STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 16,250	$ 10,042
Cost of goods sold	2,854	2,294
Gross profit	13,396	7,748
Operating expenses:
Research and development	2,603	1,730
Selling, general and administrative	19,570	11,213
Total operating expenses	22,173	12,943
Operating loss	(8,777)	(5,195)
Other (income) expense:
Interest income	(1,086)	(60)
Interest expense	537	1,385
Other (income) expense, net	38	(19)
Total other (income) expense	(511)	1,306
Loss before income taxes	(8,266)	(6,501)
Income taxes	0	0
Net loss	(8,266)	(6,501)
Other comprehensive income:
Unrealized gain on short-term investments	68	0
Total comprehensive loss	$ (8,198)	$ (6,501)
Net loss per share, basic and diluted (in dollars per share)	$ (0.35)	$ (5.05)
Weighted average common shares used to compute net loss per share, basic and diluted (in shares)	23,441,560	1,286,633