Quarterly report pursuant to Section 13 or 15(d)

Fair Value Disclosures (Financial Assets and Liabilities Not Measured at Fair Value) (Details)

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Fair Value Disclosures (Financial Assets and Liabilities Not Measured at Fair Value) (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Jun. 30, 2011
Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Cash and cash equivalents, Carrying Value $ 14,367 $ 12,765 $ 42,886 $ 78,767
Restricted cash, Carrying Value 19,853 19,424    
Mortgage notes payable, Carrying Value 425,268 427,710    
Lines of credit payable, Carrying Value 221,000 99,000    
Notes payable, Carrying Value 607,653 657,470    
Cash and cash equivalents, Fair Value 14,367 12,765    
Restricted cash, Fair Value 19,853 19,424    
Mortgage notes payable, Fair Value 459,277 463,238    
Lines of credit payable, Fair Value 221,000 99,000    
Notes Payable, Fair Value 660,803 713,797    
2445 M Street Note Receivable [Member]
       
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
2445 M Street note receivable, Carrying Value 6,481 6,975    
2445 M Street note receivable, Fair Value $ 7,540 $ 7,721