Annual report pursuant to Section 13 and 15(d)

Quarterly Data (Unaudited) Quarterly Data (Unaudited) 2 (Details)

v2.4.0.6
Quarterly Data (Unaudited) Quarterly Data (Unaudited) 2 (Details) (USD $)
 3 Months Ended 12 Months Ended
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Income (loss) from continuing operations $ 15,743,000 $ (31,850,000) $ 10,065,000 $ 12,685,000 $ (60,325,000) $ 1,669,000 $ (397,000) $ (22,851,000) $ 6,643,000 $ (81,904,000) $ 25,621,000
Net income (loss) 19,010,000 (20,765,000) 11,861,000 10,235,000 (91,102,000) 7,470,000 (25,378,000) (18,566,000) 20,341,000 (127,576,000) 45,504,000
Net income (loss) attributable to noncontrolling interests (471,000) 1,603,000 (556,000) 60,000 5,606,000 (626,000) 1,964,000 1,204,000      
Net income (loss) attributable to Corporate Office Properties Trust 18,539,000 (19,162,000) 11,305,000 10,295,000 (85,496,000) 6,844,000 (23,414,000) (17,362,000) 20,977,000 (119,428,000) 42,760,000
Net income (loss) attributable to COPT common shareholders 12,433,000 (27,535,000) 7,138,000 6,270,000 (89,522,000) 2,819,000 (27,440,000) (21,387,000) (1,694,000) (135,530,000) 26,658,000
Basic and diluted earnings per common share   $ (0.39) $ 0.10 $ 0.09           $ (1.97)  
Earnings per share, basic $ 0.16 $ (0.39) $ 0.10 $ 0.09 $ (1.26) $ 0.04 $ (0.40) $ (0.33) $ (0.03) [1] $ (1.97) [1] $ 0.43 [1]
Earnings per share, diluted $ 0.16 $ (0.39) $ 0.10 $ 0.09 $ (1.26) $ 0.04 $ (0.41) $ (0.33) $ (0.03) [1] $ (1.97) [1] $ 0.43 [1]
Scenario, Previously Reported
                      
Income (loss) from continuing operations   (31,850,000) 10,065,000 9,427,000 (56,438,000) 1,669,000 (1,026,000) (22,851,000)      
Net income (loss)   (20,765,000) 11,861,000 6,977,000 (87,215,000) 7,470,000 (26,007,000) (18,566,000)   (124,318,000)  
Net income (loss) attributable to noncontrolling interests   993,000 (1,107,000) (300,000) 4,988,000 (904,000) 1,783,000 776,000      
Net income (loss) attributable to Corporate Office Properties Trust   (19,772,000) 10,754,000 6,677,000 (82,227,000) 6,566,000 (24,224,000) (17,790,000)   (117,675,000)  
Net income (loss) attributable to COPT common shareholders   $ (28,145,000) $ 6,587,000 $ 2,652,000 $ (86,253,000) $ 2,541,000 $ (28,250,000) $ (21,815,000)   $ (133,777,000)  
Basic and diluted earnings per common share   $ (0.39) $ 0.09 $ 0.04           $ (1.94)  
Earnings per share, basic         $ (1.21) $ 0.03 $ (0.42) $ (0.33)      
Earnings per share, diluted         $ (1.21) $ 0.03 $ (0.42) $ (0.33)      
[1] Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.