Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Details 4)

v3.10.0.1
Summary of Significant Accounting Policies (Details 4) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Investment in unconsolidated real estate joint venture $ 39,845       $ 41,787       $ 39,845 $ 41,787 $ 43,661
Cumulative distributions in excess of net income (846,808)       (802,085)       (846,808) (802,085) (747,825)
Noncontrolling interests in subsidiaries 41,637       66,165       41,637 66,165 72,267
Gain on sales of real estate                 2,340 9,890 59,679
Income before equity in income of unconsolidated entities and income taxes                 75,583 74,549 33,260
Equity in income of unconsolidated entities                 2,697 1,490 752
Net income 18,456 $ 20,322 $ 21,085 $ 18,780 11,008 $ 22,334 $ 18,859 $ 22,740 78,643 74,941 33,768
Net (income) loss attributable to noncontrolling interests - Common units in COPLP                 (1,742) (1,890) (507)
Net income attributable to COPT/COPLP 17,020 18,697 19,434 17,150 9,621 20,579 17,526 21,019 72,301 68,745 28,890
Net income (loss) attributable to COPT/COPLP common share/unit holders 17,020 18,697 19,434 17,150 9,621 20,579 7,640 17,839 72,301 $ 55,679 $ 14,576
Earnings per common share/unit - basic and diluted (in dollars per share)                   $ 0.56 $ 0.15
Comprehensive income                 76,073 $ 78,968 $ 34,899
Comprehensive income attributable to COPT/ COPLP                 69,620 72,643 29,997
Common units 1,102       1,013       1,102 1,013  
Corporate Office Properties, L.P. [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Investment in unconsolidated real estate joint venture 39,845       41,787       39,845 41,787 43,661
Noncontrolling interests in subsidiaries 13,714       12,312       13,714 12,312  
Gain on sales of real estate                 2,340 9,890 59,679
Income before equity in income of unconsolidated entities and income taxes                 75,583 74,549 33,260
Equity in income of unconsolidated entities                 2,697 1,490 752
Net income 18,456 20,322 21,085 18,780 11,008 22,334 18,859 22,740 78,643 74,941 33,768
Net income attributable to COPT/COPLP 17,395 19,242 20,207 17,859 10,100 21,437 17,952 21,806 74,703 71,295 30,053
Net income (loss) attributable to COPT/COPLP common share/unit holders 17,230 $ 19,077 $ 20,042 $ 17,694 9,935 $ 21,272 $ 7,901 $ 18,461 74,043 $ 57,569 $ 15,079
Earnings per common share/unit - basic and diluted (in dollars per share)                   $ 0.56 $ 0.15
Comprehensive income                 76,073 $ 78,968 $ 34,899
Comprehensive income attributable to COPT/ COPLP                 72,133 75,322 31,184
Common units $ 1,604,655       1,445,022       $ 1,604,655 1,445,022 1,419,710
As Previously Reported [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Investment in unconsolidated real estate joint venture         25,066         25,066 25,548
Cumulative distributions in excess of net income         (818,190)         (818,190) (765,276)
Noncontrolling interests in subsidiaries         65,549         65,549 71,605
Gain on sales of real estate                   9,890 40,986
Income before equity in income of unconsolidated entities and income taxes                   74,549 14,567
Equity in income of unconsolidated entities                   2,882 1,332
Net income                   76,333 15,655
Net (income) loss attributable to noncontrolling interests - Common units in COPLP                   (1,936) 155
Net income attributable to COPT/COPLP                   70,091 11,439
Net income (loss) attributable to COPT/COPLP common share/unit holders                   $ 57,025 $ (2,875)
Earnings per common share/unit - basic and diluted (in dollars per share)                   $ 0.57 $ (0.03)
Comprehensive income                   $ 80,360 $ 16,786
Comprehensive income attributable to COPT/ COPLP                   73,989 12,546
As Previously Reported [Member] | Corporate Office Properties, L.P. [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Investment in unconsolidated real estate joint venture         25,066         25,066 25,548
Gain on sales of real estate                   9,890 40,986
Income before equity in income of unconsolidated entities and income taxes                   74,549 14,567
Equity in income of unconsolidated entities                   2,882 1,332
Net income                   76,333 15,655
Net income attributable to COPT/COPLP                   72,687 11,940
Net income (loss) attributable to COPT/COPLP common share/unit holders                   $ 58,961 $ (3,034)
Earnings per common share/unit - basic and diluted (in dollars per share)                   $ 0.57 $ (0.04)
Comprehensive income                   $ 80,360 $ 16,786
Comprehensive income attributable to COPT/ COPLP                   76,714 13,071
Common units         1,428,301         1,428,301 1,401,597
Accounting Standards Update 2017-05 [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Investment in unconsolidated real estate joint venture         16,721         16,721 18,113
Cumulative distributions in excess of net income         16,105         16,105 17,451
Noncontrolling interests in subsidiaries         616         616 662
Gain on sales of real estate                   0 18,693
Income before equity in income of unconsolidated entities and income taxes                   0 18,693
Equity in income of unconsolidated entities                   (1,392) (580)
Net income                   (1,392) 18,113
Net (income) loss attributable to noncontrolling interests - Common units in COPLP                   46 (662)
Net income attributable to COPT/COPLP                   (1,346) 17,451
Net income (loss) attributable to COPT/COPLP common share/unit holders                   $ (1,346) $ 17,451
Earnings per common share/unit - basic and diluted (in dollars per share)                   $ (0.01) $ 0.18
Comprehensive income                   $ (1,392) $ 18,113
Comprehensive income attributable to COPT/ COPLP                   (1,346) 17,451
Accounting Standards Update 2017-05 [Member] | Corporate Office Properties, L.P. [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Investment in unconsolidated real estate joint venture         16,721         16,721 18,113
Gain on sales of real estate                   0 18,693
Income before equity in income of unconsolidated entities and income taxes                   0 18,693
Equity in income of unconsolidated entities                   (1,392) (580)
Net income                   (1,392) 18,113
Net income attributable to COPT/COPLP                   (1,392) 18,113
Net income (loss) attributable to COPT/COPLP common share/unit holders                   $ (1,392) $ 18,113
Earnings per common share/unit - basic and diluted (in dollars per share)                   $ (0.01) $ 0.19
Comprehensive income                   $ (1,392) $ 18,113
Comprehensive income attributable to COPT/ COPLP                   (1,392) 18,113
Common units         $ 16,721         $ 16,721 $ 18,113