v3.26.1
Loss and Loss Adjustment Expense Reserves - Narrative (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Liability for Claims and Claims Adjustment Expense [Line Items]                
Loss and loss adjustment expenses $ 175,700,000 $ 166,500,000   $ 428,300,000        
P&C Insurance and Reinsurance (Ark/WM Outrigger)                
Liability for Claims and Claims Adjustment Expense [Line Items]                
Favorable prior loss reserve development (28,500,000) (17,100,000) $ (46,800,000) (69,900,000)        
Loss and loss adjustment expense reserves 2,623,800,000 2,288,500,000 2,623,800,000 2,288,500,000 $ 2,585,600,000 $ 2,481,000,000 $ 2,253,900,000 $ 2,127,500,000
Loss and loss adjustment expenses 175,600,000 164,000,000.0 382,300,000 397,500,000        
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Operating Segments                
Liability for Claims and Claims Adjustment Expense [Line Items]                
Loss and loss adjustment expense reserves 2,623,800,000   2,623,800,000     2,481,000,000    
Loss and loss adjustment expenses 175,600,000 164,000,000.0 382,300,000 397,500,000        
HG Global | Operating Segments                
Liability for Claims and Claims Adjustment Expense [Line Items]                
Loss and loss adjustment expense reserves 0   0     $ 0    
Loss and loss adjustment expenses $ 0 $ 0 $ 0 $ 0