Property, Plant and Equipment (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Abstract]
Depreciation of property, plant and equipment	$ 45,366,000	$ 53,074,000	$ 51,989,000	$ 53,217,000	$ 58,924,000	$ 54,672,000	$ 56,849,000	$ 58,910,000	$ 203,646,000	$ 229,355,000	$ 240,139,000
Impairment of Long-Lived Assets Held-for-use	$ 13,600,000