Risk Management and Use of Derivative Financial Instruments (Details 5) (Cash Flow Hedging) In Thousands, unless otherwise specified		6 Months Ended
	Jun. 30, 2013 USD ($)	Jun. 30, 2013 3-Month Euro Interbank Offering Rate Interest rate swap USD ($)	Jun. 30, 2013 3-Month Euro Interbank Offering Rate Interest rate swap EUR (€)	Jun. 30, 2013 1-Month London Interbank Offered rate (LIBOR) Interest rate swap USD ($)	Jun. 30, 2013 3-Month Euribor Interest rate cap USD ($)	Jun. 30, 2013 3-Month Euribor Interest rate cap EUR (€)	Jun. 30, 2013 3-Month Euribor Interest rate swap USD ($)	Jun. 30, 2013 3-Month Euribor Interest rate swap EUR (€)	Jun. 30, 2013 1-Month LIBOR July Interest rate swap USD ($)	Jun. 30, 2013 1-Month LIBOR August Interest rate swap USD ($)	Jun. 30, 2013 1-Month LIBOR June Interest rate swap USD ($)	Jun. 30, 2013 1-Month LIBOR December Interest rate swap USD ($)
Derivative Disclosure
Notional Amount			€ 6,245	$ 4,344		€ 67,000		€ 2,224	$ 33,337	$ 25,272	$ 6,811	$ 3,441
Contractual Interest Rate		4.20%	4.20%	3.00%	2.00%	2.00%	1.20%	1.20%	3.00%	3.90%	4.40%	3.70%
Effective Date		Mar. 01, 2008	Mar. 01, 2008	Apr. 01, 2010	Dec. 01, 2012	Dec. 01, 2012	Mar. 01, 2013	Mar. 01, 2013	Jul. 01, 2010	Aug. 01, 2012	Jun. 01, 2012	Dec. 01, 2012
Expiration Date		Mar. 01, 2018	Mar. 01, 2018	Apr. 01, 2015	Dec. 01, 2014	Dec. 01, 2014	Mar. 01, 2020	Mar. 01, 2020	Jul. 01, 2020	Aug. 01, 2022	Mar. 01, 2022	Feb. 01, 2019
Fair Value	$ (2,177)	$ (1,117)		$ (190)	$ 33		$ 1		$ (2,023)	$ 838	$ 220	$ 61