Shareholders’ equity (deficit) - Authorized share capital (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Mar. 08, 2019
Authorized share capital
Number of shares options exercised		33,162
Average exercise price (in dollar per share)		$ 1.3260	$ 1.2870
Amount reclassified from APIC to share capital		$ 41	$ 350
Initial public offering | Common shares
Authorized share capital
Number of shares issued during the period	6,325,000
Share Price	$ 15.00
Gross proceeds of initial public offering	$ 94,900
Number of preferred shares converted in to common shares	17,550,802
Options | Common shares
Authorized share capital
Number of shares issued upon exercise of options		33,162	356,797
Cash consideration		$ 44	$ 461
Number of shares options exercised		33,162	356,797
Employee Share Purchase Plan 2019 | Common shares
Authorized share capital
Number of common shares initially reserved for issuance				278,734
Percentage of shares reserved for future issuance		1.00%
Additional shares reserved for issuance		487,837
Number of shares issued under the ESPP		0