Geographic Information - Schedule of Geographic Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 26,334	$ 30,305	$ 51,463	$ 59,435
UNITED STATES
Segment Reporting Information [Line Items]
Total revenue	23,552	27,253	45,319	52,354
CANADA
Segment Reporting Information [Line Items]
Total revenue	1,801	2,272	3,957	5,147
Non-US [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 981	$ 780	$ 2,187	$ 1,934