Risk Management and Use of Derivative Financial Instruments (Details 5) In Thousands, unless otherwise specified		9 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month January 2011 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month February 2012 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month March 2012 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month April 2013 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month June 2012 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month July 2013 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month October 2012 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month December 2011 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month December 2012 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 1-month December 2019 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap LIBOR 3-month January 2010 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month February 2013 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month February 2013 EUR (€)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month March 2013 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month March 2013 EUR (€)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month April 2013 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month April 2013 EUR (€)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month June 2012 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month June 2012 EUR (€)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month July 2010 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 3-month July 2010 EUR (€)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 6-month September 2011 USD ($)	Sep. 30, 2013 Designated as hedging Interest rate swap Euribor 6-month September 2011 EUR (€)	Sep. 30, 2013 Designated as hedging Interest rate cap LIBOR 3-month August 2009 USD ($)	Sep. 30, 2013 Not designated Swaption LIBOR 1-month April 2018 USD ($)
Derivative [Line Items]
Derivative notional amount		$ 4,049	$ 92,400	$ 8,886	$ 14,880	$ 4,368	$ 12,374	$ 4,225	$ 1,572	$ 19,673	$ 22,841	$ 25,482		€ 9,828		€ 14,648		€ 2,922		€ 3,803		€ 5,753		€ 164,250	$ 116,581	$ 13,230
Contractual interest rate		6.00%	3.90%	5.00%	4.30%	4.60%	4.80%	4.80%	4.80%	4.80%	5.70%	5.70%	4.40%	4.40%	1.20%	1.20%	4.20%	4.20%	6.50%	6.50%	5.80%	5.80%	4.20%	4.20%
Effective date		Jan. 01, 2011	Feb. 01, 2012	Mar. 01, 2012	Apr. 01, 2013	Jun. 01, 2012	Jul. 01, 2013	Oct. 01, 2012	Dec. 01, 2011	Dec. 01, 2012	Dec. 01, 2019	Jan. 01, 2010	Feb. 01, 2013	Feb. 01, 2013	Mar. 01, 2013	Mar. 01, 2013	Apr. 01, 2013	Apr. 01, 2013	Jun. 01, 2012	Jun. 01, 2012	Jul. 01, 2010	Jul. 01, 2010	Sep. 01, 2011	Sep. 01, 2011	Aug. 01, 2009	Apr. 01, 2018
Expiration date		Jan. 01, 2021	Feb. 01, 2017	Mar. 01, 2022	Apr. 01, 2018	Jul. 01, 2022	Jan. 01, 2024	Nov. 01, 2022	Dec. 01, 2021	Dec. 01, 2022	Jan. 31, 2024	Dec. 01, 2019	Feb. 01, 2018	Feb. 01, 2018	Mar. 01, 2020	Mar. 01, 2020	Apr. 01, 2018	Apr. 01, 2018	May 01, 2017	May 01, 2017	Nov. 01, 2017	Nov. 01, 2017	Sep. 01, 2016	Sep. 01, 2016	Aug. 01, 2014	Apr. 01, 2023
Fair value	$ (12,311)	$ (333)	$ (1,532)	$ 31	$ (510)	$ 114	$ (265)	$ 129	$ (1)	$ 688	$ (29)	$ (2,567)	$ (134)		$ 16		$ (5)		$ (120)		$ (503)		$ (8,289)		$ 0	$ 1,015