Risk Management and Use of Derivative Financial Instruments (Details 7)	12 Months Ended
	Dec. 31, 2012
Portfolio Concentration Risk
Concentration Risk Percentage	100.00%
Metro AG (Europe)
Portfolio Concentration Risk
Concentration Risk Percentage	11.00%
New York Times Company (U.S.)
Portfolio Concentration Risk
Concentration Risk Percentage	10.00%
Retail
Portfolio Concentration Risk
Concentration Risk Percentage	23.00%
Media Printing And Publishing
Portfolio Concentration Risk
Concentration Risk Percentage	15.00%
Grocery
Portfolio Concentration Risk
Concentration Risk Percentage	14.00%
Other Industry
Portfolio Concentration Risk
Concentration Risk Percentage	48.00%
Office
Portfolio Concentration Risk
Concentration Risk Percentage	32.00%
Warehouse/Distribution
Portfolio Concentration Risk
Concentration Risk Percentage	26.00%
Retail Property
Portfolio Concentration Risk
Concentration Risk Percentage	24.00%
Industrial
Portfolio Concentration Risk
Concentration Risk Percentage	13.00%
All Other
Portfolio Concentration Risk
Concentration Risk Percentage	5.00%
New York
Portfolio Concentration Risk
Concentration Risk Percentage	10.00%
Other U.S
Portfolio Concentration Risk
Concentration Risk Percentage	53.00%
U.S.
Portfolio Concentration Risk
Concentration Risk Percentage	63.00%
Italy
Portfolio Concentration Risk
Concentration Risk Percentage	11.00%
Other Europe
Portfolio Concentration Risk
Concentration Risk Percentage	26.00%
International
Portfolio Concentration Risk
Concentration Risk Percentage	37.00%