Corporate Office Properties Trust 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2020	Apr. 21, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2020
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		112,169,463
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	2020
Document Fiscal Period Focus	Q1
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 Period Focus	Q1
Entity Small Business	false
Entity Emerging Growth Company	false
COPT | Common Units | Corporate Office Properties, L.P.
Entity Information [Line Items]
Percentage ownership in operating partnership	98.60%

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Properties, net:
Operating properties, net	$ 2,813,949	$ 2,772,647
Projects in development or held for future development	605,679	568,239
Total properties, net	3,419,628	3,340,886
Property - operating right-of-use assets	27,793	27,864
Property - finance right-of-use assets	40,450	40,458
Cash and cash equivalents	159,061	14,733
Investment in unconsolidated real estate joint ventures	51,220	51,949
Accounts receivable, net	30,317	35,444
Deferred rent receivable	89,690	87,736
Intangible assets on real estate acquisitions, net	26,078	27,392
Deferred leasing costs (net of accumulated amortization of $34,613 and $33,782, respectively)	58,608	58,392
Prepaid expenses and other assets, net	80,415	96,076
Total assets	4,054,457	3,854,453
Liabilities:
Debt, net	2,076,839	1,831,139
Accounts payable and accrued expenses	128,441	148,746
Rents received in advance and security deposits	33,323	33,620
Dividends and distributions payable	31,301	31,263
Deferred revenue associated with operating leases	6,972	7,361
Property - operating lease liabilities	17,365	17,317
Interest rate derivatives	63,232	25,682
Other liabilities	8,886	10,649
Total liabilities	2,366,359	2,105,777
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	22,912	29,431
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,122	1,121
Additional paid-in capital	2,476,677	2,481,558
Cumulative distributions in excess of net income	(790,600)	(778,275)
Accumulated other comprehensive loss	(62,201)	(25,444)
Total Corporate Office Properties Trust’s shareholders’ equity	1,624,998	1,678,960
Noncontrolling interests in subsidiaries:
Common units in COPLP	19,600	19,597
Preferred units in COPLP	8,800	8,800
Other consolidated entities	11,788	11,888
Noncontrolling interests in subsidiaries	40,188	40,285
Total equity	1,665,186	1,719,245
Total liabilities, redeemable noncontrolling interests and equity	4,054,457	3,854,453
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,813,949	2,772,647
Projects in development or held for future development	605,679	568,239
Total properties, net	3,419,628	3,340,886
Property - operating right-of-use assets	27,793	27,864
Property - finance right-of-use assets	40,450	40,458
Cash and cash equivalents	159,061	14,733
Investment in unconsolidated real estate joint ventures	51,220	51,949
Accounts receivable, net	30,317	35,444
Deferred rent receivable	89,690	87,736
Intangible assets on real estate acquisitions, net	26,078	27,392
Deferred leasing costs (net of accumulated amortization of $34,613 and $33,782, respectively)	58,608	58,392
Prepaid expenses and other assets, net	78,136	93,016
Total assets	4,052,178	3,851,393
Liabilities:
Debt, net	2,076,839	1,831,139
Accounts payable and accrued expenses	128,441	148,746
Rents received in advance and security deposits	33,323	33,620
Dividends and distributions payable	31,301	31,263
Deferred revenue associated with operating leases	6,972	7,361
Property - operating lease liabilities	17,365	17,317
Interest rate derivatives	63,232	25,682
Other liabilities	6,607	7,589
Total liabilities	2,364,080	2,102,717
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	22,912	29,431
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,707,395	1,724,159
Accumulated other comprehensive loss	(62,843)	(25,648)
Total Corporate Office Properties Trust’s shareholders’ equity	1,653,352	1,707,311
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	11,834	11,934
Total equity	1,665,186	1,719,245
Total liabilities, redeemable noncontrolling interests and equity	4,052,178	3,851,393
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 March 31, 2020 and December 31, 2019	8,800	8,800
Investing Receivables
Properties, net:
Investing receivables (net of allowance for credit losses of $3,598 at March 31, 2020)	71,197	73,523
Investing Receivables | Corporate Office Properties, L.P.
Properties, net:
Investing receivables (net of allowance for credit losses of $3,598 at March 31, 2020)	$ 71,197	$ 73,523

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accumulated amortization of deferred leasing costs	$ 34,613	$ 33,782
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	112,169,463	112,068,705
Common Shares of beneficial interest, shares outstanding	112,169,463	112,068,705
Corporate Office Properties, L.P.
Accumulated amortization of deferred leasing costs	$ 34,613	$ 33,782
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	112,169,463	112,068,705
Corporate Office Properties, L.P. | Limited Partner
Common Shares of beneficial interest, shares outstanding	1,620,449	1,482,425
Balance (preferred units)	352,000	352,000
Investing Receivables
Investing receivable allowance for credit loss	$ 3,598	$ 0
Investing Receivables | Corporate Office Properties, L.P.
Investing receivable allowance for credit loss	$ 3,598

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Revenues
Lease revenue		$ 131,012	$ 130,903
Construction contract and other service revenues		13,681	16,950
Total revenues		145,797	148,940
Operating expenses
Property operating expenses		49,999	49,445
Depreciation and amortization associated with real estate operations		32,596	34,796
Construction contract and other service expenses		13,121	16,326
General, administrative and leasing expenses		7,486	8,751
Business development expenses and land carry costs		1,118	1,113
Total operating expenses		104,320	110,431
Interest expense		(16,840)	(18,674)
Interest and other income		1,205	2,286
Credit loss expense		(689)	0
Gain on sales of real estate		5	0
Income before equity in income of unconsolidated entities and income taxes		25,158	22,121
Equity in income of unconsolidated entities		441	391
Income tax expense		(49)	(194)
Net income		25,550	22,318
Net income attributable to noncontrolling interests:
Common units in COPLP		(287)	(257)
Preferred units in COPLP		(77)	(165)
Other consolidated entities		(1,132)	(1,037)
Net income attributable to COPLP		24,054	20,859
Net income attributable to COPT/COPLP common share/unitholders		$ 24,054	$ 20,859
Earnings per common share/unit:
Net income attributable to COPT/COPLP common share/unitholders - basic (in dollars per share/unit)	[1]	$ 0.21	$ 0.19
Net income attributable to COPT/COPLP common share/unit holders - diluted (in dollars per share/unit)	[1]	$ 0.21	$ 0.19
Other Property Revenue
Revenues
Total revenues		$ 1,104	$ 1,087
Corporate Office Properties, L.P.
Revenues
Lease revenue		131,012	130,903
Construction contract and other service revenues		13,681	16,950
Total revenues		145,797	148,940
Operating expenses
Property operating expenses		49,999	49,445
Depreciation and amortization associated with real estate operations		32,596	34,796
Construction contract and other service expenses		13,121	16,326
General, administrative and leasing expenses		7,486	8,751
Business development expenses and land carry costs		1,118	1,113
Total operating expenses		104,320	110,431
Interest expense		(16,840)	(18,674)
Interest and other income		1,205	2,286
Credit loss expense		(689)	0
Gain on sales of real estate		5	0
Income before equity in income of unconsolidated entities and income taxes		25,158	22,121
Equity in income of unconsolidated entities		441	391
Income tax expense		(49)	(194)
Net income		25,550	22,318
Net income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities		(1,132)	(1,037)
Net income attributable to COPLP		24,418	21,281
Preferred unit distributions		(77)	(165)
Net income attributable to COPT/COPLP common share/unitholders		$ 24,341	$ 21,116
Earnings per common share/unit:
Net income attributable to COPT/COPLP common share/unitholders - basic (in dollars per share/unit)	[2]	$ 0.21	$ 0.19
Net income attributable to COPT/COPLP common share/unit holders - diluted (in dollars per share/unit)	[2]	$ 0.21	$ 0.19
Corporate Office Properties, L.P. | Other Property Revenue
Revenues
Total revenues		$ 1,104	$ 1,087
[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
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 25,550	$ 22,318
Other comprehensive loss:
Unrealized loss on interest rate derivatives	(37,705)	(8,845)
Loss (gain) on interest rate derivatives recognized in interest expense	131	(570)
Total other comprehensive loss	(37,574)	(9,415)
Comprehensive (loss) income	(12,024)	12,903
Comprehensive income attributable to noncontrolling interests	(679)	(1,344)
Comprehensive (loss) income attributable to COPT	(12,703)	11,559
Corporate Office Properties, L.P.
Net income	25,550	22,318
Other comprehensive loss:
Unrealized loss on interest rate derivatives	(37,705)	(8,845)
Loss (gain) on interest rate derivatives recognized in interest expense	131	(570)
Total other comprehensive loss	(37,574)	(9,415)
Comprehensive (loss) income	(12,024)	12,903
Comprehensive income attributable to noncontrolling interests	(753)	(1,037)
Comprehensive (loss) income attributable to COPT	$ (12,777)	$ 11,866

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

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Balance (in units/ shares)	112,169,463	111,939,790	112,068,705	110,241,868
Conversion of common units to common shares (in units/shares)	12,009	5,500
Share-based compensation issuance, net of redemptions (in units/shares)	88,749	78,335
Forward Equity Sale Agreement
Common shares issued during the period (in units/shares)		1,614,087

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities
Revenues from real estate operations received	$ 133,092	$ 126,569
Construction contract and other service revenues received	24,925	5,904
Property operating expenses paid	(46,330)	(42,974)
Construction contract and other service expenses paid	(17,631)	(4,614)
General, administrative, leasing, business development and land carry costs paid	(12,371)	(11,703)
Interest expense paid	(16,767)	(18,282)
Lease incentives paid	(3,628)	(1,158)
Other	928	910
Net cash provided by operating activities	62,218	54,652
Cash flows from investing activities
Development and redevelopment of properties	(92,802)	(100,212)
Tenant improvements on operating properties	(10,446)	(4,174)
Other capital improvements on operating properties	(5,457)	(4,476)
Investing receivables funded	0	(11,051)
Leasing costs paid	(5,950)	(2,539)
Other	192	1,297
Net cash used in investing activities	(114,463)	(121,155)
Proceeds from debt
Revolving Credit Facility	251,000	123,000
Other debt proceeds	181,595	3,350
Repayments of debt
Revolving Credit Facility	(186,000)	(74,000)
Scheduled principal amortization	(1,021)	(1,098)
Deferred financing costs paid	(1,261)	0
Net proceeds from issuance of common shares	0	46,415
Common share/unit dividends/distributions paid	(30,817)	(30,287)
Distributions paid to noncontrolling interests in COPLP	(403)	(553)
Distributions paid to redeemable noncontrolling interests	(11,870)	0
Redemption of vested equity awards	(1,492)	(1,817)
Other	(2,729)	1,318
Net cash provided by financing activities	197,002	66,328
Net increase (decrease) in cash and cash equivalents and restricted cash	144,757	(175)
Cash and cash equivalents and restricted cash
Beginning of period	18,130	11,950
End of period	162,887	11,775
Reconciliation of net income to net cash provided by operating activities:
Net income	25,550	22,318
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	33,015	35,229
Amortization of deferred financing costs and net debt discounts	961	898
Increase in deferred rent receivable	(2,230)	(2,539)
Share-based compensation	1,389	1,659
Other	(52)	(1,572)
Changes in operating assets and liabilities:
Decrease in accounts receivable	4,547	1,033
Decrease (increase) in prepaid expenses and other assets, net	15,548	(6,752)
(Decrease) increase in accounts payable, accrued expenses and other liabilities	(16,213)	8,822
Decrease in rents received in advance and security deposits	(297)	(4,444)
Net cash provided by operating activities	62,218	54,652
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	18,130	11,950
Supplemental schedule of non-cash investing and financing activities:
(Decrease) increase in accrued capital improvements, leasing and other investing activity costs	(4,795)	11,329
Finance right-of-use asset contributed by noncontrolling interest in joint venture	0	2,570
Operating right-of-use assets obtained in exchange for operating lease liabilities	0	276
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(37,573)	(9,450)
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	182	80
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	453	1,322
Increase in redeemable noncontrolling interests and decrease in equity to carry redeemable noncontrolling interests at fair value	4,101	799
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	133,092	126,569
Construction contract and other service revenues received	24,925	5,904
Property operating expenses paid	(46,330)	(42,974)
Construction contract and other service expenses paid	(17,631)	(4,614)
General, administrative, leasing, business development and land carry costs paid	(12,371)	(11,703)
Interest expense paid	(16,767)	(18,282)
Lease incentives paid	(3,628)	(1,158)
Other	928	910
Net cash provided by operating activities	62,218	54,652
Cash flows from investing activities
Development and redevelopment of properties	(92,802)	(100,212)
Tenant improvements on operating properties	(10,446)	(4,174)
Other capital improvements on operating properties	(5,457)	(4,476)
Investing receivables funded	0	(11,051)
Leasing costs paid	(5,950)	(2,539)
Other	192	1,297
Net cash used in investing activities	(114,463)	(121,155)
Proceeds from debt
Revolving Credit Facility	251,000	123,000
Other debt proceeds	181,595	3,350
Repayments of debt
Revolving Credit Facility	(186,000)	(74,000)
Scheduled principal amortization	(1,021)	(1,098)
Deferred financing costs paid	(1,261)	0
Net proceeds from issuance of common shares	0	46,415
Common share/unit dividends/distributions paid	(31,143)	(30,675)
Distributions paid to redeemable noncontrolling interests	(11,870)	0
Redemption of vested equity awards	(1,492)	(1,817)
Other	(2,806)	1,153
Net cash provided by financing activities	197,002	66,328
Net increase (decrease) in cash and cash equivalents and restricted cash	144,757	(175)
Cash and cash equivalents and restricted cash
Beginning of period	18,130	11,950
End of period	162,887	11,775
Reconciliation of net income to net cash provided by operating activities:
Net income	25,550	22,318
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	33,015	35,229
Amortization of deferred financing costs and net debt discounts	961	898
Increase in deferred rent receivable	(2,230)	(2,539)
Share-based compensation	1,389	1,659
Other	(52)	(1,572)
Changes in operating assets and liabilities:
Decrease in accounts receivable	4,547	1,033
Decrease (increase) in prepaid expenses and other assets, net	14,768	(6,406)
(Decrease) increase in accounts payable, accrued expenses and other liabilities	(15,433)	8,476
Decrease in rents received in advance and security deposits	(297)	(4,444)
Net cash provided by operating activities	62,218	54,652
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	162,887	11,775
Supplemental schedule of non-cash investing and financing activities:
(Decrease) increase in accrued capital improvements, leasing and other investing activity costs	(4,795)	11,329
Finance right-of-use asset contributed by noncontrolling interest in joint venture	0	2,570
Operating right-of-use assets obtained in exchange for operating lease liabilities	0	276
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(37,573)	(9,450)
Increase in redeemable noncontrolling interests and decrease in equity to carry redeemable noncontrolling interests at fair value	$ 4,101	$ 799

