Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 170,423	$ 219,734
Gross Unrealized Gains	48	123
Gross Unrealized Losses	(47)	(50)
Estimated Fair Value	170,424	219,807
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,067	20,710
Gross Unrealized Gains	3	41
Gross Unrealized Losses		(1)
Estimated Fair Value	10,070	20,750
U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,046	22,125
Gross Unrealized Gains	3	4
Gross Unrealized Losses	(5)	(1)
Estimated Fair Value	17,044	22,128
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	46,920	49,080
Gross Unrealized Gains	17	61
Gross Unrealized Losses	(23)	(23)
Estimated Fair Value	46,914	49,118
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	78,452	116,139
Gross Unrealized Gains	6	5
Gross Unrealized Losses	(4)	(17)
Estimated Fair Value	78,454	116,127
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,938	11,680
Gross Unrealized Gains	19	12
Gross Unrealized Losses	(15)	(8)
Estimated Fair Value	$ 17,942	$ 11,684