Accumulated Other Comprehensive Loss (Amounts Reclassified from AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reclassifications from Accumulated Other Comprehensive Income [Line Items]
Amortization of Interest Rate Protection Agreements	$ (18,431)	$ (21,172)	$ (37,394)	$ (43,865)
Write-off of Unamortized Settlement Amounts of Interest Rate Protection Agreements	(4,436)	(6,223)	(5,586)	(6,222)
Total	(23,044)	(27,996)	(43,452)	(50,512)
Interest Rate Protection Agreements | Reclassifications from Accumulated Other Comprehensive Income [Member]
Reclassifications from Accumulated Other Comprehensive Income [Line Items]
Amortization of Interest Rate Protection Agreements	598		1,183
Write-off of Unamortized Settlement Amounts of Interest Rate Protection Agreements	916		1,099
Total	$ 1,514		$ 2,282