Organization

Organization	3 Months Ended
	Mar. 31, 2020
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 (“USG”) 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 March 31, 2020 , our properties included the following: • 171 properties totaling 19.4 million square feet comprised of 15.4 million square feet in 148 office properties and 4.0 million square feet in 23 single-tenant data center shell properties (“data center shells”). We owned 15 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 development or redevelopment ( 11 office properties and three data center shells) that we estimate will total approximately 2.3 million square feet upon completion, including one partially-operational property; and • approximately 900 acres of land controlled for future development that we believe could be developed into approximately 11.2 million square feet and 43 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, development and construction 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 March 31, 2020 , 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 that of COPT common shareholders. In the case of any series of preferred units held by COPT, there would be a series of preferred shares of beneficial interest (“preferred shares”) in COPT that is equivalent in number and carries substantially the same terms as such series of COPLP preferred 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	3 Months Ended
	Mar. 31, 2020
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, 2019 included in our 2019 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 2019 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below. Reclassifications 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. Recent Accounting Pronouncements Effective January 1, 2020, we adopted guidance issued by the Financial Accounting Standards Board (“FASB”) that changes how entities measure credit losses for most financial assets and certain other instruments 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 applies to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables (excluding those arising from operating leases), loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments and guarantees). Under this guidance, we recognize an estimate of our expected credit losses on these asset types as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and be presented at the net amount expected to be collected. We adopted this guidance effective January 1, 2020 using the modified retrospective transition method under which we recognized a $5.5 million allowance for credit losses by means of a cumulative-effect adjustment to cumulative distributions in excess of net income of the Company (or common units of the Operating Partnership), and did not adjust prior comparative reporting periods. Our consolidated statements of operations reflect adjustments for changes in our expected credit losses occurring subsequent to adoption of this guidance. Effective January 1, 2020, we adopted guidance issued by the FASB that modifies disclosure requirements for fair value measurements. The resulting changes in disclosure did not have a material impact on our consolidated financial statements. Effective January 1, 2020, we adopted guidance issued by the FASB 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. Our adoption of this guidance did not have a material impact on our consolidated financial statements. Credit Losses, Financial Assets and Other Instruments As discussed above, effective January 1, 2020, we adopted guidance issued by the FASB that changed how we measure credit losses for most financial assets and certain other instruments not measured at fair value through net income from an incurred loss model to an expected loss approach. Our items within the scope of this guidance included the following: • investing receivables, as disclosed in Note 7; • tenant notes receivable; • other assets comprised of non-lease revenue related accounts receivable (primarily from construction contract services) and contract assets from unbilled construction contract revenue; and • off-balance sheet credit exposures, which included $4.8 million in unfunded commitments to fund tenant loans and a tax incremental financing obligation disclosed in Note 17. Under this guidance, we recognize an estimate of our expected credit losses on these items as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and be presented at the net amount expected to be collected (or as a separate liability in the case of off-balance sheet credit exposures). The allowance represents the portion of the amortized cost basis that we do not expect to collect (or loss we expect to incur in the case of off-balance sheet credit exposures) due to credit over the contractual life based on available information relevant to assessing the collectability of cash flows, which includes consideration of past events, current conditions and reasonable and supportable forecasts of future economic conditions (including consideration of asset- or borrower-specific factors). The guidance requires the allowance for expected credit losses to reflect the risk of loss, even when that risk is remote. An allowance for credit losses is measured and recorded upon the initial recognition of a financial asset (or off-balance sheet credit exposures), regardless of whether it is originated or purchased. Quarterly, the expected losses are re-estimated, considering any cash receipts and changes in risks or assumptions, with resulting adjustments recognized in the line entitled “credit loss expense” on our consolidated statements of operations. We estimate expected credit losses for in-scope items using historical loss rate information developed for varying classifications of credit risk and contractual lives of such items. Due to our limited quantity of items within the scope of this guidance and the unique risk characteristics of such items, we individually assign each in-scope item a credit risk classification. The credit risk classifications assigned by us are determined based on credit ratings assigned by ratings agencies (as available) or are internally-developed based on available financial information, historical payment experience, credit documentation, other publicly available information and current economic trends. In addition, for certain items in which the risk of credit loss is affected by the economic performance of a real estate development project, we develop probability weighted scenario analyses for varying levels of performance in estimating our credit loss allowance (applicable to our investing receivable from the City of Huntsville disclosed in Note 7 and a tax incremental financing obligation disclosed in Note 17). The table below sets forth the activity for the allowance for credit losses (in thousands): For the Three Months Ended March 31, 2020 Investing Receivables Tenant Notes Receivable (1) Other Assets (2) Off-Balance Sheet Credit Exposures (3) Total December 31, 2019 $ — $ (97 ) $ — $ — $ (97 ) Cumulative effect of change for adoption of credit loss guidance (3,732 ) (325 ) (144 ) (1,340 ) (5,541 ) Credit loss expense 134 23 (77 ) (769 ) (689 ) March 31, 2020 $ (3,598 ) $ (399 ) $ (221 ) $ (2,109 ) $ (6,327 ) (1) Included in the line entitled “accounts receivable, net” on our consolidated balance sheets. (2) The balance as of March 31, 2020 included $181,000 in the line entitled “accounts receivable, net” and $40,000 in the line entitled “prepaid expenses and other assets, net” on our consolidated balance sheets. (3) Included in the line entitled “other liabilities” on our consolidated balance sheets. Most of our credit loss expense for the three months ended March 31, 2020 was attributable to a new commitment to fund a tenant note receivable for improvements in a property. The following table presents the amortized cost basis of our investing receivables and tenants notes receivable by credit risk classification, by origination year as of March 31, 2020 (in thousands): Origination Year 2015 and Earlier 2016 2017 2018 2019 2020 Total as of March 31, 2020 Investing receivables: Credit risk classification: Investment grade $ 59,833 $ — $ 866 $ — $ — $ — $ 60,699 Non-investment grade 3,020 — — — 11,076 — 14,096 Total $ 62,853 $ — $ 866 $ — $ 11,076 $ — $ 74,795 Tenant notes receivable: Credit risk classification: Investment grade $ 21 $ 78 $ — $ 1,100 $ 100 $ — $ 1,299 Non-investment grade 97 219 — 185 2,079 — 2,580 Total $ 118 $ 297 $ — $ 1,285 $ 2,179 $ — $ 3,879 Our investment grade credit risk classification represents entities with investment grade credit ratings from ratings agencies (such as Standard & Poor’s Ratings Services, Moody’s Investors Service, Inc. or Fitch Ratings Ltd.), meaning that they are considered to have at least an adequate capacity to meet their financial commitments, with credit risk ranging from minimal to moderate. Our non-investment grade credit risk classification represents entities with either no credit agency credit ratings or ratings deemed to be sub-investment grade; we believe that there is significantly more credit risk associated with this classification. An insignificant portion of the investing and tenant notes receivables set forth above were past due, which we define as being delinquent by more than three months from the due date. When we believe that collection of interest income on an investing or tenant note receivable is not probable, we place the receivable on nonaccrual status, meaning interest income is recognized when payments are received rather than on an accrual basis. We had a tenant note receivable on nonaccrual status as of March 31, 2020 and December 31, 2019 with an amortized cost basis of $97,000 , which was fully reserved as of each date. We did not recognize any interest income during the three months ended March 31, 2020 on receivables on nonaccrual status. We write off receivables when we believe the facts and circumstances indicate that continued pursuit of collection is no longer warranted. When cash is received in connection with receivables for which we have previously recognized credit losses, we recognize reductions in our credit loss expense.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
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, prior to December 31, 2019, permitted participants to defer up to 100% of their compensation on a pre-tax basis and receive a tax-deferred return on such deferrals. The Company froze additional entry into the plan effective December 31, 2019. 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 and totaled $2.3 million as of March 31, 2020 , is included in the line entitled “prepaid expenses and other assets, net” on COPT’s consolidated balance sheets along with an insignificant amount of other marketable securities. 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 reported in “other liabilities” on COPT’s consolidated balance sheet. 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 March 31, 2020 , 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 value 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 March 31, 2020 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 $ 2,260 $ — $ — $ 2,260 Other 19 — — 19 Mutual funds (1) 10 — — 10 Total assets $ 2,289 $ — $ — $ 2,289 Liabilities: Deferred compensation plan liability (2) $ — $ 2,279 $ — $ 2,279 Interest rate derivatives — 63,232 — 63,232 Total liabilities $ — $ 65,511 $ — $ 65,511 (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 March 31, 2020 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: Mutual funds (1) $ 10 $ — $ — $ 10 Liabilities: Interest rate derivatives $ — $ 63,232 $ — $ 63,232 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPLP’s consolidated balance sheet.

