Supplemental cash flow information (Schedule of Supplemental cash flow) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 32,521	$ 37,046	$ 39,429
Interest received	2,338	3,802	2,888
Net income taxes paid	43,398	26,699	10,352
Non-cash purchase of property, plant and equipment under capital lease	11,326	15,282	$ 8,968
Non-cash right of use assets obtained in exchange for new lease obligations	10,588	$ 29,117
Non-cash equity consideration in connection with Rouse acquisition	$ 1,459