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Loss And Loss Adjustment Expense Reserves Incurred and Paid Claims Development with IBNR and Claim Counts (Details)
$ in Millions
Dec. 31, 2021
USD ($)
claim
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Claims Development [Line Items]                    
Liabilities for claims and claim adjustment expenses, net of reinsurance $ 19,734.9 $ 14,989.4                
Commercial Lines - Liability | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 11,695.4                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 6,388.3                  
All outstanding liabilities before 2017, net of reinsurance1 74.0                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 5,381.1 3,586.3                
Commercial Lines - Physical Damage | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,154.6                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,991.8                  
All outstanding liabilities before 2017, net of reinsurance1 0.7                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 163.5 82.7                
Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 679.5                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 476.0                  
All outstanding liabilities before 2017, net of reinsurance1 26.3                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 229.8 0.0                
Property | Property Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,277.2                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,632.8                  
All outstanding liabilities before 2017, net of reinsurance1 6.1                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 650.5 474.7                
2012 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 71.1 70.9 $ 70.0 $ 70.1 $ 71.9 $ 68.8 $ 61.7 $ 57.0 $ 59.2 $ 62.2
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 3.0                  
Cumulative Number of Incurred Claim Counts | claim 7,434                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 64.1 64.2 63.3 62.1 58.6 53.6 47.3 38.4 28.2 $ 14.0
2013 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 78.9 78.9 78.9 77.9 81.6 75.4 65.3 68.1 66.4  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 4.4                  
Cumulative Number of Incurred Claim Counts | claim 7,703                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 71.7 70.8 68.9 66.9 61.9 55.6 43.6 30.6 $ 13.7  
2014 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 70.9 70.7 69.4 70.7 70.5 68.3 70.0 74.9    
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 4.3                  
Cumulative Number of Incurred Claim Counts | claim 7,969                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 64.2 61.1 59.0 56.9 51.1 44.3 33.9 $ 18.6    
2015 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 45.1 44.8 47.0 48.3 46.1 45.4 51.2      
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 4.9                  
Cumulative Number of Incurred Claim Counts | claim 8,519                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 37.1 36.1 33.9 30.9 26.5 18.1 $ 6.5      
2016 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 40.1 40.2 41.5 41.0 43.3 51.8        
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 3.8                  
Cumulative Number of Incurred Claim Counts | claim 7,065                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 33.8 32.7 30.6 27.0 20.9 $ 8.5        
2017 | Commercial Lines - Liability | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,462.3 1,472.2 1,492.6 1,470.2 1,477.2          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 5.9                  
Cumulative Number of Incurred Claim Counts | claim 102,806                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 1,353.0 1,257.1 1,085.4 759.5 337.2          
2017 | Commercial Lines - Physical Damage | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 456.6 456.1 457.3 459.3 463.9          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.0                  
Cumulative Number of Incurred Claim Counts | claim 87,721                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 455.6 455.6 455.4 456.0 408.5          
2017 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 46.2 48.8 51.1 54.6 62.6          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 5.8                  
Cumulative Number of Incurred Claim Counts | claim 17,653                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 36.9 34.5 30.8 24.4 9.6          
2017 | Property | Property Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 681.5 681.3 683.4 680.9 672.8          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.4                  
Cumulative Number of Incurred Claim Counts | claim 76,236                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 679.1 675.0 670.1 647.1 506.7          
2018 | Commercial Lines - Liability | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,971.4 1,976.2 1,913.7 1,880.4            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 34.7                  
Cumulative Number of Incurred Claim Counts | claim 119,972                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 1,666.8 1,392.3 979.9 401.4            
2018 | Commercial Lines - Physical Damage | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 525.6 526.3 528.3 528.7            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (1.1)                  
Cumulative Number of Incurred Claim Counts | claim 93,305                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 525.4 524.9 524.8 467.6            
2018 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 77.0 76.7 81.3 81.5            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 7.8                  
Cumulative Number of Incurred Claim Counts | claim 15,389                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 56.7 49.5 39.6 17.6            
2018 | Property | Property Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 846.5 845.4 845.2 839.0            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 11.0                  
Cumulative Number of Incurred Claim Counts | claim 64,872                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 826.6 812.6 781.2 595.9            
2019 | Commercial Lines - Liability | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,426.3 2,370.9 2,301.1              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 82.0                  
Cumulative Number of Incurred Claim Counts | claim 136,273                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 1,684.5 1,184.4 474.8              
2019 | Commercial Lines - Physical Damage | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 626.6 628.3 633.1              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (1.9)                  
Cumulative Number of Incurred Claim Counts | claim 99,456                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 624.8 625.1 561.1              
2019 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 85.4 83.1 80.7              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 14.7                  
Cumulative Number of Incurred Claim Counts | claim 10,577                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 56.0 42.4 20.0              
2019 | Property | Property Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 962.8 965.2 971.7              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 2.4                  
Cumulative Number of Incurred Claim Counts | claim 75,434                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 950.5 930.4 708.0              
2020 | Commercial Lines - Liability | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,388.8 2,335.7                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 175.5                  
Cumulative Number of Incurred Claim Counts | claim 117,027                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 1,110.4 440.8                
2020 | Commercial Lines - Physical Damage | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 624.9 631.8                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (4.4)                  
Cumulative Number of Incurred Claim Counts | claim 99,436                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 621.8 540.6                
2020 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 80.7 75.0                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 24.8                  
Cumulative Number of Incurred Claim Counts | claim 9,260                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 38.6 15.8                
2020 | Property | Property Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,246.8 1,223.5                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 56.8                  
Cumulative Number of Incurred Claim Counts | claim 109,427                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 1,141.2 832.5                
2021 | Commercial Lines - Liability | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,446.6                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 650.0                  
Cumulative Number of Incurred Claim Counts | claim 153,749                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 573.6                  
