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, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value		$ 38,744
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(27)
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	0	38,744
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ 0	(27)
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value		3,185
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(2)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value		3,185
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		(2)
U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value		2,400
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		2,400
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		(1)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value		28,895
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(23)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value		28,895
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		(23)
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value		4,264
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		4,264
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		$ (1)