v3.26.3
Fair Value Measurements - Financial Assets Measured at Fair Value (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Financial Assets:    
Restricted cash [1] $ 4,600 $ 3,748
Debt Securities, Available-for-Sale [1] 1,241,444 597,329
Equity Securities 59,244 65,890
Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Cash and cash equivalents 743,527 1,210,126
Restricted cash 4,600 3,748
Debt Securities, Available-for-Sale 1,241,444 597,329
Equity Securities 59,244 65,890
Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Cash and cash equivalents 743,527 1,210,126
Restricted cash 4,600 3,748
Debt Securities, Available-for-Sale 962,973 313,420
Equity Securities 58,379 64,545
Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 278,471 283,909
Equity Securities 865 1,345
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 981,404 333,352
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 962,973 313,420
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 18,431 19,932
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 235,843 242,922
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 0 0
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 235,843 242,922
Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 24,197 21,055
Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 0 0
Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale $ 24,197 $ 21,055
[1] See Note 12 for details of balances associated with consolidated variable interest entities.