CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 93,774	$ 76,051	$ 51,326
Cost of revenue	33,419	31,634	22,531
Gross profit	41,230	29,274	21,037
Operating expenses:
Research and development	60,376	42,564	33,710
Selling, general and administrative	66,205	56,841	52,615
Total operating expenses	126,581	99,405	86,325
Loss from operations	(66,226)	(54,988)	(57,530)
Non-operating (expense) income, net:
Foreign exchange loss	(86)	(87)	(10)
Interest expense	(6,065)	(4,008)	(3,022)
Other income, net	1,396	1,748	3,864
Total non-operating (expense) income, net	(4,755)	(2,347)	832
Loss before income taxes	(70,981)	(57,335)	(56,698)
Provision for income taxes	263	229	3,887
Net loss	$ (71,244)	$ (57,564)	$ (60,585)
Net loss per share:
Basic and diluted	$ (0.51)	$ (0.44)	$ (0.56)
Weighted average shares used for calculating net loss per share:
Basic and diluted	139,831	131,663	108,221
Product
Revenue	$ 74,649	$ 60,908	$ 43,568
Government Contract
Revenue	$ 19,125	$ 15,143	$ 7,758