Fair Value of Financial Assets and Liabilities - Summary of Financial Assets and Liabilities Measured at Fair Value Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash equivalents:
Total cash equivalents	$ 3,000	$ 5,400
Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Total cash equivalents	26,751	28,716
Marketable securities:
Total marketable securities	52,315	81,363
Total cash equivalents and marketable securities	79,066	110,079
Derivative liabilities:
Derivative liabilities		223
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash equivalents:
Total cash equivalents	26,751	22,327
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Cash equivalents:
Total cash equivalents		6,389
Marketable securities:
Total marketable securities	21,458	16,876
Fair Value, Measurements, Recurring [Member] | U.S. Government Securities [Member]
Marketable securities:
Total marketable securities	16,797	37,815
Fair Value, Measurements, Recurring [Member] | U.S. Corporate Bonds [Member]
Marketable securities:
Total marketable securities	14,060	26,672
Fair Value, Measurements, Recurring [Member] | Anti-dilution Rights [Member]
Derivative liabilities:
Derivative liabilities		223
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Cash equivalents:
Total cash equivalents	26,751	28,716
Marketable securities:
Total marketable securities	52,315	81,363
Total cash equivalents and marketable securities	79,066	110,079
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Money Market Funds [Member]
Cash equivalents:
Total cash equivalents	26,751	22,327
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial Paper [Member]
Cash equivalents:
Total cash equivalents		6,389
Marketable securities:
Total marketable securities	21,458	16,876
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government Securities [Member]
Marketable securities:
Total marketable securities	16,797	37,815
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Corporate Bonds [Member]
Marketable securities:
Total marketable securities	$ 14,060	26,672
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Derivative liabilities:
Derivative liabilities		223
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Anti-dilution Rights [Member]
Derivative liabilities:
Derivative liabilities		$ 223