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Reinsurance - Additional Information (Details) - USD ($)
$ in Millions
6 Months Ended 12 Months Ended
Oct. 01, 2022
Jun. 30, 2023
Dec. 31, 2022
Jun. 30, 2022
Mar. 02, 2020
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]          
Plus reinsurance recoverable on unpaid losses at the end of the period   $ 4,658.0 $ 4,897.7 $ 5,006.5  
Reinsurance Recoverable, Allowance for Credit Loss   3.3 3.7    
Reinsurance Recoverable, Allowance for Credit Loss, Period Increase (Decrease)   $ (0.4) $ 0.4    
Reinsurance Contracts [Axis]: Funds withheld credited with interest for periods after October 1, 2022          
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]          
Reinsurance Retention Policy, Retrocession Premium, Interest Rate 1.75%        
Enstar          
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]          
Plus reinsurance recoverable on unpaid losses at the end of the period         $ 770.0
Enstar | Reinsurance Contracts [Axis]: LPT losses reinsured]          
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]          
Plus reinsurance recoverable on unpaid losses at the end of the period         $ 3,120.0