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Cash Equivalents and Short-Term Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 104,045	$ 76,831
Gross Unrealized Gains	8	34
Estimated Fair Value	104,053	76,865
Money Market Funds | Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	24,923	15,369
Estimated Fair Value	24,923	15,369
U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	55,038	51,467
Gross Unrealized Gains	4	23
Estimated Fair Value	55,042	51,490
Cash and Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	24,923	15,369
Short-Term Investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	77,959	61,496
Long-Term Investments
Schedule Of Available For Sale Securities [Line Items]
Estimated Fair Value	1,171
Federal Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	24,084	9,995
Gross Unrealized Gains	4	11
Estimated Fair Value	$ 24,088	$ 10,006

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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=121645371&loc=d3e27161-111563

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