Annual report pursuant to Section 13 and 15(d)

Earnings Per Share ("EPS") and Earnings Per Unit (“EPU”) (Details 2)

v3.8.0.1
Earnings Per Share ("EPS") and Earnings Per Unit (“EPU”) (Details 2) - shares
shares in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Conversion of common units [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 3,362 3,633 0
Conversion of Series I preferred units [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 176 176 176
Conversion of Series K preferred shares [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 0 434 434
Restricted Stock and Deferred Shares [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 433 385 410
Stock Options [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 70 285 469
Corporate Office Properties, L.P. [Member] | Restricted Stock and Deferred Shares [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 433 385 410
Corporate Office Properties, L.P. [Member] | Stock Options [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 70 285 469
Corporate Office Properties, L.P. [Member] | Conversion of Series I preferred units [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 176 176 176
Corporate Office Properties, L.P. [Member] | Conversion of Series K preferred units [Member]      
Antidilutive securities      
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) 0 434 434