COPT Defense Properties (CDP) 10-Q 5 Aug 19 2019 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2019	Jul. 26, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2019
Entity File Number	1-14023
Entity Registrant Name	Corporate Office Properties Trust
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	23-2947217
Entity Address, Address Line One	6711 Columbia Gateway Drive
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Columbia
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21046
City Area Code	443
Local Phone Number	285-5400
Title of 12(b) Security	Common Shares of beneficial interest, $0.01 par value
Trading Symbol	OFC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		111,949,887
Entity Central Index Key	0000860546
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Small Business	false
Entity Emerging Growth Company	false
Corporate Office Properties, L.P.
Entity Information [Line Items]
Entity File Number	333-189188
Entity Registrant Name	Corporate Office Properties, L.P.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	23-2930022
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Central Index Key	0001577966
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Properties, net:
Operating properties, net	$ 2,719,585	$ 2,847,265
Projects in development or held for future development	474,787	403,361
Total properties, net	3,194,372	3,250,626
Property - finance right-of-use assets	41,748
Assets held for sale, net	54,448	0
Cash and cash equivalents	46,282	8,066
Investment in unconsolidated real estate joint ventures	65,336	39,845
Accounts receivable	58,189	26,277
Deferred rent receivable	86,707	89,350
Intangible assets on real estate acquisitions, net	31,162	43,470
Deferred leasing costs (net of accumulated amortization of $33,866 and $31,994, respectively)	52,227	50,191
Investing receivables	70,656	56,982
Prepaid expenses and other assets, net	76,180	91,198
Total assets	3,803,469	3,656,005
Liabilities:
Debt, net	1,784,362	1,823,909
Accounts payable and accrued expenses	152,196	92,855
Rents received in advance and security deposits	27,477	30,079
Dividends and distributions payable	31,346	30,856
Deferred revenue associated with operating leases	8,161	9,125
Property - operating lease liabilities	16,640
Interest rate derivatives	23,547	5,459
Other liabilities	10,826	10,414
Total liabilities	2,054,555	2,002,697
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	29,803	26,260
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,119	1,102
Additional paid-in capital	2,475,293	2,431,355
Cumulative distributions in excess of net income	(780,667)	(846,808)
Accumulated other comprehensive loss	(23,465)	(238)
Total Corporate Office Properties Trust’s shareholders’ equity	1,672,280	1,585,411
Noncontrolling interests in subsidiaries:
Common units in COPLP	21,039	19,168
Preferred units in COPLP	8,800	8,800
Other consolidated entities	16,992	13,669
Noncontrolling interests in subsidiaries	46,831	41,637
Total equity	1,719,111	1,627,048
Total liabilities, redeemable noncontrolling interests and equity	3,803,469	3,656,005
Properties
Properties, net:
Property - operating right-of-use assets	27,434	0
Property - finance right-of-use assets	40,476	0
Liabilities:
Property - operating lease liabilities	16,640	0
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,719,585	2,847,265
Projects in development or held for future development	474,787	403,361
Total properties, net	3,194,372	3,250,626
Assets held for sale, net	54,448	0
Cash and cash equivalents	46,282	8,066
Investment in unconsolidated real estate joint ventures	65,336	39,845
Accounts receivable	58,189	26,277
Deferred rent receivable	86,707	89,350
Intangible assets on real estate acquisitions, net	31,162	43,470
Deferred leasing costs (net of accumulated amortization of $33,866 and $31,994, respectively)	52,227	50,191
Investing receivables	70,656	56,982
Prepaid expenses and other assets, net	71,943	87,330
Total assets	3,799,232	3,652,137
Liabilities:
Debt, net	1,784,362	1,823,909
Accounts payable and accrued expenses	152,196	92,855
Rents received in advance and security deposits	27,477	30,079
Dividends and distributions payable	31,346	30,856
Deferred revenue associated with operating leases	8,161	9,125
Interest rate derivatives	23,547	5,459
Other liabilities	6,589	6,546
Total liabilities	2,050,318	1,998,829
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	29,803	26,260
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,716,912	1,604,655
Accumulated other comprehensive loss	(23,638)	(121)
Total Corporate Office Properties Trust’s shareholders’ equity	1,702,074	1,613,334
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	17,037	13,714
Total equity	1,719,111	1,627,048
Total liabilities, redeemable noncontrolling interests and equity	3,799,232	3,652,137
Corporate Office Properties, L.P. | Properties
Properties, net:
Property - operating right-of-use assets	27,434	0
Property - finance right-of-use assets	40,476	0
Liabilities:
Property - operating lease liabilities	16,640	0
Limited Partner | Corporate Office Properties, L.P.
Corporate Office Properties Trust’s shareholders’ equity:
Preferred units held by limited partner, 352,000 preferred units outstanding at June 30, 2019 and December 31, 2018	$ 8,800	$ 8,800

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accumulated amortization of deferred leasing costs	$ 33,866	$ 31,994
Common Shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common Shares of beneficial interest, shares authorized	150,000,000	150,000,000
Common Shares of beneficial interest, shares issued	111,949,887	110,241,868
Common Shares of beneficial interest, shares outstanding	111,949,887	110,241,868
Corporate Office Properties, L.P.
Accumulated amortization of deferred leasing costs	$ 33,866	$ 31,994
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	111,949,887	110,241,868
Corporate Office Properties, L.P. | Limited Partner
Common Shares of beneficial interest, shares outstanding	1,582,844	1,332,886
Preferred Units, Outstanding	352,000	352,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018
Revenues
Lease revenue	$ 131,415		$ 127,907		$ 262,318	$ 255,040
Construction contract and other service revenues	42,299		17,581		59,249	44,779
Total revenues	175,070		146,743		324,010	302,219
Operating expenses
Property operating expenses	47,886		49,446		97,331	100,397
Depreciation and amortization associated with real estate operations	34,802		33,190		69,598	66,702
Construction contract and other service expenses	41,002		16,941		57,328	43,157
General, administrative and leasing expenses	9,386		7,628		18,137	14,920
Business development expenses and land carry costs	870		1,234		1,983	2,848
Total operating expenses	133,946		108,439		244,377	228,024
Interest expense	(18,475)		(18,945)		(37,149)	(37,729)
Interest and other income	1,849		1,439		4,135	2,798
Gain on sales of real estate	84,469		(23)		84,469	(27)
Income before equity in income of unconsolidated entities and income taxes	108,967		20,775		131,088	39,237
Equity in income of unconsolidated entities	420		373		811	746
Income tax benefit (expense)	176		(63)		(18)	(118)
Net income	109,563		21,085		131,881	39,865
Net income attributable to noncontrolling interests:
Common units in COPLP	(1,339)		(608)		(1,596)	(1,152)
Preferred units in COPLP	(165)		(165)		(330)	(330)
Other consolidated entities	(1,268)		(878)		(2,305)	(1,799)
Net income attributable to COPLP	106,791		19,434		127,650	36,584
Net income attributable to COPT common shareholders	$ 106,791		$ 19,434		$ 127,650	$ 36,584
Earnings per common share:
Net income attributable to COPT common shareholders - basic (in dollars per share/unit)	$ 0.95	[1]	$ 0.19	[1]	$ 1.15	$ 0.36
Net income attributable to COPT common shareholders - diluted (in dollars per share/unit)	$ 0.95	[1]	$ 0.19	[1]	$ 1.15	$ 0.36
Other Property Revenue
Revenues
Total revenues	$ 1,356		$ 1,255		$ 2,443	$ 2,400
Corporate Office Properties, L.P.
Revenues
Lease revenue	131,415		127,907		262,318	255,040
Construction contract and other service revenues	42,299		17,581		59,249	44,779
Total revenues	175,070		146,743		324,010	302,219
Operating expenses
Property operating expenses	47,886		49,446		97,331	100,397
Depreciation and amortization associated with real estate operations	34,802		33,190		69,598	66,702
Construction contract and other service expenses	41,002		16,941		57,328	43,157
General, administrative and leasing expenses	9,386		7,628		18,137	14,920
Business development expenses and land carry costs	870		1,234		1,983	2,848
Total operating expenses	133,946		108,439		244,377	228,024
Interest expense	(18,475)		(18,945)		(37,149)	(37,729)
Interest and other income	1,849		1,439		4,135	2,798
Gain on sales of real estate	84,469		(23)		84,469	(27)
Income before equity in income of unconsolidated entities and income taxes	108,967		20,775		131,088	39,237
Equity in income of unconsolidated entities	420		373		811	746
Income tax benefit (expense)	176		(63)		(18)	(118)
Net income	109,563		21,085		131,881	39,865
Net income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities	(1,268)		(878)		(2,305)	(1,799)
Net income attributable to COPLP	108,295		20,207		129,576	38,066
Preferred unit distributions	(165)		(165)		(330)	(330)
Net income attributable to COPT common shareholders	$ 108,130		$ 20,042		$ 129,246	$ 37,736
Earnings per common share:
Net income attributable to COPT common shareholders - basic (in dollars per share/unit)	$ 0.95	[2]	$ 0.19	[2]	$ 1.15	$ 0.36
Net income attributable to COPT common shareholders - diluted (in dollars per share/unit)	$ 0.95	[2]	$ 0.19	[2]	$ 1.15	$ 0.36
Corporate Office Properties, L.P. | Other Property Revenue
Revenues
Total revenues	$ 1,356		$ 1,255		$ 2,443	$ 2,400
[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.
[2]	Basic and diluted earnings per common unit are calculated based on amounts attributable to common unitholders of Corporate Office Properties, L.P.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income	$ 109,563	$ 21,085	$ 131,881	$ 39,865
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(13,545)	1,912	(22,390)	6,588
(Gain) loss on interest rate derivatives recognized in interest expense	(557)	(47)	(1,127)	198
Other comprehensive (loss) income	(14,102)	1,865	(23,517)	6,786
Comprehensive income	95,461	22,950	108,364	46,651
Comprehensive income attributable to noncontrolling interests	(2,597)	(1,708)	(3,941)	(3,498)
Comprehensive income attributable to COPT	92,864	21,242	104,423	43,153
Corporate Office Properties, L.P.
Net income	109,563	21,085	131,881	39,865
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(13,545)	1,912	(22,390)	6,588
(Gain) loss on interest rate derivatives recognized in interest expense	(557)	(47)	(1,127)	198
Other comprehensive (loss) income	(14,102)	1,865	(23,517)	6,786
Comprehensive income	95,461	22,950	108,364	46,651
Comprehensive income attributable to noncontrolling interests	(1,268)	(878)	(2,305)	(1,799)
Comprehensive income attributable to COPT	$ 94,193	$ 22,072	$ 106,059	$ 44,852

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Forward Equity Sale Agreement	Common Shares	Common SharesForward Equity Sale Agreement	Additional Paid-in Capital	Additional Paid-in CapitalForward Equity Sale Agreement	Cumulative Distributions in Excess of Net Income	Accumulated Other Comprehensive Income (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 SharesForward Equity Sale Agreement	Corporate Office Properties, L.P.Accumulated Other Comprehensive Income (Loss)	Corporate Office Properties, L.P.Noncontrolling Interests	Corporate Office Properties, L.P.Limited Partner	Corporate Office Properties, L.P.Limited PartnerPreferred Shares
Increase (Decrease) in Shareholders' Equity
Cumulative effect of accounting change for adoption of hedge accounting guidance							$ (276)	$ 276				$ (276)		$ 276
Balance, as adjusted	$ 1,468,307		$ 1,013		$ 2,201,047		(802,361)	2,443	$ 66,165	$ 1,468,307		1,444,746		2,449	$ 12,312		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 102,150,358, respectively and 111,939,790 shares as of March 31, 2018 and 2019, respectively) at Dec. 31, 2017	$ 1,468,307		1,013		2,201,047		(802,085)	2,167	66,165	1,468,307		$ 1,445,022		2,173	12,312		$ 8,800
Balance (preferred units) at Dec. 31, 2017																	352,000
Balance (in units/shares) at Dec. 31, 2017	101,292,299											104,543,177
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 53,817 and 5,500 shares for the six months ended June 30, 2018 and 2019, respectively)	$ 0		1		760				(761)
Common shares issued under forward equity sale agreements (COPT: 1,100,000 shares for the three months ended June 30, 2018 and 1,777,000 and 1,614,087 shares for the six months ended June 30, 2018 and 2019, respectively)	$ 52,227			$ 18		$ 52,209					$ 52,227		$ 52,227
Common shares issued under forward equity sale agreements (in units/shares)		1,777,000											1,777,000
Share-based compensation issuance, net of redemptions (in units/shares)	137,379											137,379
Share-based compensation issuance, net of redemptions (COPT: 10,137 and 10,097 shares for the three months ended June 30, 2018 and 2019 and 137,379 and 88,432 shares issued, net of redemptions for the six months ended June 30, 2018 and 2019, respectively)	$ 3,400		1		3,399					3,400		$ 3,400
Redemption of vested equity awards	(1,525)				(1,525)					(1,525)		(1,525)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				(702)				702
Comprehensive income	45,422						36,584	6,569	2,269	45,422		37,736		6,786	570		$ 330
Dividends/Distributions	(56,493)						(56,493)			(58,581)		(58,251)					$ (330)
Distributions to owners of common and preferred units in COPLP	(2,088)								(2,088)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(7)								(7)	(7)					(7)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (758)				(758)					(758)		$ (758)
Balance (in units/shares) at Jun. 30, 2018	103,260,495											106,457,556
Balance (preferred units) at Jun. 30, 2018																	352,000
Balance (COPT: 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Jun. 30, 2018	$ 1,508,485		1,033		2,254,430		(822,270)	9,012	66,280	1,508,485		$ 1,477,575		9,235	12,875		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 102,150,358, respectively and 111,939,790 shares as of March 31, 2018 and 2019, respectively) at Mar. 31, 2018	$ 1,482,024		1,022		2,221,427		(813,302)	7,204	65,673	1,482,024		$ 1,453,262		7,370	12,592		$ 8,800
Balance (preferred units) at Mar. 31, 2018																	352,000
Balance (in units/shares) at Mar. 31, 2018	102,150,358											105,347,419
Increase (Decrease) in Shareholders' Equity
Common shares issued under forward equity sale agreements (COPT: 1,100,000 shares for the three months ended June 30, 2018 and 1,777,000 and 1,614,087 shares for the six months ended June 30, 2018 and 2019, respectively)		$ 32,251		11		32,240					32,251		$ 32,251
Common shares issued under forward equity sale agreements (in units/shares)		1,100,000											1,100,000
Share-based compensation issuance, net of redemptions (in units/shares)	10,137											10,137
Share-based compensation issuance, net of redemptions (COPT: 10,137 and 10,097 shares for the three months ended June 30, 2018 and 2019 and 137,379 and 88,432 shares issued, net of redemptions for the six months ended June 30, 2018 and 2019, respectively)	$ 1,720				1,720					1,720		$ 1,720
Redemption of vested equity awards	(198)				(198)					(198)		(198)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				(538)				538
Comprehensive income	22,359						19,434	1,808	1,117	22,359		20,042		1,865	287		$ 165
Dividends/Distributions	(28,402)						(28,402)			(29,446)		(29,281)					$ (165)
Distributions to owners of common and preferred units in COPLP	(1,044)								(1,044)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(4)								(4)	(4)					(4)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (221)				(221)					(221)		$ (221)
Balance (in units/shares) at Jun. 30, 2018	103,260,495											106,457,556
Balance (preferred units) at Jun. 30, 2018																	352,000
Balance (COPT: 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Jun. 30, 2018	$ 1,508,485		1,033		2,254,430		(822,270)	9,012	66,280	1,508,485		$ 1,477,575		9,235	12,875		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 102,150,358, respectively and 111,939,790 shares as of March 31, 2018 and 2019, respectively) 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
Balance (preferred units) at Dec. 31, 2018																352,000	352,000
Balance (in units/shares) at Dec. 31, 2018	110,241,868											111,574,754				1,332,886
Increase (Decrease) in Shareholders' Equity
Redemption of common units	$ (1)								(1)	(1)		$ (1)
Redemption of common units (in units)												(44)
Conversion of common units to common shares (COPT: 53,817 and 5,500 shares for the six months ended June 30, 2018 and 2019, respectively)	$ 0				80				(80)
Common shares issued under forward equity sale agreements (COPT: 1,100,000 shares for the three months ended June 30, 2018 and 1,777,000 and 1,614,087 shares for the six months ended June 30, 2018 and 2019, respectively)		$ 46,454		$ 16		$ 46,438					$ 46,454		$ 46,454
Common shares issued under forward equity sale agreements (in units/shares)		1,614,087											1,614,087
Share-based compensation issuance, net of redemptions (in units/shares)	88,432											343,934
Share-based compensation issuance, net of redemptions (COPT: 10,137 and 10,097 shares for the three months ended June 30, 2018 and 2019 and 137,379 and 88,432 shares issued, net of redemptions for the six months ended June 30, 2018 and 2019, respectively)	$ 3,635		1		3,049				585	3,635		$ 3,635
Redemption of vested equity awards	(1,920)				(1,920)					(1,920)		(1,920)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				(834)				834
Comprehensive income	106,820						127,650	(23,227)	2,397	106,820		129,246		(23,517)	761		$ 330
Dividends/Distributions	(61,509)						(61,509)			(62,612)		(62,282)					$ (330)
Distributions to owners of common and preferred units in COPLP	(1,103)								(1,103)
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	(8)								(8)	(8)					(8)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (2,875)				(2,875)					(2,875)		$ (2,875)
Balance (in units/shares) at Jun. 30, 2019	111,949,887											113,532,731				1,582,844
Balance (preferred units) at Jun. 30, 2019																352,000	352,000
Balance (COPT: 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Jun. 30, 2019	$ 1,719,111		1,119		2,475,293		(780,667)	(23,465)	46,831	1,719,111		$ 1,716,912		(23,638)	17,037		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 102,150,358, respectively and 111,939,790 shares as of March 31, 2018 and 2019, respectively) 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
Balance (preferred units) at Mar. 31, 2019																	352,000
Balance (in units/shares) at Mar. 31, 2019	111,939,790											113,515,814
Increase (Decrease) in Shareholders' Equity
Redemption of common units	$ (1)								(1)	(1)		$ (1)
Redemption of common units (in units)												(44)
Share-based compensation issuance, net of redemptions (in units/shares)	10,097											16,961
Share-based compensation issuance, net of redemptions (COPT: 10,137 and 10,097 shares for the three months ended June 30, 2018 and 2019 and 137,379 and 88,432 shares issued, net of redemptions for the six months ended June 30, 2018 and 2019, respectively)	$ 1,833				1,487				346	1,833		$ 1,833
Redemption of vested equity awards	(103)				(103)					(103)		(103)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				488				(488)
Comprehensive income	94,592						106,791	(13,927)	1,728	94,592		108,130		(14,102)	399		$ 165
Dividends/Distributions	(30,755)						(30,755)			(31,308)		(31,143)					$ (165)
Distributions to owners of common and preferred units in COPLP	(553)								(553)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(4)								(4)	(4)					(4)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (2,076)				(2,076)					(2,076)		$ (2,076)
Balance (in units/shares) at Jun. 30, 2019	111,949,887											113,532,731				1,582,844
Balance (preferred units) at Jun. 30, 2019																352,000	352,000
Balance (COPT: 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Jun. 30, 2019	$ 1,719,111		$ 1,119		$ 2,475,293		$ (780,667)	$ (23,465)	$ 46,831	$ 1,719,111		$ 1,716,912		$ (23,638)	$ 17,037		$ 8,800

