v3.26.1
Investments - Schedule of Fixed Maturities Available for Sale by Component (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 19,133,385 $ 18,820,464    
Allowance for Credit Losses (3,297) (3,297) $ (10,355) $ (10,395)
Gross Unrealized Gains 295,833 409,982    
Gross Unrealized Losses (1,846,545) (1,637,807)    
Fair value $ 17,579,376 $ 17,589,342    
Percentage of total fixed maturities 100.00% 100.00%    
U.S. Government direct, guaranteed, and government-sponsored enterprises        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 417,459 $ 409,170    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 70 161    
Gross Unrealized Losses (28,378) (25,478)    
Fair value $ 389,151 $ 383,853    
Percentage of total fixed maturities 2.00% 2.00%    
States, municipalities, and political subdivisions        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 3,403,657 $ 3,385,433    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 27,574 26,955    
Gross Unrealized Losses (546,601) (531,762)    
Fair value $ 2,884,630 $ 2,880,626    
Percentage of total fixed maturities 16.00% 16.00%    
Foreign governments        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 48,051 $ 47,448    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 19 138    
Gross Unrealized Losses (9,235) (8,040)    
Fair value $ 38,835 $ 39,546    
Percentage of total fixed maturities 0.00% 0.00%    
Corporates        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 15,145,595 $ 14,863,082    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 267,471 380,851    
Gross Unrealized Losses (1,262,064) (1,072,415)    
Fair value $ 14,151,002 $ 14,171,518    
Percentage of total fixed maturities 81.00% 81.00%    
Corporates | Industrials        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 7,919,363 $ 7,787,885    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 125,412 175,164    
Gross Unrealized Losses (747,376) (645,363)    
Fair value $ 7,297,399 $ 7,317,686    
Percentage of total fixed maturities 42.00% 42.00%    
Corporates | Financial        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 5,056,081 $ 4,982,187    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 91,401 134,105    
Gross Unrealized Losses (400,765) (333,966)    
Fair value $ 4,746,717 $ 4,782,326    
Percentage of total fixed maturities 27.00% 27.00%    
Corporates | Utilities        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 2,170,151 $ 2,093,010    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 50,658 71,582    
Gross Unrealized Losses (113,923) (93,086)    
Fair value $ 2,106,886 $ 2,071,506    
Percentage of total fixed maturities 12.00% 12.00%    
Collateralized debt obligations        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 0 $ 0    
Allowance for Credit Losses 0 0    
Gross Unrealized Gains 0 0    
Gross Unrealized Losses 0 0    
Fair value $ 0 $ 0    
Percentage of total fixed maturities 0.00% 0.00%    
Other asset-backed securities        
Debt Securities, Available-for-sale [Line Items]        
Amortized Cost $ 118,623 $ 115,331    
Allowance for Credit Losses (3,297) (3,297)    
Gross Unrealized Gains 699 1,877    
Gross Unrealized Losses (267) (112)    
Fair value $ 115,758 $ 113,799    
Percentage of total fixed maturities 1.00% 1.00%