Annual report pursuant to Section 13 and 15(d)

Nature Of Business (Details)

v2.4.0.6
Nature Of Business (Details) (USD $)
12 Months Ended 0 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Sep. 02, 2011
Dulles Station, Phase I [Member]
Jun. 18, 2010
Parklawn Portfolio [Member]
Dec. 21, 2010
The Ridges [Member]
May 13, 2009
Avondale [Member]
Dec. 22, 2010
Ammendale I and II and Amvax [Member]
Jul. 23, 2009
Tech 100 Industrial Park [Member]
Jul. 31, 2009
Brandywine Center [Member]
Nov. 13, 2009
Crossroads Distribution Center [Member]
Dec. 31, 2011
Taxable Reit Subsidiary [Member]
Percentage of Distribution of Ordinary Taxable Income 90.00%                      
Gain and Sale $ 97,491,000 $ 21,600,000 $ 13,300,000 $ 0 $ 7,900,000 $ 4,500,000 $ 6,700,000 $ 9,200,000 $ 4,100,000 $ 1,000,000 $ 1,500,000  
Income Tax Expense (Benefit) 0                      
Discontinued Operation, Tax Effect of Income (Loss) from Disposal of Discontinued Operation 1,138,000 0 0                  
Real estate impairment 14,526,000 0 0                  
Deferred Tax Assets 5,700,000                      
Deferred Tax Assets, Net                       100,000
Deferred Tax Liabilities                       $ 500,000
Ordinary income 60.00% 55.00% 75.00%                  
Return of capital 17.00% 31.00% 17.00%                  
Qualified dividends 5.00% 0.00% 0.00%                  
Unrecaptured Section 1250 gain 13.00% 11.00% 7.00%                  
Capital gain 5.00% 3.00% 1.00%