Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 48,405	$ 35,822	$ 91,224	$ 66,341
Cost of revenue	14,739	11,532	28,720	21,192
Gross profit	33,666	24,290	62,504	45,149
Operating expenses:
Sales and marketing	22,015	19,179	42,086	34,955
Research and development	12,802	12,027	24,287	20,198
General and administrative	10,464	8,635	21,022	16,479
Total operating expenses	45,281	39,841	87,395	71,632
Operating loss	(11,615)	(15,551)	(24,891)	(26,483)
Other income (expense), net:
Interest and investment income	1,332	400	2,509	856
Interest expense	(1,654)	(1,572)	(3,289)	(3,144)
Other expense, net	12	(6)	(94)	(204)
Total other income (expense), net	(310)	(1,178)	(874)	(2,492)
Loss before income taxes	(11,925)	(16,729)	(25,765)	(28,975)
Provision for income taxes	(138)	(189)	(432)	(285)
Net loss	$ (12,063)	$ (16,918)	$ (26,197)	$ (29,260)
Net loss per share attributable to common stockholders:
Basic	$ (0.37)	$ (0.59)	$ (0.80)	$ (1.02)
Diluted	$ (0.37)	$ (0.59)	$ (0.80)	$ (1.02)
Weighted-average common shares outstanding:
Basic	33,015,861	28,848,809	32,645,522	28,642,887
Diluted	33,015,861	28,848,809	32,645,522	28,642,887