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Balance (in units/ shares)	111,949,887	103,260,495	111,949,887	103,260,495	111,939,790	110,241,868	102,150,358	101,292,299
Conversion of common units to common shares (in units/shares)			5,500	53,817
Share-based compensation issuance, net of redemptions (in units/shares)	10,097	10,137	88,432	137,379
Forward Equity Sale Agreement
Common shares issued during the period (in units/shares)		1,100,000	1,614,087	1,777,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Revenues from real estate operations received	$ 257,832	$ 262,602
Construction contract and other service revenues received	21,449	18,411
Property operating expenses paid	(83,305)	(83,642)
Construction contract and other service expenses paid	(31,157)	(62,624)
General, administrative, leasing, business development and land carry costs paid	(16,541)	(15,148)
Interest expense paid	(34,896)	(36,155)
Lease incentives paid	(3,228)	(4,825)
Other	1,661	2,093
Net cash provided by operating activities	111,815	80,712
Cash flows from investing activities
Construction, development and redevelopment	(219,633)	(67,749)
Tenant improvements on operating properties	(7,585)	(18,352)
Other capital improvements on operating properties	(8,920)	(8,584)
Proceeds from property dispositions
Distribution from unconsolidated real estate joint venture following contribution of properties	129,783	0
Sale of controlling interests in properties	107,517	0
Investing receivables funded	(11,104)	0
Leasing costs paid	(7,632)	(3,838)
Other	3,944	1,715
Net cash used in investing activities	(13,630)	(96,808)
Proceeds from debt
Revolving Credit Facility	258,000	153,000
Other debt proceeds	10,606	0
Repayments of debt
Revolving Credit Facility	(308,000)	(109,000)
Scheduled principal amortization	(2,193)	(2,101)
Payments on finance lease liabilities	(110)	(15,379)
Net proceeds from issuance of common shares/units	46,415	52,277
Common share/unit dividends/distributions paid	(61,040)	(55,950)
Distributions paid to noncontrolling interests in COPLP	(1,115)	(2,110)
Redemption of vested equity awards	(1,920)	(1,525)
Other	(44)	(5,370)
Net cash (used in) provided by financing activities	(59,401)	13,842
Net increase (decrease) in cash and cash equivalents and restricted cash	38,784	(2,254)
Cash and cash equivalents and restricted cash
Beginning of period	11,950	14,831
End of period	50,734	12,577
Reconciliation of net income to net cash provided by operating activities:
Net income	131,881	39,865
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	70,527	67,684
Amortization of deferred financing costs and net debt discounts	1,801	1,648
Increase in deferred rent receivable	(2,419)	(3,470)
Gain on sales of real estate	(84,469)	27
Share-based compensation	3,283	3,132
Other	(2,996)	(777)
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(31,846)	8,050
(Increase) decrease in prepaid expenses and other assets, net	(852)	14,718
Increase (decrease) in accounts payable, accrued expenses and other liabilities	29,507	(49,422)
Decrease in rents received in advance and security deposits	(2,602)	(743)
Net cash provided by operating activities	111,815	80,712
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	11,950	12,577
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	29,862	2,909
Finance right-of-use asset contributed by noncontrolling interest in joint venture	2,570	0
Operating right-of-use assets obtained in exchange for operating lease liabilities	255	0
Non-cash changes from property dispositions
Contribution of properties to unconsolidated real estate joint venture	99,288	0
Investment in unconsolidated real estate joint venture retained in disposition	26,500	0
(Decrease) increase in fair value of derivatives applied to accumulated other comprehensive income and noncontrolling interests	(23,585)	6,719
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	80	761
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	834	702
Increase in redeemable noncontrolling interests and decrease in equity to adjust redeemable noncontrolling interests to fair value	2,875	758
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	257,832	262,602
Construction contract and other service revenues received	21,449	18,411
Property operating expenses paid	(83,305)	(83,642)
Construction contract and other service expenses paid	(31,157)	(62,624)
General, administrative, leasing, business development and land carry costs paid	(16,541)	(15,148)
Interest expense paid	(34,896)	(36,155)
Lease incentives paid	(3,228)	(4,825)
Other	1,661	2,093
Net cash provided by operating activities	111,815	80,712
Cash flows from investing activities
Construction, development and redevelopment	(219,633)	(67,749)
Tenant improvements on operating properties	(7,585)	(18,352)
Other capital improvements on operating properties	(8,920)	(8,584)
Proceeds from property dispositions
Distribution from unconsolidated real estate joint venture following contribution of properties	129,783	0
Sale of controlling interests in properties	107,517	0
Investing receivables funded	(11,104)	0
Leasing costs paid	(7,632)	(3,838)
Other	3,944	1,715
Net cash used in investing activities	(13,630)	(96,808)
Proceeds from debt
Revolving Credit Facility	258,000	153,000
Other debt proceeds	10,606	0
Repayments of debt
Revolving Credit Facility	(308,000)	(109,000)
Scheduled principal amortization	(2,193)	(2,101)
Payments on finance lease liabilities	(110)	(15,379)
Net proceeds from issuance of common shares/units	46,415	52,277
Common share/unit dividends/distributions paid	(61,825)	(57,730)
Preferred share/unit dividends/distributions paid	(330)	(330)
Redemption of vested equity awards	(1,920)	(1,525)
Other	(44)	(5,370)
Net cash (used in) provided by financing activities	(59,401)	13,842
Net increase (decrease) in cash and cash equivalents and restricted cash	38,784	(2,254)
Cash and cash equivalents and restricted cash
Beginning of period	11,950	14,831
End of period	50,734	12,577
Reconciliation of net income to net cash provided by operating activities:
Net income	131,881	39,865
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	70,527	67,684
Amortization of deferred financing costs and net debt discounts	1,801	1,648
Increase in deferred rent receivable	(2,419)	(3,470)
Gain on sales of real estate	(84,469)	27
Share-based compensation	3,283	3,132
Other	(2,996)	(777)
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(31,846)	8,050
(Increase) decrease in prepaid expenses and other assets, net	(483)	14,296
Increase (decrease) in accounts payable, accrued expenses and other liabilities	29,138	(49,000)
Decrease in rents received in advance and security deposits	(2,602)	(743)
Net cash provided by operating activities	111,815	80,712
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	50,734	12,577
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	29,862	2,909
Finance right-of-use asset contributed by noncontrolling interest in joint venture	2,570	0
Operating right-of-use assets obtained in exchange for operating lease liabilities	255	0
Non-cash changes from property dispositions
Contribution of properties to unconsolidated real estate joint venture	99,288	0
Investment in unconsolidated real estate joint venture retained in disposition	26,500	0
(Decrease) increase in fair value of derivatives applied to accumulated other comprehensive income and noncontrolling interests	(23,585)	6,719
Increase in redeemable noncontrolling interests and decrease in equity to adjust redeemable noncontrolling interests to fair value	$ 2,875	$ 758

Organization

Organization	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Corporate Office Properties Trust (“COPT”) and subsidiaries (collectively, the “Company”) is a fully-integrated and self-managed real estate investment trust (“REIT”). Corporate Office Properties, L.P. (“COPLP”) and subsidiaries (collectively, the “Operating Partnership”) is the entity through which COPT, the sole general partner of COPLP, conducts almost all of its operations and owns almost all of its assets. Unless otherwise expressly stated or the context otherwise requires, “we”, “us” and “our” as used herein refer to each of the Company and the Operating Partnership. We own, manage, lease, develop and selectively acquire office and data center properties. The majority of our portfolio is in locations that support the United States Government and its contractors, most of whom are engaged in national security, defense and information technology (“IT”) related activities servicing what we believe are growing, durable, priority missions (“Defense/IT Locations”). We also own a portfolio of office properties located in select urban/urban-like submarkets in the Greater Washington, DC/Baltimore region with durable Class-A office fundamentals and characteristics (“Regional Office”). As of June 30, 2019 , our properties included the following: • 169 properties totaling 18.9 million square feet comprised of 15.3 million square feet in 147 office properties and 3.7 million square feet in 22 single-tenant data center shell properties (“data center shells”). We owned 13 of these data center shells through unconsolidated real estate joint ventures; • a wholesale data center with a critical load of 19.25 megawatts; • 14 properties under construction or redevelopment ( nine office properties and five data center shells) that we estimate will total approximately 2.2 million square feet upon completion, including three partially-operational properties; and • approximately 900 acres of land controlled for future development that we believe could be developed into approximately 11.6 million square feet and 150 acres of other land. COPLP owns real estate directly and through subsidiary partnerships and limited liability companies (“LLCs”). In addition to owning real estate, COPLP also owns subsidiaries that provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. Some of these services are performed by a taxable REIT subsidiary (“TRS”). Equity interests in COPLP are in the form of common and preferred units. As of June 30, 2019 , COPT owned 98.6% of the outstanding COPLP common units (“common units”); the remaining common units and all of the outstanding COPLP preferred units (“preferred units”) were owned by third parties. Common units not owned by COPT carry certain redemption rights. The number of common units owned by COPT is equivalent to the number of outstanding common shares of beneficial interest (“common shares”) of COPT, and the entitlement of common units to quarterly distributions and payments in liquidation is substantially the same as those of COPT common shareholders. However, COPLP’s common units include a special class of unit referred to as profit interest units (“PIUs”) originating from certain share-based compensation awards issued to executives (described further in Note 15) that are subject to vesting and certain tax event criteria, and accordingly may carry different rights to redemption and distributions than non-PIU common units. COPT’s common shares are publicly traded on the New York Stock Exchange (“NYSE”) under the ticker symbol “OFC”. Because COPLP is managed by COPT, and COPT conducts substantially all of its operations through COPLP, we refer to COPT’s executive officers as COPLP’s executive officers; similarly, although COPLP does not have a board of trustees, we refer to COPT’s Board of Trustees as COPLP’s Board of Trustees.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The COPT consolidated financial statements include the accounts of COPT, the Operating Partnership, their subsidiaries and other entities in which COPT has a majority voting interest and control. The COPLP consolidated financial statements include the accounts of COPLP, its subsidiaries and other entities in which COPLP has a majority voting interest and control. We also consolidate certain entities when control of such entities can be achieved through means other than voting rights (“variable interest entities” or “VIEs”) if we are deemed to be the primary beneficiary of such entities. We eliminate all intercompany balances and transactions in consolidation. We use the equity method of accounting when we own an interest in an entity and can exert significant influence over but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity. When we own an equity investment in an entity and cannot exert significant influence over its operations, we measure the investment at fair value, with changes recognized through net income. For an investment without a readily determinable fair value, we measure the investment at cost, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. These interim financial statements should be read together with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2018 included in our 2018 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2018 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below. Reclassification We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including reclassifications of our revenue from real estate operations in connection with our adoption of new lease guidance described below. Recent Accounting Pronouncements In February 2016, the FASB issued guidance setting forth principles for the recognition, measurement, presentation and disclosure of leases. This guidance requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. The resulting classification determines whether the lease expense is recognized based on an effective interest method or straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This guidance requires lessors of real estate to account for leases using an approach substantially equivalent to guidance previously in place for operating leases, direct financing leases and sales-type leases. We adopted this guidance on January 1, 2019 using a modified retrospective transition approach under which we elected to apply the guidance effective January 1, 2019 and not adjust prior comparative reporting periods (except for our presentation of lease revenue discussed below). We elected to apply a package of practical expedients that enabled us to carry forward upon adoption our historical assessments of: expired or existing leases regarding their lease classification and deferred recognition of non-incremental direct leasing costs; and whether any expired or existing contracts are, or contain, leases. We also elected a practical expedient that enabled us to avoid the need to assess whether expired or existing land easements not previously accounted for as leases are, or contain, a lease. In addition, we elected a practical expedient for our rental properties (as lessor) to avoid separating non-lease components that otherwise would need to be accounted for under the recently-adopted revenue accounting guidance (such as tenant reimbursements of property operating expenses) from the associated lease component since (1) the non-lease components have the same timing and pattern of transfer as the associated lease component and (2) the lease component, if accounted for separately, would be classified as an operating lease; this enables us to account for the combination of the lease component and non-lease components as an operating lease since the lease component is the predominant component of the combined components. Below is a summary of the primary changes in our accounting and reporting that resulted from our adoption of this guidance: • Property leases in which we are the lessor: ◦ Deferral of non-incremental leasing costs: For new or extended tenant leases, we no longer defer recognition of non-incremental leasing costs that we would have deferred under prior accounting guidance (refer to our 2018 Annual Report on Form 10-K in which we reported amounts deferred in 2018 , 2017 and 2016 ). ◦ Change in presentation of revenue: Due to our adoption of the practical expedient discussed above to not separate non-lease component revenue from the associated lease component, we are aggregating revenue from our lease components and non-lease components (comprised predominantly of tenant operating expense reimbursements) into the line entitled “lease revenue.” We are reporting other revenue from our properties in the line entitled “other property revenue.” We recast prior periods for these changes in presentation. ◦ Changes in assessment of lease revenue collectability: Changes in our assessment of lease revenue collectability that previously would have resulted in charges to bad debt expense under prior guidance are being recognized as an adjustment to rental revenue under the new guidance. Such amounts recognized by us in prior periods were not significant. ◦ Operating expenses paid directly by tenants to third parties: Operating expenses paid directly by tenants to third parties (primarily for real estate taxes) and revenue associated with such tenant payments that would have been recognized under prior guidance will no longer be reported on our Statement of Operations. Such amounts recognized by us in prior periods were not significant. • Leases (the most significant of which are ground leases) in which we are the lessee: ◦ Balance sheet presentation of property operating lease right-of-use assets: Upon adoption on January 1, 2019, we recognized property right-of-use assets and offsetting lease liabilities for existing operating leases totaling $16 million for the present value of minimum lease payments under these leases, and also reclassified an additional $11 million in amounts previously presented elsewhere on our balance sheet in connection with these leases to the right-of-use assets. We will recognize additional right-of-use assets and lease liabilities as we enter into new operating leases. ◦ Balance sheet presentation of property finance lease right-of-use assets: Property right-of-use assets of finance leases that previously were presented as properties under prior guidance are being presented as property finance right-of-use assets under the new guidance. As a result, we reclassified $38 million in assets from properties to property finance right-of-use assets upon adoption on January 1, 2019. ◦ Segment assets: We changed our definition of segment assets used for our reportable segments to include property right-of-use assets associated with operating properties, net of related lease liabilities. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance will apply to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables, loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments). Under the new guidance, an entity will recognize its estimate of expected credit losses as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and to be presented at the net amount expected to be collected. The guidance is effective for us beginning January 1, 2020, with early adoption permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2018, the FASB issued guidance that modifies disclosure requirements for fair value measurements. This guidance is effective for us beginning January 1, 2020. Early adoption is permitted for this guidance, and entities are permitted to early adopt with respect to any removed or modified disclosures while delaying adoption of additional disclosure requirements until the effective date. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. In August 2018, the FASB issued guidance that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. FASB guidance did not previously address the accounting for such implementation costs. The guidance is effective for us beginning January 1, 2020, with early adoption permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Recurring Fair Value Measurements COPT has a non-qualified elective deferred compensation plan for Trustees and certain members of our management team that permits participants to defer up to 100% of their compensation on a pre-tax basis and receive a tax-deferred return on such deferrals. The assets held in the plan (comprised primarily of mutual funds and equity securities) and the corresponding liability to the participants are measured at fair value on a recurring basis on COPT’s consolidated balance sheets using quoted market prices, as are other marketable securities that we hold. The balance of the plan, which was fully funded, totaled $4.2 million as of June 30, 2019 , and is included in the line entitled “prepaid expenses and other assets, net” on COPT’s consolidated balance sheets. The offsetting liability associated with the plan is adjusted to fair value at the end of each accounting period based on the fair value of the plan assets and included in the line entitled “other liabilities” on COPT’s consolidated balance sheets. The assets of the plan are classified in Level 1 of the fair value hierarchy, while the offsetting liability is classified in Level 2 of the fair value hierarchy. The fair values of our interest rate derivatives are determined using widely accepted valuation techniques, including a discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate market data and implied volatilities in such interest rates. While we determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our interest rate derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default. However, as of June 30, 2019 , we assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivatives and determined that these adjustments are not significant. As a result, we determined that our interest rate derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. The carrying values of cash and cash equivalents, restricted cash, accounts receivable, other assets (excluding investing receivables) and accounts payable and accrued expenses are reasonable estimates of their fair values because of the short maturities of these instruments. The fair values of our investing receivables, as disclosed in Note 7, were based on the discounted estimated future cash flows of the loans (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans with similar maturities and credit quality, and the estimated cash payments include scheduled principal and interest payments. For our disclosure of debt fair values in Note 9, we estimated the fair values of our unsecured senior notes based on quoted market rates for publicly-traded debt (categorized within Level 2 of the fair value hierarchy) and estimated the fair value of our other debt based on the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans, or groups of loans, with similar maturities and credit quality, and the estimated future payments include scheduled principal and interest payments. Fair value estimates are made as of a specific point in time, are subjective in nature and involve uncertainties and matters of significant judgment. Settlement at such fair value amounts may not be possible and may not be a prudent management decision. For additional fair value information, please refer to Note 7 for investing receivables, Note 9 for debt and Note 10 for interest rate derivatives. COPT and Subsidiaries The table below sets forth financial assets and liabilities of COPT and subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other (Level 2) Significant Inputs (Level 3) Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,212 $ — $ — $ 4,212 Other 25 — — 25 Interest rate derivatives (1) — 120 — 120 Total assets $ 4,237 $ 120 $ — $ 4,357 Liabilities: Deferred compensation plan liability (2) $ — $ 4,237 $ — $ 4,237 Interest rate derivatives — 23,547 — 23,547 Total liabilities $ — $ 27,784 $ — $ 27,784 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPT’s consolidated balance sheet. (2) Included in the line entitled “other liabilities” on COPT’s consolidated balance sheet. COPLP and Subsidiaries The table below sets forth financial assets and liabilities of COPLP and subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other Significant Inputs (Level 3) Total Assets: Interest rate derivatives (1) $ — $ 120 $ — $ 120 Liabilities: Interest rate derivatives $ — $ 23,547 $ — $ 23,547 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPLP’s consolidated balance sheet.

