v3.25.4
FAIR VALUE MEASUREMENTS - Schedule of Quantitative Information Used as Level 3 Inputs (Details)
Dec. 31, 2025
USD ($)
$ / shares
Dec. 31, 2024
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading $ 24,884,323,000 $ 23,562,514,000
Other investments 4,574,214,000 4,324,761,000
Other liabilities (22,887,000) (41,745,000)
Total assets and (liabilities) measured at fair value on a recurring basis using Level 3 inputs 35,928,451,000 32,494,941,000
Corporate    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 8,528,828,000 7,862,423,000
Asset-backed    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 1,606,790,000 1,422,393,000
Significant Unobservable Inputs (Level 3)    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 154,115,000 0
Other investments 27,995,000 43,777,000
Other liabilities (34,000) (405,000)
Total assets and (liabilities) measured at fair value on a recurring basis using Level 3 inputs 182,076,000 43,372,000
Significant Unobservable Inputs (Level 3) | Corporate    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 114,256,000 0
Significant Unobservable Inputs (Level 3) | Asset-backed    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 39,859,000 0
Significant Unobservable Inputs (Level 3) | Direct private equity investments    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Other investments 27,995,000 43,777,000
Significant Unobservable Inputs (Level 3) | Recent transaction price | Corporate    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 114,256,000  
Significant Unobservable Inputs (Level 3) | Discounted cash flow | Asset-backed    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fixed maturity investments trading 39,859,000  
Significant Unobservable Inputs (Level 3) | Internal valuation model | Direct private equity investments    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Other investments 27,995,000 43,777,000
Significant Unobservable Inputs (Level 3) | Internal valuation model | Assumed reinsurance contract    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Other liabilities $ (34,000) $ (405,000)
Significant Unobservable Inputs (Level 3) | Discount rate | Discounted cash flow | Weighted Average or Actual | Asset-backed    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Unobservable measurement input | $ / shares 0.113  
Significant Unobservable Inputs (Level 3) | Discount rate | Internal valuation model | Weighted Average or Actual | Direct private equity investments    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Significant observable and unobservable inputs 0.130 0.100
Significant Unobservable Inputs (Level 3) | Discount rate | Internal valuation model | Weighted Average or Actual | Assumed reinsurance contract    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Significant observable and unobservable inputs 0.037 0.044
Significant Unobservable Inputs (Level 3) | Liquidity discount | Internal valuation model | Weighted Average or Actual | Direct private equity investments    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Significant observable and unobservable inputs 0.100 0.150
Significant Unobservable Inputs (Level 3) | Net undiscounted cash flows | Internal valuation model | Weighted Average or Actual | Assumed reinsurance contract    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Significant observable and unobservable inputs 12,836,000 12,657,000
Significant Unobservable Inputs (Level 3) | Expected loss ratio | Internal valuation model | Weighted Average or Actual | Assumed reinsurance contract    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Significant observable and unobservable inputs 0 0.012