Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 16,521	$ 16,877
Interest received	855	392
Net income taxes paid	6,339	1,265
Non-cash purchase of property, plant and equipment under capital lease	$ 2,564	$ 573