Properties, Net

Properties, Net	3 Months Ended
	Mar. 31, 2020
Real Estate [Abstract]
Properties, Net	Properties, Net Operating properties, net consisted of the following (in thousands): March 31, December 31, Land $ 489,744 $ 472,976 Buildings and improvements 3,359,908 3,306,791 Less: Accumulated depreciation (1,035,703 ) (1,007,120 ) Operating properties, net $ 2,813,949 $ 2,772,647 2020 Development Activities During the three months ended March 31, 2020 , we placed into service 230,000 square feet in one newly-developed property. As of March 31, 2020 , we had 13 properties under development, or which we were contractually committed to develop, that we estimate will total 2.2 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	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 , 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 . Our lease revenue is comprised of: fixed lease revenue, including contractual rent billings under leases recognized on a straight-line basis over lease terms and amortization of lease incentives and above- and below- market lease intangibles; and variable lease revenue, including tenant expense recoveries, lease termination revenue and other revenue from tenants that is not fixed under the lease. The table below sets forth our allocation of lease revenue recognized between fixed and variable lease revenue (in thousands): For the Three Months Ended March 31, Lease revenue 2020 2019 Fixed $ 104,109 $ 104,644 Variable 26,903 26,259 $ 131,012 $ 130,903 Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, March 31, 2020 December 31, 2019 2020 (1) $ 301,914 $ 388,310 2021 357,747 336,482 2022 319,239 299,356 2023 264,865 245,661 2024 214,797 195,246 Thereafter 548,049 474,741 $ 2,006,611 $ 1,939,796 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 . Lessee arrangements We lease land underlying certain properties that we are operating or developing from third parties. These ground leases have long durations with remaining terms ranging from 29 years (excluding extension options) to 96 years . As of March 31, 2020 , our balance sheet included $68.2 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 96 -year remaining term, and we possess a bargain purchase option that we expect to exercise in 2020; • $10.3 million for land underlying operating 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 29 years and an option to renew for an additional 49 years that was included in the term used in determining the asset balance; • $6.6 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 63 to 74 years ; • $4.8 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 43 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 underlying operating properties in our Fort Meade/BW Corridor sub-segment under two leases with remaining terms of approximately 48 years , all of the rent on which was previously paid. Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,793 $ 27,864 Finance leases - Property Property - finance right-of-use assets 40,450 40,458 Total right-of-use assets $ 68,243 $ 68,322 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 17,365 $ 17,317 Finance leases - Property Other liabilities 702 702 Total lease liabilities $ 18,067 $ 18,019 The table below sets forth the weighted average terms and discount rates of our leases as of March 31, 2020 : Weighted average remaining lease term Operating leases 68 years Finance leases < 1 year Weighted average discount rate Operating leases 7.33 % Finance leases 3.62 % The table below presents our total lease cost (in thousands): For the Three Months Ended March 31, Lease cost Statement of Operations Location 2020 2019 Operating lease cost Property leases Property operating expenses $ 431 $ 413 Finance lease cost Amortization of property right-of-use assets Property operating expenses 9 — $ 440 $ 413 The table below presents the effect of lease payments on our consolidated statements of cash flows (in thousands): For the Three Months Ended March 31, Supplemental cash flow information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 311 $ 228 Financing cash flows for financing leases $ — $ 52 Payments on leases as of March 31, 2020 and December 31, 2019 were due as follows (in thousands): As of March 31, 2020 As of December 31, 2019 Year Ending December 31, Operating leases Finance leases Total Operating leases Finance leases Total 2020 (1) $ 826 $ 674 $ 1,500 $ 1,092 $ 674 $ 1,766 2021 1,138 14 1,152 1,138 14 1,152 2022 1,162 14 1,176 1,162 14 1,176 2023 1,167 — 1,167 1,167 — 1,167 2024 1,173 — 1,173 1,173 — 1,173 Thereafter 100,609 — 100,609 100,609 — 100,609 Total lease payments 106,075 702 106,777 106,341 702 107,043 Less: Amount representing interest (88,710 ) — (88,710 ) (89,024 ) — (89,024 ) Lease liability $ 17,365 $ 702 $ 18,067 $ 17,317 $ 702 $ 18,019 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 .
Leases	Leases Lessor Arrangements We lease real estate properties, comprised primarily of office properties and data center shells, to third parties. As of March 31, 2020 , 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 . Our lease revenue is comprised of: fixed lease revenue, including contractual rent billings under leases recognized on a straight-line basis over lease terms and amortization of lease incentives and above- and below- market lease intangibles; and variable lease revenue, including tenant expense recoveries, lease termination revenue and other revenue from tenants that is not fixed under the lease. The table below sets forth our allocation of lease revenue recognized between fixed and variable lease revenue (in thousands): For the Three Months Ended March 31, Lease revenue 2020 2019 Fixed $ 104,109 $ 104,644 Variable 26,903 26,259 $ 131,012 $ 130,903 Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, March 31, 2020 December 31, 2019 2020 (1) $ 301,914 $ 388,310 2021 357,747 336,482 2022 319,239 299,356 2023 264,865 245,661 2024 214,797 195,246 Thereafter 548,049 474,741 $ 2,006,611 $ 1,939,796 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 . Lessee arrangements We lease land underlying certain properties that we are operating or developing from third parties. These ground leases have long durations with remaining terms ranging from 29 years (excluding extension options) to 96 years . As of March 31, 2020 , our balance sheet included $68.2 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 96 -year remaining term, and we possess a bargain purchase option that we expect to exercise in 2020; • $10.3 million for land underlying operating 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 29 years and an option to renew for an additional 49 years that was included in the term used in determining the asset balance; • $6.6 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 63 to 74 years ; • $4.8 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 43 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 underlying operating properties in our Fort Meade/BW Corridor sub-segment under two leases with remaining terms of approximately 48 years , all of the rent on which was previously paid. Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,793 $ 27,864 Finance leases - Property Property - finance right-of-use assets 40,450 40,458 Total right-of-use assets $ 68,243 $ 68,322 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 17,365 $ 17,317 Finance leases - Property Other liabilities 702 702 Total lease liabilities $ 18,067 $ 18,019 The table below sets forth the weighted average terms and discount rates of our leases as of March 31, 2020 : Weighted average remaining lease term Operating leases 68 years Finance leases < 1 year Weighted average discount rate Operating leases 7.33 % Finance leases 3.62 % The table below presents our total lease cost (in thousands): For the Three Months Ended March 31, Lease cost Statement of Operations Location 2020 2019 Operating lease cost Property leases Property operating expenses $ 431 $ 413 Finance lease cost Amortization of property right-of-use assets Property operating expenses 9 — $ 440 $ 413 The table below presents the effect of lease payments on our consolidated statements of cash flows (in thousands): For the Three Months Ended March 31, Supplemental cash flow information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 311 $ 228 Financing cash flows for financing leases $ — $ 52 Payments on leases as of March 31, 2020 and December 31, 2019 were due as follows (in thousands): As of March 31, 2020 As of December 31, 2019 Year Ending December 31, Operating leases Finance leases Total Operating leases Finance leases Total 2020 (1) $ 826 $ 674 $ 1,500 $ 1,092 $ 674 $ 1,766 2021 1,138 14 1,152 1,138 14 1,152 2022 1,162 14 1,176 1,162 14 1,176 2023 1,167 — 1,167 1,167 — 1,167 2024 1,173 — 1,173 1,173 — 1,173 Thereafter 100,609 — 100,609 100,609 — 100,609 Total lease payments 106,075 702 106,777 106,341 702 107,043 Less: Amount representing interest (88,710 ) — (88,710 ) (89,024 ) — (89,024 ) Lease liability $ 17,365 $ 702 $ 18,067 $ 17,317 $ 702 $ 18,019 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 .
Leases	Leases Lessor Arrangements We lease real estate properties, comprised primarily of office properties and data center shells, to third parties. As of March 31, 2020 , 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 . Our lease revenue is comprised of: fixed lease revenue, including contractual rent billings under leases recognized on a straight-line basis over lease terms and amortization of lease incentives and above- and below- market lease intangibles; and variable lease revenue, including tenant expense recoveries, lease termination revenue and other revenue from tenants that is not fixed under the lease. The table below sets forth our allocation of lease revenue recognized between fixed and variable lease revenue (in thousands): For the Three Months Ended March 31, Lease revenue 2020 2019 Fixed $ 104,109 $ 104,644 Variable 26,903 26,259 $ 131,012 $ 130,903 Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, March 31, 2020 December 31, 2019 2020 (1) $ 301,914 $ 388,310 2021 357,747 336,482 2022 319,239 299,356 2023 264,865 245,661 2024 214,797 195,246 Thereafter 548,049 474,741 $ 2,006,611 $ 1,939,796 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 . Lessee arrangements We lease land underlying certain properties that we are operating or developing from third parties. These ground leases have long durations with remaining terms ranging from 29 years (excluding extension options) to 96 years . As of March 31, 2020 , our balance sheet included $68.2 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 96 -year remaining term, and we possess a bargain purchase option that we expect to exercise in 2020; • $10.3 million for land underlying operating 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 29 years and an option to renew for an additional 49 years that was included in the term used in determining the asset balance; • $6.6 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 63 to 74 years ; • $4.8 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 43 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 underlying operating properties in our Fort Meade/BW Corridor sub-segment under two leases with remaining terms of approximately 48 years , all of the rent on which was previously paid. Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,793 $ 27,864 Finance leases - Property Property - finance right-of-use assets 40,450 40,458 Total right-of-use assets $ 68,243 $ 68,322 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 17,365 $ 17,317 Finance leases - Property Other liabilities 702 702 Total lease liabilities $ 18,067 $ 18,019 The table below sets forth the weighted average terms and discount rates of our leases as of March 31, 2020 : Weighted average remaining lease term Operating leases 68 years Finance leases < 1 year Weighted average discount rate Operating leases 7.33 % Finance leases 3.62 % The table below presents our total lease cost (in thousands): For the Three Months Ended March 31, Lease cost Statement of Operations Location 2020 2019 Operating lease cost Property leases Property operating expenses $ 431 $ 413 Finance lease cost Amortization of property right-of-use assets Property operating expenses 9 — $ 440 $ 413 The table below presents the effect of lease payments on our consolidated statements of cash flows (in thousands): For the Three Months Ended March 31, Supplemental cash flow information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 311 $ 228 Financing cash flows for financing leases $ — $ 52 Payments on leases as of March 31, 2020 and December 31, 2019 were due as follows (in thousands): As of March 31, 2020 As of December 31, 2019 Year Ending December 31, Operating leases Finance leases Total Operating leases Finance leases Total 2020 (1) $ 826 $ 674 $ 1,500 $ 1,092 $ 674 $ 1,766 2021 1,138 14 1,152 1,138 14 1,152 2022 1,162 14 1,176 1,162 14 1,176 2023 1,167 — 1,167 1,167 — 1,167 2024 1,173 — 1,173 1,173 — 1,173 Thereafter 100,609 — 100,609 100,609 — 100,609 Total lease payments 106,075 702 106,777 106,341 702 107,043 Less: Amount representing interest (88,710 ) — (88,710 ) (89,024 ) — (89,024 ) Lease liability $ 17,365 $ 702 $ 18,067 $ 17,317 $ 702 $ 18,019 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 .

Real Estate Joint Ventures

Real Estate Joint Ventures	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 (dollars in thousands): March 31, 2020 (1) Date Acquired Nominal Ownership % Total Assets Encumbered Assets Total Liabilities Entity Location LW Redstone Company, LLC 3/23/2010 85% Huntsville, Alabama $ 285,673 $ 111,839 $ 100,415 M Square Associates, LLC 6/26/2007 50% College Park, Maryland 91,205 63,318 56,396 Stevens Investors, LLC 8/11/2015 95% Washington, DC 135,861 135,175 64,621 $ 512,739 $ 310,332 $ 221,432 (1) Excludes amounts eliminated in consolidation. In March 2020, the LW Redstone Company, LLC joint venture agreement was amended to change the distribution terms to allow the venture to distribute financing proceeds to satisfy our partner’s cumulative preferred return and to provide our partner a priority preferred return on its invested capital. 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 March 31, 2020 December 31, 2019 GI-COPT DC Partnership LLC 7/21/2016 50% 6 $ 37,275 $ 37,816 BREIT COPT DC JV LLC 6/20/2019 10% 9 13,945 14,133 15 $ 51,220 $ 51,949 (1) Included in the line entitled “investment in unconsolidated real estate joint ventures” on our consolidated balance sheets.

Investing Receivables

Investing Receivables	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables consisted of the following (in thousands): March 31, December 31, Notes receivable from the City of Huntsville $ 60,699 $ 59,427 Other investing loans receivable 14,096 14,096 Amortized cost basis 74,795 73,523 Allowance for credit losses (3,598 ) — Investing receivables, net $ 71,197 $ 73,523 The balances above include accrued interest receivable, net of allowance for credit losses, of $433,000 as of March 31, 2020 and $4.7 million as of December 31, 2019 . 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% . The fair value of these receivables was approximately $75 million as of March 31, 2020 and $74 million as of December 31, 2019 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	3 Months Ended
	Mar. 31, 2020
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): March 31, December 31, Lease incentives, net $ 29,026 $ 28,433 Prepaid expenses 12,482 18,835 Furniture, fixtures and equipment, net 7,620 7,823 Construction contract costs in excess of billings, net 7,463 17,223 Non-real estate equity investments 6,714 6,705 Restricted cash 3,826 3,397 Deferred financing costs, net (1) 3,351 3,633 Deferred tax asset, net (2) 2,279 2,328 Other assets 5,375 4,639 Total for COPLP and subsidiaries 78,136 93,016 Marketable securities in deferred compensation plan 2,279 3,060 Total for COPT and subsidiaries $ 80,415 $ 96,076 (1) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (2) Includes a valuation allowance of $480,000 as of March 31, 2020 and December 31, 2019 .

Debt, Net

Debt, Net	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt, Net	Debt, Net Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of March 31, December 31, March 31, 2020 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 142,581 $ 143,430 3.82% - 4.62% (3) 2023-2026 Variable rate secured debt (4) 100,003 68,055 LIBOR + 1.45% to 2.35% (5) 2020-2026 Total mortgage and other secured debt 242,584 211,485 Revolving Credit Facility (6) 242,000 177,000 LIBOR + 0.775% to 1.45% (7) March 2023 (6) Term Loan Facility (8) 397,863 248,706 LIBOR + 1.00% to 1.65% (9) 2022 Unsecured Senior Notes 3.60%, $350,000 aggregate principal 348,544 348,431 3.60% (10) May 2023 5.25%, $250,000 aggregate principal 247,785 247,652 5.25% (11) February 2024 3.70%, $300,000 aggregate principal 299,454 299,324 3.70% (12) June 2021 5.00%, $300,000 aggregate principal 297,605 297,503 5.00% (13) July 2025 Unsecured note payable 1,004 1,038 0% (14) May 2026 Total debt, net $ 2,076,839 $ 1,831,139 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.6 million as of March 31, 2020 and $5.8 million as of December 31, 2019 . (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 $202,000 as of March 31, 2020 and $217,000 as of December 31, 2019 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.16% as of March 31, 2020 . (4) Includes a construction loan with $55.9 million in remaining borrowing capacity as of March 31, 2020 . (5) The weighted average interest rate on our variable rate secured debt was 3.77% as of March 31, 2020 . (6) 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. In connection with this facility, we also 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. (7) The weighted average interest rate on the Revolving Credit Facility was 1.74% as of March 31, 2020 . (8) On March 6, 2020, we amended this loan facility to increase the loan amount by $150.0 million and change the interest terms. (9) The interest rate on this loan was 2.37% as of March 31, 2020 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.0 million as of March 31, 2020 and $1.1 million as of December 31, 2019 . 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 $2.0 million as of March 31, 2020 and $2.1 million as of December 31, 2019 . 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 $429,000 as of March 31, 2020 and $534,000 as of December 31, 2019 . 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 $2.0 million as of March 31, 2020 and $2.1 million as of December 31, 2019 . 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 $207,000 as of March 31, 2020 and $223,000 as of December 31, 2019 . 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 March 31, 2020 , we were compliant with these financial covenants. We capitalized interest costs of $3.4 million in the three months ended March 31, 2020 and $2.0 million in the three months ended March 31, 2019 . The following table sets forth information pertaining to the fair value of our debt (in thousands): March 31, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,193,388 $ 1,223,259 $ 1,192,910 $ 1,227,441 Other fixed-rate debt 143,585 142,201 144,468 149,907 Variable-rate debt 739,866 747,039 493,761 495,962 $ 2,076,839 $ 2,112,499 $ 1,831,139 $ 1,873,310

Interest Rate Derivatives

Interest Rate Derivatives	3 Months Ended
	Mar. 31, 2020
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 March 31, December 31, $ 12,336 (1) 1.390% One-Month LIBOR 10/13/2015 10/1/2020 $ (57 ) $ 23 100,000 1.901% One-Month LIBOR 9/1/2016 12/1/2022 (4,297 ) (1,028 ) 100,000 1.905% One-Month LIBOR 9/1/2016 12/1/2022 (4,307 ) (1,037 ) 50,000 1.908% One-Month LIBOR 9/1/2016 12/1/2022 (2,157 ) (524 ) 11,200 (2) 1.678% One-Month LIBOR 8/1/2019 8/1/2026 (778 ) (20 ) 150,000 0.498% One-Month LIBOR 4/1/2020 12/31/2020 (125 ) — 23,000 (3) 0.573% One-Month LIBOR 4/1/2020 3/26/2025 (174 ) — 75,000 3.176% Three-Month LIBOR 6/30/2020 6/30/2030 (18,132 ) (8,640 ) 75,000 3.192% Three-Month LIBOR 6/30/2020 6/30/2030 (18,249 ) (8,749 ) 75,000 2.744% Three-Month LIBOR 6/30/2020 6/30/2030 (14,956 ) (5,684 ) $ (63,232 ) $ (25,659 ) (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . (2) The notional amount of this instrument is scheduled to amortize to $10.0 million . (3) The notional amount of this instrument is scheduled to amortize to $22.1 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 March 31, December 31, 2019 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets, net $ — $ 23 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (63,232 ) $ (25,682 ) 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 Recognized in AOCL on Derivatives Amount of (Loss) Gain Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended March 31, For the Three Months Ended March 31, Derivatives in Hedging Relationships 2020 2019 2020 2019 Interest rate derivatives $ (37,705 ) $ (8,845 ) $ (131 ) $ 570 Based on the fair value of our derivatives as of March 31, 2020, we estimate that approximately $6.0 million of losses will be reclassified from accumulated other comprehensive loss (“AOCL”) as an increase to interest expense over the next 12 months. 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 March 31, 2020 , we were not in default with any of these provisions. As of March 31, 2020 , the fair value of interest rate derivatives in a liability position related to these agreements was $63.4 million , excluding the effects of accrued interest and credit valuation adjustments. As of March 31, 2020 , 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 $63.5 million as of March 31, 2020 .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	3 Months Ended
	Mar. 31, 2020
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, 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 Three Months Ended March 31, 2020 2019 Beginning balance $ 29,431 $ 26,260 Distributions to noncontrolling interests (11,578 ) (349 ) Net income attributable to noncontrolling interests 958 675 Adjustment to arrive at fair value of interests 4,101 799 Ending balance $ 22,912 $ 27,385

