Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Reclassified From OCI (Details) - Cash Flow Hedging - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amount of Gain (Loss) Reclassified from Other Comprehensive (Loss) Income into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ 4,727	$ 1,219	$ 246
Other income and (expense) | Foreign currency forward contracts
Amount of Gain (Loss) Reclassified from Other Comprehensive (Loss) Income into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	7,170	7,558	8,083
Interest expense | Interest rate swap
Amount of Gain (Loss) Reclassified from Other Comprehensive (Loss) Income into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ (2,443)	$ (6,339)	$ (7,837)