Fair Value Measurements - Schedule of Fair Value Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Assets
Total financial assets	$ 121,162	$ 148,829
Money Market Funds [Member]
Financial Assets
Total financial assets	120,962	148,604
Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	200	225
Level 1 [Member]
Financial Assets
Total financial assets	121,162	148,829
Level 1 [Member] | Money Market Funds [Member]
Financial Assets
Total financial assets	120,962	148,604
Level 1 [Member] | Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	$ 200	$ 225