v3.25.2
Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Premiums Written And Earned) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Effects of Reinsurance [Line Items]        
Direct premiums written $ 3,236,526 $ 3,299,676 $ 6,146,183 $ 6,152,101
Direct premiums earned 3,042,781 2,961,150 5,977,509 5,863,070
Assumed premiums written 1,907,965 1,412,454 3,216,538 2,500,428
Assumed premiums earned 768,201 655,332 1,450,552 1,171,545
Ceded premiums written (2,901,140) (2,433,351) (4,809,079) (4,141,713)
Ceded premiums earned (1,669,291) (1,539,383) (3,196,996) (2,829,889)
Net premiums written 2,243,351 2,278,779 4,553,642 4,510,816
Net premiums earned 2,141,691 2,077,099 4,231,065 4,204,726
Underwriting [Member]        
Effects of Reinsurance [Line Items]        
Direct premiums written 2,414,799 2,356,536 4,550,772 4,464,003
Direct premiums earned 2,210,284 2,149,773 4,405,767 4,348,011
Assumed premiums written 471,869 564,851 1,200,912 1,233,550
Assumed premiums earned 451,071 414,488 889,116 807,430
Ceded premiums written (643,567) (642,448) (1,198,292) (1,186,404)
Ceded premiums earned (519,923) (487,002) (1,064,079) (950,382)
Net premiums written 2,243,101 2,278,939 4,553,392 4,511,149
Net premiums earned 2,141,432 2,077,259 4,230,804 4,205,059
Fronting        
Effects of Reinsurance [Line Items]        
Direct premiums written 821,727 943,140 1,595,411 1,688,098
Direct premiums earned 832,497 811,377 1,571,742 1,515,059
Assumed premiums written 1,436,096 847,603 2,015,626 1,266,878
Assumed premiums earned 317,130 240,844 561,436 364,115
Ceded premiums written (2,257,573) (1,790,903) (3,610,787) (2,955,309)
Ceded premiums earned (1,149,368) (1,052,381) (2,132,917) (1,879,507)
Net premiums written 250 (160) 250 (333)
Net premiums earned $ 259 $ (160) $ 261 $ (333)