Derivative Financial Instruments Gains (losses) recognized on derivatives (cash flow hedges) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Interest Expense | Interest Rate Swap 1
Trading Activity, Gains and Losses, Net [Line Items]
Effective Portion, Recognized in OCI, Amount of Gain (Loss)	$ (44)	$ (98)
Effective Portion, Reclassified from AOCI into Income, Amount of Gain (Loss)	(151)	(287)
Interest Expense | Interest Rate Swap 2
Trading Activity, Gains and Losses, Net [Line Items]
Effective Portion, Recognized in OCI, Amount of Gain (Loss)	132	(272)
Effective Portion, Reclassified from AOCI into Income, Amount of Gain (Loss)	(262)	(295)
Interest Expense | Interest Rate Swap 3
Trading Activity, Gains and Losses, Net [Line Items]
Effective Portion, Recognized in OCI, Amount of Gain (Loss)	(150)	(295)
Effective Portion, Reclassified from AOCI into Income, Amount of Gain (Loss)	(276)	(309)
Interest Expense | Interest Rate Swap 4
Trading Activity, Gains and Losses, Net [Line Items]
Effective Portion, Recognized in OCI, Amount of Gain (Loss)	(406)
Effective Portion, Reclassified from AOCI into Income, Amount of Gain (Loss)	(296)
Other Income | Interest Rate Swap 1
Trading Activity, Gains and Losses, Net [Line Items]
Ineffective Portion, Recognized in Income on Derivatives, Amount of Gain (Loss)	0
Other Income | Interest Rate Swap 2
Trading Activity, Gains and Losses, Net [Line Items]
Ineffective Portion, Recognized in Income on Derivatives, Amount of Gain (Loss)	0	0
Other Income | Interest Rate Swap 3
Trading Activity, Gains and Losses, Net [Line Items]
Ineffective Portion, Recognized in Income on Derivatives, Amount of Gain (Loss)	0	0
Other Income | Interest Rate Swap 4
Trading Activity, Gains and Losses, Net [Line Items]
Ineffective Portion, Recognized in Income on Derivatives, Amount of Gain (Loss)	$ 0	$ 0