Risk Management and Use of Derivative Financial Instruments - Derivative Gain (Loss) Recognized in OCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)	$ (964)	$ (1,975)	$ (2,638)	$ (2,212)
Derivatives in Cash Flow Hedging Relationships | Foreign currency collars
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)	(640)	(84)	500	721
Derivatives in Cash Flow Hedging Relationships | Foreign currency forward contracts
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)	(286)	(361)	(493)	(518)
Derivatives in Cash Flow Hedging Relationships | Interest rate swaps
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)	(33)	(1,528)	(2,650)	(2,415)
Derivatives in Cash Flow Hedging Relationships | Interest rate caps
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)	15	2	(124)	3
Derivatives in Net Investment Hedging | Foreign currency collars
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)	$ (20)	(19)	$ 129	(18)
Derivatives in Net Investment Hedging | Foreign currency forward contracts
Derivative Instruments, Gain (Loss)
Amount of Loss Recognized on Derivatives in Other Comprehensive Income (Loss)		$ 15		$ 15