Warrants, stock-based compensation, stock options, restricted stock and restricted stock units - Share-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	$ 2,109	$ 1,284
Cost of product revenue
Warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	36	17
Cost of service and other revenue
Warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	68	60
Research and development
Warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	242	168
General and administrative
Warrants, stock-based compensation, stock options, restricted stock and restricted stock units
Share-based compensation expense	$ 1,763	$ 1,039