RESERVE FOR CLAIMS AND CLAIM EXPENSES - Schedule of Reserve for Claims and Claim Expenses by Segment (Details) - USD ($) $ in Thousands |
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|---|
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Case Reserves | $ 5,190,878 | $ 4,926,309 | |
| ACR | 2,007,789 | 2,200,627 | |
| IBNR | 15,103,678 | 14,176,555 | |
| Total | 22,302,345 | 21,303,491 | $ 20,486,869 |
| Property | Operating Segments | |||
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Case Reserves | 1,797,427 | 1,845,228 | |
| ACR | 1,679,848 | 1,905,553 | |
| IBNR | 2,208,709 | 2,821,958 | |
| Total | 5,685,984 | 6,572,739 | |
| Casualty and Specialty | Operating Segments | |||
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Case Reserves | 3,393,451 | 3,081,081 | |
| ACR | 327,941 | 295,074 | |
| IBNR | 12,894,969 | 11,354,597 | |
| Total | $ 16,616,361 | $ 14,730,752 |