CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 95,864	$ 51,074	$ 249,136	$ 136,467
Cost of revenue	23,297	12,098	63,225	30,690
Gross profit	72,567	38,976	185,911	105,777
Operating expenses:
Research and development	28,684	14,159	75,531	37,456
Sales and marketing	38,836	25,130	105,061	59,747
General and administrative	9,265	4,322	23,193	12,933
Total operating expenses	76,785	43,611	203,785	110,136
Operating loss	(4,218)	(4,635)	(17,874)	(4,359)
Other income, net	90	311	646	612
Loss before provision for income taxes	(4,128)	(4,324)	(17,228)	(3,747)
Provision for income taxes	(33)	(349)	(373)	(428)
Net loss	(4,161)	(4,673)	(17,601)	(4,175)
Other comprehensive (loss) income—foreign currency translation adjustments	(45)	(10)	(85)	32
Comprehensive loss	(4,206)	(4,683)	(17,686)	(4,143)
Net loss attributable to common stockholders	$ (4,161)	$ (4,673)	$ (17,601)	$ (4,175)
Basic and diluted net loss per share	$ (0.04)	$ (0.06)	$ (0.20)	$ (0.06)
Weighted average shares used in calculating basic and diluted net loss per share:	103,876	73,353	87,758	69,708