CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 80,301	$ 59,107
Cost of revenue	13,226	8,728
Gross profit	67,075	50,379
Operating expenses:
Sales and marketing	52,689	39,588
Research and development	21,935	17,185
General and administrative	15,136	9,055
Total operating expenses	89,760	65,828
Loss from operations	(22,685)	(15,449)
Interest income (expense), net	1,556	(26)
Other Nonoperating Income (Expense)	(214)	18
Loss before income taxes	(21,343)	(15,457)
Provision for income taxes	97	431
Net loss	(21,440)	(15,888)
Accretion of Series A and B redeemable convertible preferred stock	0	(188)
Net loss attributable to common stockholders	$ (21,440)	$ (16,076)
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)	$ (0.23)	$ (0.68)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	93,738	23,495