Risk Management and Use of Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	$ (10,222)	$ (7,203)	$ 3,191	$ (10,119)
Interest rate cap | Cash Flow Hedging
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	315	242	880	576
Interest rate cap | Cash Flow Hedging | Noncontrolling interest
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	142	109	396	259
Interest rate swap | Cash Flow Hedging
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	(744)	(3,780)	7,712	(10,109)
Foreign currency forward | Cash Flow Hedging
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	(7,449)	(1,777)	(4,012)	(268)
Foreign currency forward | Net Investment Hedging
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	(934)	(769)	82	816
Foreign currency collars | Cash Flow Hedging
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	(1,410)	(1,119)	(1,471)	(1,326)
Put option | Cash Flow Hedging
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	$ 0	$ 0	$ 0	$ 192