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
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of Interest Rate Protection Agreements	$ (17,284)	$ (19,695)	$ (34,932)	$ (40,904)
Write-off of Unamortized Settlement Amounts of Interest Rate Protection Agreements	(4,222)	(6,223)	(5,372)	(6,222)
Total	(21,617)	(26,449)	(40,635)	(47,410)
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	598		1,183
Write-off of Unamortized Settlement Amounts of Interest Rate Protection Agreements	916		1,099
Total	$ 1,514		$ 2,282