Properties, Net

Properties, Net	6 Months Ended
	Jun. 30, 2019
Real Estate [Abstract]
Properties, Net	Properties, Net Operating properties, net consisted of the following (in thousands): June 30, December 31, Land $ 460,138 $ 503,274 Buildings and improvements 3,208,558 3,241,894 Less: Accumulated depreciation (949,111 ) (897,903 ) Operating properties, net $ 2,719,585 $ 2,847,265 Properties we had in development or held for future development consisted of the following (in thousands): June 30, December 31, Land $ 296,809 $ 207,760 Development in progress, excluding land 177,978 195,601 Projects in development or held for future development $ 474,787 $ 403,361 As of June 30, 2019 , we were under contract to sell controlling interests in two data center shell properties in Virginia; we expect this sale to occur in the fourth quarter of 2019. The table below sets forth the components of assets held for sale on our consolidated balance sheet as of June 30, 2019 for these properties (in thousands): Properties, net $ 53,386 Deferred rent receivable 1,028 Deferred leasing costs, net 34 Assets held for sale, net $ 54,448 2019 Dispositions On June 20, 2019, through a series of transactions, we sold a 90% interest in seven data center shell properties in Virginia based on an aggregate property value of $265.0 million and retained a 10% interest in the properties through BREIT COPT DC JV LLC (“BREIT-COPT”), a newly-formed joint venture. Our partner in the joint venture acquired the 90% interest from us for $238.5 million . We account for our interest in the joint venture using the equity method of accounting as described further in Note 6. We recognized a gain on sale of $84.5 million . 2019 Construction Activities During the six months ended June 30, 2019 , we placed into service 777,000 square feet in seven newly-constructed properties (including two partially-operational properties) and 10,000 in one partially-operational property under redevelopment. As of June 30, 2019 , we had 13 properties under construction (including two partially-operational properties), or which we were contractually committed to construct, that we estimate will total 2.1 million square feet upon completion and one partially-operational property under redevelopment that we estimate will total 106,000 square feet upon completion.

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases Lessor arrangements We lease real estate properties, comprised primarily of office properties and data center shells, to third parties. As of June 30, 2019 , these leases, which may encompass all, or a portion of, a property, had remaining terms spanning from one month to 15 years and averaging approximately five years . These leases usually include options under which the tenant may renew its lease based on market rates at the time of renewal, which are then typically subject to further negotiation. These leases occasionally provide the tenant with an option to terminate its lease early usually for a defined termination fee. While a significant portion of our portfolio is leased to the United States Government, and the majority of those leases consist of a series of one -year renewal options, or provide for early termination rights, we have concluded that exercise of existing renewal options, or continuation of such leases without exercising early termination rights, is reasonably assured for virtually all of these leases. Most of our lease revenue is from fixed contractual payments defined under the lease that, in most cases, escalate annually over the term of the lease. Our lease revenue also includes variable lease payments predominantly for tenant reimbursements of property operating expenses and lease termination fees. Property operating expense reimbursement structures vary, with some tenants responsible for all of a property’s expenses, while others are responsible for their share of a property’s expense only to the extent such expenses exceed amounts defined in the lease (which are derived from the property’s historical expense levels). Lease termination fees in most cases result from a tenant’s exercise of an existing right under a lease, and are usually equal to a defined percentage of the remaining rents due under the lease and/or the remaining unamortized lease origination costs (including tenant improvements and lease commissions). The table below sets forth our allocation of lease revenue recognized between fixed contractual payments and variable lease payments (in thousands): Lease revenue For the Three Months Ended June 30, 2019 For the Six Months Ended June 30, 2019 Fixed contractual payments $ 104,768 $ 210,103 Variable lease payments 26,647 52,215 $ 131,415 $ 262,318 Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, June 30, 2019 December 31, 2018 2019 (1) $ 201,662 $ 400,617 2020 356,626 337,646 2021 299,046 280,369 2022 262,281 246,329 2023 211,966 194,888 Thereafter 586,076 523,932 $ 1,917,657 $ 1,983,781 (1) As of June 30, 2019 , represents the six months ending December 31, 2019 . Lessee arrangements We lease from third parties land underlying certain properties that we are operating or developing. These ground leases have long durations with remaining terms ranging from 30 years (excluding extension options) to 97 years . As of June 30, 2019 , our balance sheet included $67.9 million in right-of-use assets associated with ground leases that included: • $37.8 million for land on which we are developing an office property in Washington, DC through our Stevens Investors, LLC joint venture, virtually all of the rent on which was previously paid. This lease has a 97 -year remaining term, and we possess a bargain purchase option that we expect to exercise in 2020; • $10.4 million for land underlying office properties in Washington, DC under two leases with remaining terms of approximately 80 years ; • $6.5 million for land underlying a parking garage in Baltimore, Maryland under a lease with a remaining term of 30 years and an option to renew for an additional 48 years that was included in the term used in determining the asset balance; • $6.7 million for land in a research park in College Park, Maryland under four leases through our M Square Associates, LLC joint venture all of the rent on which was previously paid. These leases had remaining terms ranging from 64 years to 75 years ; • $4.2 million for land in a business park in Huntsville, Alabama under nine leases through our LW Redstone Company, LLC joint venture, with remaining terms ranging from 44 to 50 years and options to renew for an additional 25 years that were not included in the term used in determining the asset balance; and • $2.3 million for other land in our Fort Meade/BW Corridor sub-segment under two leases with remaining terms of approximately 49 years all of the rent on which was previously paid. As of June 30, 2019 , our balance sheet also included right-of-use lease assets totaling $1.3 million in connection with vehicles and office equipment that we lease from third parties. In determining operating right-of-use assets and lease liabilities for our existing operating leases upon our adoption of the new lease guidance discussed further in Note 2, as well as for new operating leases in the current period, we were required to estimate an appropriate incremental borrowing rate on a fully-collateralized basis for the terms of the leases. Since the terms under our ground leases are significantly longer than the terms of borrowings available to us on a fully-collateralized basis, our estimate of this rate required significant judgment, and considered factors such as interest rates available to us on a fully-collateralized basis for shorter-termed debt and U.S. Treasury rates. Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location June 30, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,434 Finance leases Property Property - finance right-of-use assets 40,476 Vehicles and office equipment Prepaid expenses and other assets, net 1,272 Total finance lease right-of-use assets 41,748 Total right-of-use assets $ 69,182 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location June 30, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 16,640 Finance leases Other liabilities 1,228 Total lease liabilities $ 17,868 The table below sets forth the weighted average terms and discount rates of our leases as of June 30, 2019 : Weighted average remaining lease term Operating leases 69 years Finance leases 2 years Weighted average discount rate Operating leases 7.35 % Finance leases 3.12 % The table below presents our total lease cost (in thousands): Lease cost Statement of Operations Location For the Three Months Ended June 30, 2019 For the Six Months Ended June 30, 2019 Operating lease cost Property leases Property operating expenses $ 413 $ 826 Vehicles and office equipment General, administrative and leasing expenses 18 35 Finance lease cost Amortization of vehicles and office equipment right-of-use assets General, administrative and leasing expenses 116 229 Amortization of property right-of-use assets Property operating expenses 12 12 Interest on lease liabilities Interest expense 3 7 $ 562 $ 1,109 The table below presents the effect of lease payments on our consolidated statement of cash flows (in thousands): Supplemental cash flow information For the Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 550 Operating cash flows for financing leases $ 7 Financing cash flows for financing leases $ 110 Payments on leases as of June 30, 2019 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 (1) $ 554 $ 118 $ 672 2020 1,126 862 1,988 2021 1,111 202 1,313 2022 1,129 64 1,193 2023 1,134 — 1,134 Thereafter 99,187 — 99,187 Total lease payments 104,241 1,246 105,487 Less: Amount representing interest (87,601 ) (18 ) (87,619 ) Lease liability $ 16,640 $ 1,228 $ 17,868 (1) Represents the six months ending December 31, 2019 . Future minimum rental payments on leases as of December 31, 2018 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 $ 1,101 $ 219 $ 1,320 2020 1,110 844 1,954 2021 1,094 184 1,278 2022 1,115 49 1,164 2023 1,119 — 1,119 Thereafter 83,373 — 83,373 Total lease payments $ 88,912 1,296 90,208 Less: Amount representing interest N/A (24 ) (24 ) Total N/A $ 1,272 $ 90,184

Real Estate Joint Ventures

Real Estate Joint Ventures	6 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Real Estate Joint Ventures	Real Estate Joint Ventures Consolidated Real Estate Joint Ventures The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of June 30, 2019 (dollars in thousands): Nominal Ownership % June 30, 2019 (1) Date Acquired Total Assets Encumbered Assets Total Liabilities Entity Location LW Redstone Company, LLC 3/23/2010 85% Huntsville, Alabama $ 198,389 $ 74,977 $ 69,841 M Square Associates, LLC 6/26/2007 50% College Park, Maryland 80,912 46,159 44,295 Stevens Investors, LLC 8/11/2015 95% Washington, DC 99,436 98,979 30,718 $ 378,737 $ 220,115 $ 144,854 (1) Excludes amounts eliminated in consolidation. Unconsolidated Real Estate Joint Ventures The table below sets forth information pertaining to our investments in unconsolidated real estate joint ventures accounted for using the equity method of accounting (dollars in thousands): Date Acquired Nominal Ownership % Number of Properties Carrying Value of Investment (1) Entity June 30, 2019 December 31, 2018 GI-COPT DC Partnership LLC 7/21/2016 50% 6 $ 38,790 $ 39,845 BREIT COPT DC JV LLC 6/20/2019 10% 7 26,546 — 13 $ 65,336 $ 39,845 (1) Included in the line entitled “investment in unconsolidated real estate joint ventures” on our consolidated balance sheets. These joint ventures operate triple-net leased, single-tenant data center shell properties in Virginia. As described further in Note 4, on June 20, 2019, we sold a 90% interest in seven triple-net leased, single-tenant data center shell properties in Virginia and retained a 10%

Investing Receivables

Investing Receivables	6 Months Ended
	Jun. 30, 2019
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables, including accrued interest thereon, consisted of the following (in thousands): June 30, December 31, Notes receivable from the City of Huntsville $ 56,563 $ 53,961 Other investing loans receivable 14,093 3,021 $ 70,656 $ 56,982 Our notes receivable from the City of Huntsville funded infrastructure costs in connection with our LW Redstone Company, LLC joint venture (see Note 6) and carry an interest rate of 9.95% . Our other investing loans receivable carry an interest rate of 8.0% . We did not have an allowance for credit losses in connection with our investing receivables as of June 30, 2019 or December 31, 2018 . The fair value of these receivables was approximately $74 million as of June 30, 2019 and $58 million as of December 31, 2018 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	6 Months Ended
	Jun. 30, 2019
Prepaid Expense and Other Assets [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets, net consisted of the following (in thousands): June 30, December 31, Lease incentives, net $ 23,487 $ 21,258 Construction contract costs incurred in excess of billings 12,629 3,189 Furniture, fixtures and equipment, net (1) 8,252 8,630 Non-real estate equity investments 6,023 5,940 Prepaid expenses 5,855 25,658 Restricted cash 4,452 3,884 Deferred financing costs, net (2) 4,190 4,733 Deferred tax asset, net (3) 2,164 2,084 Interest rate derivatives 120 5,617 Other assets 4,771 6,337 Total for COPLP and subsidiaries 71,943 87,330 Marketable securities in deferred compensation plan 4,237 3,868 Total for COPT and subsidiaries $ 76,180 $ 91,198 (1) Includes $1.3 million in finance right-of-use assets as of June 30, 2019 . (2) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (3) Includes a valuation allowance of $2.1 million as of June 30, 2019 and $2.7 million as of December 31, 2018 .

Debt, Net

Debt, Net	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Debt, Net	Debt, Net Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of June 30, December 31, June 30, 2019 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 145,285 $ 147,141 3.82% - 7.87% (3) 2019-2026 Variable rate secured debt (4) 34,514 23,282 LIBOR + 1.85% to 2.35% (5) 2020-2022 Total mortgage and other secured debt 179,799 170,423 Revolving Credit Facility 163,000 213,000 LIBOR + 0.775% to 1.45% (6) March 2023 (7) Term Loan Facility (8) 248,490 248,273 LIBOR + 0.85% to 1.65% (9) 2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 348,207 347,986 3.60% (10) May 2023 5.250%, $250,000 aggregate principal 247,391 247,136 5.25% (11) February 2024 3.700%, $300,000 aggregate principal 299,068 298,815 3.70% (12) June 2021 5.000%, $300,000 aggregate principal 297,304 297,109 5.00% (13) July 2025 Unsecured note payable 1,103 1,167 0% (14) May 2026 Total debt, net $ 1,784,362 $ 1,823,909 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.3 million as of June 30, 2019 and $7.2 million as of December 31, 2018 . (2) Certain of the fixed rate mortgages carry interest rates that, upon assumption, were above or below market rates and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $248,000 as of June 30, 2019 and $281,000 as of December 31, 2018 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.17% as of June 30, 2019 . (4) Includes a construction loan with $87.4 million in remaining borrowing capacity as of June 30, 2019 . (5) The weighted average interest rate on our variable rate secured debt was 4.66% as of June 30, 2019 . (6) The weighted average interest rate on the Revolving Credit Facility was 3.52% as of June 30, 2019 . (7) The facility matures in March 2023, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee of 0.075% of the total availability under the facility for each extension period. (8) As of June 30, 2019 , we have the ability to borrow an additional $150.0 million in the aggregate under this facility, provided that there is no default under the facility and subject to the approval of the lenders. In addition, in connection with our Revolving Credit Facility, we have the ability to borrow up to $500.0 million under new term loans from the facility’s lender group provided that there is no default under the facility and subject to the approval of the lenders. (9) The interest rate on this loan was 3.69% as of June 30, 2019 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.2 million as of June 30, 2019 and $1.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (11) The carrying value of these notes reflects an unamortized discount totaling $2.4 million as of June 30, 2019 and $2.6 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (12) The carrying value of these notes reflects an unamortized discount totaling $741,000 as of June 30, 2019 and $943,000 as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (13) The carrying value of these notes reflects an unamortized discount totaling $2.3 million as of June 30, 2019 and $2.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (14) This note carries an interest rate that, upon assumption, was below market rates and it therefore was recorded at its fair value based on applicable effective interest rates. The carrying value of this note reflects an unamortized discount totaling $258,000 as of June 30, 2019 and $294,000 as of December 31, 2018 . All debt is owed by COPLP. While COPT is not directly obligated by any debt, it has guaranteed COPLP’s Revolving Credit Facility, Term Loan Facilities and Unsecured Senior Notes. Certain of our debt instruments require that we comply with a number of restrictive financial covenants. As of June 30, 2019 , we were within the compliance requirements of these financial covenants. We capitalized interest costs of $2.4 million in the three months ended June 30, 2019 , $1.4 million in the three months ended June 30, 2018 , $4.4 million in the six months ended June 30, 2019 and $2.8 million in the six months ended June 30, 2018 . The following table sets forth information pertaining to the fair value of our debt (in thousands): June 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,191,970 $ 1,226,750 $ 1,191,046 $ 1,219,603 Other fixed-rate debt 146,388 148,395 148,308 147,106 Variable-rate debt 446,004 450,417 484,555 486,497 $ 1,784,362 $ 1,825,562 $ 1,823,909 $ 1,853,206

Interest Rate Derivatives

Interest Rate Derivatives	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest Rate Derivatives	Interest Rate Derivatives The following table sets forth the key terms and fair values of our interest rate swap derivatives, each of which was designated as a cash flow hedge of interest rate risk (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date June 30, December 31, $ 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 $ 58 $ 472 12,637 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 62 239 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (975 ) 1,968 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (985 ) 1,967 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (499 ) 971 75,000 3.1760% Three-Month LIBOR 6/30/2020 6/30/2030 (7,965 ) (2,676 ) 75,000 3.1920% Three-Month LIBOR 6/30/2020 6/30/2030 (8,074 ) (2,783 ) 75,000 2.7440% Three-Month LIBOR 6/30/2020 6/30/2030 (5,049 ) — $ (23,427 ) $ 158 (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location June 30, December 31, 2018 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets, net $ 120 $ 5,617 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (23,547 ) $ (5,459 ) The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): Amount of (Loss) Gain Recognized in AOCL on Derivatives Amount of Gain (Loss) Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended June 30, For the Six Months Ended June 30, For the Three Months Ended June 30, For the Six Months Ended June 30, Derivatives in Hedging Relationships 2019 2018 2019 2018 2019 2018 2019 2018 Interest rate derivatives $ (13,545 ) $ 1,912 $ (22,390 ) $ 6,588 $ 557 $ 47 $ 1,127 $ (198 ) Over the next 12 months, we estimate that approximately $1.6 million in losses will be reclassified from accumulated other comprehensive loss (“AOCL”) as an increase to interest expense. We have agreements with each of our interest rate derivative counterparties that contain provisions under which, if we default or are capable of being declared in default on defined levels of our indebtedness, we could also be declared in default on our derivative obligations. Failure to comply with the loan covenant provisions could result in our being declared in default on any derivative instrument obligations covered by the agreements. As of June 30, 2019 , we are not in default with any of these provisions. As of June 30, 2019 , the fair value of interest rate derivatives in a liability position related to these agreements was $23.6 million , excluding the effects of accrued interest and credit valuation adjustments. As of June 30, 2019 , we had not posted any collateral related to these agreements. If we breach any of these provisions, we could be required to settle our obligations under the agreements at their termination value, which was $23.5 million as of June 30, 2019 .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	6 Months Ended
	Jun. 30, 2019
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests Our partners in two real estate joint ventures, LW Redstone Company, LLC and Stevens Investors, LLC (discussed further in Note 6), have the right to require us to acquire their respective interests at fair value; accordingly, we classify the fair value of our partners’ interests as redeemable noncontrolling interests in the mezzanine section of our consolidated balance sheets. The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 26,260 $ 23,125 Contributions from noncontrolling interests — 143 Distributions to noncontrolling interests (876 ) (711 ) Net income attributable to noncontrolling interests 1,544 1,229 Adjustment to arrive at fair value of interests 2,875 758 Ending balance $ 29,803 $ 24,544

Equity

Equity	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Equity	Equity COPT issued 1.6 million common shares under its forward equity sale agreements for net proceeds of $46.5 million on March 27, 2019, after which it had no remaining capacity under the agreements. COPT contributed the net proceeds from this issuance to COPLP in exchange for an equal number of units in COPLP. As of June 30, 2019 , COPT had remaining capacity under its at-the-market stock offering program equal to an aggregate gross sales price of $300 million in common share sales. During the six months ended June 30, 2019 , certain COPLP limited partners converted 5,500 common units in COPLP for an equal number of common shares in COPT. We declared dividends per COPT common share and distributions per COPLP common unit of $0.275 in the three months ended June 30, 2019 and 2018 and $0.55 in the six months ended June 30, 2019 and 2018 . See Note 15 for disclosure of COPT common share and COPLP common unit activity pertaining to our share-based compensation plans.

