Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Details 3)

v3.8.0.1
Summary of Significant Accounting Policies (Details 3) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Investment in unconsolidated real estate joint venture $ 41,311 $ 43,182 $ 41,787 $ 43,661
Cumulative distributions in excess of net income (813,302) (757,330) (802,085) (747,825)
Noncontrolling interests in subsidiaries 65,673 67,470 66,165 72,267
Common units 1,022   1,013  
Equity in income of unconsolidated entities 373 377    
Income before gain on sales of real estate 18,784 18,502    
Net income 18,780 22,740    
Net income attributable to noncontrolling interests - Common units in COPLP (544) (622)    
Net income attributable to COPT 17,150 21,019    
Net income attributable to COPT common shareholders 17,150 17,839    
Comprehensive income 23,701 24,148    
Comprehensive income attributable to COPT 21,911 22,380    
Corporate Office Properties, L.P.        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Investment in unconsolidated real estate joint venture 41,311 43,182 41,787 43,661
Noncontrolling interests in subsidiaries 12,592   12,312  
Common units 1,453,262 1,427,397 1,445,022 1,419,710
Equity in income of unconsolidated entities 373 377    
Income before gain on sales of real estate 18,784 18,502    
Net income 18,780 22,740    
Net income attributable to COPT 17,859 21,806    
Net income attributable to COPT common shareholders 17,694 18,461    
Comprehensive income 23,701 24,148    
Comprehensive income attributable to COPT $ 22,780 23,214    
As Previously Reported        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Investment in unconsolidated real estate joint venture   25,417 25,066 25,548
Cumulative distributions in excess of net income   (774,445) (818,190) (765,276)
Noncontrolling interests in subsidiaries   66,820 65,549 71,605
Equity in income of unconsolidated entities   725    
Income before gain on sales of real estate   18,850    
Net income   23,088    
Net income attributable to noncontrolling interests - Common units in COPLP   (634)    
Net income attributable to COPT   21,355    
Net income attributable to COPT common shareholders   18,175    
Comprehensive income   24,496    
Comprehensive income attributable to COPT   22,716    
As Previously Reported | Corporate Office Properties, L.P.        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Investment in unconsolidated real estate joint venture   25,417 25,066 25,548
Common units   1,409,632 1,428,301 1,401,597
Equity in income of unconsolidated entities   725    
Income before gain on sales of real estate   18,850    
Net income   23,088    
Net income attributable to COPT   22,154    
Net income attributable to COPT common shareholders   18,809    
Comprehensive income   24,496    
Comprehensive income attributable to COPT   23,562    
Accounting Standards Update 2017-05        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Investment in unconsolidated real estate joint venture   17,765 16,721 18,113
Cumulative distributions in excess of net income   17,115 16,105 17,451
Noncontrolling interests in subsidiaries   650 616 662
Equity in income of unconsolidated entities   (348)    
Income before gain on sales of real estate   (348)    
Net income   (348)    
Net income attributable to noncontrolling interests - Common units in COPLP   12    
Net income attributable to COPT   (336)    
Net income attributable to COPT common shareholders   (336)    
Comprehensive income   (348)    
Comprehensive income attributable to COPT   (336)    
Accounting Standards Update 2017-05 | Corporate Office Properties, L.P.        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Investment in unconsolidated real estate joint venture   17,765 16,721 18,113
Common units   17,765 $ 16,721 $ 18,113
Equity in income of unconsolidated entities   (348)    
Income before gain on sales of real estate   (348)    
Net income   (348)    
Net income attributable to COPT   (348)    
Net income attributable to COPT common shareholders   (348)    
Comprehensive income   (348)    
Comprehensive income attributable to COPT   $ (348)