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RESERVES FOR LOSSES AND LOSS SETTLEMENT EXPENSES - Changes in Property and Casualty Losses and Loss Settlement Expense Reserves (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]      
Gross liability for losses and loss settlement expenses at beginning of year   $ 1,924,826 $ 1,796,782
Ceded losses and loss settlement expenses   (213,633) (198,083)
Net liability for losses and loss settlement expenses at beginning of year   1,711,193 1,598,699
Losses and loss settlement expenses incurred for claims occurring during      
Current year   426,017 778,480
Prior years $ (5,400) (5,618) (14,078)
Total incurred   420,399 764,402
Losses and loss settlement expense payments for claims occurring during      
Current year   84,998 194,149
Prior years   264,294 457,759
Total paid   349,292 651,908
Net liability for losses and loss settlement expenses at end of period 1,782,300 1,782,300 1,711,193
Ceded losses and loss settlement expenses 208,117 208,117 213,633
Gross liability for losses and loss settlement expenses at end of period $ 1,990,417 $ 1,990,417 $ 1,924,826