Risk Management and Use of Derivative Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ 1,370	$ 910	$ 3,529	$ 1,100
Foreign currency collars
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	(188)	(273)	(1,129)	(1,719)
Foreign currency forward
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	(353)	(228)	(724)	(366)
Interest rate cap
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	316	247	881	653
Interest rate swap
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ 1,595	$ 1,164	$ 4,501	$ 2,532