Information by Business Segment

Information by Business Segment	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Information by Business Segment	Information by Business Segment We have the following reportable segments: Defense/IT Locations; Regional Office; Wholesale Data Center; and Other. We also report on Defense/IT Locations sub-segments, which include the following: Fort George G. Meade and the Baltimore/Washington Corridor (referred to herein as “Fort Meade/BW Corridor”); Northern Virginia Defense/IT Locations; Lackland Air Force Base (in San Antonio); locations serving the U.S. Navy (“Navy Support Locations”), which included properties proximate to the Washington Navy Yard, the Naval Air Station Patuxent River in Maryland and the Naval Surface Warfare Center Dahlgren Division in Virginia; Redstone Arsenal (in Huntsville); and data center shells (properties leased to tenants to be operated as data centers in which the tenants generally fund the costs for the power, fiber connectivity and data center infrastructure). The table below reports segment financial information for our reportable segments (in thousands): Operating Property Segments Defense/Information Technology Locations Fort Meade/BW Corridor Northern Virginia Defense/IT Lackland Air Force Base Navy Support Locations Redstone Arsenal Data Center Shells Total Defense/IT Locations Regional Office Wholesale Other Total Three Months Ended June 30, 2019 Revenues from real estate operations $ 61,659 $ 13,912 $ 12,104 $ 8,185 $ 3,968 $ 8,624 $ 108,452 $ 15,018 $ 8,560 $ 741 $ 132,771 Property operating expenses (19,344 ) (4,694 ) (6,648 ) (3,286 ) (1,599 ) (759 ) (36,330 ) (7,590 ) (3,618 ) (348 ) (47,886 ) UJV NOI allocable to COPT — — — — — 1,251 1,251 — — — 1,251 NOI from real estate operations $ 42,315 $ 9,218 $ 5,456 $ 4,899 $ 2,369 $ 9,116 $ 73,373 $ 7,428 $ 4,942 $ 393 $ 86,136 Additions to long-lived assets $ 7,499 $ 1,703 $ — $ 928 $ 536 $ — $ 10,666 $ 4,870 $ 95 $ 34 $ 15,665 Transfers from non-operating properties $ 1,338 $ 20 $ 1,833 $ — $ 5,576 $ 92,844 $ 101,611 $ — $ — $ — $ 101,611 Three Months Ended June 30, 2018 Revenues from real estate operations $ 61,993 $ 13,118 $ 12,382 $ 8,127 $ 3,652 $ 5,955 $ 105,227 $ 15,296 $ 8,105 $ 534 $ 129,162 Property operating expenses (20,099 ) (4,909 ) (7,494 ) (3,431 ) (1,509 ) (799 ) (38,241 ) (7,169 ) (4,150 ) 114 (49,446 ) UJV NOI allocable to COPT — — — — — 1,202 1,202 — — — 1,202 NOI from real estate operations $ 41,894 $ 8,209 $ 4,888 $ 4,696 $ 2,143 $ 6,358 $ 68,188 $ 8,127 $ 3,955 $ 648 $ 80,918 Additions to long-lived assets $ 8,151 $ 1,186 $ — $ 1,450 $ 351 $ — $ 11,138 $ 5,361 $ 81 $ 188 $ 16,768 Transfers from non-operating properties $ 3,035 $ 352 $ — $ 3 $ 26 $ 29,675 $ 33,091 $ — $ 1,133 $ — $ 34,224 Six Months Ended June 30, 2019 Revenues from real estate operations $ 124,342 $ 28,743 $ 23,665 $ 16,340 $ 7,907 $ 15,978 $ 216,975 $ 29,851 $ 16,431 $ 1,504 $ 264,761 Property operating expenses (41,679 ) (9,986 ) (12,607 ) (6,690 ) (3,138 ) (1,112 ) (75,212 ) (15,006 ) (6,456 ) (657 ) (97,331 ) UJV NOI allocable to COPT — — — — — 2,470 2,470 — — — 2,470 NOI from real estate operations $ 82,663 $ 18,757 $ 11,058 $ 9,650 $ 4,769 $ 17,336 $ 144,233 $ 14,845 $ 9,975 $ 847 $ 169,900 Additions to long-lived assets $ 11,434 $ 3,150 $ — $ 5,945 $ 836 $ — $ 21,365 $ 8,859 $ 251 $ 44 $ 30,519 Transfers from non-operating properties $ 6,378 $ 4,529 $ 8,336 $ — $ 9,211 $ 112,632 $ 141,086 $ — $ — $ — $ 141,086 Segment assets at June 30, 2019 $ 1,274,336 $ 398,586 $ 146,475 $ 187,172 $ 115,222 $ 307,676 $ 2,429,467 $ 393,110 $ 209,787 $ 3,776 $ 3,036,140 Six Months Ended June 30, 2018 Revenues from real estate operations $ 124,775 $ 25,679 $ 23,825 $ 15,997 $ 7,285 $ 11,786 $ 209,347 $ 30,580 $ 16,182 $ 1,331 $ 257,440 Property operating expenses (41,703 ) (9,632 ) (14,092 ) (6,735 ) (2,949 ) (1,593 ) (76,704 ) (15,047 ) (8,408 ) (238 ) (100,397 ) UJV NOI allocable to COPT — — — — — 2,401 2,401 — — — 2,401 NOI from real estate operations $ 83,072 $ 16,047 $ 9,733 $ 9,262 $ 4,336 $ 12,594 $ 135,044 $ 15,533 $ 7,774 $ 1,093 $ 159,444 Additions to long-lived assets $ 15,272 $ 3,126 $ — $ 2,558 $ 430 $ — $ 21,386 $ 9,245 $ 117 $ 315 $ 31,063 Transfers from non-operating properties $ 20,221 $ 693 $ — $ — $ 470 $ 30,789 $ 52,173 $ — $ 2,145 $ — $ 54,318 Segment assets at June 30, 2018 $ 1,269,525 $ 396,139 $ 126,956 $ 190,537 $ 106,374 $ 330,622 $ 2,420,153 $ 396,847 $ 221,239 $ 4,213 $ 3,042,452 The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Segment revenues from real estate operations $ 132,771 $ 129,162 $ 264,761 $ 257,440 Construction contract and other service revenues 42,299 17,581 59,249 44,779 Total revenues $ 175,070 $ 146,743 $ 324,010 $ 302,219 The following table reconciles UJV NOI allocable to COPT to equity in income of unconsolidated entities as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 UJV NOI allocable to COPT $ 1,251 $ 1,202 $ 2,470 $ 2,401 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (830 ) (828 ) (1,657 ) (1,652 ) Add: Equity in loss of unconsolidated non-real estate entities (1 ) (1 ) (2 ) (3 ) Equity in income of unconsolidated entities $ 420 $ 373 $ 811 $ 746 As previously discussed, we provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. The primary manner in which we evaluate the operating performance of our service activities is through a measure we define as net operating income from service operations (“NOI from service operations”), which is based on the net of revenues and expenses from these activities. Construction contract and other service revenues and expenses consist primarily of subcontracted costs that are reimbursed to us by the customer along with a management fee. The operating margins from these activities are small relative to the revenue. We believe NOI from service operations is a useful measure in assessing both our level of activity and our profitability in conducting such operations. The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Construction contract and other service revenues $ 42,299 $ 17,581 $ 59,249 $ 44,779 Construction contract and other service expenses (41,002 ) (16,941 ) (57,328 ) (43,157 ) NOI from service operations $ 1,297 $ 640 $ 1,921 $ 1,622 The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to net income as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 NOI from real estate operations $ 86,136 $ 80,918 $ 169,900 $ 159,444 NOI from service operations 1,297 640 1,921 1,622 Interest and other income 1,849 1,439 4,135 2,798 Gain on sales of real estate 84,469 (23 ) 84,469 (27 ) Equity in income of unconsolidated entities 420 373 811 746 Income tax benefit (expense) 176 (63 ) (18 ) (118 ) Depreciation and other amortization associated with real estate operations (34,802 ) (33,190 ) (69,598 ) (66,702 ) General, administrative and leasing expenses (9,386 ) (7,628 ) (18,137 ) (14,920 ) Business development expenses and land carry costs (870 ) (1,234 ) (1,983 ) (2,848 ) Interest expense (18,475 ) (18,945 ) (37,149 ) (37,729 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,251 ) (1,202 ) (2,470 ) (2,401 ) Net income $ 109,563 $ 21,085 $ 131,881 $ 39,865 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): June 30, June 30, Segment assets $ 3,036,140 $ 3,042,452 Operating properties lease liabilities included in segment assets 16,502 — Non-operating property assets 523,801 431,661 Other assets 227,026 138,249 Total COPT consolidated assets $ 3,803,469 $ 3,612,362 The accounting policies of the segments are the same as those used to prepare our consolidated financial statements. In the segment reporting presented above, we did not allocate interest expense, depreciation and amortization, gain on sales of real estate and equity in income of unconsolidated entities not included in NOI to our real estate segments since they are not included in the measure of segment profit reviewed by management. We also did not allocate general, administrative and leasing expenses, business development expenses and land carry costs, interest and other income, income taxes and noncontrolling interests because these items represent general corporate or non-operating property items not attributable to segments.

Construction Contract and Other

Construction Contract and Other Service Revenues	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Construction Contract and Other Service Revenues	Construction Contract and Other Service Revenues We disaggregate our construction contract and other service revenues by compensation arrangement and by service type as we believe it best depicts the nature, timing and uncertainty of our revenue. The table below reports construction contract and other service revenues by compensation arrangement (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Construction contract revenues: Guaranteed maximum price $ 25,792 $ 9,539 $ 38,148 $ 30,025 Firm fixed price 1,335 6,288 3,660 12,723 Cost-plus fee 14,969 1,496 17,029 1,554 Other 203 258 412 477 $ 42,299 $ 17,581 $ 59,249 $ 44,779 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Construction contract revenues: Construction $ 42,010 $ 16,668 $ 58,499 $ 42,583 Design 86 655 338 1,719 Other 203 258 412 477 $ 42,299 $ 17,581 $ 59,249 $ 44,779 We recognized an increase (decrease) in revenue of $(14,000) and $10,000 in the three months ended June 30, 2019 and 2018 , respectively, and $18,000 and $319,000 in the six months ended June 30, 2019 and 2018 , respectively, from performance obligations satisfied (or partially satisfied) in previous periods. Accounts receivable related to our construction contract services is included in accounts receivable, net on our consolidated balance sheets. The beginning and ending balances of accounts receivable related to our construction contracts were as follows (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 6,701 $ 4,577 Ending balance $ 34,837 $ 4,805 The increase in the accounts receivable balance reported above for the six months ended June 30, 2019 was due primarily to significant amounts billed near the end of the period. Contract assets, which we refer to herein as construction costs in excess of billings, are included in prepaid expenses and other assets, net reported on our consolidated balance sheets. The beginning and ending balances of our contract assets were as follows (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 3,189 $ 4,884 Ending balance $ 12,629 $ 4,158 Contract liabilities are included in other liabilities reported on our consolidated balance sheets. Changes in contract liabilities were as follows (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 568 $ 27,402 Ending balance $ 156 $ 515 Portion of beginning balance recognized in revenue during: Three months ended June 30 $ 6 $ 7,999 Six months ended June 30 $ 445 $ 27,296 The change in the contract liabilities balance reported above for the six months ended June 30, 2018 was due primarily to our satisfaction of performance obligations during the period on a contract on which we previously received advance payments from a customer. Revenue allocated to the remaining performance obligations under existing contracts as of June 30, 2019 that will be recognized as revenue in future periods was $48.4 million , approximately $41 million of which we expect to recognize during the remainder of 2019. We have no deferred incremental costs incurred to obtain or fulfill our construction contracts or other service revenues and had no impairment losses on construction contracts receivable or unbilled construction revenue in the three or six months ended June 30, 2019 and 2018

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Restricted Shares During the six months ended June 30, 2019 , certain employees and non-employee members of our Board of Trustees (“Trustees”) were granted a total of 171,520 restricted common shares with an aggregate grant date fair value of $4.5 million (weighted average of $26.22 per share). Restricted shares granted to employees vest based on increments and over periods of time set forth under the terms of the respective awards provided that the employee remains employed by us. Restricted shares granted to non-employee Trustees vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. During the six months ended June 30, 2019 , forfeiture restrictions lapsed on 171,028 previously issued common shares; these shares had a weighted average grant date fair value of $28.03 per share, and the aggregate intrinsic value of the shares on the vesting dates was $4.5 million . Deferred Share Awards During the six months ended June 30, 2019 , certain non-employee Trustees were granted a total of 3,432 deferred share awards with an aggregate grant date fair value of $95,000 ( $27.60 per share). Deferred share awards vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. We settle deferred share awards by issuing an equivalent number of common shares upon vesting of the awards or a later date elected by the Trustee (generally upon cessation of being a Trustee). During the six months ended June 30, 2019 , we issued 3,097 common shares in settlement of deferred share awards; these shares had a grant date fair value of $26.77 per share, and the aggregate intrinsic value of the shares on the settlement date was $86,000 . Performance Share Awards (“PSUs”) We issued 44,757 common shares on January 18, 2019 to executives in settlement of PSUs granted in 2016, representing 157% of the target award for those PSUs. PIUs Commencing in 2019, we offered our executives and Trustees the opportunity to select PIUs as a form of long-term compensation in lieu of, or in combination with, other forms of share-based compensation awards (restricted shares, deferred share awards and PSUs). PIUs are a special class of common unit structured to qualify as “profit interests” for tax purposes. Our executives and certain of our Trustees selected PIUs as their form of share-based compensation for their 2019 grants. We granted two forms of PIUs: time-based PIUs (“TB-PIUs”); and performance-based PIUs (“PB-PIUs”). TB-PIUs are subject to forfeiture restrictions until the end of the requisite service period, at which time the TB-PIUs automatically convert into vested PIUs. PB-PIUs are subject to a market condition in that the number of earned awards are determined at the end of the performance period (as described further below) and then settled in vested PIUs. Vested PIUs carry substantially the same rights to redemption and distributions as non-PIU common units. TB-PIUs During the six months ended June 30, 2019 , our executives and certain non-employee Trustees were granted a total of 61,820 TB-PIUs with an aggregate grant date fair value of $1.6 million (weighted average of $26.01 per TB-PIU). TB-PIUs granted to executives vest in equal one-third increments over a three -year period beginning on the first anniversary of the date of grant. TB-PIUs granted to non-employee Trustees vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. Prior to vesting, TB-PIUs carry substantially the same rights to distributions as non-PIU common units but carry no redemption rights. PB-PIUs On January 1, 2019 , we granted our executives 193,682 PB-PIUs with a three -year performance period concluding on the earlier of December 31, 2021 or the date of: (1) termination by us without cause, death or disability of the executive or constructive discharge of the executive (collectively, “qualified termination”); or (2) a sale event. The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT’s total shareholder return relative to a peer group of companies, as set forth in the following schedule: Percentile Rank Earned Awards Payout % 75th or greater 100% of PB-PIUs granted 50th (target) 50% of PB-PIUs granted 25th 25% of PB-PIUs granted Below 25th 0% of PB-PIUs granted If the percentile rank exceeds the 25th percentile and is between two of the percentile ranks set forth in the table above, then the percentage of the earned awards will be interpolated between the ranges set forth in the table above to reflect any performance between the listed percentiles. During the performance period, PB-PIUs carry rights to distributions equal to 10% of the distribution rights of non-PIU common units but carry no redemption rights. At the end of the performance period, we will settle the award by issuing vested PIUs equal to the number of earned awards in settlement of the award plan and paying cash equal to the excess, if any, of: the aggregate distributions that would have been paid with respect to vested PIUs issued in settlement of the earned awards through the date of settlement had such vested PIUs been issued on the grant date; over the aggregate distributions made on the PB-PIUs during the performance period. If a performance period ends due to a sale event or qualified termination, the number of earned awards is prorated based on the portion of the three -year performance period that has elapsed. If employment is terminated by the employee or by us for cause, all PB-PIUs are forfeited. These PB-PIUs had an aggregate grant date fair value of $2.4 million ( $12.47 per PB-PIU) which is being recognized over the performance period. The grant date fair value was computed using a Monte Carlo model that included the following assumptions: baseline common share value of $21.03 ; expected volatility for common shares of 21.0% ; and a risk-free interest rate of 2.51%

