Derivatives (Fair Value of Derivative Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	$ 182	$ 413
Fair value, derivative liability	263	2,073
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	182	413
Fair value, derivative liability	76	1,866
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	187	207
Interest rate agreements [Member] | Designated as Hedging Instrument [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	0	1,866
Interest rate agreements [Member] | Not Designated as Hedging Instrument [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	0	207
Currency contracts [Member] | Not Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	187	0
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Prepaid and other current assets [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	182	394
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative asset	0	19
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value, derivative liability	$ 76	$ 0