Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 205,779	$ 219,734
Gross Unrealized Gains	71	123
Gross Unrealized Losses	(59)	(50)
Estimated Fair Value	205,791	219,807
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,164	20,710
Gross Unrealized Gains	3	41
Gross Unrealized Losses		(1)
Estimated Fair Value	15,167	20,750
U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,099	22,125
Gross Unrealized Gains	4	4
Gross Unrealized Losses	(6)	(1)
Estimated Fair Value	22,097	22,128
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,674	49,080
Gross Unrealized Gains	26	61
Gross Unrealized Losses	(48)	(23)
Estimated Fair Value	41,652	49,118
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	115,179	116,139
Gross Unrealized Gains	10	5
Gross Unrealized Losses	(2)	(17)
Estimated Fair Value	115,187	116,127
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,663	11,680
Gross Unrealized Gains	28	12
Gross Unrealized Losses	(3)	(8)
Estimated Fair Value	$ 11,688	$ 11,684