Annual report pursuant to Section 13 and 15(d)

Unsecured Revolving Credit Facility (Narrative) (Details)

v2.4.0.6
Unsecured Revolving Credit Facility (Narrative) (Details) (USD $)
 0 Months Ended 12 Months Ended
Oct. 21, 2011
years
Dec. 31, 2011
Dec. 31, 2010
Line Of Credit Facility By Category [Line Items]      
Borrowing capacity under the credit facility $ 600,000,000    
Expandable borrowing capacity under the credit facility 1,000,000,000    
Credit facility, extension period 1    
Credit facility fee, basis points 20    
Number of lending institutions 20    
Credit facility mature date   October 2015  
Line of credit facility, bid feature, current borrowing capacity   300,000,000  
Terms of the unsecured facility   The terms of the unsecured facility include certain restrictions and covenants which limit, among other things the incurrence of additional indebtedness, the incurrence of liens and the disposition of real estate properties (to the extent that: (i) such property dispositions cause the Company to default on any of the financial ratios of the facility described below, or (ii) the property dispositions are completed while the Company is under an event of default under the facility, unless, under certain circumstances, such disposition is being carried out to cure such default), and which require compliance with financial ratios relating to the maximum leverage ratio, the maximum amount of secured indebtedness, the minimum amount of tangible net worth, the minimum amount of fixed charge coverage, the maximum amount of unsecured indebtedness, the minimum amount of unencumbered property interest coverage and certain investment limitations.  
Outstanding borrowings under the facility   55,500,000 228,000,000
Previous Credit Facility [Member]
      
Line Of Credit Facility By Category [Line Items]      
Borrowing capacity under the credit facility   775,000,000  
Interest rate on outstanding borrowings   LIBOR plus 55 basis points  
Spread over LIBOR   55  
Money Market Loan [Member]
      
Line Of Credit Facility By Category [Line Items]      
Borrowing capacity under the credit facility   75,000,000  
Outstanding borrowings under the facility   $ 0 $ 0
Maturity period of the unsecured borrowing   30 days or less.