Summary of Short-term Investments (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, Amortized cost	$ 93,284	$ 92,840
Marketable securities, Unrealized Gains	1	62
Marketable securities, Estimated fair value	93,285	92,902
Cash equivalents, Amortized cost	90,896	60,037
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized cost	76,909	41,295
Cash equivalents, Estimated fair value	76,909	$ 41,295
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, Amortized cost	10,837
Marketable securities, Estimated fair value	$ 10,837
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, Maturity (in years)	Less than 1	Less than 1
Marketable securities, Amortized cost	$ 5,538	$ 41,507
Marketable securities, Unrealized Gains	1	50
Marketable securities, Estimated fair value	$ 5,539	$ 41,557
U.S. government securities
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, Maturity (in years)		Less than 1
Marketable securities, Amortized cost		$ 10,038
Marketable securities, Unrealized Gains		12
Marketable securities, Estimated fair value		$ 10,050