Income taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Line Items]
Loss before income taxes	$ (5,393)	$ (25,284)
Income Tax Expense (Benefit)	(185)	656
Operating Loss Carryforwards	$ 46,100
Percentage of tax earnings	80.00%
Deferred Tax Assets, Valuation Allowance	$ 19,033	$ 18,918	$ 11,300
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	19,000
No Expiration [Member]
Income Tax [Line Items]
Operating Loss Carryforwards	40,700
Expiring Through 2023 [Member]
Income Tax [Line Items]
Operating Loss Carryforwards	5,400
Operating Loss Limitation	1,300
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Operating Loss Carryforwards	$ 31,200