Stock-Based Compensation Expense Related to Stock Options and RSUs (Detail) - Stock Options and Restricted Stock Units - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	$ 791	$ 689	$ 2,182	$ 2,069
Cost of revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	43	34	124	97
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	159	107	506	334
Selling and Marketing Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	127	193	371	578
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense	$ 462	$ 355	$ 1,181	$ 1,060