RESERVE FOR CLAIMS AND CLAIM EXPENSES - Schedule of Reserve for Claims and Claim Expenses by Segment (Details) - USD ($) $ in Thousands |
Jun. 30, 2026 |
Dec. 31, 2025 |
Jun. 30, 2025 |
|---|---|---|---|
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Case Reserves | $ 5,387,864 | $ 5,190,878 | |
| ACR | 1,887,860 | 2,007,789 | |
| IBNR | 14,993,410 | 15,103,678 | |
| Total | 22,269,134 | 22,302,345 | $ 22,913,763 |
| Operating Segments | Property | |||
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Case Reserves | 1,618,503 | 1,797,427 | |
| ACR | 1,436,824 | 1,679,848 | |
| IBNR | 1,972,558 | 2,208,709 | |
| Total | 5,027,885 | 5,685,984 | |
| Operating Segments | Casualty and Specialty | |||
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Case Reserves | 3,769,361 | 3,393,451 | |
| ACR | 451,036 | 327,941 | |
| IBNR | 13,020,852 | 12,894,969 | |
| Total | $ 17,241,249 | $ 16,616,361 |