Fair Value Measurements - Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investments:
Investments	$ 20,237	$ 29,690
Fair Value, Measurements, Recurring [Member]
Investments:
Investments	41,669	64,343
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash equivalents:
Cash equivalents	11,440	25,510
Commercial Paper [Member]
Investments:
Investments	11,466	11,957
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	5,992	4,243
Investments:
Investments	11,466	11,957
Corporate Bonds [Member]
Investments:
Investments	8,771	17,733
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents		4,900
Investments:
Investments	8,771	17,733
Government Securities [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	4,000
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	11,440	25,510
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash equivalents:
Cash equivalents	11,440	25,510
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	30,229	38,833
Level 2 [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	5,992	4,243
Investments:
Investments	11,466	11,957
Level 2 [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents		4,900
Investments:
Investments	8,771	$ 17,733
Level 2 [Member] | Government Securities [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents:
Cash equivalents	$ 4,000