v3.25.1
Fair Value Measurements - Financial Assets Measured at Fair Value (Detail) - USD ($)
$ in Thousands
Mar. 31, 2025
Dec. 31, 2024
Financial Assets:    
Restricted cash [1] $ 3,722 $ 3,714
Debt Securities, Available-for-Sale 652,861 718,537
Equity Securities 55,226 56,200
Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Cash and cash equivalents 754,481 532,471
Restricted cash 3,722 3,714
Debt Securities, Available-for-Sale 652,861 718,537
Equity Securities 55,226 56,200
Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Cash and cash equivalents 754,481 532,471
Restricted cash 3,722 3,714
Debt Securities, Available-for-Sale 645,202 708,783
Equity Securities 55,226 56,200
Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 7,659 9,754
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 626,573 687,416
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 626,082 686,929
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 491 487
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 25,824 30,625
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 18,656 21,358
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 7,168 9,267
Exchange-Traded Debt [Member] | Fair Value, Measurements, Recurring [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale 464 496
Exchange-Traded Debt [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]    
Financial Assets:    
Debt Securities, Available-for-Sale $ 464 $ 496
[1] See Note 14 for details of balances associated with consolidated variable interest entities.