Derivative Instruments - Designated as hedging, Financial Position (Details) (Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 420	$ 0
Liability Derivatives	690	1,220
Interest Rate Swap [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	420	0
Liability Derivatives	0
Interest Rate Swap [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	0
Liability Derivatives	690	530
Interest Rate Swap [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	0
Liability Derivatives	$ 0	$ 690