Risk Management and Use of Derivative Financial Instruments (Details 5) (USD $)	9 Months Ended
	Sep. 30, 2012
Derivative Instrument Detail
Notional Amount	$ 222,748,000
Fair Value	10,345,000
Interest rate swap | 6-Month Euribor
Derivative Instrument Detail
Notional Amount	211,226,000
Effective Interest Rate	4.20%
Effective Date	Sep. 01, 2011
Expiration Date	Sep. 01, 2016
Fair Value	(9,971,000)
Interest rate swap | 1-Month LIBOR
Derivative Instrument Detail
Notional Amount	92,400,000
Effective Interest Rate	3.90%
Effective Date	Feb. 01, 2012
Expiration Date	Feb. 01, 2017
Fair Value	(2,842,000)
Interest rate swap | 3-Month LIBOR
Derivative Instrument Detail
Notional Amount	25,896,000
Effective Interest Rate	6.60%
Effective Date	Jan. 01, 2010
Expiration Date	Dec. 01, 2019
Fair Value	(4,017,000)
Interest rate swap | 1-Month LIBOR March
Derivative Instrument Detail
Notional Amount	9,000,000
Effective Interest Rate	5.00%
Effective Date	Mar. 01, 2012
Expiration Date	Mar. 01, 2022
Fair Value	(467,000)
Interest rate swap | 3-Month LIBOR
Derivative Instrument Detail
Notional Amount	7,555,000
Effective Interest Rate	5.80%
Effective Date	Jul. 01, 2010
Expiration Date	Nov. 01, 2017
Fair Value	(602,000)
Interest rate swap | 1-Month LIBOR January
Derivative Instrument Detail
Notional Amount	4,144,000
Effective Interest Rate	6.00%
Effective Date	Jan. 01, 2011
Expiration Date	Jan. 01, 2021
Fair Value	(579,000)
Interest rate swap | 1-Month LIBOR December
Derivative Instrument Detail
Notional Amount	1,600,000
Effective Interest Rate	4.80%
Effective Date	Dec. 01, 2011
Expiration Date	Dec. 01, 2021
Fair Value	(91,000)
Interest rate swap | 3-Month Euribor
Derivative Instrument Detail
Notional Amount	4,974,000
Effective Interest Rate	4.30%
Effective Date	Jun. 01, 2012
Expiration Date	May 01, 2017
Fair Value	(158,000)
Interest rate swap | 1-Month LIBOR June
Derivative Instrument Detail
Notional Amount	4,490,000
Effective Interest Rate	4.60%
Effective Date	Jun. 01, 2012
Expiration Date	Jul. 01, 2022
Fair Value	(128,000)
Interest rate cap | Libor London Inter Bank Offered Rate
Derivative Instrument Detail
Notional Amount	120,139,000
Effective Interest Rate	4.00%
Effective Date	Aug. 01, 2009
Expiration Date	Aug. 01, 2014
Fair Value	3,000
Cap Rate	4.00%
Derivative, Notional Amount, noncontrolling interest	54,100,000
Derivative, Fair Value, Net, noncontrolling interest	$ 100,000
Debt Instrument, Interest Rate at Period End	2.96%