Annual report pursuant to Section 13 and 15(d)

Organization (Narrative) (Details)

v3.20.4
Organization (Narrative) (Details)
ft² in Millions
12 Months Ended
Dec. 31, 2020
property
Dec. 31, 2019
Dec. 31, 2020
ft²
Dec. 31, 2020
MW
Dec. 31, 2020
a
Dec. 31, 2020
shares
Corporate Office Properties, L.P | COPT | Preferred units            
Investments in real estate            
Limited partners' capital account, units outstanding (in shares) | shares           0
Common Units | Corporate Office Properties, L.P | COPT            
Investments in real estate            
Percentage ownership in operating partnership 98.60% 98.70%        
Operating properties            
Investments in real estate            
Number of real estate properties 181          
Area of real estate property (in sqft or acres) | ft²     21.0      
Operating properties | Office Properties            
Investments in real estate            
Number of real estate properties 155          
Area of real estate property (in sqft or acres) | ft²     16.2      
Operating properties | Single-tenant data centers            
Investments in real estate            
Number of real estate properties 26          
Area of real estate property (in sqft or acres) | ft²     4.7      
Operating Wholesale Data Center            
Investments in real estate            
Critical load (in megawatts) | MW       19.25    
Properties under development            
Investments in real estate            
Number of real estate properties 11          
Area of real estate property (in sqft or acres) | ft²     1.5      
Properties under development | Office Properties            
Investments in real estate            
Number of real estate properties 9          
Properties under development | Single-tenant data centers            
Investments in real estate            
Number of real estate properties 2          
Properties Under Development, Partially-Operational            
Investments in real estate            
Number of real estate properties 3          
Land controlled for future development            
Investments in real estate            
Area of real estate property (in sqft or acres)     10.4   830  
Other land            
Investments in real estate            
Area of real estate property (in sqft or acres) | a         43  
Unconsolidated Real Estate Joint Ventures            
Investments in real estate            
Number of real estate properties 17          
Unconsolidated Real Estate Joint Ventures | Operating properties | Single-tenant data centers            
Investments in real estate            
Number of real estate properties 17