Nature of the business (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ 249,655	$ 207,885
Net loss	$ 41,595	$ 34,497

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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