Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Condensed Statements of Operations and Comprehensive Loss [Abstract]
Revenue	$ 22,053	$ 18,933
Cost of goods sold	5,538	5,250
Gross profit	16,515	13,683
Operating expenses:
Research and development	5,484	3,131
Selling, general and administrative	21,194	19,692
Total operating expenses	26,678	22,823
Loss from operations	(10,163)	(9,140)
Interest income	95	404
Interest expense	(623)	(1,202)
Other income (expense), net	(3)	(3)
Net loss	(10,694)	(9,941)
Other comprehensive loss:
Unrealized gain (loss) on investments, net	(33)	440
Net change in other comprehensive loss	(33)	440
Net loss and comprehensive loss	$ (10,727)	$ (9,501)
Net loss per share, basic and diluted	$ (0.31)	$ (0.32)
Weighted average common shares used to compute net loss per share, basic and diluted	34,336,433	31,338,310