v3.26.3
FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading $ 25,203,247   $ 25,203,247   $ 24,884,323
Debt 2,331,768   2,331,768   2,329,201
Asset-backed          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading 1,357,970   1,357,970   1,606,790
Other Investments | Income Statement Location [Axis]: us-gaap:NonoperatingGainsLosses          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Net unrealized gains recognized in earnings 51,000 $ 74,200 51,900 $ 94,000  
Significant Unobservable Inputs (Level 3)          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading 383,805   383,805   154,115
Debt 99,300   99,300   99,200
Long-term debt 92,800   92,800   100,200
Significant Unobservable Inputs (Level 3) | Asset-backed          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading 136,858   136,858   39,859
Significant Unobservable Inputs (Level 3) | Asset-backed | Non-company unobservable input          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading 101,100   101,100   0
Significant Unobservable Inputs (Level 3) | Asset-backed | Discounted cash flow          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading 35,768   35,768   39,859
Significant Other Observable Inputs (Level 2)          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading 15,782,219   15,782,219   14,088,705
Debt 2,200,000   2,200,000   2,200,000
Long-term debt 2,200,000   2,200,000   2,300,000
Significant Other Observable Inputs (Level 2) | Asset-backed          
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]          
Fixed maturity investments trading $ 1,221,112   $ 1,221,112   $ 1,566,931