Summary of Cash Equivalents and Marketable Securities Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 27,691	$ 36,611
Marketable securities	2,500
Cash Equivalents, and Marketable Securities Fair Value Disclosure, Total	30,191
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	15,202	28,777
Cash Equivalents, and Marketable Securities Fair Value Disclosure, Total	15,202
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	12,488	$ 7,834
Marketable securities	2,500
Cash Equivalents, and Marketable Securities Fair Value Disclosure, Total	$ 14,988