Risk Management and Use of Derivative Financial Instruments - Derivative Gain Loss Recognized in Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	$ (149)	$ (141)
Not designated | Stock warrants | Other income and (expense)
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	(198)	0
Not designated | Swaption | Other income and (expense)
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	(48)	(161)
Not designated | Foreign currency forward contracts | Other income and (expense)
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	33	0
Not designated | Interest rate swap | Interest expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	18	0
Designated as hedging | Foreign currency forward contracts | Interest expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	0	(4)
Designated as hedging | Interest rate swap | Interest expense
Amount of Gain (Loss) Recognized in Income on Derivatives
Amount of gain (loss) recognized income on derivatives	$ 46	$ 24