Description of the business and recent developments: Allowance for credit losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Description of the business and recent developments:
Balance at Beginning of Period	$ 1,921	$ 1,771	$ 1,263
Current-period Provision for Expected Credit Losses	5,595	4,997	6,190
Write offs Charged Against Allowance	(6,006)	(4,847)	(5,682)
Balance at End of Period	1,510	1,921	1,771
Bad debt recoveries	$ 2,200	$ 1,200	$ 1,900