Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Reclassified From OCI (Details) - Derivatives in Cash Flow Hedging Relationships - 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) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)	$ 1,903	$ 1,915	$ 7,466	$ 4,844
Foreign currency contracts | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)	1,454	1,773	5,336	5,163
Foreign currency collars | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)	735	654	3,154	1,259
Interest rate swaps and caps | Interest expense
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income (Loss) (Effective Portion)	$ (286)	$ (512)	$ (1,024)	$ (1,578)