Fair Value Measurements - Available-for-Sale Securities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Financial Assets:
Restricted cash	$ 2,900	$ 2,400
Debt Securities, Available-for-Sale	483,901	42,583
Equity securities	34,583	51,740
Fair Value, Measurements, Recurring [Member]
Financial Assets:
Cash and cash equivalents	234,863	628,943
Restricted cash	2,900	2,400
Debt Securities, Available-for-Sale	483,901	42,583
Equity securities	34,583	51,740
Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Cash and cash equivalents	234,863	628,943
Restricted cash	2,900	2,400
Debt Securities, Available-for-Sale	474,149	39,287
Equity securities	34,583	51,740
Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	9,752	3,296
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale	454,602	17,024
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	446,233	15,536
U.S. Treasury and U.S. Government Agencies [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	8,369	1,488
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale	27,193	22,492
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	27,193	22,492
State, Municipalities, and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale	1,383	1,808
State, Municipalities, and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member] | (Level 2) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	1,383	1,808
Exchange-Traded Debt [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale	633	811
Exchange-Traded Debt [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	633	811
Redeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Debt Securities, Available-for-Sale	90	448
Redeemable Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | (Level 1) [Member]
Financial Assets:
Debt Securities, Available-for-Sale	$ 90	$ 448