Risk Management and Use of Derivative Financial Instruments - Derivative Gain (Loss) Recognized in Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Amount of Gain on Derivatives Recognized in Income
Amount of Gain on Derivatives Recognized in Income	$ 347	$ 8	$ 622	$ 132
Derivatives Not Designated as Hedging Instruments | Foreign currency collars | Other gains and (losses)
Amount of Gain on Derivatives Recognized in Income
Amount of Gain on Derivatives Recognized in Income	(90)	(5)	(9)	113
Derivatives Not Designated as Hedging Instruments | Interest rate swaps | Interest expense
Amount of Gain on Derivatives Recognized in Income
Amount of Gain on Derivatives Recognized in Income	3	0	11	0
Derivatives Not Designated as Hedging Instruments | Foreign currency forward contracts | Other gains and (losses)
Amount of Gain on Derivatives Recognized in Income
Amount of Gain on Derivatives Recognized in Income	0	0	7	0
Derivatives Designated as Hedging Instruments | Foreign currency collars | Other gains and (losses)
Amount of Gain on Derivatives Recognized in Income
Amount of Gain on Derivatives Recognized in Income	0	0	0	7
Derivatives Designated as Hedging Instruments | Interest rate swaps | Interest expense
Amount of Gain on Derivatives Recognized in Income
Amount of Gain on Derivatives Recognized in Income	$ 434	$ 13	$ 613	$ 12