Risk Management and Use of Derivative Financial Instruments (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	$ (3,885)	$ (1,573)	$ 19,057	$ (4,024)
Foreign currency forward | Cash Flow Hedging
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	(7,601)	400	16,604	(409)
Foreign currency forward | Net Investment Hedging
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	198	0	386	0
Foreign currency forward | Derivatives Formerly in Net Investment Hedging Relationships
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	0	257	0	318
Interest rate swap | Cash Flow Hedging
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	3,518	(2,502)	2,067	(4,421)
Interest rate cap | Cash Flow Hedging
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	0	355	0	687
Foreign currency collars | Cash Flow Hedging
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net	$ 0	(83)	$ 0	(199)
Noncontrolling interest | Interest rate cap | Cash Flow Hedging
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Loss (Effective Portion)
Derivatives, gain (loss) recognized in OCI, effective portion, net		$ 200		$ 300