Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments (Carrying amounts and fair value of the financial instruments) (Details)

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Financial Instruments (Carrying amounts and fair value of the financial instruments) (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Carrying Value Disclosures [Abstract]    
Current and Long-term Debt and Capital Lease Obligations $ 959,787 $ 947,326
Other Liabilities 109,785 106,002
Fair Value Disclosure [Abstract]    
Current and Long-term Debt and Capital Lease Obligations, Fair Value Disclosure 989,096 942,895
Other Liabilities, Fair Value Disclosure $ 108,893 $ 105,173