Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Product	$ 30,458	$ 20,555	$ 9,620
Service	3,109	1,504	530
Distribution rights	475	178	0
Grant	0	0	240
Total revenue	34,042	22,237	10,390
Cost of revenue:
Product	25,488	23,897	12,673
Service	2,222	1,969	1,871
Total cost of revenue	27,710	25,866	14,544
Gross margin	6,332	(3,629)	(4,154)
Operating expenses:
Research and development	14,709	11,442	10,449
Selling and marketing	8,412	5,601	5,139
General and administrative	31,375	23,503	21,685
Total operating expenses	54,496	40,546	37,273
Loss from operations	(48,164)	(44,175)	(41,427)
Interest income	5	2	2
Interest expense	(7,247)	(5,951)	(3,452)
Other expense, net	(16,770)	(512)	(117)
Loss before provision for income taxes	(72,176)	(50,636)	(44,994)
Provision for income taxes	0	0	1
Net loss and comprehensive loss	$ (72,176)	$ (50,636)	$ (44,995)
Net loss per share, basic and diluted	$ (1.23)	$ (1.26)	$ (2.58)
Weighted-average common shares used to compute net loss per share attributable to common stockholders, basic and diluted	58,457,868	40,068,307	17,432,434