Operations and summary of significant accounting policies - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at Beginning of Period	$ 3,490	$ 2,892	$ 1,867
Provisions	396	1,135	1,383
Write-Offs	343	537	358
Balance at End of Period	$ 3,543	$ 3,490	$ 2,892