Financial Instruments and Fair Value Measurements (Details Textuals) (USD $)	9 Months Ended
	Sep. 30, 2011 PartnershipUnit Segments Entity Property sqft ac Country Notes InterestRateSwapContract	Dec. 31, 2010
Derivative [Line Items]
Number of interest rate swap contracts	44
Financial Instruments and Fair Value Measurements (Textuals) [Abstract]
Maximum length of time hedged in Cash Flow Hedge	less than 10 years
Interest rate swap contract value outstanding	$ 1,600,000,000
Interest rate cap contract value outstanding	25,700,000
Unsettled derivative contract included in accounts payable and accrued expenses	30,100,000	1,400,000
Estimated additional amount reclassified to interest expense	$ 8,200,000
Euro [Member]
Derivative [Line Items]
Number of interest rate swap contracts	34
British sterling pound [Member]
Derivative [Line Items]
Number of interest rate swap contracts	3
Japanese yen [Member]
Derivative [Line Items]
Number of interest rate swap contracts	7
USD [Member]
Derivative [Line Items]
Number of interest rate swap contracts	1