2021 | Commercial Lines - Physical Damage | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 920.9                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (11.4)                  
Cumulative Number of Incurred Claim Counts | claim 123,801                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 764.2                  
2021 | Commercial Lines - Other | Commercial Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 84.1                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 45.9                  
Cumulative Number of Incurred Claim Counts | claim 8,472                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 16.9                  
2021 | Property | Property Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,539.6                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 333.4                  
Cumulative Number of Incurred Claim Counts | claim 118,874                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 1,035.4                  
Agency Channel | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 27,787.9                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 21,599.3                  
All outstanding liabilities before 2017, net of reinsurance1 85.7                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 6,274.3 5,378.7                
Agency Channel | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 16,753.2                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 16,477.7                  
All outstanding liabilities before 2017, net of reinsurance1 2.1                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 277.6 82.4                
Agency Channel | 2017 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,509.2 4,546.4 4,511.1 4,485.8 4,474.8          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.0                  
Cumulative Number of Incurred Claim Counts | claim 779,396                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,418.3 4,285.5 4,048.5 3,478.5 2,074.0          
Agency Channel | 2017 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,645.1 2,640.6 2,643.5 2,638.5 2,635.5          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.8                  
Cumulative Number of Incurred Claim Counts | claim 1,514,952                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 2,641.7 2,640.8 2,640.9 2,643.2 2,599.8          
Agency Channel | 2018 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,238.7 5,192.7 5,182.1 5,141.8            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 89.3                  
Cumulative Number of Incurred Claim Counts | claim 856,502                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,940.6 4,635.0 4,028.7 2,378.0            
Agency Channel | 2018 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,818.9 2,821.7 2,822.6 2,819.0            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (4.6)                  
Cumulative Number of Incurred Claim Counts | claim 1,695,396                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 2,819.5 2,819.9 2,827.4 2,769.1            
Agency Channel | 2019 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,918.2 5,886.9 5,885.0              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 112.5                  
Cumulative Number of Incurred Claim Counts | claim 915,954                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 5,272.8 4,533.2 2,715.2              
Agency Channel | 2019 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,261.1 3,254.7 3,277.9              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (3.1)                  
Cumulative Number of Incurred Claim Counts | claim 1,878,499                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 3,255.9 3,259.2 3,242.5              
Agency Channel | 2020 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,405.4 5,433.8                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 280.3                  
Cumulative Number of Incurred Claim Counts | claim 754,470                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,112.2 2,383.0                
Agency Channel | 2020 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,319.8 3,328.5                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (14.6)                  
Cumulative Number of Incurred Claim Counts | claim 1,782,861                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 3,322.5 3,250.1                
Agency Channel | 2021 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 6,716.4                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 991.0                  
Cumulative Number of Incurred Claim Counts | claim 875,200                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 2,855.4                  
Agency Channel | 2021 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,708.3                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (222.0)                  
Cumulative Number of Incurred Claim Counts | claim 2,094,032                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,438.1                  
Direct Channel | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 27,397.0                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 21,087.3                  
All outstanding liabilities before 2017, net of reinsurance1 63.5                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 6,373.2 5,277.3                
Direct Channel | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 19,185.3                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 18,865.1                  
All outstanding liabilities before 2017, net of reinsurance1 2.1                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 322.3 40.6                
Direct Channel | 2017 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,219.2 4,254.4 4,229.3 4,209.9 4,209.5          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (0.5)                  
Cumulative Number of Incurred Claim Counts | claim 772,945                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,147.1 4,035.6 3,808.3 3,255.2 1,912.6          
Direct Channel | 2017 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,750.8 2,745.6 2,749.0 2,743.7 2,750.6          
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 0.8                  
Cumulative Number of Incurred Claim Counts | claim 1,791,658                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 2,747.9 2,747.6 2,748.4 2,753.5 $ 2,742.1          
Direct Channel | 2018 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,052.5 5,003.2 4,980.9 4,904.8            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 77.1                  
Cumulative Number of Incurred Claim Counts | claim 871,243                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,787.7 4,481.7 3,863.5 2,235.1            
Direct Channel | 2018 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,179.3 3,182.0 3,181.9 3,202.3            
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (6.2)                  
Cumulative Number of Incurred Claim Counts | claim 2,070,183                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 3,182.6 3,183.0 3,193.8 $ 3,170.0            
Direct Channel | 2019 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,837.9 5,811.7 5,756.5              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 91.9                  
Cumulative Number of Incurred Claim Counts | claim 957,488                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 5,218.8 4,452.5 2,630.3              
Direct Channel | 2019 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,749.6 3,737.8 3,787.9              
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (5.5)                  
Cumulative Number of Incurred Claim Counts | claim 2,271,699                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 3,746.8 3,751.3 $ 3,782.6              
Direct Channel | 2020 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,322.7 5,356.9                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 263.2                  
Cumulative Number of Incurred Claim Counts | claim 787,231                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 4,018.7 2,301.3                
Direct Channel | 2020 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,753.3 3,775.6                
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (26.1)                  
Cumulative Number of Incurred Claim Counts | claim 2,136,940                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 3,765.9 $ 3,720.0                
Direct Channel | 2021 | Personal Lines - Liability | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 6,964.7                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ 972.2                  
Cumulative Number of Incurred Claim Counts | claim 970,710                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 2,915.0                  
Direct Channel | 2021 | Personal Lines - Physical Damage | Personal Lines Segment                    
Claims Development [Line Items]                    
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,752.3                  
Total of IBNR Liabilities Plus Expected Development on Reported Claims $ (311.9)                  
Cumulative Number of Incurred Claim Counts | claim 2,618,463                  
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 5,421.9