Significant accounting policies - Revenue recognition - Disaggregated revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue recognition
Revenue	$ 15,917	$ 14,944	$ 13,536	$ 12,337	$ 10,877	$ 10,591	$ 8,643	$ 7,521	$ 56,734	$ 37,632	$ 22,874
Product revenue
Revenue recognition
Revenue	11,431	10,737	8,776	9,547	7,458	5,962	5,200	4,745	40,491	23,365	14,124
Product revenue | NA
Revenue recognition
Revenue									20,398
Product revenue | EMEA
Revenue recognition
Revenue									14,917
Product revenue | Asia Pacific
Revenue recognition
Revenue									5,176
Instruments
Revenue recognition
Revenue									14,886
Instruments | NA
Revenue recognition
Revenue									6,250
Instruments | EMEA
Revenue recognition
Revenue									5,243
Instruments | Asia Pacific
Revenue recognition
Revenue									3,393
Consumable and other products
Revenue recognition
Revenue									25,605
Consumable and other products | NA
Revenue recognition
Revenue									14,148
Consumable and other products | EMEA
Revenue recognition
Revenue									9,674
Consumable and other products | Asia Pacific
Revenue recognition
Revenue									1,783
Service and other revenue
Revenue recognition
Revenue	4,302	$ 4,207	$ 4,760	$ 2,790	$ 3,419	3,017	3,174	2,507	16,059	12,117	7,676
Service and other revenue | NA
Revenue recognition
Revenue									12,809
Service and other revenue | EMEA
Revenue recognition
Revenue									2,592
Service and other revenue | Asia Pacific
Revenue recognition
Revenue									658
Service-type warranties
Revenue recognition
Revenue									4,633
Service-type warranties | NA
Revenue recognition
Revenue									3,139
Service-type warranties | EMEA
Revenue recognition
Revenue									1,323
Service-type warranties | Asia Pacific
Revenue recognition
Revenue									171
Research services
Revenue recognition
Revenue									10,005
Research services | NA
Revenue recognition
Revenue									8,845
Research services | EMEA
Revenue recognition
Revenue									704
Research services | Asia Pacific
Revenue recognition
Revenue									456
Other services
Revenue recognition
Revenue									1,421
Other services | NA
Revenue recognition
Revenue									825
Other services | EMEA
Revenue recognition
Revenue									565
Other services | Asia Pacific
Revenue recognition
Revenue									31
Collaboration and license revenue
Revenue recognition
Revenue	$ 184					$ 1,612	$ 269	$ 269	184	$ 2,150	$ 1,074
Collaboration and license revenue | NA
Revenue recognition
Revenue									167
Collaboration and license revenue | EMEA
Revenue recognition
Revenue									$ 17