CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue	$ 14,049	$ 16,317	$ 30,870	$ 31,308
Cost of goods sold	2,117	1,588	4,049	3,114
Gross profit	11,932	14,729	26,821	28,194
Operating expenses:
Sales and marketing	15,755	16,727	35,036	32,542
Research and development	2,165	1,946	4,255	3,629
General and administrative	4,151	4,194	9,551	8,960
Total operating expenses	22,071	22,867	48,842	45,131
Loss from operations	(10,139)	(8,138)	(22,021)	(16,937)
Interest and other income (expense), net:
Interest income	329	695	827	1,439
Interest expense	(2,683)	(1,233)	(3,914)	(2,463)
Other income (expense), net	21	22	(136)	(38)
Net loss	(12,472)	(8,654)	(25,244)	(17,999)
Other comprehensive income (loss):
Changes in foreign currency translation	(2)	12	10	(7)
Unrealized gain (loss) on marketable securities	(85)	59	136	84
Comprehensive loss	$ (12,559)	$ (8,583)	$ (25,098)	$ (17,922)
Net loss per share, basic and diluted (in dollars per share)	$ (0.44)	$ (0.35)	$ (0.91)	$ (0.74)
Weighted-average number of common shares used to compute basic and diluted net loss per share (in shares)	28,492,582	24,577,938	27,872,505	24,484,608