Fair Value of Financial Instruments - Summary of Contractual Maturities of Short and Long Term Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Amortized Cost Basis, Due within one year	$ 52,609	$ 49,068
Amortized Cost Basis, Due after 1 year through 2 years	37,704	40,858
Amortized Cost	90,313	89,926
Aggregate Fair Value, Due within one year	52,555	48,972
Aggregate Fair Value, Due after 1 year through 2 years	37,669	40,566
Aggregate Fair Value, Total	$ 90,224	$ 89,538