Supplemental cash flow information (Schedule of Supplemental cash flow) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 14,914	$ 15,171
Interest received	303	778
Net income taxes paid	23,681	12,442
Non-cash purchase of property, plant and equipment under capital lease	2,084	3,502
Non-cash right of use assets obtained (reassessed) in exchange for new lease obligations	$ 6,234	$ (1,001)