Amortization Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 364	$ 364	$ 728	$ 728
Cost of revenue
Finite Lived Intangible Assets [Line Items]
Amortization expense	112	112	224	224
Selling and Marketing Expense
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 252	$ 252	$ 504	$ 504