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