Available-for-Sale Marketable Securities - Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 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	$ 67,278	$ 113,891
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(47)	(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	67,278	113,891
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(47)	(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	9,495	2,500
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(5)	(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	9,495	2,500
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(5)	(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	24,488	23,553
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(23)	(23)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	24,488	23,553
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(23)	(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	25,976	68,897
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(4)	(17)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	25,976	68,897
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(4)	(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	7,319	6,259
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(15)	(8)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	7,319	6,259
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (15)	$ (8)