Risk Management and Use of Derivative Financial Instruments (Details 2) (Derivatives in Cash Flow Hedging Relationships, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives (Effective Portion)	$ (506)	$ (2,262)	$ (3,564)
Interest rate swap
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives (Effective Portion)	4,720	(1,059)	(3,564)
Interest rate cap
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives (Effective Portion)	(15)	277	0
Foreign currency contracts
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives (Effective Portion)	(5,211)	(1,480)	0
Equity method investments
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss) Activity
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivatives (Effective Portion)	$ 500	$ 300	$ (100)