v3.25.4
SEGMENT REPORTING - Schedule of Gross Premiums Written Allocated to the Territory of Coverage Exposure (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 11,738,420 $ 11,733,066 $ 8,862,366
Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 100.00% 100.00% 100.00%
Property      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 4,942,141 $ 4,823,731 $ 3,562,414
Property | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 42.10% 41.10% 40.30%
Property | U.S. and Caribbean      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 3,162,323 $ 2,996,981 $ 2,303,013
Property | U.S. and Caribbean | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 26.90% 25.50% 26.00%
Property | Worldwide      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 1,038,625 $ 1,063,292 $ 798,623
Property | Worldwide | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 8.80% 9.10% 9.00%
Property | Europe      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 233,440 $ 244,523 $ 163,500
Property | Europe | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 2.00% 2.10% 1.90%
Property | Worldwide (excluding U.S.)      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 152,653 $ 180,688 $ 70,646
Property | Worldwide (excluding U.S.) | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 1.30% 1.50% 0.80%
Property | Japan      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 103,383 $ 106,533 $ 85,823
Property | Japan | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 0.90% 0.90% 1.00%
Property | Australia and New Zealand      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 94,161 $ 101,976 $ 70,107
Property | Australia and New Zealand | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 0.80% 0.90% 0.80%
Property | Other      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 157,556 $ 129,738 $ 70,702
Property | Other | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 1.40% 1.10% 0.80%
Casualty and Specialty      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 6,796,279 $ 6,909,335 $ 5,299,952
Casualty and Specialty | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 57.90% 58.90% 59.70%
Casualty and Specialty | U.S. and Caribbean      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 3,127,671 $ 2,986,956 $ 2,333,096
Casualty and Specialty | U.S. and Caribbean | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 26.60% 25.50% 26.30%
Casualty and Specialty | Worldwide      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 3,070,027 $ 3,217,662 $ 2,280,687
Casualty and Specialty | Worldwide | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 26.20% 27.30% 25.70%
Casualty and Specialty | Europe      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 274,346 $ 353,863 $ 197,228
Casualty and Specialty | Europe | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 2.30% 3.00% 2.20%
Casualty and Specialty | Worldwide (excluding U.S.)      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 165,274 $ 195,489 $ 130,334
Casualty and Specialty | Worldwide (excluding U.S.) | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 1.40% 1.70% 1.50%
Casualty and Specialty | Australia and New Zealand      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 22,076 $ 43,183 $ 27,397
Casualty and Specialty | Australia and New Zealand | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 0.20% 0.40% 0.30%
Casualty and Specialty | Other      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Gross premiums written (Note 7) $ 136,885 $ 112,182 $ 331,210
Casualty and Specialty | Other | Gross Premiums Written, Benchmark | Geographic Concentration Risk      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Concentration risk , percentage 1.20% 1.00% 3.70%