Stock-Based Compensation - Stock-Based Non-Cash Compensation Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation expense	$ 408	$ 527	$ 1,173	$ 1,627
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation expense		3	3	9
Selling and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation expense	84	84	238	242
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation expense	128	153	375	473
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation expense	$ 196	$ 287	$ 557	$ 903