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”)	Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”) COPT and Subsidiaries EPS We present both basic and diluted EPS. We compute basic EPS by dividing net income available to common shareholders allocable to unrestricted common shares under the two-class method by the weighted average number of unrestricted common shares outstanding during the period. Our computation of diluted EPS is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common shares that would have been outstanding if securities that are convertible into common shares were converted; and (2) the effect of dilutive potential common shares outstanding during the period attributable to COPT’s forward equity sale agreements, redeemable noncontrolling interests and our share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common shares that we add to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPT $ 106,791 $ 19,434 $ 127,650 $ 36,584 Income attributable to share-based compensation awards (364 ) (117 ) (413 ) (234 ) Numerator for basic EPS on net income attributable to COPT common shareholders 106,427 19,317 127,237 36,350 Preferred unit distributions 165 — — — Redeemable noncontrolling interests 902 — 66 — Common units in the Operating Partnership — — 1,515 — Income attributable to share-based compensation awards 18 — 22 — Numerator for diluted EPS on net income attributable to COPT common shareholders $ 107,512 $ 19,317 $ 128,840 $ 36,350 Denominator (all weighted averages): Denominator for basic EPS (common shares) 111,557 101,789 110,759 101,397 Dilutive convertible preferred units 176 — — — Dilutive effect of common units — — 1,329 — Dilutive effect of share-based compensation awards 310 119 289 131 Dilutive effect of redeemable noncontrolling interests 1,062 — 130 — Denominator for diluted EPS (common shares) 113,105 101,908 112,507 101,528 Basic EPS $ 0.95 $ 0.19 $ 1.15 $ 0.36 Diluted EPS $ 0.95 $ 0.19 $ 1.15 $ 0.36 Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Conversion of common units 1,327 3,197 — 3,208 Conversion of redeemable noncontrolling interests — — 907 — Conversion of Series I preferred units — 176 176 176 The following securities were also excluded from the computation of diluted EPS because their effect was antidilutive: • weighted average shares related to COPT’s forward equity sale agreements for the three months ended June 30, 2018 of 6.8 million , and for the six months ended June 30, 2019 and 2018 of 758,000 and 7.1 million , respectively; • weighted average restricted shares and deferred share awards for the three months ended June 30, 2019 and 2018 of 425,000 and 458,000 , respectively, and for the six months ended June 30, 2019 and 2018 of 444,000 and 451,000 , respectively; • weighted average options for the three months ended June 30, 2019 and 2018 of 17,000 and 47,000 , respectively, and for the six months ended June 30, 2019 and 2018 of 23,000 and 53,000 , respectively; and • weighted average unvested PIUs of 59,000 and 39,000 for the three and six months ended June 30, 2019 , respectively. COPLP and Subsidiaries EPU We present both basic and diluted EPU. We compute basic EPU by dividing net income available to common unitholders allocable to unrestricted common units under the two-class method by the weighted average number of unrestricted common units outstanding during the period. Our computation of diluted EPU is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common units that would have been outstanding if securities that are convertible into our common units were converted; and (2) the effect of dilutive potential common units outstanding during the period attributable to COPT’s forward equity sale agreements, redeemable noncontrolling interests and our share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common units that we add to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPLP $ 108,295 $ 20,207 $ 129,576 $ 38,066 Preferred unit distributions (165 ) (165 ) (330 ) (330 ) Income attributable to share-based compensation awards (438 ) (117 ) (494 ) (234 ) Numerator for basic EPU on net income attributable to COPLP common unitholders 107,692 19,925 128,752 37,502 Redeemable noncontrolling interests 902 — 66 — Income attributable to share-based compensation awards 18 — 22 — Dilutive effective of preferred units 165 — — — Numerator for diluted EPU on net income attributable to COPLP common unitholders $ 108,777 $ 19,925 $ 128,840 $ 37,502 Denominator (all weighted averages): Denominator for basic EPU (common units) 112,884 104,986 112,088 104,605 Dilutive convertible preferred units 176 — — — Dilutive effect of redeemable noncontrolling interests 1,062 — 130 — Dilutive effect of share-based compensation awards 310 119 289 131 Denominator for diluted EPU (common units) 114,432 105,105 112,507 104,736 Basic EPU $ 0.95 $ 0.19 $ 1.15 $ 0.36 Diluted EPU $ 0.95 $ 0.19 $ 1.15 $ 0.36 Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Conversion of redeemable noncontrolling interests — — 907 — Conversion of Series I preferred units — 176 176 176 The following securities were also excluded from the computation of diluted EPU because their effect was antidilutive: • weighted average shares related to COPT’s forward equity sale agreements for the three months ended June 30, 2018 of 6.8 million , and for the six months ended June 30, 2019 and 2018 of 758,000 and 7.1 million , respectively; • weighted average restricted units and deferred share awards for the three months ended June 30, 2019 and 2018 of 425,000 and 458,000 , respectively, and for the six months ended June 30, 2019 and 2018 of 444,000 and 451,000 , respectively; • weighted average options for the three months ended June 30, 2019 and 2018 of 17,000 and 47,000 , respectively, and for the six months ended June 30, 2019 and 2018 of 23,000 and 53,000 , respectively; and • weighted average unvested PIUs of 59,000 and 39,000 for the three and six months ended June 30, 2019 , respectively.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation and Claims In the normal course of business, we are subject to legal actions and other claims. We record losses for specific legal proceedings and claims when we determine that a loss is probable and the amount of loss can be reasonably estimated. Management believes that it is reasonably possible that we could incur losses pursuant to such claims but do not believe such losses would materially affect our financial position, liquidity or results of operations. Our assessment of the potential outcomes of these matters involves significant judgment and is subject to change based on future developments. Environmental We are subject to various Federal, state and local environmental regulations related to our property ownership and operation. We have performed environmental assessments of our properties, the results of which have not revealed any environmental liability that we believe would have a materially adverse effect on our financial position, operations or liquidity. In connection with a lease and subsequent sale in 2008 and 2010 of three properties in Dayton, New Jersey, we agreed to provide certain environmental indemnifications limited to $19 million in the aggregate. We have insurance coverage in place to mitigate much of any potential future losses that may result from these indemnification agreements. Tax Incremental Financing Obligation Anne Arundel County, Maryland issued tax incremental financing bonds to third-party investors in order to finance public improvements needed in connection with our project known as the National Business Park. These bonds had a remaining principal balance of approximately $35 million as of June 30, 2019 . The real estate taxes on increases in assessed values post-bond issuance of properties in development districts encompassing the National Business Park are transferred to a special fund pledged to the repayment of the bonds. While we are obligated to fund, through a special tax, any future shortfalls between debt service of the bonds and real estate taxes available to repay the bonds, as of June 30, 2019 , we do not expect any such future fundings will be required. Contractual Obligations We had amounts remaining to be incurred under various contractual obligations as of June 30, 2019 that included the following (excluding amounts incurred and therefore reflected as liabilities reported on our consolidated balance sheets): • development and redevelopment obligations of $174.0 million ; • tenant and other capital improvements of $51.8 million ; • third party construction obligations of $15.4 million ; and • other obligations of $1.7 million .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The COPT consolidated financial statements include the accounts of COPT, the Operating Partnership, their subsidiaries and other entities in which COPT has a majority voting interest and control. The COPLP consolidated financial statements include the accounts of COPLP, its subsidiaries and other entities in which COPLP has a majority voting interest and control. We also consolidate certain entities when control of such entities can be achieved through means other than voting rights (“variable interest entities” or “VIEs”) if we are deemed to be the primary beneficiary of such entities. We eliminate all intercompany balances and transactions in consolidation. We use the equity method of accounting when we own an interest in an entity and can exert significant influence over but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity. When we own an equity investment in an entity and cannot exert significant influence over its operations, we measure the investment at fair value, with changes recognized through net income. For an investment without a readily determinable fair value, we measure the investment at cost, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. These interim financial statements should be read together with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2018 included in our 2018 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2018 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below.
Reclassification	Reclassification We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including reclassifications of our revenue from real estate operations in connection with our adoption of new lease guidance described below.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued guidance setting forth principles for the recognition, measurement, presentation and disclosure of leases. This guidance requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. The resulting classification determines whether the lease expense is recognized based on an effective interest method or straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This guidance requires lessors of real estate to account for leases using an approach substantially equivalent to guidance previously in place for operating leases, direct financing leases and sales-type leases. We adopted this guidance on January 1, 2019 using a modified retrospective transition approach under which we elected to apply the guidance effective January 1, 2019 and not adjust prior comparative reporting periods (except for our presentation of lease revenue discussed below). We elected to apply a package of practical expedients that enabled us to carry forward upon adoption our historical assessments of: expired or existing leases regarding their lease classification and deferred recognition of non-incremental direct leasing costs; and whether any expired or existing contracts are, or contain, leases. We also elected a practical expedient that enabled us to avoid the need to assess whether expired or existing land easements not previously accounted for as leases are, or contain, a lease. In addition, we elected a practical expedient for our rental properties (as lessor) to avoid separating non-lease components that otherwise would need to be accounted for under the recently-adopted revenue accounting guidance (such as tenant reimbursements of property operating expenses) from the associated lease component since (1) the non-lease components have the same timing and pattern of transfer as the associated lease component and (2) the lease component, if accounted for separately, would be classified as an operating lease; this enables us to account for the combination of the lease component and non-lease components as an operating lease since the lease component is the predominant component of the combined components. Below is a summary of the primary changes in our accounting and reporting that resulted from our adoption of this guidance: • Property leases in which we are the lessor: ◦ Deferral of non-incremental leasing costs: For new or extended tenant leases, we no longer defer recognition of non-incremental leasing costs that we would have deferred under prior accounting guidance (refer to our 2018 Annual Report on Form 10-K in which we reported amounts deferred in 2018 , 2017 and 2016 ). ◦ Change in presentation of revenue: Due to our adoption of the practical expedient discussed above to not separate non-lease component revenue from the associated lease component, we are aggregating revenue from our lease components and non-lease components (comprised predominantly of tenant operating expense reimbursements) into the line entitled “lease revenue.” We are reporting other revenue from our properties in the line entitled “other property revenue.” We recast prior periods for these changes in presentation. ◦ Changes in assessment of lease revenue collectability: Changes in our assessment of lease revenue collectability that previously would have resulted in charges to bad debt expense under prior guidance are being recognized as an adjustment to rental revenue under the new guidance. Such amounts recognized by us in prior periods were not significant. ◦ Operating expenses paid directly by tenants to third parties: Operating expenses paid directly by tenants to third parties (primarily for real estate taxes) and revenue associated with such tenant payments that would have been recognized under prior guidance will no longer be reported on our Statement of Operations. Such amounts recognized by us in prior periods were not significant. • Leases (the most significant of which are ground leases) in which we are the lessee: ◦ Balance sheet presentation of property operating lease right-of-use assets: Upon adoption on January 1, 2019, we recognized property right-of-use assets and offsetting lease liabilities for existing operating leases totaling $16 million for the present value of minimum lease payments under these leases, and also reclassified an additional $11 million in amounts previously presented elsewhere on our balance sheet in connection with these leases to the right-of-use assets. We will recognize additional right-of-use assets and lease liabilities as we enter into new operating leases. ◦ Balance sheet presentation of property finance lease right-of-use assets: Property right-of-use assets of finance leases that previously were presented as properties under prior guidance are being presented as property finance right-of-use assets under the new guidance. As a result, we reclassified $38 million in assets from properties to property finance right-of-use assets upon adoption on January 1, 2019. ◦ Segment assets: We changed our definition of segment assets used for our reportable segments to include property right-of-use assets associated with operating properties, net of related lease liabilities. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance will apply to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables, loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments). Under the new guidance, an entity will recognize its estimate of expected credit losses as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and to be presented at the net amount expected to be collected. The guidance is effective for us beginning January 1, 2020, with early adoption permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2018, the FASB issued guidance that modifies disclosure requirements for fair value measurements. This guidance is effective for us beginning January 1, 2020. Early adoption is permitted for this guidance, and entities are permitted to early adopt with respect to any removed or modified disclosures while delaying adoption of additional disclosure requirements until the effective date. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. In August 2018, the FASB issued guidance that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. FASB guidance did not previously address the accounting for such implementation costs. The guidance is effective for us beginning January 1, 2020, with early adoption permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of fair value assets and liabilities measured on recurring basis	The table below sets forth financial assets and liabilities of COPT and subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other (Level 2) Significant Inputs (Level 3) Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,212 $ — $ — $ 4,212 Other 25 — — 25 Interest rate derivatives (1) — 120 — 120 Total assets $ 4,237 $ 120 $ — $ 4,357 Liabilities: Deferred compensation plan liability (2) $ — $ 4,237 $ — $ 4,237 Interest rate derivatives — 23,547 — 23,547 Total liabilities $ — $ 27,784 $ — $ 27,784 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPT’s consolidated balance sheet. (2) Included in the line entitled “other liabilities” on COPT’s consolidated balance sheet. The table below sets forth financial assets and liabilities of COPLP and subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other Significant Inputs (Level 3) Total Assets: Interest rate derivatives (1) $ — $ 120 $ — $ 120 Liabilities: Interest rate derivatives $ — $ 23,547 $ — $ 23,547 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPLP’s consolidated balance sheet.

Properties, Net (Tables)

Properties, Net (Tables)	6 Months Ended
	Jun. 30, 2019
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): June 30, December 31, Land $ 460,138 $ 503,274 Buildings and improvements 3,208,558 3,241,894 Less: Accumulated depreciation (949,111 ) (897,903 ) Operating properties, net $ 2,719,585 $ 2,847,265
Schedule of projects in development or held for future development	Properties we had in development or held for future development consisted of the following (in thousands): June 30, December 31, Land $ 296,809 $ 207,760 Development in progress, excluding land 177,978 195,601 Projects in development or held for future development $ 474,787 $ 403,361
Components of assets held for sale	(in thousands): Properties, net $ 53,386 Deferred rent receivable 1,028 Deferred leasing costs, net 34 Assets held for sale, net $ 54,448

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Operating Lease Revenue Recognized	The table below sets forth our allocation of lease revenue recognized between fixed contractual payments and variable lease payments (in thousands): Lease revenue For the Three Months Ended June 30, 2019 For the Six Months Ended June 30, 2019 Fixed contractual payments $ 104,768 $ 210,103 Variable lease payments 26,647 52,215 $ 131,415 $ 262,318
Fixed Contractual Payments Due	Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, June 30, 2019 December 31, 2018 2019 (1) $ 201,662 $ 400,617 2020 356,626 337,646 2021 299,046 280,369 2022 262,281 246,329 2023 211,966 194,888 Thereafter 586,076 523,932 $ 1,917,657 $ 1,983,781 (1) As of June 30, 2019 , represents the six months ending December 31, 2019
Right-of-Use Assets and Lease Liabilities	Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location June 30, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,434 Finance leases Property Property - finance right-of-use assets 40,476 Vehicles and office equipment Prepaid expenses and other assets, net 1,272 Total finance lease right-of-use assets 41,748 Total right-of-use assets $ 69,182 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location June 30, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 16,640 Finance leases Other liabilities 1,228 Total lease liabilities $ 17,868
Lease Costs	The table below sets forth the weighted average terms and discount rates of our leases as of June 30, 2019 : Weighted average remaining lease term Operating leases 69 years Finance leases 2 years Weighted average discount rate Operating leases 7.35 % Finance leases 3.12 % The table below presents our total lease cost (in thousands): Lease cost Statement of Operations Location For the Three Months Ended June 30, 2019 For the Six Months Ended June 30, 2019 Operating lease cost Property leases Property operating expenses $ 413 $ 826 Vehicles and office equipment General, administrative and leasing expenses 18 35 Finance lease cost Amortization of vehicles and office equipment right-of-use assets General, administrative and leasing expenses 116 229 Amortization of property right-of-use assets Property operating expenses 12 12 Interest on lease liabilities Interest expense 3 7 $ 562 $ 1,109 The table below presents the effect of lease payments on our consolidated statement of cash flows (in thousands): Supplemental cash flow information For the Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 550 Operating cash flows for financing leases $ 7 Financing cash flows for financing leases $ 110
Maturity of Lease Liabilities	Payments on leases as of June 30, 2019 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 (1) $ 554 $ 118 $ 672 2020 1,126 862 1,988 2021 1,111 202 1,313 2022 1,129 64 1,193 2023 1,134 — 1,134 Thereafter 99,187 — 99,187 Total lease payments 104,241 1,246 105,487 Less: Amount representing interest (87,601 ) (18 ) (87,619 ) Lease liability $ 16,640 $ 1,228 $ 17,868 (1) Represents the six months ending December 31, 2019 . Future minimum rental payments on leases as of December 31, 2018 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 $ 1,101 $ 219 $ 1,320 2020 1,110 844 1,954 2021 1,094 184 1,278 2022 1,115 49 1,164 2023 1,119 — 1,119 Thereafter 83,373 — 83,373 Total lease payments $ 88,912 1,296 90,208 Less: Amount representing interest N/A (24 ) (24 ) Total N/A $ 1,272 $ 90,184

Real Estate Joint Ventures (Tab

Real Estate Joint Ventures (Tables)	6 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of information related to investments in consolidated real estate joint ventures	The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of June 30, 2019 (dollars in thousands): Nominal Ownership % June 30, 2019 (1) Date Acquired Total Assets Encumbered Assets Total Liabilities Entity Location LW Redstone Company, LLC 3/23/2010 85% Huntsville, Alabama $ 198,389 $ 74,977 $ 69,841 M Square Associates, LLC 6/26/2007 50% College Park, Maryland 80,912 46,159 44,295 Stevens Investors, LLC 8/11/2015 95% Washington, DC 99,436 98,979 30,718 $ 378,737 $ 220,115 $ 144,854 (1) Excludes amounts eliminated in consolidation.
Schedule of information related to investments in unconsolidated real estate joint ventures	The table below sets forth information pertaining to our investments in unconsolidated real estate joint ventures accounted for using the equity method of accounting (dollars in thousands): Date Acquired Nominal Ownership % Number of Properties Carrying Value of Investment (1) Entity June 30, 2019 December 31, 2018 GI-COPT DC Partnership LLC 7/21/2016 50% 6 $ 38,790 $ 39,845 BREIT COPT DC JV LLC 6/20/2019 10% 7 26,546 — 13 $ 65,336 $ 39,845 (1) Included in the line entitled “investment in unconsolidated real estate joint ventures” on our consolidated balance sheets.

Investing Receivables (Tables)

Investing Receivables (Tables)	6 Months Ended
	Jun. 30, 2019
Receivables [Abstract]
Schedule of investing receivables	Investing receivables, including accrued interest thereon, consisted of the following (in thousands): June 30, December 31, Notes receivable from the City of Huntsville $ 56,563 $ 53,961 Other investing loans receivable 14,093 3,021 $ 70,656 $ 56,982

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets, Net (Tables)	6 Months Ended
	Jun. 30, 2019
Prepaid Expense and Other Assets [Abstract]
Schedule of prepaid expenses and other assets	Prepaid expenses and other assets, net consisted of the following (in thousands): June 30, December 31, Lease incentives, net $ 23,487 $ 21,258 Construction contract costs incurred in excess of billings 12,629 3,189 Furniture, fixtures and equipment, net (1) 8,252 8,630 Non-real estate equity investments 6,023 5,940 Prepaid expenses 5,855 25,658 Restricted cash 4,452 3,884 Deferred financing costs, net (2) 4,190 4,733 Deferred tax asset, net (3) 2,164 2,084 Interest rate derivatives 120 5,617 Other assets 4,771 6,337 Total for COPLP and subsidiaries 71,943 87,330 Marketable securities in deferred compensation plan 4,237 3,868 Total for COPT and subsidiaries $ 76,180 $ 91,198 (1) Includes $1.3 million in finance right-of-use assets as of June 30, 2019 . (2) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (3) Includes a valuation allowance of $2.1 million as of June 30, 2019 and $2.7 million as of December 31, 2018 .

