Accumulated Other Comprehensive Loss (Amounts Reclassified from AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of Interest Rate Protection Agreements	$ 18,963	$ 22,693
Write-off of Unamortized Settlement Amounts of Interest Rate Protection Agreements	(1,150)	1
Total	(20,408)	(22,516)
Interest Rate Protection Agreements | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of Interest Rate Protection Agreements	585
Write-off of Unamortized Settlement Amounts of Interest Rate Protection Agreements	183
Total	$ 768