Derivative Financial Instruments Effect of Cash Flow Derivatives on the Balance Sheet and Income Statement, Before Tax (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Interest Rate Swap Contracts [Abstract]
Amount of Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$ (4,200)	$ (4,542)	$ (11,023)
Interest Expense [Member]
Interest Rate Swap Contracts [Abstract]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(7,254)	(11,829)	(13,975)
Gain (Loss) Recognized in Income on Derivative (Ineffective Portion)	$ (201)	$ (100)	$ (302)

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

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Pre tax reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk.

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