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Summary of Significant Accounting Policies 1 (Details)
12 Months Ended
Dec. 31, 2013
Form
Cash and Cash Equivalents  
Maximum term until original maturity to classify cash and liquid investments as cash and cash equivalent (in months) 3 months
Share-Based Compensation  
Number of forms of share based compensation plans 2
Market concentration premium
 
Useful Lifes Related To Intangible Assets and Property [Abstract]  
Finite-Lived Intangible Asset, Useful Life 40 years
Corporate Office Properties, L.P.
 
Noncontrolling Interest [Abstract]  
Interests in several real estate entities owned directly by COPT 1.00%