COPT Defense Properties Quarterly report pursuant to Section 13 or 15(d)

Information by Business Segment (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Reconciliation of segment assets to total assets
Assets	$ 3,777,155us-gaap_Assets	$ 3,670,257us-gaap_Assets	$ 3,605,897us-gaap_Assets
Segment assets
Reconciliation of segment assets to total assets
Assets	3,110,380		2,932,749
Non-operating property assets
Reconciliation of segment assets to total assets
Assets	496,930		503,030
Other assets
Reconciliation of segment assets to total assets
Assets	$ 169,845		$ 170,118