v3.26.1
SEGMENT REPORTING - Schedule of Underwriting Results for Segments (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]        
Gross written premiums $ 3,772 $ 4,680 $ 7,374 $ 9,071
Net written premiums 3,037 4,119 6,224 7,853
Premiums earned 3,490 3,991 7,064 7,843
Incurred losses and LAE 2,170 2,472 4,388 5,366
Commission and brokerage 814 880 1,638 1,704
Other underwriting expenses 225 254 441 492
Underwriting gain (loss) 281 385 597 281
Net investment income 523 532 1,091 1,023
Net gains (losses) on investments (8) (5) (17) (12)
Corporate expenses (33) (31) (71) (52)
Interest, fee and bond issue cost amortization expense (36) (38) (71) (76)
Other income (expense) (45) (27) (108) (100)
Income tax expense (benefit) (124) (135) (207) (173)
NET INCOME (LOSS) 559 680 1,213 890
Reinsurance Treaty | Operating Segments        
Segment Reporting [Line Items]        
Gross written premiums 2,720 2,951 5,394 5,885
Net written premiums 2,228 2,785 4,632 5,313
Premiums earned 2,459 2,726 4,915 5,306
Incurred losses and LAE 1,478 1,568 2,926 3,573
Commission and brokerage 626 682 1,258 1,318
Other underwriting expenses 71 64 132 124
Underwriting gain (loss) 283 413 598 291
Global Wholesale & Specialty | Operating Segments        
Segment Reporting [Line Items]        
Gross written premiums 958 957 1,751 1,728
Net written premiums 738 765 1,430 1,420
Premiums earned 709 728 1,427 1,460
Incurred losses and LAE 439 471 892 952
Commission and brokerage 146 148 298 291
Other underwriting expenses 89 74 180 150
Underwriting gain (loss) 34 35 57 67
Legacy | Operating Segments        
Segment Reporting [Line Items]        
Gross written premiums 94 772 229 1,459
Net written premiums 72 569 161 1,120
Premiums earned 323 538 722 1,078
Incurred losses and LAE 253 433 569 841
Commission and brokerage 41 50 82 95
Other underwriting expenses 64 116 129 219
Underwriting gain (loss) $ (36) $ (63) $ (58) $ (77)