Risk Management and Use of Derivative Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivatives in Cash Flow Hedging Relationships
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Amount of Gain (Loss) Reclassified from Other Comprehensive Income into Income (Effective Portion)	$ 2,282	$ 1,778	$ 344
Derivatives in Cash Flow Hedging Relationships | Interest rate swap
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Amount of Gain (Loss) Reclassified from Other Comprehensive Income into Income (Effective Portion)	1,745	1,539	344
Derivatives in Cash Flow Hedging Relationships | Foreign currency contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Amount of Gain (Loss) Reclassified from Other Comprehensive Income into Income (Effective Portion)	537	239	0
Equity method investments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Amount of Gain (Loss) Reclassified from Other Comprehensive Income into Income (Effective Portion)	$ 500	$ 400	$ 200