Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 52,547	$ 38,925	$ 143,771	$ 105,266
Cost of revenue	16,454	12,296	45,174	33,488
Gross profit	36,093	26,629	98,597	71,778
Operating expenses:
Sales and marketing	21,903	16,348	63,989	51,303
Research and development	12,877	10,350	37,164	30,548
General and administrative	13,435	7,130	34,457	23,609
Total operating expenses	48,215	33,828	135,610	105,460
Operating loss	(12,122)	(7,199)	(37,013)	(33,682)
Other income (expense), net:
Interest and investment income	1,032	460	3,541	1,316
Interest expense	(1,697)	(1,592)	(4,986)	(4,736)
Other expense, net	(35)	(33)	(129)	(237)
Total other income (expense), net	(700)	(1,165)	(1,574)	(3,657)
Loss before income taxes	(12,822)	(8,364)	(38,587)	(37,339)
Provision for income taxes	(99)	(86)	(531)	(371)
Net loss	$ (12,921)	$ (8,450)	$ (39,118)	$ (37,710)
Net loss per share attributable to common stockholders:
Basic	$ (0.39)	$ (0.29)	$ (1.19)	$ (1.30)
Diluted	$ (0.39)	$ (0.29)	$ (1.19)	$ (1.30)
Weighted-average common shares outstanding:
Basic	33,524,771	29,460,156	32,941,826	28,918,304
Diluted	33,524,771	29,460,156	32,941,826	28,918,304