Properties, net (Details 3) (Linthicum Maryland, USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013 sqft
Linthicum Maryland
Dispositions [Line Items]
Square footage of real estate properties (in square feet)	103,000
Sales Price of Operating Properties Sold	$ 6.9

Represents the total sales price of operating properties sold during the period.

No definition available.

Name:	ofc_SalesPriceOfOperatingPropertiesSold
Namespace Prefix:	ofc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration