v3.26.3
Fair Value Measurements - Schedule of Quantitative Information about Significant Unobservable Inputs in the Fair Value Measurement of Level 3 Assets (Details)
$ in Thousands
Sep. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Sep. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Fixed income securities $ 9,810,058 $ 9,457,176    
Corporate securities        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Fixed income securities 3,753,825 3,404,164    
Total Level 3 securities 378,398 369,111 $ 317,267 $ 242,679
CLO and other ABS        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Fixed income securities 2,505,402 2,550,286    
Total Level 3 securities 397,129 565,089 $ 496,036 $ 367,994
Significant Unobservable Inputs (Level 3)        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Other investment assets measured at fair value 707,255 471,204    
Total Level 3 securities 783,162 941,944    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Fixed income securities 75,907 470,740    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Corporate securities        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Fixed income securities   175,433    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | CLO and other ABS        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Fixed income securities $ 75,907 $ 295,307    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Illiquidity Spread | Minimum | Corporate securities        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt securities, available-for-sale, measurement input   (0.044)    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Illiquidity Spread | Minimum | CLO and other ABS        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt securities, available-for-sale, measurement input 0.020 (0.018)    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Illiquidity Spread | Maximum | Corporate securities        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt securities, available-for-sale, measurement input   0.053    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Illiquidity Spread | Maximum | CLO and other ABS        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt securities, available-for-sale, measurement input 0.196 0.196    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Illiquidity Spread | Weighted Average | Corporate securities        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt securities, available-for-sale, measurement input   0.019    
Significant Unobservable Inputs (Level 3) | Valuation Technique, Discounted Cash Flow | Illiquidity Spread | Weighted Average | CLO and other ABS        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Debt securities, available-for-sale, measurement input 0.081 0.023