Annual report pursuant to Section 13 and 15(d)

Properties, net (Details 5)

v3.6.0.2
Properties, net (Details 5)
$ / shares in Units, ft² in Thousands, $ in Thousands
 12 Months Ended
Aug. 07, 2015
USD ($)
ft²
Apr. 15, 2015
USD ($)
ft²
Mar. 19, 2015
USD ($)
ft²
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
$ / shares
Dec. 31, 2014
USD ($)
$ / shares
Business Combination            
Weighted average amortization period of intangible assets       11 years    
Pro Forma Information            
Pro forma total revenues         $ 641,982 $ 623,013
Pro forma net income attributable to COPT common shareholders         $ 167,079 $ 20,796
Basic (in dollars per share) | $ / shares         $ 1.77 $ 0.23
Diluted (in dollars per share) | $ / shares         $ 1.77 $ 0.23
Tenant relationship value [Member]            
Business Combination            
Weighted average amortization period of intangible assets       10 years    
Below-market cost arrangements [Member]            
Business Combination            
Weighted average amortization period of intangible assets       35 years    
250 W Pratt St [Member] | Baltimore, Maryland [Member]            
Business Acquisition [Line Items]            
Square footage of real estate properties (in square feet) | ft²     367      
Acquired property percentage leased     96.20%      
Purchase price     $ 61,800      
2600 Park Tower Drive [Member] | Vienna, Virginia [Member]            
Business Acquisition [Line Items]            
Square footage of real estate properties (in square feet) | ft²   237        
Acquired property percentage leased   100.00%        
Purchase price   $ 80,500        
100 and 30 Light Street [Member] | Baltimore, Maryland [Member]            
Business Acquisition [Line Items]            
Square footage of real estate properties (in square feet) | ft² 558          
Acquired property percentage leased 93.50%          
Purchase price $ 121,200          
Liabilities incurred 55,000          
Fair value assumption of debt $ 55,500          
2015 Property Acquisitions [Member]            
Business Combination            
Land, operating properties         $ 55,076  
Building and improvements         139,540  
Intangible assets on real estate acquisitions         75,729  
Total assets         270,345  
Below-market leases         (6,808)  
Total acquisition cost         263,537  
Finite-lived intangible assets acquired         $ 75,729  
Weighted average amortization period of intangible assets         10 years  
Contributed revenues       $ 36,900 $ 20,200  
Net income from continuing operations since acquisition date       $ 2,200 1,200  
Acquisition related costs         4,100  
2015 Property Acquisitions [Member] | Tenant relationship value [Member]            
Business Combination            
Finite-lived intangible assets acquired         $ 31,183  
Weighted average amortization period of intangible assets         12 years  
2015 Property Acquisitions [Member] | In-place lease value [Member]            
Business Combination            
Finite-lived intangible assets acquired         $ 35,139  
Weighted average amortization period of intangible assets         7 years  
2015 Property Acquisitions [Member] | Above-market leases [Member]            
Business Combination            
Finite-lived intangible assets acquired         $ 6,720  
Weighted average amortization period of intangible assets         4 years  
2015 Property Acquisitions [Member] | Below-market cost arrangements [Member]            
Business Combination            
Finite-lived intangible assets acquired         $ 2,687  
Weighted average amortization period of intangible assets         40 years