| 
           Discontinued Operations (Details) (USD $) 
        In Thousands, unless otherwise specified  | 
        3 Months Ended | 9 Months Ended | 0 Months Ended | ||||
|---|---|---|---|---|---|---|---|
| 
           Sep. 30, 2014 
         | 
        
           Sep. 30, 2013 
         | 
        
           Sep. 30, 2014 
         | 
        
           Sep. 30, 2013 
         | 
        
           Dec. 12, 2013
 
          December 2013 Colorado Springs Portfolio Disposition
 
          Property 
         | 
        
           Dec. 23, 2013
 
          Baltimore and Washington Corridor
 
          Property 
         | 
        
           Dec. 23, 2013
 
          Colorado Springs
 
          Property 
         | 
      |
| Properties | |||||||
| Number of properties sold | 15 | ||||||
| Number of properties transferred | 9 | 5 | |||||
| Revenue from real estate operations | $ (36) | $ 9,740 | $ (12) | $ 29,403 | |||
| Property operating expenses | 175 | (3,524) | 111 | (10,523) | |||
| Depreciation and amortization | 0 | (1,005) | 0 | (3,509) | |||
| Impairment recoveries (losses) | 24 | (16,217) | (3) | (25,269) | |||
| General, administrative and leasing expenses | 0 | 0 | 0 | (1) | |||
| Interest expense | 0 | (1,968) | 0 | (6,316) | |||
| Gain on sales of real estate | 28 | 0 | 24 | 0 | |||
| Loss on early extinguishment of debt | 0 | 0 | (116) | 0 | |||
| Discontinued operations | $ 191 | $ (12,974) | $ 4 | $ (16,215) | |||
| X | ||||||||||
| 
             
- Definition 
          Amount, if any, of gain on sales of real estate allocated to the disposal group, including a component of the entity (discontinued operation), during the reporting period. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of depreciation and amortization costs attributable to the disposal group, including a component of the entity (discontinued operation), during the reporting period. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of gain or loss on early extinguishment of debt attributable to the disposal group, including a component of the entity (discontinued operation), during the reporting period. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of property operating expenses attributable to the disposal group, including a component of the entity (discontinued operation), during the reporting period. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Disposal Group Including Discontinued Operations, General and Administrative and Leasing Expenses No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Represents the aggregate impairment losses recognized during the period related to properties disposed or expected to be disposed that are included in discontinued operations. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Represents the number of real estate properties sold during the period. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Number of Real Estate Properties, Title Transfer to Lender No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of interest expense allocated to disposal group, including a discontinued operation. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of sales or other form of revenues attributable to the disposal group, including a component of the entity (discontinued operation), during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of income (loss) from a disposal group, net of income tax before extraordinary items allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Details 
          
  |