Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Details 1)

v3.10.0.1
Summary of Significant Accounting Policies (Details 1)
12 Months Ended
Dec. 31, 2018
compensation_arrangement
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 | Form 3
Corporate Office Properties, L.P. [Member]  
Noncontrolling Interest [Abstract]  
Interests in several real estate entities owned directly by COPT 1.00%
Construction contract revenue [Member]  
Noncontrolling Interest [Abstract]  
Number of compensation arrangements | compensation_arrangement 3
Typical period from billing for payment to be due (in days) 30 days