v3.26.1
Fair Value of Financial Instruments -Schedule of Fair Value Measurements of Financial Instruments (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities $ 3,257,940 $ 3,137,023
U.S. Treasury securities and obligations of U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 214,800 307,028
Municipal debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 565,824 611,569
Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 2,198,547 2,019,611
U.S. agency mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 38,907 42,071
Other asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 150,721 70,125
Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash, cash equivalents and short-term investments 161,263 130,556
Total assets 3,330,062 3,180,960
Recurring | U.S. Treasury securities and obligations of U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 214,800 307,028
Recurring | Municipal debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 565,824 611,569
Recurring | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 2,198,547 2,019,611
Recurring | U.S. agency mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 38,907 42,071
Recurring | Other asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 150,721 70,125
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash, cash equivalents and short-term investments 161,263 130,556
Total assets 376,063 437,584
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities and obligations of U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 214,800 307,028
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. agency mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash, cash equivalents and short-term investments 0 0
Total assets 2,953,999 2,743,376
Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities and obligations of U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Significant Other Observable Inputs (Level 2) | Municipal debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 565,824 611,569
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 2,198,547 2,019,611
Recurring | Significant Other Observable Inputs (Level 2) | U.S. agency mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 38,907 42,071
Recurring | Significant Other Observable Inputs (Level 2) | Other asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 150,721 70,125
Recurring | Significant Unobservable Inputs (Level 3)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash, cash equivalents and short-term investments 0 0
Total assets 0 0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities and obligations of U.S. government agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Municipal debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. agency mortgage-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities 0 0
Recurring | Significant Unobservable Inputs (Level 3) | Other asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of securities $ 0 $ 0