Derivatives (Fair Value of Derivative Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	$ 458	$ 339
Fair value, derivative liability	1,893	420
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	0	298
Fair value, derivative liability	1,893	420
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	458	41
Interest rate agreements [Member] | Designated as Hedging Instrument [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	0	298
Interest rate agreements [Member] | Designated as Hedging Instrument [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	1,781	0
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Derivative Liability, Current [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	69	420
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	43	0
Currency contracts [Member] | Not Designated as Hedging Instrument [Member] | Prepaid and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	$ 458	$ 41