| 
           Consolidated Balance Sheets (Parenthetical 2) (USD $) 
        In Thousands, except Share data, unless otherwise specified  | 
        
           Jun. 30, 2014 
         | 
        
           Dec. 31, 2013 
         | 
      
|---|---|---|
| Allowance for doubtful accounts - AR | $ 2,282 | $ 2,976 | 
| Allowance - Deferred rent receivable | 1,491 | 2,126 | 
| Common Shares of beneficial interest, shares outstanding | 87,668,308 | 87,394,512 | 
| 
           Corporate Office Properties, L.P. 
         | 
        ||
| Allowance for doubtful accounts - AR | 2,282 | 2,976 | 
| Allowance - Deferred rent receivable | $ 1,491 | $ 2,126 | 
| 
           Corporate Office Properties, L.P. | General Partner 
         | 
        ||
| Preferred Units, Outstanding | 7,431,667 | 9,431,667 | 
| Common Shares of beneficial interest, shares outstanding | 87,668,308 | 87,394,512 | 
| 
           Corporate Office Properties, L.P. | Limited Partner 
         | 
        ||
| Preferred Units, Outstanding | 352,000 | 352,000 | 
| Common Shares of beneficial interest, shares outstanding | 3,899,202 | 3,977,700 | 
| X | ||||||||||
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- Definition 
          Valuation allowance for deferred rent receivables attributable to, for instance, credit risk associated with a lessee. No definition available. 
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| X | ||||||||||
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- Definition 
          For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition 
          The number of preferred units outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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