v3.26.1
Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Premiums Written And Earned) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Effects of Reinsurance [Line Items]    
Direct premiums written $ 2,997,190 $ 2,909,657
Direct premiums earned 3,080,198 2,934,728
Assumed premiums written 787,832 1,308,573
Assumed premiums earned 708,578 682,351
Ceded premiums written (1,939,976) (1,907,939)
Ceded premiums earned (1,739,890) (1,527,705)
Net premiums written 1,845,046 2,310,291
Net premiums earned 2,048,886 2,089,374
Underwriting [Member]    
Effects of Reinsurance [Line Items]    
Direct premiums written 2,069,454 2,135,972
Direct premiums earned 2,222,658 2,195,483
Assumed premiums written 219,774 729,042
Assumed premiums earned 340,669 438,045
Ceded premiums written (444,345) (554,725)
Ceded premiums earned (514,558) (544,156)
Net premiums written 1,844,883 2,310,289
Net premiums earned 2,048,769 2,089,372
Fronting    
Effects of Reinsurance [Line Items]    
Direct premiums written 927,736 773,685
Direct premiums earned 857,540 739,245
Assumed premiums written 568,058 579,531
Assumed premiums earned 367,909 244,306
Ceded premiums written (1,495,631) (1,353,214)
Ceded premiums earned (1,225,332) (983,549)
Net premiums written 163 2
Net premiums earned $ 117 $ 2