Derivative Financial Instruments (Details) (USD $) In Thousands			3 Months Ended		6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Interest rate contracts [Member] Cash Flow Hedges [Member] Interest Expense [Member]	Jun. 30, 2010 Interest rate contracts [Member] Cash Flow Hedges [Member] Interest Expense [Member]	Jun. 30, 2011 Interest rate contracts [Member] Cash Flow Hedges [Member] Interest Expense [Member]	Jun. 30, 2010 Interest rate contracts [Member] Cash Flow Hedges [Member] Interest Expense [Member]	Jun. 30, 2011 Interest rate contracts [Member]	Dec. 31, 2010 Interest rate contracts [Member]	Jun. 30, 2011 Designated as Hedging Instrument [Member]	Dec. 31, 2010 Designated as Hedging Instrument [Member]
Derivatives In Fair Value And Cash Flow Hedging Relationships
Amount of Gain or (Loss) Recognized in OCI on Derivative			$ (578)	$ (1,552)	$ (676)	$ (3,202)
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income			(787)	(657)	(1,540)	(1,317)
Fair values of derivative instruments recorded in Balance Sheet
Cash flow hedges, assets							0
Derivative Asset, Fair Value, Gross Asset									0
Cash flow hedges	5,552	6,807					5,552	6,807
Derivative Liability, Fair Value, Gross Liability									$ 5,552	$ 6,807