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%