Common Stock, warrants, stock-based compensation, stock options, restricted stock and restricted stock units - Share-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock, warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	$ 4,884	$ 2,168	$ 928
Cost of product revenue
Common Stock, warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	55	24	6
Cost of service and other revenue
Common Stock, warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	173	52	12
Research and development
Common Stock, warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	513	180	59
General and administrative
Common Stock, warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	$ 4,143	$ 1,912	$ 851