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 ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)
Collaboration and license arrangements
Revenue related to the License and prototype unit																			$ 8,300
Revenue						$ 15,917	$ 14,944	$ 13,536	$ 12,337	$ 10,877	$ 10,591	$ 8,643	$ 7,521		$ 56,734	$ 37,632	$ 22,874
Deferred revenue						1,700									1,700
Increase to deferred revenue															(708)	(1,849)	2,895
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
Revenue															200	$ 2,100	200	$ 200
Deferred revenue	$ 1,200
Evaluation and option agreements and license agreement
Collaboration and license arrangements
Revenue				$ 1,800
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
Amount allocated to the option of the specific field															1,200
Exclusive agreement
Collaboration and license arrangements
Consideration on collaboration activities		$ 500
Deferred revenue						500									500
2016 Amendment
Collaboration and license arrangements
Total allocable consideration	$ 3,200
Increase to deferred revenue														$ 2,000
Royalties						$ 0									$ 0
2016 Amendment | Maximum
Collaboration and license arrangements
Feasibility Period	3 years
2016 Amendment | bioMerieux
Collaboration and license arrangements
Cash received			$ 2,000