Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Recognized in OCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	$ (7,911)	$ (9,520)
Derivatives in Cash Flow Hedging Relationships | Equity method investments
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	(100)	(100)
Derivatives in Cash Flow Hedging Relationships | Foreign currency collars
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	(6,149)	(2,458)
Derivatives in Cash Flow Hedging Relationships | Foreign currency contracts
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	(3,164)	(3,636)
Derivatives in Cash Flow Hedging Relationships | Interest rate swaps
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	1,006	549
Derivatives in Cash Flow Hedging Relationships | Interest rate cap
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	(7)	6
Derivatives in Net Investment Hedging Relationships | Foreign currency contracts
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) Recognized on Derivatives in Other Comprehensive Income (Loss) (Effective Portion)	$ 403	$ (3,981)