Fair Value Measurements - Available-for-Sale Securities Measured at Fair Value (Detail) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Financial Assets:
Restricted cash	[1]	$ 3,287	$ 2,900
Debt Securities, Available-for-Sale		383,238	483,901
Equity securities, at fair value		45,537	34,583
Fair Value, Measurements, Recurring [Member]
Financial Assets:
Cash and cash equivalents		536,478	234,863
Restricted cash		3,287	2,900
Debt Securities, Available-for-Sale		383,238	483,901
Equity securities, at fair value		45,537	34,583
Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Cash and cash equivalents		536,478	234,863
Restricted cash		3,287	2,900
Debt Securities, Available-for-Sale		368,892	474,149
Equity securities, at fair value		45,537	34,583
Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale		14,346	9,752
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale		356,054	454,602
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale		348,145	446,233
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale		7,909	8,369
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale		26,704	27,193
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale		20,267	27,193
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale		6,437
State, Municipalities, and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale			1,383
State, Municipalities, and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale			1,383
Exchange-Traded Debt [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale		480	633
Exchange-Traded Debt [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale		$ 480	633
Redeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale			90
Redeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale			$ 90

[1] See Note 16 for details of balances associated with variable interest entity.