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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
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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

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