Collaboration and license arrangements (Details) $ in Thousands		1 Months Ended				3 Months Ended								12 Months Ended
	Dec. 22, 2016 USD ($)	Dec. 31, 2018 USD ($)	Jan. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Nov. 30, 2012 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)
Collaboration and license arrangements
Revenue related to the License and prototype unit																		$ 8,300
Revenues recognized						$ 10,877	$ 10,591	$ 8,643	$ 7,521	$ 6,589	$ 5,734	$ 5,213	$ 5,338	$ 37,632	$ 22,874	$ 17,585
Increase to deferred revenue														(1,849)	2,895	919
Joint development and license agreement
Collaboration and license arrangements
Consideration on collaboration activities					$ 10,000
Number of additional payments					2
Amount of additional payment					$ 5,000
Revenues recognized														2,100	1,100	200	$ 200
Deferred revenue	$ 1,200
2016 Amendment
Collaboration and license arrangements
Total allocable consideration	$ 3,200
Increase to deferred revenue													$ 2,000
Royalties		$ 0				$ 0								$ 0
2016 Amendment | Maximum
Collaboration and license arrangements
Feasibility Period	3 years
2016 Amendment | bioMerieux
Collaboration and license arrangements
Cash received			$ 2,000
Evaluation and option agreements and license agreement
Collaboration and license arrangements
Revenues recognized				$ 1,800
Deferred revenue										$ 1,200					$ 1,200
Number of agreements																	3
Number of fields for which the agreements were entered																	3
Non-refundable license fee				1,000												$ 1,000	$ 2,000
Amount allocated to the option of the related field				$ 800
Exclusive agreement
Collaboration and license arrangements
Consideration on collaboration activities		$ 500