Debt, Net (Tables)

Debt, Net (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of debt	Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of June 30, December 31, June 30, 2019 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 145,285 $ 147,141 3.82% - 7.87% (3) 2019-2026 Variable rate secured debt (4) 34,514 23,282 LIBOR + 1.85% to 2.35% (5) 2020-2022 Total mortgage and other secured debt 179,799 170,423 Revolving Credit Facility 163,000 213,000 LIBOR + 0.775% to 1.45% (6) March 2023 (7) Term Loan Facility (8) 248,490 248,273 LIBOR + 0.85% to 1.65% (9) 2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 348,207 347,986 3.60% (10) May 2023 5.250%, $250,000 aggregate principal 247,391 247,136 5.25% (11) February 2024 3.700%, $300,000 aggregate principal 299,068 298,815 3.70% (12) June 2021 5.000%, $300,000 aggregate principal 297,304 297,109 5.00% (13) July 2025 Unsecured note payable 1,103 1,167 0% (14) May 2026 Total debt, net $ 1,784,362 $ 1,823,909 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.3 million as of June 30, 2019 and $7.2 million as of December 31, 2018 . (2) Certain of the fixed rate mortgages carry interest rates that, upon assumption, were above or below market rates and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $248,000 as of June 30, 2019 and $281,000 as of December 31, 2018 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.17% as of June 30, 2019 . (4) Includes a construction loan with $87.4 million in remaining borrowing capacity as of June 30, 2019 . (5) The weighted average interest rate on our variable rate secured debt was 4.66% as of June 30, 2019 . (6) The weighted average interest rate on the Revolving Credit Facility was 3.52% as of June 30, 2019 . (7) The facility matures in March 2023, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee of 0.075% of the total availability under the facility for each extension period. (8) As of June 30, 2019 , we have the ability to borrow an additional $150.0 million in the aggregate under this facility, provided that there is no default under the facility and subject to the approval of the lenders. In addition, in connection with our Revolving Credit Facility, we have the ability to borrow up to $500.0 million under new term loans from the facility’s lender group provided that there is no default under the facility and subject to the approval of the lenders. (9) The interest rate on this loan was 3.69% as of June 30, 2019 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.2 million as of June 30, 2019 and $1.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (11) The carrying value of these notes reflects an unamortized discount totaling $2.4 million as of June 30, 2019 and $2.6 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (12) The carrying value of these notes reflects an unamortized discount totaling $741,000 as of June 30, 2019 and $943,000 as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (13) The carrying value of these notes reflects an unamortized discount totaling $2.3 million as of June 30, 2019 and $2.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (14) This note carries an interest rate that, upon assumption, was below market rates and it therefore was recorded at its fair value based on applicable effective interest rates. The carrying value of this note reflects an unamortized discount totaling $258,000 as of June 30, 2019 and $294,000 as of December 31, 2018 .
Schedule of the fair value of debt	The following table sets forth information pertaining to the fair value of our debt (in thousands): June 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,191,970 $ 1,226,750 $ 1,191,046 $ 1,219,603 Other fixed-rate debt 146,388 148,395 148,308 147,106 Variable-rate debt 446,004 450,417 484,555 486,497 $ 1,784,362 $ 1,825,562 $ 1,823,909 $ 1,853,206

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of key terms and fair values of interest rate swap derivatives	The following table sets forth the key terms and fair values of our interest rate swap derivatives, each of which was designated as a cash flow hedge of interest rate risk (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date June 30, December 31, $ 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 $ 58 $ 472 12,637 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 62 239 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (975 ) 1,968 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (985 ) 1,967 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (499 ) 971 75,000 3.1760% Three-Month LIBOR 6/30/2020 6/30/2030 (7,965 ) (2,676 ) 75,000 3.1920% Three-Month LIBOR 6/30/2020 6/30/2030 (8,074 ) (2,783 ) 75,000 2.7440% Three-Month LIBOR 6/30/2020 6/30/2030 (5,049 ) — $ (23,427 ) $ 158 (1) The notional amount of this instrument is scheduled to amortize to $12.1 million .
Schedule of fair value and balance sheet classification of interest rate derivatives	The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location June 30, December 31, 2018 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets, net $ 120 $ 5,617 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (23,547 ) $ (5,459 )
Schedule of effect of interest rate derivatives on consolidated statements of operations and comprehensive income	The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): Amount of (Loss) Gain Recognized in AOCL on Derivatives Amount of Gain (Loss) Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended June 30, For the Six Months Ended June 30, For the Three Months Ended June 30, For the Six Months Ended June 30, Derivatives in Hedging Relationships 2019 2018 2019 2018 2019 2018 2019 2018 Interest rate derivatives $ (13,545 ) $ 1,912 $ (22,390 ) $ 6,588 $ 557 $ 47 $ 1,127 $ (198 )

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interests (Tables)	6 Months Ended
	Jun. 30, 2019
Noncontrolling Interest [Abstract]
Schedule of activity for redeemable noncontrolling interest	The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 26,260 $ 23,125 Contributions from noncontrolling interests — 143 Distributions to noncontrolling interests (876 ) (711 ) Net income attributable to noncontrolling interests 1,544 1,229 Adjustment to arrive at fair value of interests 2,875 758 Ending balance $ 29,803 $ 24,544

Information by Business Segme_2

Information by Business Segment (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Schedule of segment financial information for real estate operations	The table below reports segment financial information for our reportable segments (in thousands): Operating Property Segments Defense/Information Technology Locations Fort Meade/BW Corridor Northern Virginia Defense/IT Lackland Air Force Base Navy Support Locations Redstone Arsenal Data Center Shells Total Defense/IT Locations Regional Office Wholesale Other Total Three Months Ended June 30, 2019 Revenues from real estate operations $ 61,659 $ 13,912 $ 12,104 $ 8,185 $ 3,968 $ 8,624 $ 108,452 $ 15,018 $ 8,560 $ 741 $ 132,771 Property operating expenses (19,344 ) (4,694 ) (6,648 ) (3,286 ) (1,599 ) (759 ) (36,330 ) (7,590 ) (3,618 ) (348 ) (47,886 ) UJV NOI allocable to COPT — — — — — 1,251 1,251 — — — 1,251 NOI from real estate operations $ 42,315 $ 9,218 $ 5,456 $ 4,899 $ 2,369 $ 9,116 $ 73,373 $ 7,428 $ 4,942 $ 393 $ 86,136 Additions to long-lived assets $ 7,499 $ 1,703 $ — $ 928 $ 536 $ — $ 10,666 $ 4,870 $ 95 $ 34 $ 15,665 Transfers from non-operating properties $ 1,338 $ 20 $ 1,833 $ — $ 5,576 $ 92,844 $ 101,611 $ — $ — $ — $ 101,611 Three Months Ended June 30, 2018 Revenues from real estate operations $ 61,993 $ 13,118 $ 12,382 $ 8,127 $ 3,652 $ 5,955 $ 105,227 $ 15,296 $ 8,105 $ 534 $ 129,162 Property operating expenses (20,099 ) (4,909 ) (7,494 ) (3,431 ) (1,509 ) (799 ) (38,241 ) (7,169 ) (4,150 ) 114 (49,446 ) UJV NOI allocable to COPT — — — — — 1,202 1,202 — — — 1,202 NOI from real estate operations $ 41,894 $ 8,209 $ 4,888 $ 4,696 $ 2,143 $ 6,358 $ 68,188 $ 8,127 $ 3,955 $ 648 $ 80,918 Additions to long-lived assets $ 8,151 $ 1,186 $ — $ 1,450 $ 351 $ — $ 11,138 $ 5,361 $ 81 $ 188 $ 16,768 Transfers from non-operating properties $ 3,035 $ 352 $ — $ 3 $ 26 $ 29,675 $ 33,091 $ — $ 1,133 $ — $ 34,224 Six Months Ended June 30, 2019 Revenues from real estate operations $ 124,342 $ 28,743 $ 23,665 $ 16,340 $ 7,907 $ 15,978 $ 216,975 $ 29,851 $ 16,431 $ 1,504 $ 264,761 Property operating expenses (41,679 ) (9,986 ) (12,607 ) (6,690 ) (3,138 ) (1,112 ) (75,212 ) (15,006 ) (6,456 ) (657 ) (97,331 ) UJV NOI allocable to COPT — — — — — 2,470 2,470 — — — 2,470 NOI from real estate operations $ 82,663 $ 18,757 $ 11,058 $ 9,650 $ 4,769 $ 17,336 $ 144,233 $ 14,845 $ 9,975 $ 847 $ 169,900 Additions to long-lived assets $ 11,434 $ 3,150 $ — $ 5,945 $ 836 $ — $ 21,365 $ 8,859 $ 251 $ 44 $ 30,519 Transfers from non-operating properties $ 6,378 $ 4,529 $ 8,336 $ — $ 9,211 $ 112,632 $ 141,086 $ — $ — $ — $ 141,086 Segment assets at June 30, 2019 $ 1,274,336 $ 398,586 $ 146,475 $ 187,172 $ 115,222 $ 307,676 $ 2,429,467 $ 393,110 $ 209,787 $ 3,776 $ 3,036,140 Six Months Ended June 30, 2018 Revenues from real estate operations $ 124,775 $ 25,679 $ 23,825 $ 15,997 $ 7,285 $ 11,786 $ 209,347 $ 30,580 $ 16,182 $ 1,331 $ 257,440 Property operating expenses (41,703 ) (9,632 ) (14,092 ) (6,735 ) (2,949 ) (1,593 ) (76,704 ) (15,047 ) (8,408 ) (238 ) (100,397 ) UJV NOI allocable to COPT — — — — — 2,401 2,401 — — — 2,401 NOI from real estate operations $ 83,072 $ 16,047 $ 9,733 $ 9,262 $ 4,336 $ 12,594 $ 135,044 $ 15,533 $ 7,774 $ 1,093 $ 159,444 Additions to long-lived assets $ 15,272 $ 3,126 $ — $ 2,558 $ 430 $ — $ 21,386 $ 9,245 $ 117 $ 315 $ 31,063 Transfers from non-operating properties $ 20,221 $ 693 $ — $ — $ 470 $ 30,789 $ 52,173 $ — $ 2,145 $ — $ 54,318 Segment assets at June 30, 2018 $ 1,269,525 $ 396,139 $ 126,956 $ 190,537 $ 106,374 $ 330,622 $ 2,420,153 $ 396,847 $ 221,239 $ 4,213 $ 3,042,452
Schedule of reconciliation of segment revenues to total revenues	The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Segment revenues from real estate operations $ 132,771 $ 129,162 $ 264,761 $ 257,440 Construction contract and other service revenues 42,299 17,581 59,249 44,779 Total revenues $ 175,070 $ 146,743 $ 324,010 $ 302,219
Reconciliation of UJV NOI allocable to COPT to equity in income of unconsolidated entities	The following table reconciles UJV NOI allocable to COPT to equity in income of unconsolidated entities as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 UJV NOI allocable to COPT $ 1,251 $ 1,202 $ 2,470 $ 2,401 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (830 ) (828 ) (1,657 ) (1,652 ) Add: Equity in loss of unconsolidated non-real estate entities (1 ) (1 ) (2 ) (3 ) Equity in income of unconsolidated entities $ 420 $ 373 $ 811 $ 746
Schedule of computation of net operating income from service operations	The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Construction contract and other service revenues $ 42,299 $ 17,581 $ 59,249 $ 44,779 Construction contract and other service expenses (41,002 ) (16,941 ) (57,328 ) (43,157 ) NOI from service operations $ 1,297 $ 640 $ 1,921 $ 1,622
Schedule of reconciliation of net operating income from real estate operations and service operations to net income	The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to net income as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 NOI from real estate operations $ 86,136 $ 80,918 $ 169,900 $ 159,444 NOI from service operations 1,297 640 1,921 1,622 Interest and other income 1,849 1,439 4,135 2,798 Gain on sales of real estate 84,469 (23 ) 84,469 (27 ) Equity in income of unconsolidated entities 420 373 811 746 Income tax benefit (expense) 176 (63 ) (18 ) (118 ) Depreciation and other amortization associated with real estate operations (34,802 ) (33,190 ) (69,598 ) (66,702 ) General, administrative and leasing expenses (9,386 ) (7,628 ) (18,137 ) (14,920 ) Business development expenses and land carry costs (870 ) (1,234 ) (1,983 ) (2,848 ) Interest expense (18,475 ) (18,945 ) (37,149 ) (37,729 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,251 ) (1,202 ) (2,470 ) (2,401 ) Net income $ 109,563 $ 21,085 $ 131,881 $ 39,865
Schedule of reconciliation of segment assets to total assets	The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): June 30, June 30, Segment assets $ 3,036,140 $ 3,042,452 Operating properties lease liabilities included in segment assets 16,502 — Non-operating property assets 523,801 431,661 Other assets 227,026 138,249 Total COPT consolidated assets $ 3,803,469 $ 3,612,362

Construction Contract and Oth_2

Construction Contract and Other Service Revenues (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The table below reports construction contract and other service revenues by compensation arrangement (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Construction contract revenues: Guaranteed maximum price $ 25,792 $ 9,539 $ 38,148 $ 30,025 Firm fixed price 1,335 6,288 3,660 12,723 Cost-plus fee 14,969 1,496 17,029 1,554 Other 203 258 412 477 $ 42,299 $ 17,581 $ 59,249 $ 44,779 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Construction contract revenues: Construction $ 42,010 $ 16,668 $ 58,499 $ 42,583 Design 86 655 338 1,719 Other 203 258 412 477 $ 42,299 $ 17,581 $ 59,249 $ 44,779
Schedule of Accounts Receivable	The beginning and ending balances of accounts receivable related to our construction contracts were as follows (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 6,701 $ 4,577 Ending balance $ 34,837 $ 4,805
Contract with Customer, Asset and Liability	Changes in contract liabilities were as follows (in thousands): For the Six Months Ended June 30, 2019 2018 Beginning balance $ 568 $ 27,402 Ending balance $ 156 $ 515 Portion of beginning balance recognized in revenue during: Three months ended June 30 $ 6 $ 7,999 Six months ended June 30 $ 445 $ 27,296 For the Six Months Ended June 30, 2019 2018 Beginning balance $ 3,189 $ 4,884 Ending balance $ 12,629 $ 4,158

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of payouts for defined performance under performance-based awards of share-based compensation	The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT’s total shareholder return relative to a peer group of companies, as set forth in the following schedule: Percentile Rank Earned Awards Payout % 75th or greater 100% of PB-PIUs granted 50th (target) 50% of PB-PIUs granted 25th 25% of PB-PIUs granted Below 25th 0% of PB-PIUs granted

Earnings Per Share ("EPS") an_2

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPT $ 106,791 $ 19,434 $ 127,650 $ 36,584 Income attributable to share-based compensation awards (364 ) (117 ) (413 ) (234 ) Numerator for basic EPS on net income attributable to COPT common shareholders 106,427 19,317 127,237 36,350 Preferred unit distributions 165 — — — Redeemable noncontrolling interests 902 — 66 — Common units in the Operating Partnership — — 1,515 — Income attributable to share-based compensation awards 18 — 22 — Numerator for diluted EPS on net income attributable to COPT common shareholders $ 107,512 $ 19,317 $ 128,840 $ 36,350 Denominator (all weighted averages): Denominator for basic EPS (common shares) 111,557 101,789 110,759 101,397 Dilutive convertible preferred units 176 — — — Dilutive effect of common units — — 1,329 — Dilutive effect of share-based compensation awards 310 119 289 131 Dilutive effect of redeemable noncontrolling interests 1,062 — 130 — Denominator for diluted EPS (common shares) 113,105 101,908 112,507 101,528 Basic EPS $ 0.95 $ 0.19 $ 1.15 $ 0.36 Diluted EPS $ 0.95 $ 0.19 $ 1.15 $ 0.36
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Conversion of common units 1,327 3,197 — 3,208 Conversion of redeemable noncontrolling interests — — 907 — Conversion of Series I preferred units — 176 176 176
Corporate Office Properties, L.P.
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPLP $ 108,295 $ 20,207 $ 129,576 $ 38,066 Preferred unit distributions (165 ) (165 ) (330 ) (330 ) Income attributable to share-based compensation awards (438 ) (117 ) (494 ) (234 ) Numerator for basic EPU on net income attributable to COPLP common unitholders 107,692 19,925 128,752 37,502 Redeemable noncontrolling interests 902 — 66 — Income attributable to share-based compensation awards 18 — 22 — Dilutive effective of preferred units 165 — — — Numerator for diluted EPU on net income attributable to COPLP common unitholders $ 108,777 $ 19,925 $ 128,840 $ 37,502 Denominator (all weighted averages): Denominator for basic EPU (common units) 112,884 104,986 112,088 104,605 Dilutive convertible preferred units 176 — — — Dilutive effect of redeemable noncontrolling interests 1,062 — 130 — Dilutive effect of share-based compensation awards 310 119 289 131 Denominator for diluted EPU (common units) 114,432 105,105 112,507 104,736 Basic EPU $ 0.95 $ 0.19 $ 1.15 $ 0.36 Diluted EPU $ 0.95 $ 0.19 $ 1.15 $ 0.36
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2019 2018 2019 2018 Conversion of redeemable noncontrolling interests — — 907 — Conversion of Series I preferred units — 176 176 176

Organization (Details)

Organization (Details) - Jun. 30, 2019 ft² in Millions	ft²	property	MW	a
Unconsolidated Real Estate Joint Ventures
Investments in real estate
Number of real estate properties		13
Operating Properties
Investments in real estate
Number of real estate properties		169
Area of real estate property (in sq ft or acres) | ft²	18.9
Operating Properties | Office Properties
Investments in real estate
Number of real estate properties		147
Area of real estate property (in sq ft or acres) | ft²	15.3
Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties		22
Area of real estate property (in sq ft or acres) | ft²	3.7
Operating Properties | Single-tenant data centers | Unconsolidated Real Estate Joint Ventures
Investments in real estate
Number of real estate properties		13
Operating wholesale data center
Investments in real estate
Critical load (in megawatts) | MW			19.25
Properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties		14
Area of real estate property (in sq ft or acres) | ft²	2.2
Properties under, or contractually committed for, construction or approved for redevelopment | Office Properties
Investments in real estate
Number of real estate properties		9
Properties under, or contractually committed for, construction or approved for redevelopment | Single-tenant data centers
Investments in real estate
Number of real estate properties		5
Properties under, or contractually committed for, construction or approved for redevelopment | Partially operational properties
Investments in real estate
Number of real estate properties		3
Land controlled for future development
Investments in real estate
Area of real estate property (in sq ft or acres)	11.6			900
Other Land
Investments in real estate
Area of real estate property (in sq ft or acres) | a				150