Equity

Equity	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Equity	Equity Common Shares/Units As of March 31, 2020 , 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 three months ended March 31, 2020 , certain COPLP limited partners converted 12,009 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 March 31, 2020 and 2019 . 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	3 Months Ended
	Mar. 31, 2020
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 (“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). We measure the performance of our segments through the measure we define as net operating income from real estate operations (“NOI from real estate operations”), which includes: real estate revenues and property operating expenses; and the net of revenues and property operating expenses of real estate operations owned through unconsolidated real estate joint ventures (“UJVs”) that is allocable to COPT’s ownership interest (“UJV NOI allocable to COPT”). Amounts reported for segment assets represent long-lived assets associated with consolidated operating properties (including the carrying value of properties, right-of-use assets, net of related lease liabilities, intangible assets, deferred leasing costs, deferred rents receivable and lease incentives) and the carrying value of investments in UJVs owning operating properties. Amounts reported as additions to long-lived assets represent additions to existing consolidated operating properties, excluding transfers from non-operating properties, which we report separately. 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 March 31, 2020 Revenues from real estate operations $ 64,438 $ 13,678 $ 12,076 $ 8,341 $ 4,676 $ 5,577 $ 108,786 $ 15,460 $ 7,172 $ 698 $ 132,116 Property operating expenses (21,222 ) (5,185 ) (6,795 ) (3,285 ) (1,847 ) (657 ) (38,991 ) (7,537 ) (3,233 ) (238 ) (49,999 ) UJV NOI allocable to COPT — — — — — 1,713 1,713 — — — 1,713 NOI from real estate operations $ 43,216 $ 8,493 $ 5,281 $ 5,056 $ 2,829 $ 6,633 $ 71,508 $ 7,923 $ 3,939 $ 460 $ 83,830 Additions to long-lived assets $ 7,675 $ 2,691 $ — $ 1,758 $ 170 $ — $ 12,294 $ 3,357 $ 878 $ 65 $ 16,594 Transfers from non-operating properties $ 538 $ 256 $ 15 $ — $ 1,136 $ 56,232 $ 58,177 $ — $ — $ — $ 58,177 Segment assets at March 31, 2020 $ 1,275,601 $ 395,108 $ 145,363 $ 183,054 $ 138,797 $ 334,102 $ 2,472,025 $ 390,352 $ 200,891 $ 3,677 $ 3,066,945 Three Months Ended March 31, 2019 Revenues from real estate operations $ 62,683 $ 14,831 $ 11,561 $ 8,155 $ 3,939 $ 7,354 $ 108,523 $ 14,833 $ 7,871 $ 763 $ 131,990 Property operating expenses (22,335 ) (5,292 ) (5,959 ) (3,404 ) (1,539 ) (353 ) (38,882 ) (7,416 ) (2,838 ) (309 ) (49,445 ) UJV NOI allocable to COPT — — — — — 1,219 1,219 — — — 1,219 NOI from real estate operations $ 40,348 $ 9,539 $ 5,602 $ 4,751 $ 2,400 $ 8,220 $ 70,860 $ 7,417 $ 5,033 $ 454 $ 83,764 Additions to long-lived assets $ 3,935 $ 1,447 $ — $ 5,017 $ 300 $ — $ 10,699 $ 3,989 $ 156 $ 10 $ 14,854 Transfers from non-operating properties $ 5,040 $ 4,509 $ 6,503 $ — $ 3,635 $ 19,788 $ 39,475 $ — $ — $ — $ 39,475 Segment assets at March 31, 2019 $ 1,279,983 $ 400,741 $ 145,697 $ 189,192 $ 110,195 $ 370,447 $ 2,496,255 $ 394,001 $ 213,993 $ 3,904 $ 3,108,153 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 March 31, 2020 2019 Segment revenues from real estate operations $ 132,116 $ 131,990 Construction contract and other service revenues 13,681 16,950 Total revenues $ 145,797 $ 148,940 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 March 31, 2020 2019 UJV NOI allocable to COPT $ 1,713 $ 1,219 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (1,270 ) (827 ) Add: Equity in loss of unconsolidated non-real estate entities (2 ) (1 ) Equity in income of unconsolidated entities $ 441 $ 391 As previously discussed, we provide real estate services such as property management, development and construction 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 March 31, 2020 2019 Construction contract and other service revenues $ 13,681 $ 16,950 Construction contract and other service expenses (13,121 ) (16,326 ) NOI from service operations $ 560 $ 624 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 March 31, 2020 2019 NOI from real estate operations $ 83,830 $ 83,764 NOI from service operations 560 624 Interest and other income 1,205 2,286 Credit loss expense (689 ) — Gain on sales of real estate 5 — Equity in income of unconsolidated entities 441 391 Income tax expense (49 ) (194 ) Depreciation and other amortization associated with real estate operations (32,596 ) (34,796 ) General, administrative and leasing expenses (7,486 ) (8,751 ) Business development expenses and land carry costs (1,118 ) (1,113 ) Interest expense (16,840 ) (18,674 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,713 ) (1,219 ) Net income $ 25,550 $ 22,318 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): March 31, March 31, Segment assets $ 3,066,945 $ 3,108,153 Operating properties lease liabilities included in segment assets 17,365 16,342 Non-operating property assets 658,978 485,911 Other assets 311,169 165,453 Total COPT consolidated assets $ 4,054,457 $ 3,775,859 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, credit loss expense, 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	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 2019 Construction contract revenue: Guaranteed maximum price $ 5,044 $ 12,356 Firm fixed price 5,072 2,325 Cost-plus fee 3,309 2,060 Other 256 209 $ 13,681 $ 16,950 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended March 31, 2020 2019 Construction contract revenue: Construction $ 12,883 $ 16,489 Design 542 252 Other 256 209 $ 13,681 $ 16,950 We recognized revenue of $32,000 in the three months ended March 31, 2019 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 Three Months Ended March 31, 2020 2019 Beginning balance $ 12,378 $ 6,701 Ending balance $ 10,852 $ 6,569 Contract assets, which we refer to herein as construction contract costs in excess of billings, net 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 Three Months Ended March 31, 2020 2019 Beginning balance $ 17,223 $ 3,189 Ending balance $ 7,463 $ 14,834 Contract liabilities are included in other liabilities reported on our consolidated balance sheets. Changes in contract liabilities were as follows (in thousands): For the Three Months Ended March 31, 2020 2019 Beginning balance $ 1,184 $ 568 Ending balance $ 1,417 $ 1,005 Portion of beginning balance recognized in revenue during period $ 646 $ 439 Revenue allocated to the remaining performance obligations under existing contracts as of March 31, 2020 that will be recognized as revenue in future periods was $74.1 million , approximately $26 million of which we expect to recognize during the remainder of 2020. We incurred no deferred incremental costs to obtain or fulfill our construction contracts or other service revenues and had no significant credit loss expense on construction contracts receivable or unbilled construction revenue in the three months ended March 31, 2020 and 2019

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation Restricted Shares During the three months ended March 31, 2020 , certain employees were granted a total of 133,335 restricted common shares with an aggregate grant date fair value of $3.4 million ( $25.34 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. During the three months ended March 31, 2020 , forfeiture restrictions lapsed on 132,703 previously issued common shares; these shares had a weighted average grant date fair value of $28.13 per share, and the aggregate intrinsic value of the shares on the vesting dates was $3.4 million . Performance Share Awards (“PSUs”) We issued 23,181 common shares on January 13, 2020 to executives in settlement of PSUs granted in 2017, representing 53% of the target awards for those PSUs. Profit Interest Units (“PIUs”) For 2020, we offered our executives 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), and our executives selected PIUs. 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 three months ended March 31, 2020 , our executives were granted a total of 67,081 TB-PIUs with an aggregate grant date fair value of $1.7 million ( $25.34 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. Prior to vesting, TB-PIUs carry substantially the same rights to distributions as non-PIU common units but carry no redemption rights. During the three months ended March 31, 2020 , 20,622 TB-PIUs awarded to our former Executive Vice President and Chief Operating Officer were forfeited upon his resignation. During the three months ended March 31, 2020 , forfeiture restrictions lapsed on 18,318 previously issued TB-PIUs; these TB-PIUs had a grant date fair value of $25.81 per unit, and the aggregate intrinsic value of the TB-PIUs on the vesting date was $464,000 . PB-PIUs On January 1, 2020, we granted our executives 176,758 PB-PIUs with a three -year performance period concluding on the earlier of December 31, 2022 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 (“TSR”) 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. If COPT’s TSR during the measurement period is negative, the maximum number of earned awards will be limited to the target level payout percentage. 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-PIU grants had an aggregate grant date fair value of $2.9 million ( $16.36 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 $29.38 ; expected volatility for common shares of 18.0% ; and a risk-free interest rate of 1.65% . During the three months ended March 31, 2020 , 73,184

