Fair Values on Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair value of financial assets and liabilities
Total financial assets	$ 88,978	$ 103,625
Money market funds
Fair value of financial assets and liabilities
Total short-term investments	46,570	6,203
Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	88,071	103,203
United States government agency securities | Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	7,025	30,683
Corporate debt securities | Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	34,476	66,317
Warrant | Other Assets
Fair value of financial assets and liabilities
Warrants	907	422
Level 1
Fair value of financial assets and liabilities
Total financial assets	46,570	6,203
Level 1 | Money market funds
Fair value of financial assets and liabilities
Total short-term investments	46,570	6,203
Level 1 | Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	46,570	6,203
Level 2
Fair value of financial assets and liabilities
Total financial assets	41,501	97,000
Level 2 | Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	41,501	97,000
Level 2 | United States government agency securities | Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	7,025	30,683
Level 2 | Corporate debt securities | Short-term Investments
Fair value of financial assets and liabilities
Total short-term investments	34,476	66,317
Level 3
Fair value of financial assets and liabilities
Total financial assets	907	422
Level 3 | Warrant | Other Assets
Fair value of financial assets and liabilities
Warrants	$ 907	$ 422