v3.25.4
Property and Casualty Insurance Reserves - Short-duration Insurance Contracts, Claims Development (Details)
$ in Millions
Dec. 31, 2025
USD ($)
claim
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Loss and Allocated LAE Reserves, Net of Reinsurance $ 2,704.5        
Specialty Personal Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 7,862.2        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 6,274.1        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance 49.5        
Loss and Allocated LAE Reserves, Net of Reinsurance 1,637.6        
Specialty Personal Automobile Insurance—Physical Damage          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 3,676.2        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 3,650.5        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance (2.2)        
Loss and Allocated LAE Reserves, Net of Reinsurance 23.5        
Commercial Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 1,934.3        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 1,060.1        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance 13.8        
Loss and Allocated LAE Reserves, Net of Reinsurance 888.0        
Commercial Automobile Insurance—Physical Damage          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 368.0        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 352.2        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance 0.0        
Loss and Allocated LAE Reserves, Net of Reinsurance 15.8        
Preferred Personal Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 576.7        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 489.2        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance 5.1        
Loss and Allocated LAE Reserves, Net of Reinsurance 92.6        
Preferred Personal Automobile Insurance—Physical Damage          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 356.2        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 356.1        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance 0.0        
Loss and Allocated LAE Reserves, Net of Reinsurance 0.1        
Homeowners Insurance          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 525.1        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net 509.8        
Outstanding Loss and Allocated LAE Reserves on Accident Years before 2015, Net of Reinsurance 1.7        
Loss and Allocated LAE Reserves, Net of Reinsurance 17.0        
2021 | Specialty Personal Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 1,876.3 $ 1,861.0 $ 1,844.2 $ 1,824.7 $ 1,856.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 40.8        
Cumulative Number of Reported Claims | claim 586,733        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 1,815.9 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, 969.5 967.4 967.2 967.5 958.0
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.1        
Cumulative Number of Reported Claims | claim 362,023        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 968.0 967.2 968.3 977.5 890.1
2021 | Commercial Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 263.6 250.4 240.4 228.6 225.6
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 10.5        
Cumulative Number of Reported Claims | claim 27,517        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 241.5 208.3 168.6 128.0 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 51.8 51.6 51.9 52.4
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.3        
Cumulative Number of Reported Claims | claim 17,705        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 51.5 51.5 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, 181.7 182.0 180.6 179.8 176.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.3        
Cumulative Number of Reported Claims | claim 27,263        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 172.3 161.9 144.1 106.1 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, 117.1 117.1 117.1 117.9 118.5
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.0        
Cumulative Number of Reported Claims | claim 53,493        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 117.1 117.1 117.2 118.1 113.1
2021 | Homeowners Insurance          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 143.8 144.3 143.9 149.8 149.9
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.4        
Cumulative Number of Reported Claims | claim 13,457        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 142.1 141.3 139.7 132.6 $ 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, 1,908.3 1,880.7 1,848.7 1,765.9  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 69.5        
Cumulative Number of Reported Claims | claim 475,955        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 1,800.3 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, 992.6 990.0 989.5 993.5  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.5        
Cumulative Number of Reported Claims | claim 309,194        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 990.5 990.5 997.8 921.9  
2022 | Commercial Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 343.8 317.9 309.1 305.1  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 33.2        
Cumulative Number of Reported Claims | claim 32,562        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 273.0 222.1 159.0 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, 74.9 74.8 74.7 74.5  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.5        
Cumulative Number of Reported Claims | claim 21,578        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 74.4 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, 174.5 173.5 172.4 165.0  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 3.1        
Cumulative Number of Reported Claims | claim 24,308        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 158.3 139.1 111.0 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, 113.6 113.6 113.5 110.9  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.0        
Cumulative Number of Reported Claims | claim 48,165        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 113.6 113.7 114.6 108.7  
2022 | Homeowners Insurance          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 154.9 155.2 152.7 142.7  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.0        
Cumulative Number of Reported Claims | claim 11,533        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 152.6 149.3 141.2 $ 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, 1,398.9 1,391.7 1,448.7    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 89.2        
Cumulative Number of Reported Claims | claim 307,191        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 1,259.3 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, 720.4 715.8 722.6    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 2.6        
Cumulative Number of Reported Claims | claim 206,702        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 717.5 720.7 699.2    
2023 | Commercial Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 408.7 361.7 379.9    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 68.6        
Cumulative Number of Reported Claims | claim 35,702        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 278.9 189.6 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, 87.4 87.5 90.0    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.7        
Cumulative Number of Reported Claims | claim 20,263        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 86.6 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, 139.3 137.5 135.0    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 8.1        
Cumulative Number of Reported Claims | claim 16,917        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 113.0 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, 84.9 84.7 86.6    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (0.1)        
Cumulative Number of Reported Claims | claim 33,966        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 85.0 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, 135.8 135.3 126.6    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.1        
Cumulative Number of Reported Claims | claim 9,979        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 132.8 127.8 $ 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, 1,142.7 1,224.4      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 148.5        
Cumulative Number of Reported Claims | claim 238,155        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 879.8 422.6      
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, 491.4 500.8      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.6        
Cumulative Number of Reported Claims | claim 143,660        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 489.4 466.7      
2024 | Commercial Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 398.8 406.6      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 139.8        
Cumulative Number of Reported Claims | claim 33,611        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 179.7 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, 73.8 81.6      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (0.6)        
Cumulative Number of Reported Claims | claim 17,716        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 74.3 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, 59.6 58.7      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 7.4        
Cumulative Number of Reported Claims | claim 6,956        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 39.0 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, 32.3 31.7      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (0.2)        
Cumulative Number of Reported Claims | claim 12,938        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 32.5 32.1      
2024 | Homeowners Insurance          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 78.4 80.6      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.0        
Cumulative Number of Reported Claims | claim 4,411        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 74.1 $ 59.2      
2025 | Specialty Personal Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 1,536.0        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 630.3        
Cumulative Number of Reported Claims | claim 219,453        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 518.8        
2025 | Specialty Personal Automobile Insurance—Physical Damage          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 502.3        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (10.6)        
Cumulative Number of Reported Claims | claim 138,631        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 485.1        
2025 | Commercial Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 519.4        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 334.6        
Cumulative Number of Reported Claims | claim 32,794        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 87.0        
2025 | Commercial Automobile Insurance—Physical Damage          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 80.1        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 7.4        
Cumulative Number of Reported Claims | claim 18,183        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 65.4        
2025 | Preferred Personal Automobile Insurance—Liability          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 21.6        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 8.3        
Cumulative Number of Reported Claims | claim 1,720        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 6.6        
2025 | Preferred Personal Automobile Insurance—Physical Damage          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 8.3        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.0        
Cumulative Number of Reported Claims | claim 2,689        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 7.9        
2025 | Homeowners Insurance          
Claims Development [Line Items]          
Incurred Losses and Allocated LAE, Net of Reinsurance For the Years Ended December 31, 12.2        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 1.8        
Cumulative Number of Reported Claims | claim 526        
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]          
Cumulative Paid Losses and Allocated LAE, Net $ 8.2