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 2019 Numerator: Net income attributable to COPT $ 24,054 $ 20,859 Income attributable to share-based compensation awards (105 ) (86 ) Numerator for basic EPS on net income attributable to COPT common shareholders 23,949 20,773 Income attributable to share-based compensation awards 8 — Numerator for diluted EPS on net income attributable to COPT common shareholders $ 23,957 $ 20,773 Denominator (all weighted averages): Denominator for basic EPS (common shares) 111,724 109,951 Dilutive effect of share-based compensation awards 239 267 Denominator for diluted EPS (common shares) 111,963 110,218 Basic EPS $ 0.21 $ 0.19 Diluted EPS $ 0.21 $ 0.19 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 March 31, 2020 2019 Conversion of common units 1,226 1,331 Conversion of redeemable noncontrolling interests 1,011 1,013 Conversion of Series I preferred units 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 March 31, 2019 of 1.5 million ; • weighted average restricted shares and deferred share awards for the three months ended March 31, 2020 and 2019 of 440,000 and 463,000 , respectively; • weighted average options for the three months ended March 31, 2019 of 30,000 ; and • weighted average unvested TB-PIUs for the three months ended March 31, 2020 and 2019 of 75,000 and 19,000 , 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 March 31, 2020 2019 Numerator: Net income attributable to COPLP $ 24,418 $ 21,281 Preferred unit distributions (77 ) (165 ) Income attributable to share-based compensation awards (121 ) (93 ) Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ 24,220 $ 21,023 Denominator (all weighted averages): Denominator for basic EPU (common units) 112,950 111,282 Dilutive effect of share-based compensation awards 239 267 Denominator for diluted EPU (common units) 113,189 111,549 Basic EPU $ 0.21 $ 0.19 Diluted EPU $ 0.21 $ 0.19 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 March 31, 2020 2019 Conversion of redeemable noncontrolling interests 1,011 1,013 Conversion of Series I preferred units 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 March 31, 2019 of 1.5 million ; • weighted average restricted units and deferred share awards for the three months ended March 31, 2020 and 2019 of 440,000 and 463,000 , respectively; • weighted average options for the three months ended March 31, 2019 of 30,000 ; and • weighted average unvested TB-PIUs for the three months ended March 31, 2020 and 2019 of 75,000 and 19,000 , respectively.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
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. As of March 31, 2020 , management believes that it is reasonably possible that we could recognize a loss of up to $3.1 million for certain municipal tax claims. While we do not believe this loss would materially affect our financial position or liquidity, it could be material to our results of operations. Management believes that it is also reasonably possible that we could incur losses pursuant to other 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 $34 million as of March 31, 2020 . 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 March 31, 2020 , we do not expect any such future fundings will be significant. Effects of COVID-19 Since first being declared a pandemic by the World Health Organization in early March 2020, the coronavirus, or COVID-19, has spread worldwide and throughout the United States. As of May 8, 2020, there continued to be significant uncertainty regarding the duration of COVID-19’s spread, and the potential, once its spread subsides, for the virus to reoccur on a significant scale in the future. The COVID-19 outbreak has prompted governments and other authorities around the world, including federal, state and local authorities in the United States, to impose measures intended to control its spread, including restrictions on freedom of movement and business operations such as travel bans, border closings, business closures, quarantines and shelter-in-place orders. The outbreak has significantly disrupted economic markets worldwide, as well as in the United States at a national, regional and local level, and created significant volatility in financial markets. Furthermore, conditions could potentially continue to deteriorate as a result of the pandemic. COVID-19 and measures instituted to prevent spread, may adversely affect us in many ways, including by disrupting: • our tenants’ operations, which could adversely affect their ability, or willingness, to sustain their businesses and/or fulfill their lease obligations; • our ability to maintain occupancy in our properties and obtain new leases for unoccupied and new development space at favorable terms or at all; • access to debt and equity capital on attractive terms or at all. Severe disruption and instability in the global financial markets or deteriorations in credit and financing conditions may affect our or our tenants’ ability to access capital necessary to fund operations, refinance debt or fund planned investments on a timely basis, and may adversely affect the valuation of financial assets and liabilities; • the supply of products or services from our and our tenants’ vendors that are needed for us and our tenants to operate effectively; and • our and our tenants’ ability to continue or complete planned development, including the potential for delays in the supply of materials or labor necessary for development. The extent of COVID-19’s effect on our operational and financial performance is dependent on future developments, including the duration, spread and intensity of the outbreak, all of which are uncertain and difficult to predict. Due to the speed with which the effects of COVID-19 have developed, we are unable at this time to estimate the magnitude of the effect of these factors on our business, but the adverse impact on our business, results of operations, financial condition and cash flows could be material.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
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, 2019 included in our 2019 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 2019 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below.
Reclassifications	Reclassifications 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Effective January 1, 2020, we adopted guidance issued by the Financial Accounting Standards Board (“FASB”) that changes how entities measure credit losses for most financial assets and certain other instruments 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 applies to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables (excluding those arising from operating leases), loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments and guarantees). Under this guidance, we recognize an estimate of our expected credit losses on these asset types as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and be presented at the net amount expected to be collected. We adopted this guidance effective January 1, 2020 using the modified retrospective transition method under which we recognized a $5.5 million allowance for credit losses by means of a cumulative-effect adjustment to cumulative distributions in excess of net income of the Company (or common units of the Operating Partnership), and did not adjust prior comparative reporting periods. Our consolidated statements of operations reflect adjustments for changes in our expected credit losses occurring subsequent to adoption of this guidance. Effective January 1, 2020, we adopted guidance issued by the FASB that modifies disclosure requirements for fair value measurements. The resulting changes in disclosure did not have a material impact on our consolidated financial statements. Effective January 1, 2020, we adopted guidance issued by the FASB 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. Our adoption of this guidance did not have a material impact on our consolidated financial statements.
Credit Losses, Financial Assets and Other Instruments	Credit Losses, Financial Assets and Other Instruments As discussed above, effective January 1, 2020, we adopted guidance issued by the FASB that changed how we measure credit losses for most financial assets and certain other instruments not measured at fair value through net income from an incurred loss model to an expected loss approach. Our items within the scope of this guidance included the following: • investing receivables, as disclosed in Note 7; • tenant notes receivable; • other assets comprised of non-lease revenue related accounts receivable (primarily from construction contract services) and contract assets from unbilled construction contract revenue; and • off-balance sheet credit exposures, which included $4.8 million in unfunded commitments to fund tenant loans and a tax incremental financing obligation disclosed in Note 17. Under this guidance, we recognize an estimate of our expected credit losses on these items as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and be presented at the net amount expected to be collected (or as a separate liability in the case of off-balance sheet credit exposures). The allowance represents the portion of the amortized cost basis that we do not expect to collect (or loss we expect to incur in the case of off-balance sheet credit exposures) due to credit over the contractual life based on available information relevant to assessing the collectability of cash flows, which includes consideration of past events, current conditions and reasonable and supportable forecasts of future economic conditions (including consideration of asset- or borrower-specific factors). The guidance requires the allowance for expected credit losses to reflect the risk of loss, even when that risk is remote. An allowance for credit losses is measured and recorded upon the initial recognition of a financial asset (or off-balance sheet credit exposures), regardless of whether it is originated or purchased. Quarterly, the expected losses are re-estimated, considering any cash receipts and changes in risks or assumptions, with resulting adjustments recognized in the line entitled “credit loss expense” on our consolidated statements of operations. We estimate expected credit losses for in-scope items using historical loss rate information developed for varying classifications of credit risk and contractual lives of such items. Due to our limited quantity of items within the scope of this guidance and the unique risk characteristics of such items, we individually assign each in-scope item a credit risk classification. The credit risk classifications assigned by us are determined based on credit ratings assigned by ratings agencies (as available) or are internally-developed based on available financial information, historical payment experience, credit documentation, other publicly available information and current economic trends. In addition, for certain items in which the risk of credit loss is affected by the economic performance of a real estate development project, we develop probability weighted scenario analyses for varying levels of performance in estimating our credit loss allowance (applicable to our investing receivable from the City of Huntsville disclosed in Note 7 and a tax incremental financing obligation disclosed in Note 17). We write off receivables when we believe the facts and circumstances indicate that continued pursuit of collection is no longer warranted. When cash is received in connection with receivables for which we have previously recognized credit losses, we recognize reductions in our credit loss expense.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss	The table below sets forth the activity for the allowance for credit losses (in thousands): For the Three Months Ended March 31, 2020 Investing Receivables Tenant Notes Receivable (1) Other Assets (2) Off-Balance Sheet Credit Exposures (3) Total December 31, 2019 $ — $ (97 ) $ — $ — $ (97 ) Cumulative effect of change for adoption of credit loss guidance (3,732 ) (325 ) (144 ) (1,340 ) (5,541 ) Credit loss expense 134 23 (77 ) (769 ) (689 ) March 31, 2020 $ (3,598 ) $ (399 ) $ (221 ) $ (2,109 ) $ (6,327 ) (1) Included in the line entitled “accounts receivable, net” on our consolidated balance sheets. (2) The balance as of March 31, 2020 included $181,000 in the line entitled “accounts receivable, net” and $40,000 in the line entitled “prepaid expenses and other assets, net” on our consolidated balance sheets. (3) Included in the line entitled “other liabilities” on our consolidated balance sheets.
Accounts Receivable, Noncurrent, Credit Quality Indicator	The following table presents the amortized cost basis of our investing receivables and tenants notes receivable by credit risk classification, by origination year as of March 31, 2020 (in thousands): Origination Year 2015 and Earlier 2016 2017 2018 2019 2020 Total as of March 31, 2020 Investing receivables: Credit risk classification: Investment grade $ 59,833 $ — $ 866 $ — $ — $ — $ 60,699 Non-investment grade 3,020 — — — 11,076 — 14,096 Total $ 62,853 $ — $ 866 $ — $ 11,076 $ — $ 74,795 Tenant notes receivable: Credit risk classification: Investment grade $ 21 $ 78 $ — $ 1,100 $ 100 $ — $ 1,299 Non-investment grade 97 219 — 185 2,079 — 2,580 Total $ 118 $ 297 $ — $ 1,285 $ 2,179 $ — $ 3,879

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 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 $ 2,260 $ — $ — $ 2,260 Other 19 — — 19 Mutual funds (1) 10 — — 10 Total assets $ 2,289 $ — $ — $ 2,289 Liabilities: Deferred compensation plan liability (2) $ — $ 2,279 $ — $ 2,279 Interest rate derivatives — 63,232 — 63,232 Total liabilities $ — $ 65,511 $ — $ 65,511 (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 March 31, 2020 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: Mutual funds (1) $ 10 $ — $ — $ 10 Liabilities: Interest rate derivatives $ — $ 63,232 $ — $ 63,232 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPLP’s consolidated balance sheet.

Properties, Net (Tables)

Properties, Net (Tables)	3 Months Ended
	Mar. 31, 2020
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): March 31, December 31, Land $ 489,744 $ 472,976 Buildings and improvements 3,359,908 3,306,791 Less: Accumulated depreciation (1,035,703 ) (1,007,120 ) Operating properties, net $ 2,813,949 $ 2,772,647

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Operating Lease Revenue Recognized	The table below sets forth our allocation of lease revenue recognized between fixed and variable lease revenue (in thousands): For the Three Months Ended March 31, Lease revenue 2020 2019 Fixed $ 104,109 $ 104,644 Variable 26,903 26,259 $ 131,012 $ 130,903
Fixed Contractual Payments Due	Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, March 31, 2020 December 31, 2019 2020 (1) $ 301,914 $ 388,310 2021 357,747 336,482 2022 319,239 299,356 2023 264,865 245,661 2024 214,797 195,246 Thereafter 548,049 474,741 $ 2,006,611 $ 1,939,796 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020
Right-of-Use Assets and Lease Liabilities	Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,793 $ 27,864 Finance leases - Property Property - finance right-of-use assets 40,450 40,458 Total right-of-use assets $ 68,243 $ 68,322 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2020 December 31, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 17,365 $ 17,317 Finance leases - Property Other liabilities 702 702 Total lease liabilities $ 18,067 $ 18,019
Lease Costs	The table below sets forth the weighted average terms and discount rates of our leases as of March 31, 2020 : Weighted average remaining lease term Operating leases 68 years Finance leases < 1 year Weighted average discount rate Operating leases 7.33 % Finance leases 3.62 % The table below presents our total lease cost (in thousands): For the Three Months Ended March 31, Lease cost Statement of Operations Location 2020 2019 Operating lease cost Property leases Property operating expenses $ 431 $ 413 Finance lease cost Amortization of property right-of-use assets Property operating expenses 9 — $ 440 $ 413 The table below presents the effect of lease payments on our consolidated statements of cash flows (in thousands): For the Three Months Ended March 31, Supplemental cash flow information 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 311 $ 228 Financing cash flows for financing leases $ — $ 52
Finance Lease, Liability, Maturity	Payments on leases as of March 31, 2020 and December 31, 2019 were due as follows (in thousands): As of March 31, 2020 As of December 31, 2019 Year Ending December 31, Operating leases Finance leases Total Operating leases Finance leases Total 2020 (1) $ 826 $ 674 $ 1,500 $ 1,092 $ 674 $ 1,766 2021 1,138 14 1,152 1,138 14 1,152 2022 1,162 14 1,176 1,162 14 1,176 2023 1,167 — 1,167 1,167 — 1,167 2024 1,173 — 1,173 1,173 — 1,173 Thereafter 100,609 — 100,609 100,609 — 100,609 Total lease payments 106,075 702 106,777 106,341 702 107,043 Less: Amount representing interest (88,710 ) — (88,710 ) (89,024 ) — (89,024 ) Lease liability $ 17,365 $ 702 $ 18,067 $ 17,317 $ 702 $ 18,019 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 .
Lessee, Operating Lease, Liability, Maturity	As of March 31, 2020 As of December 31, 2019 Year Ending December 31, Operating leases Finance leases Total Operating leases Finance leases Total 2020 (1) $ 826 $ 674 $ 1,500 $ 1,092 $ 674 $ 1,766 2021 1,138 14 1,152 1,138 14 1,152 2022 1,162 14 1,176 1,162 14 1,176 2023 1,167 — 1,167 1,167 — 1,167 2024 1,173 — 1,173 1,173 — 1,173 Thereafter 100,609 — 100,609 100,609 — 100,609 Total lease payments 106,075 702 106,777 106,341 702 107,043 Less: Amount representing interest (88,710 ) — (88,710 ) (89,024 ) — (89,024 ) Lease liability $ 17,365 $ 702 $ 18,067 $ 17,317 $ 702 $ 18,019 (1) As of March 31, 2020 , represents the nine months ending December 31, 2020 .

Real Estate Joint Ventures (Tab

Real Estate Joint Ventures (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 (dollars in thousands): March 31, 2020 (1) Date Acquired Nominal Ownership % Total Assets Encumbered Assets Total Liabilities Entity Location LW Redstone Company, LLC 3/23/2010 85% Huntsville, Alabama $ 285,673 $ 111,839 $ 100,415 M Square Associates, LLC 6/26/2007 50% College Park, Maryland 91,205 63,318 56,396 Stevens Investors, LLC 8/11/2015 95% Washington, DC 135,861 135,175 64,621 $ 512,739 $ 310,332 $ 221,432 (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 March 31, 2020 December 31, 2019 GI-COPT DC Partnership LLC 7/21/2016 50% 6 $ 37,275 $ 37,816 BREIT COPT DC JV LLC 6/20/2019 10% 9 13,945 14,133 15 $ 51,220 $ 51,949 (1) Included in the line entitled “investment in unconsolidated real estate joint ventures” on our consolidated balance sheets.

Investing Receivables (Tables)

Investing Receivables (Tables)	3 Months Ended
	Mar. 31, 2020
Receivables [Abstract]
Schedule of investing receivables	Investing receivables consisted of the following (in thousands): March 31, December 31, Notes receivable from the City of Huntsville $ 60,699 $ 59,427 Other investing loans receivable 14,096 14,096 Amortized cost basis 74,795 73,523 Allowance for credit losses (3,598 ) — Investing receivables, net $ 71,197 $ 73,523

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets, Net (Tables)	3 Months Ended
	Mar. 31, 2020
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): March 31, December 31, Lease incentives, net $ 29,026 $ 28,433 Prepaid expenses 12,482 18,835 Furniture, fixtures and equipment, net 7,620 7,823 Construction contract costs in excess of billings, net 7,463 17,223 Non-real estate equity investments 6,714 6,705 Restricted cash 3,826 3,397 Deferred financing costs, net (1) 3,351 3,633 Deferred tax asset, net (2) 2,279 2,328 Other assets 5,375 4,639 Total for COPLP and subsidiaries 78,136 93,016 Marketable securities in deferred compensation plan 2,279 3,060 Total for COPT and subsidiaries $ 80,415 $ 96,076 (1) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (2) Includes a valuation allowance of $480,000 as of March 31, 2020 and December 31, 2019 .

