v3.26.1
SEGMENT REPORTING - Schedule of Underwriting Results for Segments (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Segment Reporting Information [Line Items]    
Gross written premiums $ 3,602 $ 4,391
Net written premiums 3,186 3,735
Premiums earned 3,574 3,852
Incurred losses and LAE 2,217 2,893
Commission and brokerage 825 824
Other underwriting expenses 216 238
Underwriting gain (loss) 316 (104)
Net investment income 567 491
Net gains (losses) on investments (10) (7)
Corporate expenses (38) (21)
Interest, fee and bond issue cost amortization expense (36) (38)
Other income (expense) (63) (73)
INCOME (LOSS) BEFORE TAXES 736 248
Reinsurance Treaty    
Segment Reporting Information [Line Items]    
Gross written premiums 2,674 2,935
Net written premiums 2,405 2,528
Premiums earned 2,456 2,579
Incurred losses and LAE 1,448 2,005
Commission and brokerage 632 637
Other underwriting expenses 61 60
Underwriting gain (loss) 315 (122)
Global Wholesale & Specialty    
Segment Reporting Information [Line Items]    
Gross written premiums 793 770
Net written premiums 692 655
Premiums earned 719 732
Incurred losses and LAE 453 482
Commission and brokerage 152 143
Other underwriting expenses 90 76
Underwriting gain (loss) 23 32
Legacy    
Segment Reporting Information [Line Items]    
Gross written premiums 135 686
Net written premiums 89 552
Premiums earned 399 540
Incurred losses and LAE 316 407
Commission and brokerage 41 44
Other underwriting expenses 65 103
Underwriting gain (loss) $ (22) $ (14)