,796 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 84.6 | 43.7 |  |  |
2023 | Preferred Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 84.7 | 86.6 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (0.7) |  |  |  |
Cumulative Number of Reported Claims | claim | 33,951 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 85.4 | 84.8 |  |  |
2023 | Homeowners Insurance |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 135.3 | 126.6 |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 1.6 |  |  |  |
Cumulative Number of Reported Claims | claim | 9,919 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 127.8 | $ 84.7 |  |  |
2024 | Specialty Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 1,224.4 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 506.0 |  |  |  |
Cumulative Number of Reported Claims | claim | 216,146 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 422.6 |  |  |  |
2024 | Specialty Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 500.8 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 7.1 |  |  |  |
Cumulative Number of Reported Claims | claim | 136,921 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 466.7 |  |  |  |
2024 | Commercial Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 406.6 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 249.0 |  |  |  |
Cumulative Number of Reported Claims | claim | 29,666 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 69.1 |  |  |  |
2024 | Commercial Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 81.6 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 7.7 |  |  |  |
Cumulative Number of Reported Claims | claim | 16,312 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 66.1 |  |  |  |
2024 | Preferred Personal Automobile Insurance—Liability |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 58.7 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 19.8 |  |  |  |
Cumulative Number of Reported Claims | claim | 6,666 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 19.6 |  |  |  |
2024 | Preferred Personal Automobile Insurance—Physical Damage |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 31.7 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ (1.2) |  |  |  |
Cumulative Number of Reported Claims | claim | 12,556 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 32.1 |  |  |  |
2024 | Homeowners Insurance |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, | 80.6 |  |  |  |
Total of IBNR Liabilities Plus Expected Development on Reported Claims | $ 7.2 |  |  |  |
Cumulative Number of Reported Claims | claim | 4,153 |  |  |  |
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract] |  |  |  |  |
Cumulative Paid Losses and Allocated LAE, Net | $ 59.2 |  |  |  |

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