Amortization Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 364	$ 364	$ 1,092	$ 1,092
Cost of revenue
Finite Lived Intangible Assets [Line Items]
Amortization expense	112	112	336	336
Selling and Marketing Expense
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 252	$ 252	$ 756	$ 756