CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 20,373	$ 16,182	$ 51,243	$ 47,490
Cost of goods sold	2,578	1,630	6,627	4,744
Gross profit	17,795	14,552	44,616	42,746
Operating expenses:
Sales and marketing	18,772	16,443	53,808	48,985
Research and development	2,778	1,874	7,033	5,503
General and administrative	4,920	6,816	14,471	15,776
Total operating expenses	26,470	25,133	75,312	70,264
Loss from operations	(8,675)	(10,581)	(30,696)	(27,518)
Interest and other income (expense), net:
Interest income	192	612	1,019	2,051
Interest expense	(1,102)	(1,243)	(5,016)	(3,706)
Other income (expense), net	111	(94)	(25)	(132)
Net loss	(9,474)	(11,306)	(34,718)	(29,305)
Other comprehensive income (loss):
Changes in foreign currency translation	(33)	(4)	(23)	(11)
Unrealized gain (loss) on marketable securities	(147)	(37)	(11)	47
Comprehensive loss	$ (9,654)	$ (11,347)	$ (34,752)	$ (29,269)
Net loss per share, basic and diluted (in dollars per share)	$ (0.33)	$ (0.46)	$ (1.23)	$ (1.19)
Weighted-average number of common shares used to compute basic and diluted net loss per share (in shares)	28,713,418	24,803,452	28,155,561	24,596,788