Debt, Net (Tables)

Debt, Net (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of debt	Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of March 31, December 31, March 31, 2020 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 142,581 $ 143,430 3.82% - 4.62% (3) 2023-2026 Variable rate secured debt (4) 100,003 68,055 LIBOR + 1.45% to 2.35% (5) 2020-2026 Total mortgage and other secured debt 242,584 211,485 Revolving Credit Facility (6) 242,000 177,000 LIBOR + 0.775% to 1.45% (7) March 2023 (6) Term Loan Facility (8) 397,863 248,706 LIBOR + 1.00% to 1.65% (9) 2022 Unsecured Senior Notes 3.60%, $350,000 aggregate principal 348,544 348,431 3.60% (10) May 2023 5.25%, $250,000 aggregate principal 247,785 247,652 5.25% (11) February 2024 3.70%, $300,000 aggregate principal 299,454 299,324 3.70% (12) June 2021 5.00%, $300,000 aggregate principal 297,605 297,503 5.00% (13) July 2025 Unsecured note payable 1,004 1,038 0% (14) May 2026 Total debt, net $ 2,076,839 $ 1,831,139 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.6 million as of March 31, 2020 and $5.8 million as of December 31, 2019 . (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 $202,000 as of March 31, 2020 and $217,000 as of December 31, 2019 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.16% as of March 31, 2020 . (4) Includes a construction loan with $55.9 million in remaining borrowing capacity as of March 31, 2020 . (5) The weighted average interest rate on our variable rate secured debt was 3.77% as of March 31, 2020 . (6) 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. In connection with this facility, we also 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. (7) The weighted average interest rate on the Revolving Credit Facility was 1.74% as of March 31, 2020 . (8) On March 6, 2020, we amended this loan facility to increase the loan amount by $150.0 million and change the interest terms. (9) The interest rate on this loan was 2.37% as of March 31, 2020 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.0 million as of March 31, 2020 and $1.1 million as of December 31, 2019 . 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 $2.0 million as of March 31, 2020 and $2.1 million as of December 31, 2019 . 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 $429,000 as of March 31, 2020 and $534,000 as of December 31, 2019 . 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 $2.0 million as of March 31, 2020 and $2.1 million as of December 31, 2019 . 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 $207,000 as of March 31, 2020 and $223,000 as of December 31, 2019 .
Schedule of the fair value of debt	The following table sets forth information pertaining to the fair value of our debt (in thousands): March 31, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,193,388 $ 1,223,259 $ 1,192,910 $ 1,227,441 Other fixed-rate debt 143,585 142,201 144,468 149,907 Variable-rate debt 739,866 747,039 493,761 495,962 $ 2,076,839 $ 2,112,499 $ 1,831,139 $ 1,873,310

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, December 31, $ 12,336 (1) 1.390% One-Month LIBOR 10/13/2015 10/1/2020 $ (57 ) $ 23 100,000 1.901% One-Month LIBOR 9/1/2016 12/1/2022 (4,297 ) (1,028 ) 100,000 1.905% One-Month LIBOR 9/1/2016 12/1/2022 (4,307 ) (1,037 ) 50,000 1.908% One-Month LIBOR 9/1/2016 12/1/2022 (2,157 ) (524 ) 11,200 (2) 1.678% One-Month LIBOR 8/1/2019 8/1/2026 (778 ) (20 ) 150,000 0.498% One-Month LIBOR 4/1/2020 12/31/2020 (125 ) — 23,000 (3) 0.573% One-Month LIBOR 4/1/2020 3/26/2025 (174 ) — 75,000 3.176% Three-Month LIBOR 6/30/2020 6/30/2030 (18,132 ) (8,640 ) 75,000 3.192% Three-Month LIBOR 6/30/2020 6/30/2030 (18,249 ) (8,749 ) 75,000 2.744% Three-Month LIBOR 6/30/2020 6/30/2030 (14,956 ) (5,684 ) $ (63,232 ) $ (25,659 ) (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . (2) The notional amount of this instrument is scheduled to amortize to $10.0 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 March 31, December 31, 2019 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets, net $ — $ 23 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (63,232 ) $ (25,682 )
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 Recognized in AOCL on Derivatives Amount of (Loss) Gain Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended March 31, For the Three Months Ended March 31, Derivatives in Hedging Relationships 2020 2019 2020 2019 Interest rate derivatives $ (37,705 ) $ (8,845 ) $ (131 ) $ 570

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2020
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 Three Months Ended March 31, 2020 2019 Beginning balance $ 29,431 $ 26,260 Distributions to noncontrolling interests (11,578 ) (349 ) Net income attributable to noncontrolling interests 958 675 Adjustment to arrive at fair value of interests 4,101 799 Ending balance $ 22,912 $ 27,385

Information by Business Segme_2

Information by Business Segment (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 Revenues from real estate operations $ 64,438 $ 13,678 $ 12,076 $ 8,341 $ 4,676 $ 5,577 $ 108,786 $ 15,460 $ 7,172 $ 698 $ 132,116 Property operating expenses (21,222 ) (5,185 ) (6,795 ) (3,285 ) (1,847 ) (657 ) (38,991 ) (7,537 ) (3,233 ) (238 ) (49,999 ) UJV NOI allocable to COPT — — — — — 1,713 1,713 — — — 1,713 NOI from real estate operations $ 43,216 $ 8,493 $ 5,281 $ 5,056 $ 2,829 $ 6,633 $ 71,508 $ 7,923 $ 3,939 $ 460 $ 83,830 Additions to long-lived assets $ 7,675 $ 2,691 $ — $ 1,758 $ 170 $ — $ 12,294 $ 3,357 $ 878 $ 65 $ 16,594 Transfers from non-operating properties $ 538 $ 256 $ 15 $ — $ 1,136 $ 56,232 $ 58,177 $ — $ — $ — $ 58,177 Segment assets at March 31, 2020 $ 1,275,601 $ 395,108 $ 145,363 $ 183,054 $ 138,797 $ 334,102 $ 2,472,025 $ 390,352 $ 200,891 $ 3,677 $ 3,066,945 Three Months Ended March 31, 2019 Revenues from real estate operations $ 62,683 $ 14,831 $ 11,561 $ 8,155 $ 3,939 $ 7,354 $ 108,523 $ 14,833 $ 7,871 $ 763 $ 131,990 Property operating expenses (22,335 ) (5,292 ) (5,959 ) (3,404 ) (1,539 ) (353 ) (38,882 ) (7,416 ) (2,838 ) (309 ) (49,445 ) UJV NOI allocable to COPT — — — — — 1,219 1,219 — — — 1,219 NOI from real estate operations $ 40,348 $ 9,539 $ 5,602 $ 4,751 $ 2,400 $ 8,220 $ 70,860 $ 7,417 $ 5,033 $ 454 $ 83,764 Additions to long-lived assets $ 3,935 $ 1,447 $ — $ 5,017 $ 300 $ — $ 10,699 $ 3,989 $ 156 $ 10 $ 14,854 Transfers from non-operating properties $ 5,040 $ 4,509 $ 6,503 $ — $ 3,635 $ 19,788 $ 39,475 $ — $ — $ — $ 39,475 Segment assets at March 31, 2019 $ 1,279,983 $ 400,741 $ 145,697 $ 189,192 $ 110,195 $ 370,447 $ 2,496,255 $ 394,001 $ 213,993 $ 3,904 $ 3,108,153
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 March 31, 2020 2019 Segment revenues from real estate operations $ 132,116 $ 131,990 Construction contract and other service revenues 13,681 16,950 Total revenues $ 145,797 $ 148,940
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 March 31, 2020 2019 UJV NOI allocable to COPT $ 1,713 $ 1,219 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (1,270 ) (827 ) Add: Equity in loss of unconsolidated non-real estate entities (2 ) (1 ) Equity in income of unconsolidated entities $ 441 $ 391
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 March 31, 2020 2019 Construction contract and other service revenues $ 13,681 $ 16,950 Construction contract and other service expenses (13,121 ) (16,326 ) NOI from service operations $ 560 $ 624
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 March 31, 2020 2019 NOI from real estate operations $ 83,830 $ 83,764 NOI from service operations 560 624 Interest and other income 1,205 2,286 Credit loss expense (689 ) — Gain on sales of real estate 5 — Equity in income of unconsolidated entities 441 391 Income tax expense (49 ) (194 ) Depreciation and other amortization associated with real estate operations (32,596 ) (34,796 ) General, administrative and leasing expenses (7,486 ) (8,751 ) Business development expenses and land carry costs (1,118 ) (1,113 ) Interest expense (16,840 ) (18,674 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,713 ) (1,219 ) Net income $ 25,550 $ 22,318
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): March 31, March 31, Segment assets $ 3,066,945 $ 3,108,153 Operating properties lease liabilities included in segment assets 17,365 16,342 Non-operating property assets 658,978 485,911 Other assets 311,169 165,453 Total COPT consolidated assets $ 4,054,457 $ 3,775,859

Construction Contract and Oth_2

Construction Contract and Other Service Revenues (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 2019 Construction contract revenue: Guaranteed maximum price $ 5,044 $ 12,356 Firm fixed price 5,072 2,325 Cost-plus fee 3,309 2,060 Other 256 209 $ 13,681 $ 16,950 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended March 31, 2020 2019 Construction contract revenue: Construction $ 12,883 $ 16,489 Design 542 252 Other 256 209 $ 13,681 $ 16,950
Schedule of Accounts Receivable	The beginning and ending balances of accounts receivable related to our construction contracts were as follows (in thousands): For the Three Months Ended March 31, 2020 2019 Beginning balance $ 12,378 $ 6,701 Ending balance $ 10,852 $ 6,569
Contract with Customer, Asset and Liability	Changes in contract liabilities were as follows (in thousands): For the Three Months Ended March 31, 2020 2019 Beginning balance $ 1,184 $ 568 Ending balance $ 1,417 $ 1,005 Portion of beginning balance recognized in revenue during period $ 646 $ 439 For the Three Months Ended March 31, 2020 2019 Beginning balance $ 17,223 $ 3,189 Ending balance $ 7,463 $ 14,834

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [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 (“TSR”) 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)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
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 March 31, 2020 2019 Numerator: Net income attributable to COPLP $ 24,418 $ 21,281 Preferred unit distributions (77 ) (165 ) Income attributable to share-based compensation awards (121 ) (93 ) Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ 24,220 $ 21,023 Denominator (all weighted averages): Denominator for basic EPU (common units) 112,950 111,282 Dilutive effect of share-based compensation awards 239 267 Denominator for diluted EPU (common units) 113,189 111,549 Basic EPU $ 0.21 $ 0.19 Diluted EPU $ 0.21 $ 0.19 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 March 31, 2020 2019 Numerator: Net income attributable to COPT $ 24,054 $ 20,859 Income attributable to share-based compensation awards (105 ) (86 ) Numerator for basic EPS on net income attributable to COPT common shareholders 23,949 20,773 Income attributable to share-based compensation awards 8 — Numerator for diluted EPS on net income attributable to COPT common shareholders $ 23,957 $ 20,773 Denominator (all weighted averages): Denominator for basic EPS (common shares) 111,724 109,951 Dilutive effect of share-based compensation awards 239 267 Denominator for diluted EPS (common shares) 111,963 110,218 Basic EPS $ 0.21 $ 0.19 Diluted EPS $ 0.21 $ 0.19
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 March 31, 2020 2019 Conversion of redeemable noncontrolling interests 1,011 1,013 Conversion of Series I preferred units 176 176 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 March 31, 2020 2019 Conversion of common units 1,226 1,331 Conversion of redeemable noncontrolling interests 1,011 1,013 Conversion of Series I preferred units 176 176

Organization (Details)

Organization (Details) - Mar. 31, 2020 ft² in Millions	ft²	property	MW	a
Unconsolidated Real Estate Joint Ventures
Investments in real estate
Number of real estate properties		15
Operating Properties
Investments in real estate
Number of real estate properties		171
Area of real estate property (in sqft or acres) | ft²	19.4
Operating Properties | Office Properties
Investments in real estate
Number of real estate properties		148
Area of real estate property (in sqft or acres) | ft²	15.4
Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties		23
Area of real estate property (in sqft or acres) | ft²	4
Operating Properties | Single-tenant data centers | Unconsolidated Real Estate Joint Ventures
Investments in real estate
Number of real estate properties		15
Operating wholesale data center
Investments in real estate
Critical load (in megawatts) | MW			19.25
Properties under development or redevelopment
Investments in real estate
Number of real estate properties		14
Area of real estate property (in sqft or acres) | ft²	2.3
Properties under development or redevelopment | Office Properties
Investments in real estate
Number of real estate properties		11
Properties under development or redevelopment | Single-tenant data centers
Investments in real estate
Number of real estate properties		3
Properties under development or redevelopment | Partially operational properties
Investments in real estate
Number of real estate properties		1
Land controlled for future development
Investments in real estate
Area of real estate property (in sqft or acres)	11.2			900
Other Land
Investments in real estate
Area of real estate property (in sqft or acres) | a				43

Organization (Details 2)

Organization (Details 2)	3 Months Ended
	Mar. 31, 2020
COPT | 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_4

Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Mar. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss impact		$ 5,541
Unfunded commitments to fund tenant loans		$ 4,800
Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss impact	$ 5,500

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Allowance for Credit Loss Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Off-Balance Sheet, Credit Loss, Exposure, Credit Loss Expense (Reversal) Allowance for Credit Loss [Roll Forward]
December 31, 2019	$ 0
Cumulative effect of change for adoption of credit loss guidance	(1,340)
Credit loss expense	769
March 31, 2020	(2,109)
Credit Losses, Financial Assets and Other Instruments [Roll Forward]
December 31, 2019	(97)
Cumulative effect of change for adoption of credit loss guidance	(5,541)
Credit loss expense	689	$ 0
March 31, 2020	(6,327)
Investing Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
December 31, 2019	0
Cumulative effect of change for adoption of credit loss guidance	(3,732)
Credit loss expense	134
March 31, 2020	(3,598)
Tenant Notes Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
December 31, 2019	(97)
Cumulative effect of change for adoption of credit loss guidance	(325)
Credit loss expense	23
March 31, 2020	(399)
Other Assets
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
December 31, 2019	0
Cumulative effect of change for adoption of credit loss guidance	(144)
Credit loss expense	(77)
March 31, 2020	(221)
Accounts receivable, allowance for credit loss	221
Accounts Receivable, Net | Other Assets
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
March 31, 2020	(181)
Accounts receivable, allowance for credit loss	181
Prepaid Expenses and Other Assets, Net | Other Assets
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
March 31, 2020	(40)
Accounts receivable, allowance for credit loss	$ 40

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Credit Risk Classification (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investing Receivables
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	$ 62,853
2016	0
2017	866
2018	0
2019	11,076
2020	0
Total as of March 31, 2020	74,795	$ 73,523
Investing Receivables | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	59,833
2016	0
2017	866
2018	0
2019	0
2020	0
Total as of March 31, 2020	60,699
Investing Receivables | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	3,020
2016	0
2017	0
2018	0
2019	11,076
2020	0
Total as of March 31, 2020	14,096
Tenant Notes Receivables
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	118
2016	297
2017	0
2018	1,285
2019	2,179
2020	0
Total as of March 31, 2020	3,879
Tenant Notes Receivables | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	21
2016	78
2017	0
2018	1,100
2019	100
2020	0
Total as of March 31, 2020	1,299
Tenant Notes Receivables | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	97
2016	219
2017	0
2018	185
2019	2,079
2020	0
Total as of March 31, 2020	$ 2,580

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Credit Loss Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Tenant Notes Receivables
Financing Receivable, Nonaccrual [Line Items]
Accounts receivable, nonaccrual status	$ 97	$ 97

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Assets and liabilities measured at fair value on a recurring basis
Marketable securities in deferred compensation plan	$ 2,279	$ 3,060
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	$ 2,300

