Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 7,622	$ 1,393
Interest received	956	498
Net income taxes paid	14,756	27,172
Non-cash purchase of property, plant and equipment under capital lease	$ 207	$ 361