Receivables and allowance for expected credit losses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
Credit Loss [Abstract]
Receivables past due 90 days or more	$ 45,100		$ 46,700	$ 47,200
Accounts Receivable, Allowance for Credit Loss	$ 11,090	$ 11,125	$ 8,497	$ 8,200