Fair Value Measurements (Deta_2

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Marketable securities in deferred compensation plan	$ 2,279	$ 3,060
Fair value measurement on a recurring basis
Assets:
Total assets	2,289
Liabilities:
Deferred compensation plan liability	2,279
Interest rate derivatives	63,232
Total liabilities	65,511
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	2,260
Mutual funds	10
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	19
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total assets	2,289
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	2,260
Mutual funds	10
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	19
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Total assets	0
Liabilities:
Deferred compensation plan liability	2,279
Interest rate derivatives	63,232
Total liabilities	65,511
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	0
Mutual funds	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:
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
Mutual funds	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.
Liabilities:
Interest rate derivatives	63,232
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Mutual funds
Assets:
Mutual funds	10
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Interest rate derivatives	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds
Assets:
Mutual funds	10
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Liabilities:
Interest rate derivatives	63,232
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2) | Mutual funds
Assets:
Mutual funds	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Unobservable Inputs (Level 3)
Liabilities:
Interest rate derivatives	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Unobservable Inputs (Level 3) | Mutual funds
Assets:
Mutual funds	$ 0

Properties, Net - Operating pro

Properties, Net - Operating properties, net (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Operating properties, net
Operating properties, net	$ 2,813,949	$ 2,772,647
Operating Properties, net
Operating properties, net
Less: accumulated depreciation	(1,035,703)	(1,007,120)
Operating properties, net	2,813,949	2,772,647
Operating Properties, net | Land
Operating properties, net
Gross	489,744	472,976
Operating Properties, net | Buildings and improvements
Operating properties, net
Gross	$ 3,359,908	$ 3,306,791

Properties, Net - 2020 Developm

Properties, Net - 2020 Development Activities (Details) ft² in Thousands	Mar. 31, 2020ft²property
Newly developed properties placed in service
Real Estate [Line Items]
Area of real estate property (in sqft or acres) | ft²	230
Number of real estate properties | property	1
Properties under development or contractually committed for construction
Real Estate [Line Items]
Area of real estate property (in sqft or acres) | ft²	2,200
Number of real estate properties | property	13
Properties under or approved for redevelopment partially-operational
Real Estate [Line Items]
Area of real estate property (in sqft or acres) | ft²	106
Number of real estate properties | property	1

Leases (Details)

Leases (Details)	3 Months Ended
	Mar. 31, 2020
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

Leases (Details 1)

Leases (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Leases [Abstract]
Fixed	$ 104,109	$ 104,644
Variable	26,903	26,259
Lease revenue	131,012	$ 130,903
Lease Payments to be Received
2020			$ 388,310
2020	301,914
2021	357,747		336,482
2022	319,239		299,356
2023	264,865		245,661
2024	214,797		195,246
Thereafter	548,049		474,741
Total	$ 2,006,611		$ 1,939,796

Leases (Details 2)

Leases (Details 2) - Land $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)Lease
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 68.2
Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	29 years
Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	96 years
Washington, DC
Lessee, Lease, Description [Line Items]
Remaining term of contract	80 years
Lessee right-of-use asset	$ 10.3
Number of contracts | Lease	2
Baltimore, Maryland
Lessee, Lease, Description [Line Items]
Remaining term of contract	29 years
Lessee right-of-use asset	$ 6.5
Renewal term	49 years
Stevens Investors, LLC | Washington, DC
Lessee, Lease, Description [Line Items]
Remaining term of contract	96 years
Lessee right-of-use asset	$ 37.8
M Square Associates, LLC | College Park, Maryland
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 6.6
Number of contracts | Lease	4
M Square Associates, LLC | College Park, Maryland | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	63 years
M Square Associates, LLC | College Park, Maryland | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	74 years
LW Redstone Company, LLC | Huntsville, Alabama
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 4.8
Renewal term	25 years
Number of contracts | Lease	9
LW Redstone Company, LLC | Huntsville, Alabama | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	43 years
LW Redstone Company, LLC | Huntsville, Alabama | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	50 years
Fort Meade/BW Corridor
Lessee, Lease, Description [Line Items]
Remaining term of contract	48 years
Lessee right-of-use asset	$ 2.3
Number of contracts | Lease	2

Leases (Details 3)

Leases (Details 3) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating leases - Property	$ 27,793	$ 27,864
Finance leases - Property	40,450	40,458
Total right-of-use assets	68,243	68,322
Property - operating lease liabilities	17,365	17,317
Finance leases - Property	702	702
Total lease liabilities	18,067	18,019
Property - operating right-of-use assets | Properties
Lessee, Lease, Description [Line Items]
Operating leases - Property	27,793	27,864
Property - finance right-of-use assets | Properties
Lessee, Lease, Description [Line Items]
Finance leases - Property	$ 40,450	$ 40,458

Leases (Details 4)

Leases (Details 4)	Mar. 31, 2020
Leases [Abstract]
Operating leases, Weighted average remaining lease term	68 years
Finance leases, Weighted average remaining lease term (less than)	1 year
Operating lease, Weighted average discount rate	7.33%
Finance lease, Weighted average discount rate	3.62%

Leases (Details 5)

Leases (Details 5) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Lease costs	$ 440	$ 413
Property Operating Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	431	413
Finance lease right-of use amortization	$ 9	$ 0

Leases (Details 6)

Leases (Details 6) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Operating cash flows for operating leases	$ 311	$ 228
Financing cash flows for financing leases	$ 0	$ 52

Leases (Details 7)

Leases (Details 7) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Operating leases
2020	$ 826	$ 1,092
2021	1,138	1,138
2022	1,162	1,162
2023	1,167	1,167
2024	1,173	1,173
Thereafter	100,609	100,609
Total lease payments	106,075	106,341
Less: Amount representing interest	(88,710)	(89,024)
Lease liability	17,365	17,317
Finance leases
2020	674	674
2021	14	14
2022	14	14
2023	0	0
2024	0	0
Thereafter	0	0
Total lease payments	702	702
Less: Amount representing interest	0	0
Lease liability	702	702
Total
2020	1,500	1,766
2021	1,152	1,152
2022	1,176	1,176
2023	1,167	1,167
2024	1,173	1,173
Thereafter	100,609	100,609
Total lease payments	106,777	107,043
Less: Amount representing interest	(88,710)	(89,024)
Total lease liabilities	$ 18,067	$ 18,019

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Investments in consolidated real estate joint ventures
Total Assets	$ 4,054,457	$ 3,854,453	$ 3,775,859
Total Liabilities	2,366,359	$ 2,105,777
Variable Interest Entity, Primary Beneficiary
Investments in consolidated real estate joint ventures
Total Assets	512,739
Encumbered Assets	310,332
Total Liabilities	$ 221,432
Variable Interest Entity, Primary Beneficiary | LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Nominal Ownership %	85.00%
Total Assets	$ 285,673
Encumbered Assets	111,839
Total Liabilities	$ 100,415
Variable Interest Entity, Primary Beneficiary | M Square Associates, LLC
Investments in consolidated real estate joint ventures
Nominal Ownership %	50.00%
Total Assets	$ 91,205
Encumbered Assets	63,318
Total Liabilities	$ 56,396
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC
Investments in consolidated real estate joint ventures
Nominal Ownership %	95.00%
Total Assets	$ 135,861
Encumbered Assets	135,175
Total Liabilities	$ 64,621

Real Estate Joint Ventures (D_2

Real Estate Joint Ventures (Details 2) $ in Thousands	Mar. 31, 2020USD ($)property	Dec. 31, 2019USD ($)
Unconsolidated Real Estate Joint Ventures
Schedule of Equity Method Investments [Line Items]
Number of Properties | property	15
Carrying value of Investments | $	$ 51,220	$ 51,949
GI-COPT DC Partnership LLC
Schedule of Equity Method Investments [Line Items]
Nominal Ownership %	50.00%
Number of Properties | property	6
Carrying value of Investments | $	$ 37,275	37,816
Variable Interest Entity, Not Primary Beneficiary | BREIT COPT DC JV LLC
Schedule of Equity Method Investments [Line Items]
Nominal Ownership %	10.00%
Number of Properties | property	9
Carrying value of Investments | $	$ 13,945	$ 14,133

Investing Receivables (Details)

Investing Receivables (Details) - Investing Receivables - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 74,795	$ 73,523
Allowance for credit losses	(3,598)	0
Investing receivables, net	71,197	73,523
Notes receivable from the City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	60,699	59,427
Other investing loans receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 14,096	$ 14,096

Investing Receivables - Narrati

Investing Receivables - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Other investing loans receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest rate	8.00%
LW Redstone Company, LLC | Notes receivable from the City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest rate	9.95%
Investing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable, fair value disclosure	$ 75,000	$ 74,000
Investing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable, net of allowance for credit losses	$ 433	$ 4,700

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Restricted cash	$ 3,826	$ 3,397	$ 3,995	$ 3,884
Marketable securities in deferred compensation plan	2,279	3,060
Total	80,415	96,076
Taxable REIT Subsidiary
Property, Plant and Equipment [Line Items]
Deferred tax assets, valuation allowance	(480)	(480)
Corporate Office Properties, L.P.
Property, Plant and Equipment [Line Items]
Lease incentives, net	29,026	28,433
Prepaid expenses	12,482	18,835
Furniture, fixtures and equipment, net	7,620	7,823
Construction contract costs in excess of billings, net	7,463	17,223
Non-real estate equity investments	6,714	6,705
Restricted cash	3,826	3,397	$ 3,995	$ 3,884
Deferred financing costs, net	3,351	3,633
Deferred tax asset, net	2,279	2,328
Other assets	5,375	4,639
Total	$ 78,136	$ 93,016

Debt, Net (Details)

Debt, Net (Details)	Mar. 06, 2020USD ($)	Mar. 31, 2020USD ($)extension	Dec. 31, 2019USD ($)
Debt
Carrying Value		$ 2,076,839,000	$ 1,831,139,000
Mortgage and other secured debt
Debt
Carrying Value		$ 242,584,000	211,485,000
Line of Credit | Revolving Credit Facility
Debt
Number of extensions | extension		2
Extension option period (in years)		6 months
Line of credit facility, extension fee percentage		0.075%
Loans payable
Debt
Deferred financing costs, net		$ 6,600,000	5,800,000
Fixed rate mortgage debt | Mortgage and other secured debt
Debt
Carrying Value		142,581,000	143,430,000
Unamortized premium included in carrying value		$ 202,000	217,000
Weighted average interest rate (as a percent)		4.16%
Fixed rate mortgage debt | Mortgage and other secured debt | Minimum
Debt
Interest rate (as a percent)		3.82%
Fixed rate mortgage debt | Mortgage and other secured debt | Maximum
Debt
Interest rate (as a percent)		4.62%
Variable-rate secured debt | Mortgage and other secured debt
Debt
Carrying Value		$ 100,003,000	68,055,000
Weighted average interest rate (as a percent)		3.77%
Variable-rate secured debt | Mortgage and other secured debt | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		1.45%
Variable-rate secured 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		$ 55,900,000
Revolving Credit Facility
Debt
Carrying Value		$ 242,000,000	177,000,000
Weighted average interest rate (as a percent)		1.74%
Aggregate additional borrowing capacity available		$ 500,000,000
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		$ 397,863,000	248,706,000
Interest rate (as a percent)		2.37%
Loan increase	$ 150,000,000
Term Loan Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		1.00%
Term Loan Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		1.65%
3.60%, $350,000 aggregate principal | Unsecured senior notes
Debt
Carrying Value		$ 348,544,000	348,431,000
Debt instrument, face amount		$ 350,000,000
Interest rate (as a percent)		3.60%
Unamortized discount included in carrying value		$ 1,000,000	1,100,000
Effective interest rate on debt (as a percent)		3.70%
5.25%, $250,000 aggregate principal | Unsecured senior notes
Debt
Carrying Value		$ 247,785,000	247,652,000
Debt instrument, face amount		$ 250,000,000
Interest rate (as a percent)		5.25%
Unamortized discount included in carrying value		$ 2,000,000	2,100,000
Effective interest rate on debt (as a percent)		5.49%
3.70%, $300,000 aggregate principal | Unsecured senior notes
Debt
Carrying Value		$ 299,454,000	299,324,000
Debt instrument, face amount		$ 300,000,000
Interest rate (as a percent)		3.70%
Unamortized discount included in carrying value		$ 429,000	534,000
Effective interest rate on debt (as a percent)		3.85%
5.00%, $300,000 aggregate principal | Unsecured senior notes
Debt
Carrying Value		$ 297,605,000	297,503,000
Debt instrument, face amount		$ 300,000,000
Interest rate (as a percent)		5.00%
Unamortized discount included in carrying value		$ 2,000,000	2,100,000
Effective interest rate on debt (as a percent)		5.15%
Unsecured note payable
Debt
Carrying Value		$ 1,004,000	1,038,000
Interest rate (as a percent)		0.00%
Unamortized discount included in carrying value		$ 207,000	$ 223,000

Debt, Net (Narrative) (Details)

Debt, Net (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Debt Disclosure [Abstract]
Interest costs capitalized	$ 3.4	$ 2

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Carrying Amount
Carrying amount and estimated fair value of debt
Long-term debt	$ 2,076,839	$ 1,831,139
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,193,388	1,192,910
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	143,585	144,468
Carrying Amount | Variable-rate secured debt
Carrying amount and estimated fair value of debt
Long-term debt	739,866	493,761
Estimated Fair Value
Carrying amount and estimated fair value of debt
Long-term debt	2,112,499	1,873,310
Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,223,259	1,227,441
Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	142,201	149,907
Estimated Fair Value | Variable-rate secured debt
Carrying amount and estimated fair value of debt
Long-term debt	$ 747,039	$ 495,962

