Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 3,859	$ 3,856
Interest received	1,353	2,072
Net income taxes paid	44,869	32,775
Non-cash purchase of property, plant and equipment under capital lease	$ 1,009	$ 53