Cash Equivalents and Investments in Marketable Securities - Summary of Investment Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 16,905	$ 21,696
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(1)	(5)
Fair Value	16,905	21,691
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,111	4,830
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	9,111	4,830
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,804	1,497
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	3,803	1,497
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		6,994
Gross Unrealized Gains		0
Gross Unrealized Losses		(5)
Fair Value		6,989
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,990	8,375
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Fair Value	$ 3,991	$ 8,375

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
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