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, Net [Abstract]
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ 642	$ 486	$ 1,493	$ 1,152
Interest rate swap
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	436	344	1,311	1,010
Foreign currency contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	206	142	182	142
Foreign currency contracts | Unconsolidated jointly owned investment
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Derivatives, gain (loss) reclassified from AOCI to Income, effective portion, net	$ 100	$ 100	$ 500	$ 300