Summary of significant accounting policies - Trade receivables, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 530	$ 200	$ 60
Provision	143	824	279
Write-offs	(373)	(494)	(139)
Recoveries of amounts previously written off	91	0	0
Ending balance	$ 391	$ 530	$ 200