Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation	$ 191,285	$ 175,495	$ 167,516
Cost	2,603,871	2,468,930
Accumulated depreciation	(1,604,099)	(1,523,260)
Total	999,772	945,670
Land [Member]
Property, Plant and Equipment [Line Items]
Cost	68,476	68,575
Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	616,282	597,523
Machinery, equipment and other [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 1,919,113	$ 1,802,832