CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue	$ 114,249	$ 93,774	$ 76,051
Cost of revenue	41,157	33,419	31,634
Gross profit	50,763	41,230	29,274
Operating expenses:
Research and development	64,410	60,376	42,564
Selling, general and administrative	67,015	66,205	56,841
Total operating expenses	131,425	126,581	99,405
Loss from operations	(58,333)	(66,226)	(54,988)
Non-operating expense, net:
Foreign exchange gain (loss)	793	(86)	(87)
Interest expense	(3,746)	(6,065)	(4,008)
Other income, net	1,713	1,396	1,748
Total non-operating expense, net	(1,240)	(4,755)	(2,347)
Loss before income taxes	(59,573)	(70,981)	(57,335)
Provision for income taxes	284	263	229
Net loss	$ (59,857)	$ (71,244)	$ (57,564)
Net loss per share:
Basic and diluted	$ (0.37)	$ (0.51)	$ (0.44)
Weighted average shares used for calculating net loss per share:
Basic and diluted	163,949	139,831	131,663
Product
Revenue	$ 91,920	$ 74,649	$ 60,908
Government Contract
Revenue	$ 22,329	$ 19,125	$ 15,143