Organization (Details 2)

Organization (Details 2)	6 Months Ended
	Jun. 30, 2019
Corporate Office Properties, L.P. | Common Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	98.60%

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - Accounting Standards Update 2016-02 $ in Millions	Jan. 01, 2019USD ($)
Operating Lease, Right-of-use Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of new accounting principle	$ 11
Operating Lease, Right-of-use Assets | Properties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of new accounting principle	16
Operating Lease Liability | Properties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of new accounting principle	16
Finance Lease, Right-of Use Assets | Properties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of new accounting principle	38
Total Properties, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of new accounting principle	$ (38)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Assets and liabilities measured at fair value on a recurring basis
Marketable securities in deferred compensation plan	$ 4,237	$ 3,868
Fair value measurement on a recurring basis | Deferred compensation plan | Trustees and Management
Assets and liabilities measured at fair value on a recurring basis
Maximum percentage of participants' compensation which is deferrable (as a percent)	100.00%
Marketable securities in deferred compensation plan	$ 4,200

Fair Value Measurements (Deta_2

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets:
Marketable securities in deferred compensation plan	$ 4,237	$ 3,868
Fair value measurement on a recurring basis
Assets:
Interest rate derivatives	120
Total assets	4,357
Liabilities:
Deferred compensation plan liability	4,237
Interest rate derivatives	23,547
Total liabilities	27,784
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,212
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	25
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate derivatives	0
Total assets	4,237
Liabilities:
Deferred compensation plan liability	0
Interest rate derivatives	0
Total liabilities	0
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,212
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Assets:
Marketable securities in deferred compensation plan	25
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	120
Total assets	120
Liabilities:
Deferred compensation plan liability	4,237
Interest rate derivatives	23,547
Total liabilities	27,784
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2) | Other
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate derivatives	0
Total assets	0
Liabilities:
Deferred compensation plan liability	0
Interest rate derivatives	0
Total liabilities	0
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3) | Other
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Assets:
Interest rate derivatives	120
Liabilities:
Interest rate derivatives	23,547
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate derivatives	0
Liabilities:
Interest rate derivatives	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	120
Liabilities:
Interest rate derivatives	23,547
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate derivatives	0
Liabilities:
Interest rate derivatives	$ 0

Properties, Net (Details)

Properties, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investments in real estate
Operating properties, net	$ 2,719,585	$ 2,847,265
Operating Properties, net
Investments in real estate
Less: accumulated depreciation	(949,111)	(897,903)
Operating properties, net	2,719,585	2,847,265
Operating Properties, net | Land
Investments in real estate
Gross	460,138	503,274
Operating Properties, net | Buildings and improvements
Investments in real estate
Gross	$ 3,208,558	$ 3,241,894

Properties, Net (Details 2)

Properties, Net (Details 2) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Properties
Projects in development or held for future development	$ 474,787	$ 403,361
Projects in development or held for future development
Properties
Projects in development or held for future development	474,787	403,361
Projects in development or held for future development | Land
Properties
Projects in development or held for future development	296,809	207,760
Projects in development or held for future development | Development in progress, excluding land
Properties
Projects in development or held for future development	$ 177,978	$ 195,601

Properties, Net (Details 3)

Properties, Net (Details 3) $ in Thousands	Jun. 30, 2019USD ($)property	Dec. 31, 2018USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, net	$ 54,448	$ 0
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties, net	53,386
Deferred rent receivable	1,028
Deferred leasing costs, net	34
Assets held for sale, net	$ 54,448
Held-for-sale | Single-tenant data centers | Data Center Shells
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties | property	2

Properties, Net (Details 4)

Properties, Net (Details 4) - Disposed of by sale - Single-tenant data centers $ in Millions	Jun. 20, 2019USD ($)property
Investments in real estate
Ownership percentage sold	90.00%
Proceeds from Divestiture of Businesses	$ 238.5
Data Center Shells
Investments in real estate
Ownership percentage sold	90.00%
Number of real estate properties | property	7
Consideration received from sale of ownership interest	$ 265
Gain on sale of ownership interest	$ 84.5

Properties, Net (Details 5)

Properties, Net (Details 5) ft² in Thousands	Jun. 30, 2019ft²property
Newly constructed properties placed in service
Construction Activities
Square footage of real estate properties (in square feet) | ft²	777
Number of real estate properties	7
Newly constructed properties partially operational
Construction Activities
Number of real estate properties	2
Redeveloped Property Placed in Service, Partially-Operational [Member]
Construction Activities
Square footage of real estate properties (in square feet) | ft²	10
Number of real estate properties	1
Properties under construction or contractually committed for construction
Construction Activities
Square footage of real estate properties (in square feet) | ft²	2,100
Number of real estate properties	13
Properties under construction or contractually committed, partially operational property
Construction Activities
Number of real estate properties	2
Properties under or approved for redevelopment partially-operational
Construction Activities
Square footage of real estate properties (in square feet) | ft²	106
Number of real estate properties	1

Leases (Details)

Leases (Details)	6 Months Ended
	Jun. 30, 2019
Lessor, Lease, Description [Line Items]
Average term of contract	5 years
Minimum
Lessor, Lease, Description [Line Items]
Term of contract	1 month
Maximum
Lessor, Lease, Description [Line Items]
Term of contract	15 years
United States Government
Lessor, Lease, Description [Line Items]
Renewal term	1 year

Leases (Details 1)

Leases (Details 1) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Fixed contractual payments	$ 104,768	$ 210,103
Variable lease payments	26,647	52,215
Lease revenue	131,415	262,318
Lease Payments to be Received
2019	201,662	201,662
2019			$ 400,617
2020	356,626	356,626	337,646
2021	299,046	299,046	280,369
2022	262,281	262,281	246,329
2023	211,966	211,966	194,888
Thereafter	586,076	586,076	523,932
Operating Lease Payments to be Received	$ 1,917,657	$ 1,917,657	$ 1,983,781

Leases (Details 2)

Leases (Details 2) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)Lease
Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 67.9
Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	30 years
Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	97 years
Vehicles and Office Equipment
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 1.3
Washington, DC | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	80 years
Lessee right-of-use asset	$ 10.4
Number of contracts | Lease	2
Baltimore, Maryland | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	30 years
Lessee right-of-use asset	$ 6.5
Renewal term	48 years
Stevens Investors, LLC | Washington, DC | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	97 years
Lessee right-of-use asset	$ 37.8
M Square Associates, LLC | College Park, Maryland | Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 6.7
Number of contracts | Lease	4
M Square Associates, LLC | College Park, Maryland | Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	64 years
M Square Associates, LLC | College Park, Maryland | Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	75 years
LW Redstone Company, LLC | Huntsville, Alabama | Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 4.2
Renewal term	25 years
Number of contracts | Lease	9
LW Redstone Company, LLC | Huntsville, Alabama | Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	44 years
LW Redstone Company, LLC | Huntsville, Alabama | Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	50 years
Fort Meade/BW Corridor | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	49 years
Lessee right-of-use asset	$ 2.3
Number of contracts | Lease	2

Leases (Details 3)

Leases (Details 3) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Finance right-of-use assets	$ 41,748
Total right-of-use assets	69,182
Property - operating lease liabilities	16,640
Property - finance lease liabilities	1,228
Total lease liabilities	17,868	$ 90,184
Properties
Lessee, Lease, Description [Line Items]
Property - operating right-of-use assets	27,434	0
Finance right-of-use assets	40,476	0
Property - operating lease liabilities	16,640	$ 0
Property - operating right-of-use assets | Properties
Lessee, Lease, Description [Line Items]
Property - operating right-of-use assets	27,434
Property - finance right-of-use assets | Properties
Lessee, Lease, Description [Line Items]
Finance right-of-use assets	40,476
Prepaid expenses and other assets, net | Vehicles and Office Equipment
Lessee, Lease, Description [Line Items]
Finance right-of-use assets	$ 1,272

Leases (Details 4)

Leases (Details 4)	Jun. 30, 2019
Leases [Abstract]
Operating leases, Weighted average remaining lease term	69 years
Finance leases, Weighted average remaining lease term	2 years
Operating lease, Weighted average discount rate	7.35%
Finance lease, Weighted average discount rate	3.12%

Leases (Details 5)

Leases (Details 5) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Lease costs	$ 562	$ 1,109
Property Operating Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	413	826
Finance lease right-of use amortization	12	12
General, Administrative and Leasing Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	18	35
Finance lease right-of use amortization	116	229
Interest Expense
Lessee, Lease, Description [Line Items]
Interest on lease liabilities	$ 3	$ 7

Leases (Details 6)

Leases (Details 6) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Leases [Abstract]
Operating cash flows for operating leases	$ 550
Operating cash flows for financing leases	7
Financing cash flows for financing leases	$ 110	$ 15,379

Leases (Details 7)

Leases (Details 7) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Operating leases
2019	$ 554
2019		$ 1,101
2020	1,126
2020		1,110
2021		1,094
2021	1,111
2022		1,115
2022	1,129
2023	1,134
2023		1,119
Thereafter		83,373
Thereafter	99,187
Total lease payments	104,241
Total lease payments		88,912
Less: Amount representing interest	(87,601)
Lease liability	16,640
Finance leases
2019	118
2019		219
2020	862
2020		844
2021	202
2021		184
2022	64
2022		49
2023		0
2023	0
Thereafter	0
Thereafter		0
Total lease payments		1,296
Total lease payments	1,246
Less: Amount representing interest	(18)
Less: Amount representing interest		(24)
Lease liability	1,228
Lease liability		1,272
Total
2019	672
2019		1,320
2020	1,988	1,954
2021	1,313	1,278
2022	1,193	1,164
2023	1,134	1,119
Thereafter	99,187	83,373
Total lease payments	105,487	90,208
Less: Amount representing interest	(87,619)	(24)
Total lease liabilities	$ 17,868	$ 90,184

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 20, 2019property
Consolidated real estate joint ventures
Investments in consolidated real estate joint ventures
Total Assets	$ 378,737
Encumbered Assets	220,115
Total Liabilities	$ 144,854
Variable Interest Entity, Primary Beneficiary | LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	85.00%
Total Assets	$ 198,389
Encumbered Assets	74,977
Total Liabilities	$ 69,841
Variable Interest Entity, Primary Beneficiary | M Square Associates, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	50.00%
Total Assets	$ 80,912
Encumbered Assets	46,159
Total Liabilities	$ 44,295
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	95.00%
Total Assets	$ 99,436
Encumbered Assets	98,979
Total Liabilities	$ 30,718
Operating Properties | Single-tenant data centers | Variable Interest Entity, Not Primary Beneficiary | BREIT COPT
Investments in consolidated real estate joint ventures
Ownership percentage (percent)		10.00%
Disposed of by sale | Single-tenant data centers
Investments in consolidated real estate joint ventures
Ownership percentage sold		90.00%
Disposed of by sale | Data Center Shells | Single-tenant data centers
Investments in consolidated real estate joint ventures
Ownership percentage sold		90.00%
Number of real estate properties | property		7

Real Estate Joint Ventures (D_2

Real Estate Joint Ventures (Details 2) $ in Thousands	Jun. 30, 2019USD ($)property	Dec. 31, 2018USD ($)
Unconsolidated Real Estate Joint Ventures
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property	13
Equity method investments | $	$ 65,336	$ 39,845
GI-COPT DC Partnership LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage (percent)	50.00%
Number of real estate properties | property	6
Equity method investments | $	$ 38,790	39,845
Variable Interest Entity, Not Primary Beneficiary | BREIT COPT DC JV LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage (percent)	10.00%
Number of real estate properties | property	7
Equity method investments | $	$ 26,546	$ 0

Investing Receivables (Details)

Investing Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 70,656	$ 56,982
Investing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of investing receivables	74,000	58,000
Notes Receivable from the City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 56,563	53,961
Notes Receivable from the City of Huntsville | LW Redstone Company, LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Stated interest rate (as a percent)	9.95%
Other investing loans receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 14,093	$ 3,021
Stated interest rate (as a percent)	8.00%

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Properties
Restricted cash	$ 4,452	$ 3,884	$ 4,105	$ 2,570
Marketable securities in deferred compensation plan	4,237	3,868
Total for COPT and subsidiaries	76,180	91,198
Finance right-of-use assets	41,748
Furniture, Fixtures and Equipment, Net
Properties
Finance right-of-use assets	1,300
Taxable REIT Subsidiary
Properties
Deferred tax assets, valuation allowance	2,100	2,700
Corporate Office Properties, L.P.
Properties
Lease incentives, net	23,487	21,258
Construction contract costs incurred in excess of billings	12,629	3,189
Furniture, fixtures and equipment, net	8,252	8,630
Non-real estate equity investments	6,023	5,940
Prepaid expenses	5,855	25,658
Restricted cash	4,452	3,884	$ 4,105	$ 2,570
Deferred financing costs, net	4,190	4,733
Deferred tax asset, net	2,164	2,084
Interest rate derivatives	120	5,617
Other assets	4,771	6,337
Total for COPT and subsidiaries	$ 71,943	$ 87,330

Debt, Net (Details)

Debt, Net (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)extension	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)extension	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Debt
Carrying Value	$ 1,784,362,000		$ 1,784,362,000		$ 1,823,909,000
Interest costs capitalized	2,400,000	$ 1,400,000	4,400,000	$ 2,800,000
Mortgage and other secured debt
Debt
Carrying Value	$ 179,799,000		$ 179,799,000		170,423,000
Line of Credit | Revolving Credit Facility
Debt
Number of extensions | extension	2		2
Extension option period (in years)			6 months
Line of credit facility, extension fee percentage			0.075%
Loans payable
Debt
Deferred financing costs, net	$ 6,300,000		$ 6,300,000		7,200,000
Fixed rate mortgage debt | Mortgage and other secured debt
Debt
Carrying Value	145,285,000		145,285,000		147,141,000
Unamortized premium included in carrying value	$ 248,000		$ 248,000		281,000
Weighted average interest rate (as a percent)	4.17%		4.17%
Fixed rate mortgage debt | Mortgage and other secured debt | Minimum
Debt
Interest rate (as a percent)	3.82%		3.82%
Fixed rate mortgage debt | Mortgage and other secured debt | Maximum
Debt
Interest rate (as a percent)	7.87%		7.87%
Variable-rate debt | Mortgage and other secured debt
Debt
Carrying Value	$ 34,514,000		$ 34,514,000		23,282,000
Weighted average interest rate (as a percent)	4.66%		4.66%
Variable-rate debt | Mortgage and other secured debt | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.85%
Variable-rate debt | Mortgage and other secured debt | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			2.35%
Construction Loan | Mortgage and other secured debt | London Interbank Offered Rate (LIBOR)
Debt
Remaining borrowing capacity	$ 87,400,000		$ 87,400,000
Revolving Credit Facility
Debt
Carrying Value	$ 163,000,000		$ 163,000,000		213,000,000
Weighted average interest rate (as a percent)	3.52%		3.52%
Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			0.775%
Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.45%
Term Loan Facility
Debt
Carrying Value	$ 248,490,000		$ 248,490,000		248,273,000
Interest rate (as a percent)	3.69%		3.69%
Aggregate additional borrowing capacity available	$ 150,000,000		$ 150,000,000
Maximum availability	500,000,000		$ 500,000,000
Term Loan Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			0.85%
Term Loan Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.65%
3.600% Senior Notes | Unsecured senior notes
Debt
Carrying Value	348,207,000		$ 348,207,000		347,986,000
Debt instrument, face amount	$ 350,000,000		$ 350,000,000
Interest rate (as a percent)	3.60%		3.60%
Unamortized discount included in carrying value	$ 1,200,000		$ 1,200,000		1,400,000
Effective interest rate on debt (as a percent)	3.70%		3.70%
5.250% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 247,391,000		$ 247,391,000		247,136,000
Debt instrument, face amount	$ 250,000,000		$ 250,000,000
Interest rate (as a percent)	5.25%		5.25%
Unamortized discount included in carrying value	$ 2,400,000		$ 2,400,000		2,600,000
Effective interest rate on debt (as a percent)	5.49%		5.49%
3.700% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 299,068,000		$ 299,068,000		298,815,000
Debt instrument, face amount	$ 300,000,000		$ 300,000,000
Interest rate (as a percent)	3.70%		3.70%
Unamortized discount included in carrying value	$ 741,000		$ 741,000		943,000
Effective interest rate on debt (as a percent)	3.85%		3.85%
5.000% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 297,304,000		$ 297,304,000		297,109,000
Debt instrument, face amount	$ 300,000,000		$ 300,000,000
Interest rate (as a percent)	5.00%		5.00%
Unamortized discount included in carrying value	$ 2,300,000		$ 2,300,000		2,400,000
Effective interest rate on debt (as a percent)	5.15%		5.15%
Unsecured notes payable
Debt
Carrying Value	$ 1,103,000		$ 1,103,000		1,167,000
Interest rate (as a percent)	0.00%		0.00%
Unamortized discount included in carrying value	$ 258,000		$ 258,000		$ 294,000

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Carrying Amount
Carrying amount and estimated fair value of debt
Long-term debt	$ 1,784,362	$ 1,823,909
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,191,970	1,191,046
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	146,388	148,308
Carrying Amount | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	446,004	484,555
Estimated Fair Value
Carrying amount and estimated fair value of debt
Long-term debt	1,825,562	1,853,206
Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,226,750	1,219,603
Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	148,395	147,106
Estimated Fair Value | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	$ 450,417	$ 486,497

