Information by Business Segment (Details 4) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 3,775,859	$ 3,656,005	$ 3,596,238
Operating properties lease liabilities included in segment assets	16,619
Segment assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	3,108,153		3,025,966
Operating properties lease liabilities included in segment assets	16,342		0
Non-operating property assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	485,911		425,951
Other assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 165,453		$ 144,321