Amortization Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 364	$ 364
Cost of revenue
Finite Lived Intangible Assets [Line Items]
Amortization expense	112	112
Selling and Marketing Expense
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 252	$ 252