| 
           Unsecured Revolving Credit Facility (Tables) 
         | 
        6 Months Ended | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 
           Jun. 30, 2011 
         | 
      |||||||||||||||||||||||||||||||
| Unsecured Revolving Credit Facility | |||||||||||||||||||||||||||||||
| Change In The Operating Partnership's Unsecured Debt Ratings | 
  | 
      ||||||||||||||||||||||||||||||
| X | ||||||||||
| 
             
- Definition 
          Schedule of Unsecured Credit Rating, Operating Partnerships [Table Text Block] 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Unsecured Revolving Credit Facility [Abstract] 
  |