Classification of Compensation Expense Associated with Share-Based Payments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 464	$ 688	$ 1,604	$ 2,468
Cost Of Revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated Share-based Compensation Expense	69	29	176	198
Sales and Marketing
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated Share-based Compensation Expense	53	89	219	410
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated Share-based Compensation Expense	279	522	978	1,614
Engineering And Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 63	$ 48	$ 231	$ 246