Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Derivatives [Line Items]
Liability derivatives	$ 14,828	$ 14,195
Derivatives designated as hedges [Member]
Derivatives [Line Items]
Liability derivatives	6,326	7,025
Derivatives designated as hedges [Member] | Accrued expenses [Member] | Interest rate swap [Member]
Derivatives [Line Items]
Liability derivatives	4,269	4,143
Derivatives designated as hedges [Member] | Other long-term liabilities [Member] | Interest rate swap [Member]
Derivatives [Line Items]
Liability derivatives	2,057	2,882
Derivatives not designated as hedges [Member]
Derivatives [Line Items]
Liability derivatives	8,502	7,170
Derivatives not designated as hedges [Member] | Accrued expenses [Member] | Cross-currency swap [Member]
Derivatives [Line Items]
Liability derivatives	$ 8,502	$ 7,170