Fair Value Measurement - Summary of Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	$ 302,848	$ 307,947
Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	1,675	40,942
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	7,857	6,301
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	293,316	260,704
Cash and Cash Equivalents [Member] | U.S. Treasuries [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	8,398
Cash and Cash Equivalents [Member] | U.S. Treasuries [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	8,398
Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	1,502	40,296
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	1,502	40,296
Investments [Member] | U.S. Treasuries [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	15,007
Investments [Member] | U.S. Treasuries [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	15,007
Investments [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	33,437	33,308
Investments [Member] | Corporate Bonds [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	33,437	33,308
Investments [Member] | Mortgage Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	11,675	12,996
Investments [Member] | Mortgage Backed Securities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	11,675	12,996
Investments [Member] | U.S. Government Agency Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	12,218	7,067
Investments [Member] | U.S. Government Agency Securities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	12,218	7,067
Investments [Member] | Emerging Markets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	1,985	1,982
Investments [Member] | Emerging Markets [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	1,985	1,982
Investments [Member] | Asset Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	13,331	12,972
Investments [Member] | Asset Backed Securities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	13,331	12,972
Restricted Cash and Investments [Member] | U.S. Treasuries [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	74,532	57,257
Restricted Cash and Investments [Member] | U.S. Treasuries [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	74,532	57,257
Restricted Cash and Investments [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	173	646
Restricted Cash and Investments [Member] | Money Market Funds [Member] | Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	173	646
Restricted Cash and Investments [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	70,885	70,697
Restricted Cash and Investments [Member] | Corporate Bonds [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	70,885	70,697
Restricted Cash and Investments [Member] | Mortgage Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	35,815	40,093
Restricted Cash and Investments [Member] | Mortgage Backed Securities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	35,815	40,093
Restricted Cash and Investments [Member] | U.S. Government Agency Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	15,243	24,323
Restricted Cash and Investments [Member] | U.S. Government Agency Securities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	15,243	24,323
Restricted Cash and Investments [Member] | Asset Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	790	9
Restricted Cash and Investments [Member] | Asset Backed Securities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	790	9
Restricted Cash and Investments [Member] | Mutual Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	7,857	6,301
Restricted Cash and Investments [Member] | Mutual Funds [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Recorded Basis	$ 7,857	$ 6,301