Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies (Narrative) (Details)

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Significant Accounting Policies (Narrative) (Details) (USD $)
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Jul. 05, 2012
Jan. 05, 2012
Significant Accounting Policies [Abstract]              
Capitalized development and construction salaries and other related costs $ 770,000   $ 909,000 $ 1,570,000 $ 1,979,000    
Rental property in-progress 34,862,000 37,069,000   34,862,000      
Maximum period after cessation of major construction activity that projects are considered complete       1 year      
Amortization of deferred financing costs 661,000   584,000 1,272,000 1,168,000    
Deferred leasing costs 1,060,000   982,000 2,156,000 2,036,000    
Minimum percentage of REIT taxable income distributed to shareholders       90.00%      
Common stock, shares outstanding 87,819,278 87,799,479   87,819,278   87,819,863 87,800,047
Common units outstanding 12,177,122 12,197,122   12,177,122   12,177,122 12,197,122
Distributions payable, record date Jul. 05, 2012 Jan. 05, 2012          
Common unit distributions per share $ 0.45 $ 0.45          
Common stock dividends and common unit distributions payable, date Jul. 13, 2012 Jan. 13, 2012          
Restricted stock expense $ 579,000   $ 690,000 $ 1,393,000 $ 1,380,000