Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Liability derivative	$ 5,358	$ 7,025
Designated as Hedging Instrument [Member] | Accrued expenses [Member] | Interest rate swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Liability derivative	4,288	4,143
Designated as Hedging Instrument [Member] | Other long-term liabilities [Member] | Interest rate swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Liability derivative	1,070	2,882
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Liability derivative	7,232	7,170
Not Designated as Hedging Instrument [Member] | Accrued expenses [Member] | Cross-currency swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Liability derivative	$ 7,232	$ 7,170