Geographic Information - Schedule of Geographic Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 25,129	$ 29,130
UNITED STATES
Segment Reporting Information [Line Items]
Total revenue	21,767	25,100
CANADA
Segment Reporting Information [Line Items]
Total revenue	2,155	2,876
Non-US [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 1,207	$ 1,154