Risk Management and Use of Derivative Financial Instruments (Narratives) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instrument Detail
Foreign Currency Exchange Rate	$ 1.3218	$ 1.2950
Estimated amount reclassified from OCI to income, derivatives	6,800,000
Derivative Instruments Gain Loss Reclassification From Accumulated OCI To Other Income Noncontrolling Interest	14,300,000
Derivative Instruments Gain Loss Reclassification From Accumulated OCI To Interest Expense Noncontrolling Interest	500,000
Total credit exposure on derivatives	1,200,000
Derivative liability, fair value	(23,000,000)	(9,000,000)
Loss on contract termination	25,100,000	9,700,000
Interest rate cap
Derivative Instrument Detail
Debt, interest rate at period end	2.86%
Cap Rate	4.00%
Amounts attributable to noncontrolling interests	400,000	(100,000)	(1,000,000)
Derivative, fair value, noncontrolling interest	100,000
Derivative, notional, noncontrolling interest	53,700,000
Embedded derivatives
Derivative Instrument Detail
Foreign Currency Exchange Rate	$ 1.278