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
	Mar. 31, 2019	Mar. 31, 2018
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income	$ 381	$ (46)
Foreign currency forward contracts | Other gains and (losses)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income	346	222
Interest rate swaps | Interest expense
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income	27	(83)
Foreign currency collars | Other gains and (losses)
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income	11	(154)
Interest rate caps | Interest expense
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income
Amount of Gain (Loss) on Derivatives Reclassified from Other Comprehensive Income into Income	$ (3)	$ (31)