Risk Management and Use of Derivative Financial Instruments (Details 2) (Derivatives in Cash Flow Hedging Relationships, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive (Loss) Income on Derivatives (Effective Portion)	$ 16,075	$ (4,065)	$ 11,321	$ 771
Interest rate swap
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive (Loss) Income on Derivatives (Effective Portion)	689	16	(928)	3,669
Interest rate caps
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive (Loss) Income on Derivatives (Effective Portion)	14	(23)	(7)	(13)
Foreign currency contracts
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive (Loss) Income on Derivatives (Effective Portion)	$ 15,372	$ (4,058)	$ 12,256	$ (2,885)