Stock-Based Compensation Expense Related to Stock Options and RSUs (Detail) - Stock Options and Restricted Stock Units - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	$ 661	$ 445	$ 1,252	$ 1,382
Cost of revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	23	23	47	46
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	116	52	231	136
Selling and Marketing Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	110	78	270	285
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	$ 412	$ 292	$ 704	$ 915