Schedule III - Real Estate and Accumulated Depreciation (Details Textual) (USD $)						12 Months Ended
	Dec. 31, 2013 property	Dec. 31, 2012 property	Dec. 31, 2011 property	Dec. 31, 2013 Mortgage notes payable [Member] 5.000%-7.625% Mortgage Notes Payable [Member]	Dec. 31, 2012 Mortgage notes payable [Member] 5.000%-7.625% Mortgage Notes Payable [Member]	Dec. 31, 2013 Building and improvements [Member] Minimum [Member]	Dec. 31, 2013 Building and improvements [Member] Maximum [Member]	Dec. 31, 2013 Lease intangibles [Member] Minimum [Member]	Dec. 31, 2013 Lease intangibles [Member] Maximum [Member]	Dec. 31, 2013 Personal property [Member]	Dec. 31, 2013 Personal property [Member] Minimum [Member]	Dec. 31, 2013 Personal property [Member] Maximum [Member]	Dec. 31, 2013 Land improvements [Member] Minimum [Member]	Dec. 31, 2013 Land improvements [Member] Maximum [Member]
Real Estate and Accumulated Depreciation (Textual) [Abstract]
Number of real estate assets held for sale	3	1	15
Gross value of assets held for sale	$ 17,000,000	$ 9,600,000	$ 52,800,000
Accumulated depreciation on real estate assets held for sale	10,200,000	6,300,000	24,600,000
Estimated aggregate total cost of total assets for federal income tax purposes	3,100,000,000	2,800,000,000	2,700,000,000
Asset estimated useful life						3 years 3 months 18 days	39 years	2 years	93 years 1 month 6 days	1 year 10 months 24 days	1 year 10 months 24 days	15 years 9 months 18 days	15 years	38 years 1 month 6 days
Unaccreted discount				$ 888,000	$ 2,755,000