Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenue	$ 38,925	$ 27,312	$ 105,266	$ 75,177
Cost of revenue	12,296	8,076	33,488	22,969
Gross profit	26,629	19,236	71,778	52,208
Operating expenses:
Sales and marketing	16,348	11,626	51,303	33,589
Research and development	10,350	5,626	30,548	16,082
General and administrative	7,130	6,375	23,609	16,640
Total operating expenses	33,828	23,627	105,460	66,311
Operating loss	(7,199)	(4,391)	(33,682)	(14,103)
Other income (expense), net:
Interest and investment income	460	106	1,316	234
Interest expense	(1,592)	(2)	(4,736)	(5)
Other expense, net	(33)	(23)	(237)	(61)
Total other (expense) income, net	(1,165)	81	(3,657)	168
Loss before income taxes	(8,364)	(4,310)	(37,339)	(13,935)
(Provision for) benefit from income taxes	(86)	79	(371)	65
Net loss	$ (8,450)	$ (4,231)	$ (37,710)	$ (13,870)
Net loss per share attributable to common stockholders:
Basic	$ (0.29)	$ (0.15)	$ (1.30)	$ (0.50)
Diluted	$ (0.29)	$ (0.15)	$ (1.30)	$ (0.50)
Weighted-average common shares outstanding:
Basic	29,460,156	28,100,172	28,918,304	27,719,519
Diluted	29,460,156	28,100,172	28,918,304	27,719,519