Investments - Schedule of Investments by Security Type (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 205,985	$ 187,439
Gross Unrealized Gain	32	14
Gross Unrealized Loss	(47)	(61)
Fair Value	205,970	187,392
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,491	12,343
Fair Value	14,491	12,343
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	78,337	68,333
Gross Unrealized Gain	5	8
Gross Unrealized Loss	(42)	(52)
Fair Value	78,300	68,289
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,272	2,272
Fair Value	2,272	2,272
US Government Agencies Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	110,885	104,491
Gross Unrealized Gain	27	6
Gross Unrealized Loss	(5)	(9)
Fair Value	$ 110,907	$ 104,488

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).

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