| Schedule of selected quarterly information | 
The tables below set forth selected quarterly information for the years ended December 31, 2017 and 2016 (in thousands, except per share/unit data). 
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   | 
For the Year Ended December 31, 2017  | 
   | 
For the Year Ended December 31, 2016  | 
 
   | 
First Quarter  | 
   | 
Second Quarter  | 
   | 
Third Quarter  | 
   | 
Fourth Quarter  | 
   | 
First Quarter  | 
   | 
Second Quarter  | 
   | 
Third Quarter  | 
   | 
Fourth Quarter  | 
 
COPT and Subsidiaries  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
Revenues  | 
$  | 
139,801  | 
 
  | 
   | 
$  | 
151,435  | 
 
  | 
   | 
$  | 
157,017  | 
 
  | 
   | 
$  | 
164,567  | 
 
  | 
   | 
$  | 
144,307  | 
 
  | 
   | 
$  | 
145,927  | 
 
  | 
   | 
$  | 
142,103  | 
 
  | 
   | 
$  | 
141,991  | 
 
  | 
 
Operating income  | 
$  | 
35,433  | 
 
  | 
   | 
$  | 
36,618  | 
 
  | 
   | 
$  | 
38,939  | 
 
  | 
   | 
$  | 
24,847  | 
 
  | 
   | 
$  | 
30,464  | 
 
  | 
   | 
$  | 
(27,021  | 
)  | 
   | 
$  | 
11,525  | 
 
  | 
   | 
$  | 
37,442  | 
 
  | 
 
Income (loss) from continuing operations  | 
$  | 
18,850  | 
 
  | 
   | 
$  | 
19,195  | 
 
  | 
   | 
$  | 
21,494  | 
 
  | 
   | 
$  | 
6,904  | 
 
  | 
   | 
$  | 
8,096  | 
 
  | 
   | 
$  | 
(48,316  | 
)  | 
   | 
$  | 
(4,829  | 
)  | 
   | 
$  | 
19,718  | 
 
  | 
 
Net income (loss)  | 
$  | 
23,088  | 
 
  | 
   | 
$  | 
19,207  | 
 
  | 
   | 
$  | 
22,682  | 
 
  | 
   | 
$  | 
11,356  | 
 
  | 
   | 
$  | 
8,096  | 
 
  | 
   | 
$  | 
(48,316  | 
)  | 
   | 
$  | 
29,272  | 
 
  | 
   | 
$  | 
26,603  | 
 
  | 
 
Net (income) loss attributable to noncontrolling interests  | 
(1,733  | 
)  | 
   | 
(1,345  | 
)  | 
   | 
(1,766  | 
)  | 
   | 
(1,398  | 
)  | 
   | 
(1,270  | 
)  | 
   | 
897  | 
 
  | 
   | 
(1,973  | 
)  | 
   | 
(1,870  | 
)  | 
 
Net income (loss) attributable to COPT  | 
21,355  | 
 
  | 
   | 
17,862  | 
 
  | 
   | 
20,916  | 
 
  | 
   | 
9,958  | 
 
  | 
   | 
6,826  | 
 
  | 
   | 
(47,419  | 
)  | 
   | 
27,299  | 
 
  | 
   | 
24,733  | 
 
  | 
 
Preferred share dividends  | 
(3,180  | 
)  | 
   | 
(3,039  | 
)  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
(3,552  | 
)  | 
   | 
(3,553  | 
)  | 
   | 
(3,552  | 
)  | 
   | 
(3,640  | 
)  | 
 
Issuance costs associated with redeemed preferred shares  | 
—  | 
 
  | 
   | 
(6,847  | 
)  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
(17  | 
)  | 
 
Net income (loss) attributable to COPT common shareholders  | 
$  | 
18,175  | 
 
  | 
   | 
$  | 
7,976  | 
 
  | 
   | 
$  | 
20,916  | 
 
  | 
   | 
$  | 
9,958  | 
 
  | 
   | 
$  | 
3,274  | 
 
  | 
   | 
$  | 
(50,972  | 
)  | 
   | 
$  | 
23,747  | 
 
  | 
   | 
$  | 
21,076  | 
 
  | 
 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
Basic EPS  | 
$  | 
0.18  | 
 
  | 
   | 
$  | 
0.08  | 
 
  | 
   | 
$  | 
0.21  | 
 
  | 
   | 
$  | 
0.10  | 
 
  | 
   | 
$  | 
0.03  | 
 
  | 
   | 
$  | 
(0.54  | 
)  | 
   | 
$  | 
0.25  | 
 
  | 
   | 
$  | 
0.22  | 
 
  | 
 
Diluted EPS  | 
$  | 
0.18  | 
 
  | 
   | 
$  | 
0.08  | 
 
  | 
   | 
$  | 
0.21  | 
 
  | 
   | 
$  | 
0.10  | 
 
  | 
   | 
$  | 
0.03  | 
 
  | 
   | 
$  | 
(0.54  | 
)  | 
   | 
$  | 
0.25  | 
 
  | 
   | 
$  | 
0.22  | 
 
  | 
 
  
  
