Amortization Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 642	$ 531	$ 1,925	$ 1,510
Cost of revenue
Finite Lived Intangible Assets [Line Items]
Amortization expense	224	186	672	522
Selling and Marketing Expense
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 418	$ 345	$ 1,253	$ 988