Fair Value of Financial Assets and Liabilities - Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investments:
Commercial paper	$ 29,690
Fair Value, Measurements, Recurring [Member]
Investments:
Investments	64,343	$ 39,982
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash Equivalents:
Money market funds	25,510	39,982
Commercial Paper [Member]
Investments:
Commercial paper	11,957
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Cash Equivalents:
Money market funds	4,243
Investments:
Commercial paper	11,957
Corporate Bonds [Member]
Investments:
Commercial paper	17,733
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Cash Equivalents:
Money market funds	4,900
Investments:
Commercial paper	17,733
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	25,510	39,982
Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash Equivalents:
Money market funds	25,510	$ 39,982
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Investments:
Investments	38,833
Level 2 [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Cash Equivalents:
Money market funds	4,243
Investments:
Commercial paper	11,957
Level 2 [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Cash Equivalents:
Money market funds	4,900
Investments:
Commercial paper	$ 17,733