Supplemental Cash Flow Information (Schedule Of Supplemental Cash Flow) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Cash Flow Information [Abstract]
Interest paid, net of interest capitalized	$ 4,989	$ 4,823	$ 8,251
Interest received	2,657	2,218	2,401
Net income taxes paid	34,661	29,089	27,738
Non-cash purchase of property, plant and equipment under capital lease	$ 943	$ 2,143	$ 2,174