CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 170,198	$ 68,431	$ 30,850
Cost of revenue	46,158	20,269	8,312
Gross profit	124,040	48,162	22,538
Operating expenses:
Research and development	49,842	24,861	12,028
Sales and marketing	78,060	36,433	16,502
General and administrative	55,676	23,063	11,050
Change in fair value of contingent consideration	843	(1,200)	0
Total operating expenses	184,421	83,157	39,580
Loss from operations	(60,381)	(34,995)	(17,042)
Other income, net	3,742	1,641	123
Loss before provision for income taxes	(56,639)	(33,354)	(16,919)
Provision for (benefit from) income taxes	(1,369)	28	(61)
Net loss	(55,270)	(33,382)	(16,858)
Accretion of redeemable convertible preferred stock	(96)	(162)	(143)
Net loss attributable to common stockholders	$ (55,366)	$ (33,544)	$ (17,001)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (1.09)	$ (2.02)	$ (1.18)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	50,930	16,573	14,442