Real Estate Acquisitions (Details) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Property
Jun. 30, 2011
Property
Business Acquisition [Line Items]        
Percentage of interest acquired in commercial properties   100.00%   100.00%
Number of businesses acquired (in properties)     0 24
Business Acquisition, Purchase Price Allocation [Abstract]        
Land   $ 23,208,000   $ 23,208,000
Buildings and improvements   41,879,000   41,879,000
Total purchase price   76,898,000   76,898,000
Revenue of acquiree since acquisition date   1,300,000   1,400,000
Loss of acquiree since acquisition date   1,000,000   1,200,000
Acquisition costs 0 1,956,000 17,000 2,318,000
Tenant improvement allowance       12,000,000
Acquired-in-place leases
       
Business Acquisition, Purchase Price Allocation [Abstract]        
Acquired finite-lived intangible asset - leases, amount   11,450,000   11,450,000
Acquired above-market leases
       
Business Acquisition, Purchase Price Allocation [Abstract]        
Acquired finite-lived intangible asset - leases, amount   805,000   805,000
Acquired below-market leases
       
Business Acquisition, Purchase Price Allocation [Abstract]        
Acquired below-market leases   $ (444,000)   $ (444,000)