Intangible assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Cost	$ 35,324	$ 30,100
Accumulated amortization	(20,998)	(16,931)
Net	14,326	13,169
Developed technology
Finite-Lived Intangible Assets [Line Items]
Cost	30,100	30,100
Accumulated amortization	(20,694)	(16,931)
Net	9,406	13,169
In-licensed rights
Finite-Lived Intangible Assets [Line Items]
Cost	5,224	0
Accumulated amortization	(304)	0
Net	$ 4,920	$ 0