Derivative Instruments - Designated as hedging, Financial Position (Details) (Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 0	$ 0
Liability Derivatives	1,220	0
Interest Rate Swap [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	0
Liability Derivatives	530	0
Interest Rate Swap [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	0
Liability Derivatives	$ 690	$ 0