Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Forward Equity Sale Agreement	Common Shares	Common Shares Forward Equity Sale Agreement	Additional Paid-in Capital	Additional Paid-in Capital Forward Equity Sale Agreement	Cumulative Distributions in Excess of Net Income	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Corporate Office Properties, L.P.	Corporate Office Properties, L.P. Forward Equity Sale Agreement	Corporate Office Properties, L.P. Common Shares	Corporate Office Properties, L.P. Common Shares Forward Equity Sale Agreement	Corporate Office Properties, L.P. Accumulated Other Comprehensive Loss	Corporate Office Properties, L.P. Noncontrolling Interests	Corporate Office Properties, L.P. Limited Partner	Corporate Office Properties, L.P. Limited Partner Preferred Shares
Balance, preferred units (in share/units) at Dec. 31, 2018																	352,000
Balance (in units/ shares) at Dec. 31, 2018	110,241,868											111,574,754
Balance at Dec. 31, 2018	$ 1,627,048		$ 1,102		$ 2,431,355		$ (846,808)	$ (238)	$ 41,637	$ 1,627,048		$ 1,604,655		$ (121)	$ 13,714		$ 8,800
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares	$ 0				80				(80)
Issuance of common units resulting from common shares issued under COPT forward equity sale agreements (in units)		1,614,087											1,614,087
Common shares issued under sale agreements and programs		$ 46,454		$ 16		$ 46,438					$ 46,454		$ 46,454
Share-based compensation issuance, net of redemptions (in units)	78,335											326,973
Share-based compensation issuance, net of redemptions	$ 1,802		1		1,562				239	1,802		$ 1,802
Redemption of vested equity awards	(1,817)				(1,817)					(1,817)		(1,817)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				(1,322)				1,322
Comprehensive income	12,228						20,859	(9,300)	669	12,228		21,116		(9,415)	362		165
Dividends/Distributions	(30,754)						(30,754)			(31,304)		(31,139)					$ (165)
Distributions to owners of common and preferred units in COPLP	(550)								(550)
Contributions from noncontrolling interests in other consolidated entities	2,570								2,570	2,570					2,570
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(4)								(4)	(4)					(4)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (799)				(799)					(799)		$ (799)
Balance, preferred units (in shares/units) at Mar. 31, 2019																	352,000
Balance (in units/ shares) at Mar. 31, 2019	111,939,790											113,515,814
Balance at Mar. 31, 2019	$ 1,656,178		1,119		2,475,497		(856,703)	(9,538)	45,803	1,656,178		$ 1,640,272		(9,536)	16,642		$ 8,800
Increase (Decrease) in Shareholders' Equity
Balance, as adjusted	$ 1,713,704		1,121		2,481,558		(783,816)	(25,444)	40,285	1,713,704		$ 1,718,618		(25,648)	11,934		$ 8,800
Balance, preferred units (in share/units) at Dec. 31, 2019																352,000	352,000
Balance (in units/ shares) at Dec. 31, 2019	112,068,705											113,551,130				1,482,425
Balance at Dec. 31, 2019	$ 1,719,245		1,121		2,481,558		(778,275)	(25,444)	40,285	1,719,245		$ 1,724,159		(25,648)	11,934		$ 8,800
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares	$ 0				182				(182)
Share-based compensation issuance, net of redemptions (in units)	88,749											238,782
Share-based compensation issuance, net of redemptions	$ 1,210		1		983				226	1,210		$ 1,210
Redemption of vested equity awards	(1,492)				(1,492)					(1,492)		(1,492)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				(453)				453
Comprehensive income	(12,982)						24,054	(36,757)	(279)	(12,982)		24,341		(37,195)	(205)		77
Dividends/Distributions	(30,838)						(30,838)			(31,258)		(31,181)					$ (77)
Distributions to owners of common and preferred units in COPLP	(420)								(420)
Contributions from noncontrolling interests in other consolidated entities	112								112	112					112
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(7)								(7)	(7)					(7)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (4,101)				(4,101)					(4,101)		$ (4,101)
Balance, preferred units (in shares/units) at Mar. 31, 2020																352,000	352,000
Balance (in units/ shares) at Mar. 31, 2020	112,169,463											113,789,912				1,620,449
Balance at Mar. 31, 2020	$ 1,665,186		$ 1,122		$ 2,476,677		$ (790,600)	$ (62,201)	$ 40,188	$ 1,665,186		$ 1,707,395		$ (62,843)	$ 11,834		$ 8,800