COPT Defense Properties Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

Equity - COPLP and Subsidiaries (Details)

Equity - COPLP and Subsidiaries (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 27, 2017	Jun. 27, 2017	Jan. 21, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Preferred Stock
Stock redeemed or called during period value						$ 172,500	$ 26,583
Preferred units in COPLP				$ 8,800	$ 8,800	8,800	$ 8,800
Common Shares
Common shares issued under forward equity sale agreements						$ 49,944
Number of common shares for each converted common unit (in shares)						1
Number of operating partnerships units converted into common shares (in units)						339,513	87,000	160,160
Dividends declared per common share (in dollars per share)						$ 1.1	$ 1.10	$ 1.10
Common Stock Issued to Public Under At-the-Market Program [Member]
Common Shares
Shares issued to the public					3,720,000	591,042.000	3,720,000	890,241
Issuance of stock, weighted average price per share (in dollars per share)				$ 33.84	$ 29.56	$ 33.84	$ 29.56	$ 30.29
Net proceeds from issue of shares after underwriter discounts but before offering expenses						$ 19,700	$ 109,100	$ 26,600
Payments of stock issuance costs					$ 900	300	900	$ 400
Forward Equity Sale Agreement [Member]
Common Shares
Shares issued to the public	1,700,000			1,700,000
Common shares issued under forward equity sale agreements	$ 50,000			$ 50,000
Series K Preferred Shares [Member]
Preferred Stock
Annual dividend yield			5.60%
Issuance costs associated with redeemed preferred shares					17
Series L [Member]
Preferred Stock
Annual dividend yield		7.375%
Issuance costs associated with redeemed preferred shares						6,800
Corporate Office Properties, L.P. [Member]
Preferred Stock
Stock redeemed or called during period value						172,500	$ 26,583
Common Shares
Common shares issued under forward equity sale agreements						$ 49,944
Number of common shares for each converted common unit (in shares)						1
Number of operating partnerships units converted into common shares (in units)						339,513.000	87,000	160,160.00
Dividends declared per common share (in dollars per share)						$ 1.1	$ 1.10	$ 1.10
Corporate Office Properties, L.P. [Member] \| Common Units [Member]
Common Shares
Percentage ownership in operating partnership						96.90%	96.50%
Corporate Office Properties, L.P. [Member] \| Conversion of Series I preferred units [Member]
Preferred Stock
Annual dividend yield						7.50%
Limited partners' capital account, units issued				352,000		352,000
Preferred units in COPLP				$ 8,800		$ 8,800
Preferred stock, liquidation preference per share				$ 25		$ 25
Annual cumulative preferred return increment frequency						5 years
Common units conversion basis units issuable						0.5
Corporate Office Properties, L.P. [Member] \| Series K Preferred Shares [Member]
Preferred Stock
Annual dividend yield			5.60%
Preferred stock, redemption price per share (in dollars per share)			$ 50.00
Stock redeemed or called during period value			$ 26,600
Issuance costs associated with redeemed preferred shares					$ 17
Corporate Office Properties, L.P. [Member] \| Series L [Member]
Preferred Stock
Annual dividend yield		7.375%
Preferred stock, redemption price per share (in dollars per share)		$ 25.00
Stock redeemed or called during period value		$ 172,500
Issuance costs associated with redeemed preferred shares						$ 6,800