Risk Management and Use of Derivative Financial Instruments (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivatives Not Designated as Hedging Instruments
Stock warrants	$ 2,000	$ 1,720
Interest rate swap	(14,556)	(16,686)
Total derivatives, assets	2,355	1,745
Total derivatives, liabilities	(19,674)	(24,578)
Foreign currency contracts
Derivatives Designated as Hedging Instruments
Derivative Instruments in Hedges, Assets, at Fair Value	335
Derivative Instruments in Hedges, Liabilities, at Fair Value	(73)	(2,067)
Interest rate swap
Derivatives Designated as Hedging Instruments
Derivative Instruments in Hedges, Liabilities, at Fair Value	(5,045)	(5,825)
Interest rate cap
Derivatives Designated as Hedging Instruments
Derivative Instruments in Hedges, Assets, at Fair Value	$ 20	$ 25