Annual report pursuant to Section 13 and 15(d)

Accounting Policies Real Estate and Depreciation (Details)

v2.4.0.6
Accounting Policies Real Estate and Depreciation (Details) (USD $)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2008
Accounting Policies [Abstract]        
Impairment of Long-Lived Assets Held-for-use $ 600,000 $ 0 $ 100,000  
Property, Plant and Equipment [Line Items]        
Impairment of real estate 14,526,000 0 0  
Accumulated other comprehensive income or loss $ 862,832,000 $ 860,858,000 $ 749,063,000 $ 640,425,000
Property, Plant and Equipment, Useful Life, Minimum 3      
Property, Plant and Equipment, Useful Life, Maximum 50      
Building [Member]
       
Property, Plant and Equipment [Line Items]        
Property, Plant and Equipment, Useful Life, Minimum 28      
Property, Plant and Equipment, Useful Life, Maximum 50      
Building and Building Improvements [Member]
       
Property, Plant and Equipment [Line Items]        
Property, Plant and Equipment, Useful Life, Minimum 3      
Property, Plant and Equipment, Useful Life, Maximum 30