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Cash Equivalents, Restricted Cash and Short-Term Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 76,831 | $ 119,057
Gross Unrealized Gains | 34 | 2
Gross Unrealized Losses |  | (6)
Estimated Fair Value | 76,865 | 119,053
Restricted cash |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost |  | 50
Estimated Fair Value |  | 50
Federal Agency Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 9,995 | 14,774
Gross Unrealized Gains | 11 | 1
Estimated Fair Value | 10,006 | 14,775
Federal Agency Securities | Cash Equivalents |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost |  | 999
Estimated Fair Value |  | 999
Money Market Funds | Cash Equivalents |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 15,369 | 29,090
Estimated Fair Value | 15,369 | 29,090
U.S. Government Agency Securities |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 51,467 | 74,144
Gross Unrealized Gains | 23 | 1
Gross Unrealized Losses |  | (6)
Estimated Fair Value | 51,490 | 74,139
Cash and Cash Equivalents |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Estimated Fair Value | 15,369 | 30,089
Short-Term Investments |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Estimated Fair Value | $ 61,496 | $ 88,914

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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=118939692&loc=d3e27161-111563 + Details
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- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + 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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