Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 104,352	$ 76,846	$ 58,720
Cost of revenue	31,503	23,767	19,789
Gross profit	72,849	53,079	38,931
Operating expenses:
Sales and marketing	46,998	34,847	25,925
Research and development	22,241	14,765	11,521
General and administrative	22,895	14,293	12,272
Total operating expenses	92,134	63,905	49,718
Operating loss	(19,285)	(10,826)	(10,787)
Other income (expense), net:
Interest income	475	34	1
Interest expense	(691)	(506)	(538)
Other expenses, net	(86)	(12)	(62)
Total other expense, net	(302)	(484)	(599)
Loss before income taxes	(19,587)	(11,310)	(11,386)
(Provision for) benefit from income taxes	(47)	24	562
Net loss	$ (19,634)	$ (11,286)	$ (10,824)
Net loss per share attributable to common stockholders:
Basic	$ (0.70)	$ (0.68)	$ (0.88)
Diluted	$ (0.70)	$ (0.68)	$ (0.88)
Weighted-average common shares outstanding:
Basic	27,862,375	16,659,561	12,257,413
Diluted	27,862,375	16,659,561	12,257,413
Other comprehensive (loss) income:
Foreign currency translation adjustment, net of taxes	$ 523	$ (290)	$ 29
Total other comprehensive (loss) income	523	(290)	29
Total comprehensive loss	$ (19,111)	$ (11,576)	$ (10,795)