Financial Instruments (Carrying amounts and fair value of the financial instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Carrying Value Disclosures [Abstract]
Current and Long-term Debt and Capital Lease Obligations	$ 975,675	$ 957,663
Other Liabilities	25,899	25,511
Fair Value Disclosure [Abstract]
Current and Long-term Debt and Capital Lease Obligations, Fair Value Disclosure	963,152	979,594
Other Liabilities, Fair Value Disclosure	$ 25,069	$ 24,766