Risk Management and Use of Derivative Financial Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	$ (84)	$ 614	$ (63)	$ 680
Interest rate swap
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	(18)	0	5	0
Put option
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	0	0	(2)	0
Stock warrants
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	(66)	(264)	(66)	(198)
Foreign currency forward
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	$ 0	$ 878	$ 0	$ 878