Marketable Securities - Summary of unrealized loss on available-for-sale securities, net, presented in the statements of operations and comprehensive loss (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Investments Debt And Equity Securities [Abstract]
Unrealized loss before reclassifications	$ (1,001)	$ (755)
Realized gains reclassified to investment income	(7)	(30)
Unrealized loss on available-for-sale securities, net	$ (1,008)	$ (785)

Amount, before tax and adjustment, of unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration