Property, Plant and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Capitalized interest included in property, plant and equipment	$ 8,543	$ 5,608	$ 7,091
Depreciation expense	408,646	366,233	$ 328,486
Capital leases included in the property, plant and equipment, cost	5,984	7,986
Capital leases included in the property, plant and equipment, accumulated depreciation	$ 2,071	$ 4,436