v3.26.1
Investments - Schedule of Fixed Maturities Available for Sale by Component (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 19,307,295   $ 18,820,464      
Allowance for Credit Losses (3,297) $ (3,297) (3,297) $ (10,355) $ (10,355) $ (10,395)
Gross Unrealized Gains 311,292   409,982      
Gross Unrealized Losses (1,675,101)   (1,637,807)      
Fair Value $ 17,940,189   $ 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 $ 418,056   $ 409,170      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 5   161      
Gross Unrealized Losses (31,097)   (25,478)      
Fair Value $ 386,964   $ 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 $ 3,425,038   $ 3,385,433      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 22,865   26,955      
Gross Unrealized Losses (479,879)   (531,762)      
Fair Value $ 2,968,024   $ 2,880,626      
Percentage of Total Fixed Maturities 17.00%   16.00%      
Foreign governments            
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 46,371   $ 47,448      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 329   138      
Gross Unrealized Losses (7,699)   (8,040)      
Fair Value $ 39,001   $ 39,546      
Percentage of Total Fixed Maturities 0.00%   0.00%      
Corporates            
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 15,268,892   $ 14,863,082      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 287,528   380,851      
Gross Unrealized Losses (1,156,258)   (1,072,415)      
Fair Value $ 14,400,162   $ 14,171,518      
Percentage of Total Fixed Maturities 80.00%   81.00%      
Corporates | Industrials            
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 8,015,069   $ 7,787,885      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 141,850   175,164      
Gross Unrealized Losses (684,998)   (645,363)      
Fair Value $ 7,471,921   $ 7,317,686      
Percentage of Total Fixed Maturities 42.00%   42.00%      
Corporates | Financial            
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 5,051,600   $ 4,982,187      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 92,973   134,105      
Gross Unrealized Losses (367,486)   (333,966)      
Fair Value $ 4,777,087   $ 4,782,326      
Percentage of Total Fixed Maturities 26.00%   27.00%      
Corporates | Utilities            
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 2,202,223   $ 2,093,010      
Allowance for Credit Losses 0   0      
Gross Unrealized Gains 52,705   71,582      
Gross Unrealized Losses (103,774)   (93,086)      
Fair Value $ 2,151,154   $ 2,071,506      
Percentage of Total Fixed Maturities 12.00%   12.00%      
Other asset-backed securities            
Debt Securities, Available-for-sale [Line Items]            
Amortized Cost $ 148,938   $ 115,331      
Allowance for Credit Losses (3,297)   (3,297)      
Gross Unrealized Gains 565   1,877      
Gross Unrealized Losses (168)   (112)      
Fair Value $ 146,038   $ 113,799      
Percentage of Total Fixed Maturities 1.00%   1.00%