Supplemental cash flow information (Schedule of Supplemental cash flow) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 31,054	$ 31,173
Interest received	1,010	1,775
Net income taxes paid	56,016	32,750
Non-cash purchase of property, plant and equipment under finance lease	6,173	8,431
Non-cash right of use assets obtained (reassessed) in exchange for new lease obligations	$ 13,545	$ 595