v3.26.1
SEGMENT REPORTING - Schedule of Underwriting Results for Operating 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 $ 2,329 $ 2,992 $ 4,552 $ 5,748
Net written premiums 1,805 2,493 3,610 4,538
Premiums earned 2,039 2,372 4,137 4,653
Incurred losses and LAE 1,289 1,532 2,520 3,400
Commission and brokerage 479 533 974 1,022
Other underwriting expenses 130 146 249 296
Underwriting gain (loss) 141 161 393 (65)
Net investment income 335 314 696 633
Net gains (losses) on investments (8) (2) (38) 93
Corporate expenses (10) (11) (23) (17)
Interest, fees and bond issue cost amortization expense (42) (44) (84) (88)
Other income (expense) (39) (29) (41) (41)
Income tax expense (benefit) (72) (65) (167) (89)
NET INCOME (LOSS) 305 324 738 424
Affiliated Cession to Bermuda Entities        
Segment Reporting [Line Items]        
Gross written premiums 0 0 0 0
Net written premiums (75) (88) (205) (294)
Premiums earned (88) (118) (178) (234)
Incurred losses and LAE (1) 7 (1) 5
Commission and brokerage 0 0 0 0
Other underwriting expenses 0 0 0 0
Underwriting gain (loss) (87) (125) (177) (238)
Reinsurance Treaty | Operating Segments        
Segment Reporting [Line Items]        
Gross written premiums 1,612 1,710 3,205 3,477
Net written premiums 1,338 1,595 2,731 3,010
Premiums earned 1,403 1,557 2,798 3,007
Incurred losses and LAE 798 810 1,471 2,007
Commission and brokerage 351 390 709 741
Other underwriting expenses 40 36 74 75
Underwriting gain (loss) 214 322 542 185
Global Wholesale & Specialty | Operating Segments        
Segment Reporting [Line Items]        
Gross written premiums 689 747 1,260 1,340
Net written premiums 518 612 1,024 1,134
Premiums earned 529 577 1,066 1,147
Incurred losses and LAE 328 391 664 765
Commission and brokerage 110 119 227 234
Other underwriting expenses 60 42 121 85
Underwriting gain (loss) 31 25 55 62
Legacy | Operating Segments        
Segment Reporting [Line Items]        
Gross written premiums 28 535 87 931
Net written premiums 23 374 59 689
Premiums earned 195 355 451 733
Incurred losses and LAE 163 323 386 623
Commission and brokerage 19 24 38 48
Other underwriting expenses 29 68 54 136
Underwriting gain (loss) $ (17) $ (61) $ (27) $ (74)