CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 55,380	$ 47,983
Cost of goods sold	4,833	5,112
Gross profit	50,547	42,871
Operating expenses:
Sales and marketing	44,497	41,646
Research and development	5,376	5,513
General and administrative	12,639	13,062
Total operating expenses	62,512	60,221
Loss from operations	(11,965)	(17,350)
Interest and other income (expense), net:
Interest income	769	175
Interest expense	(5,108)	(6,204)
Other income (expense), net	(1,149)	340
Net loss	(17,453)	(23,039)
Other comprehensive income:
Unrealized gain of marketable securities	10	0
Changes in foreign currency translation	27	(70)
Comprehensive loss	$ (17,416)	$ (23,109)
Net loss per share, basic and diluted (in dollars per share)	$ (2.20)	$ (6.65)
Weighted-average number of common shares used to compute basic and diluted net loss per share (in shares)	7,950,284	3,467,096