Summary of significant accounting policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Period	$ 643	$ 582	$ 422
Charged to Expenses	326	182	642
Charges Utilized/Written-off	(291)	(121)	(482)
Balance at End of Period	$ 678	$ 643	$ 582