Fair Value Measurements and Marketable Debt Securities - Summary of Cash Equivalents and Marketable Debt Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 14,671	$ 12,635
Marketable debt securities	6,499	24,490
Total cash equivalents and marketable debt securities	21,170	37,125
Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	5,172	4,229
Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	9,499	6,499
Marketable debt securities	6,499	22,485
Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		1,907
U.S. Government Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities		2,005
Quoted Prices in Active Markets, (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	5,172	4,229
Total cash equivalents and marketable debt securities	5,172	4,229
Quoted Prices in Active Markets, (Level 1) [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	5,172	4,229
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	9,499	8,406
Marketable debt securities	6,499	24,490
Total cash equivalents and marketable debt securities	15,998	32,896
Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	9,499	6,499
Marketable debt securities	$ 6,499	22,485
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		1,907
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities		$ 2,005