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of Loss Recognized in AOCL on Derivatives	$ (37,705)	$ (8,845)
Amount of (Loss) Gain Reclassified from AOCL into Interest Expense on Statement of Operations	(131)	570
Interest rate swaps | Interest Expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (Loss) Gain Reclassified from AOCL into Interest Expense on Statement of Operations	(131)	$ 570
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	0		$ 23
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	(63,232)		(25,682)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(63,232)		(25,659)
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	6,000
Fair value of derivative liability	63,400
Settlement amount of derivative obligation at termination value	63,500
Designated | Interest rate swap, effective October 13, 2015
Fair values of interest rate swap derivatives
Notional Amount	$ 12,336
Fixed Rate	1.39%
Fair value of interest rate swaps	$ (57)		23
Notional amount of interest rate derivatives after scheduled amortization	12,100
Designated | Interest rate swap, effective September 1, 2016, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000
Fixed Rate	1.901%
Fair value of interest rate swaps	$ (4,297)		(1,028)
Designated | Interest rate swap, effective September 1, 2016, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000
Fixed Rate	1.905%
Fair value of interest rate swaps	$ (4,307)		(1,037)
Designated | Interest rate swap, effective September 1, 2016, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 50,000
Fixed Rate	1.908%
Fair value of interest rate swaps	$ (2,157)		(524)
Designated | Interest rate swap, effective August 1, 2019
Fair values of interest rate swap derivatives
Notional Amount	$ 11,200
Fixed Rate	1.678%
Fair value of interest rate swaps	$ (778)		(20)
Notional amount of interest rate derivatives after scheduled amortization	10,000
Designated | Interest rate swap, effective April 1, 2020, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 150,000
Fixed Rate	0.498%
Fair value of interest rate swaps	$ (125)		0
Designated | Interest rate swap, effective April 1, 2020, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 23,000
Fixed Rate	0.573%
Fair value of interest rate swaps	$ (174)		0
Notional amount of interest rate derivatives after scheduled amortization	22,100
Designated | Interest rate swap, effective June 30, 2020, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000
Fixed Rate	3.176%
Fair value of interest rate swaps	$ (18,132)		(8,640)
Designated | Interest rate swap, effective June 30, 2020, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000
Fixed Rate	3.192%
Fair value of interest rate swaps	$ (18,249)		(8,749)
Designated | Interest rate swap, effective June 30, 2020, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000
Fixed Rate	2.744%
Fair value of interest rate swaps	$ (14,956)		$ (5,684)

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interests (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)joint_venture	Mar. 31, 2019USD ($)
Noncontrolling Interest [Abstract]
Number of joint ventures with redeemable noncontrolling interests | joint_venture	2
Redeemable Noncontrolling Interest [Roll Forward]
Beginning balance	$ 29,431	$ 26,260
Distributions to noncontrolling interests	(11,578)	(349)
Net income attributable to noncontrolling interests	958	675
Adjustment to arrive at fair value of interests	4,101	799
Ending balance	$ 22,912	$ 27,385

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019
Class of Stock [Line Items]
Conversion of common units to common shares (in units/shares)		12,009	5,500
Dividends declared per share (in usd per share)		$ 0.275	$ 0.275
Common Shares | 2018 Common Stock Issued to Public Under At-the-Market Program
Class of Stock [Line Items]
At the market, offering program established, aggregate value	$ 300
Corporate Office Properties, L.P.
Class of Stock [Line Items]
Dividends declared per share (in usd per share)		$ 0.275	$ 0.275

Information by Business Segme_3

Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment financial information for real estate operations
Revenues from real estate operations	$ 145,797	$ 148,940
Property operating expenses	(49,999)	(49,445)
UJV NOI allocable to COPT	1,713	1,219
Segment assets	4,054,457	3,775,859	$ 3,854,453
Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	132,116	131,990
Property operating expenses	(49,999)	(49,445)
UJV NOI allocable to COPT	1,713	1,219
NOI from real estate operations	83,830	83,764
Additions to long-lived assets	16,594	14,854
Transfers from non-operating properties	58,177	39,475
Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	108,786	108,523
Property operating expenses	(38,991)	(38,882)
UJV NOI allocable to COPT	1,713	1,219
NOI from real estate operations	71,508	70,860
Additions to long-lived assets	12,294	10,699
Transfers from non-operating properties	58,177	39,475
Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	64,438	62,683
Property operating expenses	(21,222)	(22,335)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	43,216	40,348
Additions to long-lived assets	7,675	3,935
Transfers from non-operating properties	538	5,040
Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	13,678	14,831
Property operating expenses	(5,185)	(5,292)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	8,493	9,539
Additions to long-lived assets	2,691	1,447
Transfers from non-operating properties	256	4,509
Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	12,076	11,561
Property operating expenses	(6,795)	(5,959)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	5,281	5,602
Additions to long-lived assets	0	0
Transfers from non-operating properties	15	6,503
Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	8,341	8,155
Property operating expenses	(3,285)	(3,404)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	5,056	4,751
Additions to long-lived assets	1,758	5,017
Transfers from non-operating properties	0	0
Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	4,676	3,939
Property operating expenses	(1,847)	(1,539)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	2,829	2,400
Additions to long-lived assets	170	300
Transfers from non-operating properties	1,136	3,635
Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	5,577	7,354
Property operating expenses	(657)	(353)
UJV NOI allocable to COPT	1,713	1,219
NOI from real estate operations	6,633	8,220
Additions to long-lived assets	0	0
Transfers from non-operating properties	56,232	19,788
Regional Office | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	15,460	14,833
Property operating expenses	(7,537)	(7,416)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	7,923	7,417
Additions to long-lived assets	3,357	3,989
Transfers from non-operating properties	0	0
Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	7,172	7,871
Property operating expenses	(3,233)	(2,838)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	3,939	5,033
Additions to long-lived assets	878	156
Transfers from non-operating properties	0	0
Other | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	698	763
Property operating expenses	(238)	(309)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	460	454
Additions to long-lived assets	65	10
Transfers from non-operating properties	0	0
Segment assets
Segment financial information for real estate operations
Segment assets	3,066,945	3,108,153
Segment assets | Real estate operations
Segment financial information for real estate operations
Segment assets	3,066,945	3,108,153
Segment assets | Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	2,472,025	2,496,255
Segment assets | Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Segment assets	1,275,601	1,279,983
Segment assets | Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Segment assets	395,108	400,741
Segment assets | Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Segment assets	145,363	145,697
Segment assets | Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	183,054	189,192
Segment assets | Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Segment assets	138,797	110,195
Segment assets | Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Segment assets	334,102	370,447
Segment assets | Regional Office | Real estate operations
Segment financial information for real estate operations
Segment assets	390,352	394,001
Segment assets | Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Segment assets	200,891	213,993
Segment assets | Other | Real estate operations
Segment financial information for real estate operations
Segment assets	$ 3,677	$ 3,904

Information by Business Segme_4

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reconciliation of segment revenues to total revenues
Construction contract and other service revenues	$ 13,681	$ 16,950
Total revenues	145,797	148,940
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,713	1,219
Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense	(1,270)	(827)
Add: Equity in loss of unconsolidated non-real estate entities	(2)	(1)
Equity in income of unconsolidated entities	441	391
Computation of net operating income from service operations
Construction contract and other service revenues	13,681	16,950
Construction contract and other service expenses	(13,121)	(16,326)
Real estate operations
Reconciliation of segment revenues to total revenues
Total revenues	132,116	131,990
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,713	1,219
Service operations
Computation of net operating income from service operations
NOI from service operations	$ 560	$ 624

Information by Business Segme_5

Information by Business Segment (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment financial information for real estate operations
Interest and other income	$ 1,205	$ 2,286
Credit loss expense	(689)	0
Gain on sales of real estate	5	0
Equity in income of unconsolidated entities	441	391
Income tax expense	(49)	(194)
Depreciation and other amortization associated with real estate operations	(32,596)	(34,796)
General, administrative and leasing expenses	(7,486)	(8,751)
Business development expenses and land carry costs	(1,118)	(1,113)
Interest expense	(16,840)	(18,674)
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,713)	(1,219)
Net income	25,550	22,318
Real estate operations
Segment financial information for real estate operations
NOI from real estate operations	83,830	83,764
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,713)	(1,219)
Service operations
Segment financial information for real estate operations
NOI from service operations	$ 560	$ 624

Information by Business Segme_6

Information by Business Segment (Details 4) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 4,054,457	$ 3,854,453	$ 3,775,859
Operating properties lease liabilities included in segment assets	17,365	$ 17,317
Segment assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	3,066,945		3,108,153
Operating properties lease liabilities included in segment assets	17,365		16,342
Non-operating property assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	658,978		485,911
Other assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 311,169		$ 165,453

Construction Contract and Oth_3

Construction Contract and Other Service Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Remaining performance obligations	$ 74,100
Remaining performance obligation expected to be recognized during the remainder of year	26,000
Construction Contract Revenue
Disaggregation of Revenue [Line Items]
Performance obligations satisfied or already satisfied		$ 32
Deferred incremental costs incurred	$ 0	$ 0

Construction Contract and Oth_4

Construction Contract and Other Service Revenues (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 13,681	$ 16,950
Construction
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	12,883	16,489
Design
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	542	252
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	256	209
Guaranteed Maximum Price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	5,044	12,356
Firm fixed price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	5,072	2,325
Cost-plus fee
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	3,309	2,060
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 256	$ 209

Construction Contract and Oth_5

Construction Contract and Other Service Revenues (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Change in Accounts Receivable
Beginning balance	$ 35,444
Ending balance	30,317
Construction Contract Revenue
Change in Accounts Receivable
Beginning balance	12,378	$ 6,701
Ending balance	10,852	6,569
Change in Contract with Customer, Asset
Beginning balance	17,223	3,189
Ending balance	7,463	14,834
Change in Contract with Customer, Liability
Beginning balance	1,184	568
Ending balance	1,417	1,005
Portion of beginning balance recognized in revenue during period	$ 646	$ 439

Share-Based Compensation (Detai

Share-Based Compensation (Details) $ / shares in Units, $ in Thousands	Jan. 13, 2020shares	Jan. 01, 2020USD ($)Percentile_Rank$ / sharesshares	Mar. 31, 2020USD ($)form$ / sharesshares
PIUs
Share-Based Compensation
Number of forms of executive compensation | form			2
Performance-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units)		176,758
Aggregate grant date fair value | $		$ 2,900
Aggregate grant date fair value (in dollars per share) | $ / shares		$ 16.36
Award vesting period		3 years
Shares canceled (in shares)			73,184
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		$ 29.38
Expected volatility of common shares (as a percent)		18.00%
Risk-free interest rate (as a percent)		1.65%
Time-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units)			67,081
Aggregate grant date fair value | $			$ 1,700
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 25.34
Shares vested (in shares)			18,318
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 25.81
Aggregate intrinsic value of awards upon vesting | $			$ 464
Award vesting period			3 years
Award annual vesting increments			33.33%
Shares canceled (in shares)			20,622
Restricted shares
Share-Based Compensation
Stock awards granted (in shares or units)			133,335
Aggregate grant date fair value | $			$ 3,400
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 25.34
Shares vested (in shares)			132,703
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 28.13
Aggregate intrinsic value of awards upon vesting | $			$ 3,400
2017 PSU Grants | Performance share units
Share-Based Compensation
Shares issued (in shares)	23,181
Percentage of target	53.00%

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
		Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income attributable to COPT/COPLP		$ 24,054	$ 20,859
Income attributable to share-based compensation awards		(105)	(86)
Numerator for basic EPS/EPU on net income attributable to COPT/COPLP common shareholders/unitholders		23,949	20,773
Income attributable to share-based compensation awards		8	0
Numerator for diluted EPS/EPU on net income attributable to COPT/COPLP common shareholders/unitholders		$ 23,957	$ 20,773
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)		111,724	109,951
Dilutive effect of share-based compensation awards (in shares/units)		239	267
Denominator for diluted EPS/EPU (common shares/units)		111,963	110,218
Basic EPS:
Basic EPS/EPU (in dollars per share/unit)	[1]	$ 0.21	$ 0.19
Diluted EPS:
Diluted EPS/EPU (in dollars per share/unit)	[1]	$ 0.21	$ 0.19
Corporate Office Properties, L.P.
Numerator:
Net income attributable to COPT/COPLP		$ 24,418	$ 21,281
Preferred share/unit dividends/distributions		(77)	(165)
Income attributable to share-based compensation awards		(121)	(93)
Numerator for diluted EPS/EPU on net income attributable to COPT/COPLP common shareholders/unitholders		$ 24,220	$ 21,023
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)		112,950	111,282
Dilutive effect of share-based compensation awards (in shares/units)		239	267
Denominator for diluted EPS/EPU (common shares/units)		113,189	111,549
Basic EPS:
Basic EPS/EPU (in dollars per share/unit)	[2]	$ 0.21	$ 0.19
Diluted EPS:
Diluted EPS/EPU (in dollars per share/unit)	[2]	$ 0.21	$ 0.19
[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
	Mar. 31, 2020	Mar. 31, 2019
Conversion of common units
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,226	1,331
Conversion of redeemable noncontrolling interests
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,011	1,013
Conversion of Series I preferred units
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	176	176
Weighted average shares related to forward equity sale agreements
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)		1,500
Weighted average restricted shares/units and deferred shares
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	440	463
Weighted average options
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)		30
Weighted average unvested TB-PIUs
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	75	19
Corporate Office Properties, L.P. | Conversion of redeemable noncontrolling interests
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,011	1,013
Corporate Office Properties, L.P. | Conversion of Series I preferred units
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	176	176
Corporate Office Properties, L.P. | Weighted average shares related to forward equity sale agreements
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)		1,500
Corporate Office Properties, L.P. | Weighted average restricted shares/units and deferred shares
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	440	463
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)		30
Corporate Office Properties, L.P. | Weighted average unvested TB-PIUs
Antidilutive securities
Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares)	75	19

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Mar. 31, 2020USD ($)property
Commitments and Contingencies Disclosure [Abstract]
Estimate of possible loss	$ 3.1
Environmental Indemnity Agreement
Number of lease properties which were provided environmental indemnifications | property	3
Maximum environmental indemnification to the tenant against consequential damages after acquisition of property	$ 19
Tax Incremental Financing Bond | Anne Arundel County, Maryland | Specialty Tax Guarantee
Environmental Indemnity Agreement
Purchase obligations	$ 34

Uncategorized Items - copt10qdo

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (5,541,000)
Accumulated Distributions in Excess of Net Income [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(5,541,000)
Subsidiaries [Member] | Common Stock [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (5,541,000)