CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Product sales, net	$ 31,020	$ 30,499	$ 77,712	$ 78,460
Other revenue	1,238	0	1,238	0
Total revenue	32,258	30,499	78,950	78,460
Cost of product sales	9,787	9,324	28,369	26,986
Gross profit	22,471	21,175	50,581	51,474
Research and development	2,913	3,096	9,902	27,174
Selling, general and administrative	16,041	14,982	50,596	44,761
Total operating expenses	18,954	18,078	60,498	71,935
Income (loss) from operations	3,517	3,097	(9,917)	(20,461)
Other income (expense):
Interest income	121	385	574	1,293
Other income (expense)	(2)	(2)	(5)	(6)
Interest expense	(18)	(10)	(8)	8
Total other income	101	373	561	1,295
Net income (loss)	$ 3,618	$ 3,470	$ (9,356)	$ (19,166)
Net (loss) income per share (Basic) (in USD per share)	$ 0.08	$ 0.08	$ (0.21)	$ (0.44)
Weighted average number of common shares outstanding (Basic) (in shares)	45,272	44,251	45,112	43,979
Net (loss) income per share (Diluted) (in USD per share)	$ 0.08	$ 0.07	$ (0.21)	$ (0.44)
Weighted average number of common shares outstanding (Diluted) (in shares)	47,314	46,667	45,112	43,979
Revenue, Product and Service [Extensible List]			us-gaap:ProductMember
Cost, Product and Service [Extensible List]			us-gaap:ProductMember