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Cash Equivalents and Short-Term Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 64,527 | $ 81,892
Gross Unrealized Gains | 1 | 5
Estimated Fair Value | 64,528 | 81,897
Money Market Funds | Cash Equivalents |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 59,157 | 30,360
Estimated Fair Value | 59,157 | 30,360
U.S. Government Agency Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 2,513 | 37,835
Gross Unrealized Gains | 1 | 2
Estimated Fair Value | 2,514 | 37,837
Cash and Cash Equivalents |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Estimated Fair Value | 59,157 | 30,360
Short-Term Investments |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Estimated Fair Value | 5,371 | 48,994
Long Term Investments |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Estimated Fair Value |  | 2,543
Federal Agency Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 2,857 | 13,697
Gross Unrealized Gains |  | 3
Estimated Fair Value | $ 2,857 | $ 13,700

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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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