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (Loss) Gain Recognized in AOCL on Derivatives	$ (13,545)	$ 1,912	$ (22,390)	$ 6,588
Interest rate swaps | Interest Expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of Gain (Loss) Reclassified from AOCL into Interest Expense on Statement of Operations	557	$ 47	1,127	$ (198)
Interest rate swaps | Prepaid expenses and other assets, net
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	120		120		$ 5,617
Interest rate swaps | Interest rate derivatives (liabilities)
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	(23,547)		(23,547)		(5,459)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(23,427)		(23,427)		158
Designated | Interest rate swaps
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Approximate amount to be reclassified from AOCL to interest expense over the next 12 months	1,600		1,600
Fair value of derivative liability	23,600		23,600
Settlement amount of derivative obligation at termination value	23,500		23,500
Designated | Interest rate swap, effective date September 1, 2015, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.73%		1.73%
Fair value of interest rate swaps	$ 58		$ 58		472
Designated | Interest rate swap, effective October 13, 2015
Fair values of interest rate swap derivatives
Notional Amount	$ 12,637		$ 12,637
Fixed rate (as a percent)	1.39%		1.39%
Fair value of interest rate swaps	$ 62		$ 62		239
Notional amount of interest rate derivatives after scheduled amortization	12,100		12,100
Designated | Interest rate swap, effective September 1, 2016, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.9013%		1.9013%
Fair value of interest rate swaps	$ (975)		$ (975)		1,968
Designated | Interest rate swap, effective September 1, 2016, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.905%		1.905%
Fair value of interest rate swaps	$ (985)		$ (985)		1,967
Designated | Interest rate swap, effective September 1, 2016, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 50,000		$ 50,000
Fixed rate (as a percent)	1.9079%		1.9079%
Fair value of interest rate swaps	$ (499)		$ (499)		971
Designated | Interest rate swap, effective June 30, 2020, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000		$ 75,000
Fixed rate (as a percent)	3.176%		3.176%
Fair value of interest rate swaps	$ (7,965)		$ (7,965)		(2,676)
Designated | Interest rate swap, effective June 30, 2020, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000		$ 75,000
Fixed rate (as a percent)	3.192%		3.192%
Fair value of interest rate swaps	$ (8,074)		$ (8,074)		(2,783)
Designated | Interest rate swap, effective June 30, 2020, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000		$ 75,000
Fixed rate (as a percent)	2.744%		2.744%
Fair value of interest rate swaps	$ (5,049)		$ (5,049)		$ 0

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interests (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)joint_venture	Jun. 30, 2018USD ($)
Noncontrolling Interest [Abstract]
Number of joint ventures with redeemable noncontrolling interests | joint_venture	2
Redeemable Noncontrolling Interest [Roll Forward]
Beginning balance	$ 26,260	$ 23,125
Contributions from noncontrolling interests	0	143
Distributions to noncontrolling interests	(876)	(711)
Net income attributable to noncontrolling interests	1,544	1,229
Adjustment to arrive at fair value of interests	2,875	758
Ending balance	$ 29,803	$ 24,544

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Class of Stock [Line Items]
Conversion of common units to common shares (in units/shares)			5,500	53,817
Dividends declared per share (in usd per share)	$ 0.275	$ 0.275	$ 0.55	$ 0.55
Common Shares | Forward Equity Sale Agreement
Class of Stock [Line Items]
Number of shares issued			1,600,000
Proceeds from common shares issued under forward equity sale agreements			$ 46.5
Common Shares | 2018 Common Stock Issued to Public Under At-the-Market Program
Class of Stock [Line Items]
Aggregate gross sales price	$ 300		$ 300
Corporate Office Properties, L.P.
Class of Stock [Line Items]
Dividends declared per share (in usd per share)	$ 0.275	$ 0.275	$ 0.55	$ 0.55

Information by Business Segme_3

Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment financial information for real estate operations
Revenues from real estate operations	$ 175,070	$ 146,743	$ 324,010	$ 302,219
Property operating expenses	(47,886)	(49,446)	(97,331)	(100,397)
UJV NOI allocable to COPT	1,251	1,202	2,470	2,401
Segment assets	3,803,469	3,612,362	3,803,469	3,612,362	$ 3,656,005
Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	132,771	129,162	264,761	257,440
Property operating expenses	(47,886)	(49,446)	(97,331)	(100,397)
UJV NOI allocable to COPT	1,251	1,202	2,470	2,401
NOI from real estate operations	86,136	80,918	169,900	159,444
Additions to long-lived assets	15,665	16,768	30,519	31,063
Transfers from non-operating properties	101,611	34,224	141,086	54,318
Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	108,452	105,227	216,975	209,347
Property operating expenses	(36,330)	(38,241)	(75,212)	(76,704)
UJV NOI allocable to COPT	1,251	1,202	2,470	2,401
NOI from real estate operations	73,373	68,188	144,233	135,044
Additions to long-lived assets	10,666	11,138	21,365	21,386
Transfers from non-operating properties	101,611	33,091	141,086	52,173
Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	61,659	61,993	124,342	124,775
Property operating expenses	(19,344)	(20,099)	(41,679)	(41,703)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	42,315	41,894	82,663	83,072
Additions to long-lived assets	7,499	8,151	11,434	15,272
Transfers from non-operating properties	1,338	3,035	6,378	20,221
Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	13,912	13,118	28,743	25,679
Property operating expenses	(4,694)	(4,909)	(9,986)	(9,632)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	9,218	8,209	18,757	16,047
Additions to long-lived assets	1,703	1,186	3,150	3,126
Transfers from non-operating properties	20	352	4,529	693
Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	12,104	12,382	23,665	23,825
Property operating expenses	(6,648)	(7,494)	(12,607)	(14,092)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	5,456	4,888	11,058	9,733
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	1,833	0	8,336	0
Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	8,185	8,127	16,340	15,997
Property operating expenses	(3,286)	(3,431)	(6,690)	(6,735)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	4,899	4,696	9,650	9,262
Additions to long-lived assets	928	1,450	5,945	2,558
Transfers from non-operating properties	0	3	0	0
Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	3,968	3,652	7,907	7,285
Property operating expenses	(1,599)	(1,509)	(3,138)	(2,949)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	2,369	2,143	4,769	4,336
Additions to long-lived assets	536	351	836	430
Transfers from non-operating properties	5,576	26	9,211	470
Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	8,624	5,955	15,978	11,786
Property operating expenses	(759)	(799)	(1,112)	(1,593)
UJV NOI allocable to COPT	1,251	1,202	2,470	2,401
NOI from real estate operations	9,116	6,358	17,336	12,594
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	92,844	29,675	112,632	30,789
Regional Office | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	15,018	15,296	29,851	30,580
Property operating expenses	(7,590)	(7,169)	(15,006)	(15,047)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	7,428	8,127	14,845	15,533
Additions to long-lived assets	4,870	5,361	8,859	9,245
Transfers from non-operating properties	0	0	0	0
Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	8,560	8,105	16,431	16,182
Property operating expenses	(3,618)	(4,150)	(6,456)	(8,408)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	4,942	3,955	9,975	7,774
Additions to long-lived assets	95	81	251	117
Transfers from non-operating properties	0	1,133	0	2,145
Other | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	741	534	1,504	1,331
Property operating expenses	(348)	114	(657)	(238)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	393	648	847	1,093
Additions to long-lived assets	34	188	44	315
Transfers from non-operating properties	0	0	0	0
Segment assets
Segment financial information for real estate operations
Segment assets	3,036,140	3,042,452	3,036,140	3,042,452
Segment assets | Real estate operations
Segment financial information for real estate operations
Segment assets	3,036,140	3,042,452	3,036,140	3,042,452
Segment assets | Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	2,429,467	2,420,153	2,429,467	2,420,153
Segment assets | Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Segment assets	1,274,336	1,269,525	1,274,336	1,269,525
Segment assets | Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Segment assets	398,586	396,139	398,586	396,139
Segment assets | Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Segment assets	146,475	126,956	146,475	126,956
Segment assets | Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	187,172	190,537	187,172	190,537
Segment assets | Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Segment assets	115,222	106,374	115,222	106,374
Segment assets | Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Segment assets	307,676	330,622	307,676	330,622
Segment assets | Regional Office | Real estate operations
Segment financial information for real estate operations
Segment assets	393,110	396,847	393,110	396,847
Segment assets | Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Segment assets	209,787	221,239	209,787	221,239
Segment assets | Other | Real estate operations
Segment financial information for real estate operations
Segment assets	$ 3,776	$ 4,213	$ 3,776	$ 4,213

Information by Business Segme_4

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reconciliation of segment revenues to total revenues
Construction contract and other service revenues	$ 42,299	$ 17,581	$ 59,249	$ 44,779
Total revenues	175,070	146,743	324,010	302,219
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,251	1,202	2,470	2,401
Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense	(830)	(828)	(1,657)	(1,652)
Add: Equity in loss of unconsolidated non-real estate entities	(1)	(1)	(2)	(3)
Equity in income of unconsolidated entities	420	373	811	746
Computation of net operating income from service operations
Construction contract and other service revenues	42,299	17,581	59,249	44,779
Construction contract and other service expenses	(41,002)	(16,941)	(57,328)	(43,157)
Real estate operations
Reconciliation of segment revenues to total revenues
Total revenues	132,771	129,162	264,761	257,440
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,251	1,202	2,470	2,401
Service operations
Computation of net operating income from service operations
NOI from service operations	$ 1,297	$ 640	$ 1,921	$ 1,622

Information by Business Segme_5

Information by Business Segment (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
Interest and other income	$ 1,849	$ 1,439	$ 4,135	$ 2,798
Equity in income of unconsolidated entities	420	373	811	746
Income tax benefit (expense)	176	(63)	(18)	(118)
Depreciation and other amortization associated with real estate operations	(34,802)	(33,190)	(69,598)	(66,702)
General, administrative and leasing expenses	(9,386)	(7,628)	(18,137)	(14,920)
Business development expenses and land carry costs	(870)	(1,234)	(1,983)	(2,848)
Interest expense	(18,475)	(18,945)	(37,149)	(37,729)
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,251)	(1,202)	(2,470)	(2,401)
Net income	109,563	21,085	131,881	39,865
Real estate operations
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from real estate operations	86,136	80,918	169,900	159,444
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,251)	(1,202)	(2,470)	(2,401)
Service operations
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from service operations	$ 1,297	$ 640	$ 1,921	$ 1,622

Information by Business Segme_6

Information by Business Segment (Details 4) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 3,803,469	$ 3,656,005	$ 3,612,362
Operating properties lease liabilities included in segment assets	16,640
Segment assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	3,036,140		3,042,452
Operating properties lease liabilities included in segment assets	16,502		0
Non-operating property assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	523,801		431,661
Other assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 227,026		$ 138,249

Construction Contract and Oth_3

Construction Contract and Other Service Revenues (Details) - Construction Contract Revenue - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Performance obligations satisfied or already satisfied	$ (14)	$ 10	$ 18	$ 319
Remaining performance obligations	48,400		48,400
Remaining performance obligation expected to be recognized during the remainder of year	$ 41,000		$ 41,000

Construction Contract and Oth_4

Construction Contract and Other Service Revenues (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 42,299	$ 17,581	$ 59,249	$ 44,779
Construction
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	42,010	16,668	58,499	42,583
Design
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	86	655	338	1,719
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	203	258	412	477
Guaranteed Maximum Price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	25,792	9,539	38,148	30,025
Firm fixed price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	1,335	6,288	3,660	12,723
Cost-plus fee
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	14,969	1,496	17,029	1,554
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 203	$ 258	$ 412	$ 477

Construction Contract and Oth_5

Construction Contract and Other Service Revenues (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Change in Accounts Receivable
Beginning balance	$ 58,189		$ 58,189		$ 26,277
Ending balance	58,189		58,189		26,277
Construction Contract Revenue
Change in Accounts Receivable
Beginning balance	34,837	$ 4,805	34,837	$ 4,805	6,701	$ 4,577
Ending balance	34,837	4,805	34,837	4,805	6,701	4,577
Change in Contract with Customer, Asset
Beginning balance	12,629	4,158	12,629	4,158	3,189	4,884
Ending balance	12,629	4,158	12,629	4,158	3,189	4,884
Change in Contract with Customer, Liability
Beginning balance	156	515	156	515	568	27,402
Ending balance	156	515	156	515	$ 568	$ 27,402
Revenue recognized included in beginning balance	$ 6	$ 7,999	$ 445	$ 27,296

Share-Based Compensation (Detai

Share-Based Compensation (Details) $ / shares in Units, $ in Thousands	Jan. 18, 2019shares	Jan. 01, 2019USD ($)$ / sharesshares	Jun. 30, 2019USD ($)FormPercentile_Rank$ / sharesshares
PIUs
Share-Based Compensation
Number of forms of executive compensation | Form			2
Time-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units) | shares			61,820
Aggregate grant date fair value | $			$ 1,600
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 26.01
Annual award vesting rights (percent)			33.33%
Award vesting period			3 years
Restricted shares
Share-Based Compensation
Stock awards granted (in shares or units) | shares			171,520
Aggregate grant date fair value | $			$ 4,500
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 26.22
Shares vested (in shares) | shares			171,028
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 28.03
Aggregate intrinsic value of awards upon vesting | $			$ 4,500
Deferred share awards
Share-Based Compensation
Stock awards granted (in shares or units) | shares			3,432
Aggregate grant date fair value | $			$ 95
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 27.60
Shares vested (in shares) | shares			3,097
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 26.77
Aggregate intrinsic value of awards upon vesting | $			$ 86
2016 PSU Grants | Performance share units | Executives
Share-Based Compensation
Shares issued (in shares) | shares	44,757
Percentage of target	157.00%
2019 PIU Grants | Performance-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units) | shares		193,682
Aggregate grant date fair value | $		$ 2,400
Aggregate grant date fair value (in dollars per share) | $ / shares		$ 12.47
Award vesting period		3 years
Potential earned PSUs payout for defined levels of performance under awards
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 75th or greater percentile rank		100.00%
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 50th percentile rank		50.00%
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 25th percentile rank		25.00%
Earned PB-PIUs granted on percentile rank below 25th (as a percent)		0.00%
The number of percentile ranks to fall between to earn interpolated PB-PIUs between such percentile ranks, conditioned on the percentile rank exceeding 25% | Percentile_Rank			2
Assumptions used to value stock awards
Percent of award distribution rights			10.00%
Award performance period			3 years
Baseline value per common share (in dollars per share) | $ / shares		$ 21.03
Expected volatility of common shares (as a percent)		21.00%
Risk-free interest rate (as a percent)		2.51%

Earnings Per Share ("EPS") an_3

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income attributable to COPT/COPLP	$ 106,791		$ 19,434		$ 127,650	$ 36,584
Income attributable to share-based compensation awards	(364)		(117)		(413)	(234)
Numerator for basic EPS on net income attributable to COPT common shareholders	106,427		19,317		127,237	36,350
Dilutive effective of preferred units	165		0		0	0
Redeemable noncontrolling interests	902		0		66	0
Common units in the Operating Partnership	0		0		1,515	0
Income attributable to share-based compensation awards	18		0		22	0
Numerator for diluted EPS on net income attributable to COPT/COPLP common share/unit holders	$ 107,512		$ 19,317		$ 128,840	$ 36,350
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)	111,557		101,789		110,759	101,397
Dilutive convertible preferred units	176		0		0	0
Dilutive effect of common units	0		0		1,329	0
Dilutive effect of share-based compensation awards	310		119		289	131
Dilutive effect of redeemable noncontrolling interests	1,062		0		130	0
Denominator for diluted EPS/EPU (common shares/units)	113,105		101,908		112,507	101,528
Basic EPS:
Basic earnings per common share (in dollars per share/unit)	$ 0.95	[1]	$ 0.19	[1]	$ 1.15	$ 0.36
Diluted EPS:
Diluted earnings per common share (in dollars per share/unit)	$ 0.95	[1]	$ 0.19	[1]	$ 1.15	$ 0.36
Corporate Office Properties, L.P.
Numerator:
Net income attributable to COPT/COPLP	$ 108,295		$ 20,207		$ 129,576	$ 38,066
Preferred share/unit dividends/distributions	(165)		(165)		(330)	(330)
Income attributable to share-based compensation awards	(438)		(117)		(494)	(234)
Numerator for basic EPS on net income attributable to COPT common shareholders	107,692		19,925		128,752	37,502
Dilutive effective of preferred units	165		0		0	0
Redeemable noncontrolling interests	902		0		66	0
Income attributable to share-based compensation awards	18		0		22	0
Numerator for diluted EPS on net income attributable to COPT/COPLP common share/unit holders	$ 108,777		$ 19,925		$ 128,840	$ 37,502
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)	112,884		104,986		112,088	104,605
Dilutive convertible preferred units	176		0		0	0
Dilutive effect of share-based compensation awards	310		119		289	131
Dilutive effect of redeemable noncontrolling interests	1,062		0		130	0
Denominator for diluted EPS/EPU (common shares/units)	114,432		105,105		112,507	104,736
Basic EPS:
Basic earnings per common share (in dollars per share/unit)	$ 0.95	[2]	$ 0.19	[2]	$ 1.15	$ 0.36
Diluted EPS:
Diluted earnings per common share (in dollars per share/unit)	$ 0.95	[2]	$ 0.19	[2]	$ 1.15	$ 0.36
[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.
[2]	Basic and diluted earnings per common unit are calculated based on amounts attributable to common unitholders of Corporate Office Properties, L.P.

Earnings Per Share ("EPS") an_4

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details 2) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Conversion of common units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,327	3,197	0	3,208
Conversion of redeemable noncontrolling interests
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	0	0	907	0
Conversion of Series I preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	0	176	176	176
Weighted average shares related to forward equity sale agreements
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)		6,800	758	7,100
Weighted average restricted shares/units and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	425	458	444	451
Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	17	47	23	53
Weighted average unvested PIUs
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	59		39
Corporate Office Properties, L.P. | Conversion of redeemable noncontrolling interests
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	0	0	907	0
Corporate Office Properties, L.P. | Conversion of Series I preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	0	176	176	176
Corporate Office Properties, L.P. | Weighted average shares related to forward equity sale agreements
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)		6,800	758	7,100
Corporate Office Properties, L.P. | Weighted average restricted shares/units and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	425	458	444	451
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	17	47	23	53
Corporate Office Properties, L.P. | Weighted average unvested PIUs
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	59		39

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	Jun. 30, 2019USD ($)property	Dec. 31, 2018USD ($)
Environmental Indemnity Agreement
Number of properties which were provided environmental indemnifications | property	3
Maximum additional costs agreed to be paid by the entity under environmental indemnification agreement	$ 19,000
Carrying Value	1,784,362	$ 1,823,909
Development and Redevelopment Obligations
Environmental Indemnity Agreement
Purchase obligations	174,000
Tenant and Other Capital Improvements
Environmental Indemnity Agreement
Purchase obligations	51,800
Third Party Construction
Environmental Indemnity Agreement
Purchase obligations	15,400
Other Obligations
Environmental Indemnity Agreement
Purchase obligations	1,700
Specialty Tax Guarantee | Anne Arundel County, Maryland | Tax Incremental Financing Bond
Environmental Indemnity Agreement
Carrying Value	$ 35,000