Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Details)

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Summary of Significant Accounting Policies (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Dec. 31, 2011
Misapplication Of Accounting Guidance Related To Recognition Of Deferred Tax Asset
Previously reported
Mar. 31, 2012
Misapplication Of Accounting Guidance Related To Recognition Of Deferred Tax Asset
Scenario Adjustment
Dec. 31, 2011
Over accrual Of Incentive Compensation Cost
Previously reported
Mar. 31, 2012
Over accrual Of Incentive Compensation Cost
Scenario Adjustment
Dec. 31, 2011
Misapplication Of Accounting Guidance Related To Recognition Of Deferred Tax Asset And Over-accrual Of Incentive Compensation Cost
Previously reported
Mar. 31, 2012
Misapplication Of Accounting Guidance Related To Recognition Of Deferred Tax Asset And Over-accrual Of Incentive Compensation Cost
Scenario Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]                
Net income (loss) $ 6,977 $ (18,566) $ 4,000   $ (700)   $ 3,300 $ (3,300)
Income tax (expense) benefit 4,173 (544) (4,000) 4,000        
General and administrative expenses $ 7,017 $ 6,777     $ 700 $ (700)    
Net income (loss) attributable to COPT common shareholders (in dollars per share) $ 0.04 [1] $ (0.33) [1] $ 0.05 $ (0.05) $ (0.01) $ 0.01 $ 0.04 $ (0.04)
Net income (loss) attributable to COPT common shareholders (in dollars per share) $ 0.04 [1] $ (0.33) [1] $ 0.05 $ (0.05) $ (0.01) $ 0.01 $ 0.04 $ (0.04)
[1] Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.