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Cash Equivalents and Investments - Schedule of Investments (Detail) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Available-for-sale [Line Items] |  |
Available-for-sale Securities | $ 81,574 | $ 74,510
Corporate Securities [Member] |  |
Available-for-sale [Line Items] |  |
Available-for-sale Securities | 56,680 | 32,962
Municipal Debt Securities [Member] |  |
Available-for-sale [Line Items] |  |
Available-for-sale Securities | 13,523 | 29,066
Federal Home Loan Securities [Member] |  |
Available-for-sale [Line Items] |  |
Available-for-sale Securities | 6,529 | 8,013
Certificates of Deposit [Member] |  |
Available-for-sale [Line Items] |  |
Available-for-sale Securities | $ 4,842 | $ 4,469

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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