Annual report pursuant to Section 13 and 15(d)

Information by Business Segment (Details 4)

v3.8.0.1
Information by Business Segment (Details 4) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Reconciliation of segment assets to total assets      
Total COPT consolidated assets $ 3,578,484 $ 3,780,885  
Segment assets [Member]      
Reconciliation of segment assets to total assets      
Total COPT consolidated assets 3,011,284 3,004,247 $ 3,265,469
Non-operating property assets [Member]      
Reconciliation of segment assets to total assets      
Total COPT consolidated assets 411,041 418,171  
Other assets [Member]      
Reconciliation of segment assets to total assets      
Total COPT consolidated assets $ 156,159 $ 358,467