v3.26.1
Fair Value Measurements - Financial Assets Measured at Fair Value (Detail) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Financial Assets:    
Restricted cash [1] $ 3,757 $ 3,748
Debt Securities, Available-for-Sale 914,846 597,329
Equity Securities 65,056 65,890
Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Cash and cash equivalents 1,014,049 1,210,126
Restricted cash 3,757 3,748
Debt Securities, Available-for-Sale 914,846 597,329
Equity Securities 65,056 65,890
Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Cash and cash equivalents 1,014,049 1,210,126
Restricted cash 3,757 3,748
Debt Securities, Available-for-Sale 628,617 313,420
Equity Securities 63,735 64,545
Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 286,229 283,909
Equity Securities 1,321 1,345
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 648,288 333,352
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 628,617 313,420
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 19,671 19,932
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 241,138 242,922
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 241,138 242,922
Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 25,420 21,055
Commercial Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale $ 25,420 $ 21,055
[1] See Note 12 for details of balances associated with consolidated variable interest entities.