Risk Management and Use of Derivative Financial Instruments (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Amount of Gain (Loss) Reclassified from Other Comprehensive Loss into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ (610)	$ (2,365)	$ 234	$ (4,525)
Foreign currency forward | Other income and (expense)
Amount of Gain (Loss) Reclassified from Other Comprehensive Loss into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	1,237	89	4,365	(100)
Interest rate swap | Interest expense
Amount of Gain (Loss) Reclassified from Other Comprehensive Loss into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	(1,847)	(2,217)	(4,131)	(3,932)
Interest rate cap | Interest expense
Amount of Gain (Loss) Reclassified from Other Comprehensive Loss into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	0	(355)	0	(687)
Foreign currency collars | Other income and (expense)
Amount of Gain (Loss) Reclassified from Other Comprehensive Loss into Income (Effective Portion)
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ 0	$ 118	$ 0	$ 194