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| Schedule of selected quarterly information | 
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COPLP and Subsidiaries  | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
Revenues  | 
$  | 
139,801  | 
 
  | 
   | 
$  | 
151,435  | 
 
  | 
   | 
$  | 
157,017  | 
 
  | 
   | 
$  | 
164,567  | 
 
  | 
   | 
$  | 
144,307  | 
 
  | 
   | 
$  | 
145,927  | 
 
  | 
   | 
$  | 
142,103  | 
 
  | 
   | 
$  | 
141,991  | 
 
  | 
 
Operating income  | 
$  | 
35,433  | 
 
  | 
   | 
$  | 
36,618  | 
 
  | 
   | 
$  | 
38,939  | 
 
  | 
   | 
$  | 
24,847  | 
 
  | 
   | 
$  | 
30,464  | 
 
  | 
   | 
$  | 
(27,021  | 
)  | 
   | 
$  | 
11,525  | 
 
  | 
   | 
$  | 
37,442  | 
 
  | 
 
Income (loss) from continuing operations  | 
$  | 
18,850  | 
 
  | 
   | 
$  | 
19,195  | 
 
  | 
   | 
$  | 
21,494  | 
 
  | 
   | 
$  | 
6,904  | 
 
  | 
   | 
$  | 
8,096  | 
 
  | 
   | 
$  | 
(48,316  | 
)  | 
   | 
$  | 
(4,829  | 
)  | 
   | 
$  | 
19,718  | 
 
  | 
 
Net income (loss)  | 
$  | 
23,088  | 
 
  | 
   | 
$  | 
19,207  | 
 
  | 
   | 
$  | 
22,682  | 
 
  | 
   | 
$  | 
11,356  | 
 
  | 
   | 
$  | 
8,096  | 
 
  | 
   | 
$  | 
(48,316  | 
)  | 
   | 
$  | 
29,272  | 
 
  | 
   | 
$  | 
26,603  | 
 
  | 
 
Net income attributable to noncontrolling interests  | 
(934  | 
)  | 
   | 
(907  | 
)  | 
   | 
(897  | 
)  | 
   | 
(908  | 
)  | 
   | 
(979  | 
)  | 
   | 
(911  | 
)  | 
   | 
(913  | 
)  | 
   | 
(912  | 
)  | 
 
Net income (loss) attributable to COPLP  | 
22,154  | 
 
  | 
   | 
18,300  | 
 
  | 
   | 
21,785  | 
 
  | 
   | 
10,448  | 
 
  | 
   | 
7,117  | 
 
  | 
   | 
(49,227  | 
)  | 
   | 
28,359  | 
 
  | 
   | 
25,691  | 
 
  | 
 
Preferred unit distributions  | 
(3,345  | 
)  | 
   | 
(3,204  | 
)  | 
   | 
(165  | 
)  | 
   | 
(165  | 
)  | 
   | 
(3,717  | 
)  | 
   | 
(3,718  | 
)  | 
   | 
(3,717  | 
)  | 
   | 
(3,805  | 
)  | 
 
Issuance costs associated with redeemed preferred units  | 
—  | 
 
  | 
   | 
(6,847  | 
)  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
—  | 
 
  | 
   | 
(17  | 
)  | 
 
Net income (loss) attributable to COPLP common unitholders  | 
$  | 
18,809  | 
 
  | 
   | 
$  | 
8,249  | 
 
  | 
   | 
$  | 
21,620  | 
 
  | 
   | 
$  | 
10,283  | 
 
  | 
   | 
$  | 
3,400  | 
 
  | 
   | 
$  | 
(52,945  | 
)  | 
   | 
$  | 
24,642  | 
 
  | 
   | 
$  | 
21,869  | 
 
  | 
 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
   | 
 
Basic EPU  | 
$  | 
0.18  | 
 
  | 
   | 
$  | 
0.08  | 
 
  | 
   | 
$  | 
0.21  | 
 
  | 
   | 
$  | 
0.10  | 
 
  | 
   | 
$  | 
0.03  | 
 
  | 
   | 
$  | 
(0.54  | 
)  | 
   | 
$  | 
0.25  | 
 
  | 
   | 
$  | 
0.22  | 
 
  | 
 
Diluted EPU  | 
$  | 
0.18  | 
 
  | 
   | 
$  | 
0.08  | 
 
  | 
   | 
$  | 
0.21  | 
 
  | 
   | 
$  | 
0.10  | 
 
  | 
   | 
$  | 
0.03  | 
 
  | 
   | 
$  | 
(0.54  | 
)  | 
   | 
$  | 
0.25  | 
 
  | 
   | 
$  | 
0.22  | 
 
  | 
 
  
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