Description of the business and recent developments: Allowance for credit losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Description of the business and recent developments:
Balance	$ 2,115	$ 1,771
Current-period Provision for Expected Credit Losses	1,174	3,942
Write offs Charged Against Allowance (Write-offs)	(1,085)	(3,509)
Balance	2,204	2,204
Bad debt expense, net of recoveries	800	3,200
Bad debt recoveries	$ 400	$ 800