Risk Management and Use of Derivative Financial Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	$ (857)	$ 234	$ 0
Interest rate swap
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	(34)	0	0
Put option
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	(2)	0	0
Stock warrants
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	66	(198)	0
Foreign currency forward
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	254	432	0
Embedded derivatives
Amount of Gain (Loss) Recognized in Income on Derivatives
Derivative Instruments Not in Cash Flow Hedging Relationships	$ (1,141)	$ 0	$ 0