Summary of Cash Equivalents and Marketable Securities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 5,749	$ 7,501
Fair Value Measurements Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	9,050	16,274
Marketable securities	5,749	7,501
Cash Equivalents, and Marketable Securities Fair Value Disclosure, Total	14,799	23,775
Fair Value Measurements Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	6,907	11,462
Cash Equivalents, and Marketable Securities Fair Value Disclosure, Total	6,907	11,462
Fair Value Measurements Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,143	4,812
Marketable securities	5,749	7,501
Cash Equivalents, and Marketable Securities Fair Value Disclosure, Total	$ 7,892	$ 12,313