Available-for-Sale Marketable Securities - Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	$ 80,747	$ 113,891
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(59)	(50)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	80,747	113,891
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(59)	(50)
U.S. Treasury Securities [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value		12,682
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value		12,682
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		(1)
U.S. Government Agency Obligations [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	9,494	2,500
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(6)	(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	9,494	2,500
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(6)	(1)
Corporate Bonds [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	30,751	23,553
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(48)	(23)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	30,751	23,553
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(48)	(23)
Commercial Paper [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	39,480	68,897
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(2)	(17)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	39,480	68,897
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(2)	(17)
Municipal Bonds [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	1,022	6,259
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(3)	(8)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	1,022	6,259
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (3)	$ (8)