Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Recognized in Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	$ 4,330	$ 4,965	$ 4,081
Not Designated as Hedging Instrument | Interest rate swap | Interest expense
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	2,682	4,164	3,186
Not Designated as Hedging Instrument | Foreign currency collars | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	824	514	0
Not Designated as Hedging Instrument | Stock warrants | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	134	(134)	134
Not Designated as Hedging Instrument | Foreign currency forward contracts | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	0	(296)	0
Cash Flow Hedging | Interest rate swap | Interest expense
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	657	649	761
Cash Flow Hedging | Foreign currency collars | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	(7)	23	0
Cash Flow Hedging | Foreign currency forward contracts | Other income and (expenses)
Amount of Gain (Loss) on Derivatives Recognized in Income
Amount of Gain (Loss) on Derivatives Recognized in Income	$ 40	$ 45	$ 0