Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 147,094	$ 104,352	$ 76,846
Cost of revenue	46,810	31,503	23,767
Gross profit	100,284	72,849	53,079
Operating expenses:
Sales and marketing	69,608	46,998	34,847
Research and development	41,305	22,241	14,765
General and administrative	31,462	22,895	14,293
Total operating expenses	142,375	92,134	63,905
Operating loss	(42,091)	(19,285)	(10,826)
Other income (expense), net:
Interest income	1,842	475	34
Interest expense	(6,346)	(691)	(506)
Other expenses, net	(124)	(86)	(12)
Total other expense, net	(4,628)	(302)	(484)
Loss before income taxes	(46,719)	(19,587)	(11,310)
(Provision for) benefit from income taxes	(796)	(47)	24
Net loss	$ (47,515)	$ (19,634)	$ (11,286)
Net loss per share attributable to common stockholders:
Basic	$ (1.63)	$ (0.70)	$ (0.68)
Diluted	$ (1.63)	$ (0.70)	$ (0.68)
Weighted-average common shares outstanding:
Basic	29,107,267	27,862,375	16,659,561
Diluted	29,107,267	27,862,375	16,659,561
Other comprehensive (loss) income:
Foreign currency translation adjustment, net of taxes	$ (5,288)	$ 523	$ (290)
Total other comprehensive (loss) income	(5,288)	523	(290)
Total comprehensive loss	$ (52,803)	$ (19,111)	$ (11,576)