v3.26.1
Reserve for Losses and Loss Adjustment Expenses (Schedule of Reserve for Losses and Loss Adjustment Expenses) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Summary of reserve for losses and loss adjustment expenses      
Balance, beginning of year $ 3,018,396 $ 3,257,696 $ 3,257,696
Less reinsurance recoverables on unpaid losses and loss adjustment expenses 334,612 409,069 409,069
Net balance, beginning of year 2,683,784 2,848,627 2,848,627
Net losses:      
Current year 179,100 190,852 755,732
(Favorable) unfavorable development of reserves established in prior years, net (4,906) (892) (90,314)
Total 174,194 189,960 665,418
Paid related to:      
Current year (9,601) (10,051) (102,589)
Prior years (200,500) (221,980) (743,592)
Total paid (210,101) (232,031) (846,181)
Foreign currency exchange rate gains (losses) (2,499) 4,798 15,920
Net balance, end of period 2,645,378 2,811,354 2,683,784
Plus reinsurance recoverables on unpaid losses and loss adjustment expenses 334,900 369,413 334,612
Balance, end of period 2,980,278 3,180,767 3,018,396
NORCAL Group      
Net losses:      
(Favorable) unfavorable development of reserves established in prior years, net $ 700 $ 1,000 $ 3,400