Segment Information - Total Revenue from Customers by Geographic Area, Based on Location of Customer (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 41,121	$ 39,487	$ 123,969	$ 115,812
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	21,834	22,726	67,351	68,205
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	7,491	6,097	20,538	18,177
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	5,464	4,129	16,319	12,416
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,125	6,363	19,292	16,490
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 207	$ 172	$ 469	$ 524