Amortization Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 643	$ 532	$ 1,283	$ 979
Cost of revenue
Finite Lived Intangible Assets [Line Items]
Amortization expense	224	187	445	336
Selling and Marketing Expense
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 419	$ 345	$ 838	$ 643