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
Mar. 31, 2013
Dec. 31, 2012
Carrying Value Disclosures [Abstract]    
Current and Long-term Debt and Capital Lease Obligations $ 966,394 $ 957,663
Other Liabilities 25,675 25,511
Fair Value Disclosure [Abstract]    
Current and Long-term Debt and Capital Lease Obligations, Fair Value Disclosure 970,071 979,594
Other Liabilities, Fair Value Disclosure $ 24,850 $ 24,766