Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Recognized in OCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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)	$ (11,088)	$ (5,329)	$ (37,018)	$ (9,126)
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)	(400)	100	(900)	(200)
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)	(5,398)	(439)	(16,002)	3,618
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)	(4,752)	(3,622)	(16,422)	(7,830)
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)	250	961	779	(1,536)
Derivatives in Cash Flow Hedging Relationships | Interest rate caps
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)	(17)	(29)	(26)	(21)
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)	$ (1,171)	$ (2,200)	$ (5,347)	$ (3,357)