COPT Defense Properties (CDP) 10-Q 7 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Entity Information [Line Items]
Entity Registrant Name	CORPORATE OFFICE PROPERTIES TRUST
Entity Central Index Key	0000860546
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		111,917,479
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Small Business	false
Entity Emerging Growth Company	false
Corporate Office Properties, L.P.
Entity Information [Line Items]
Entity Registrant Name	CORPORATE OFFICE PROPERTIES, L.P.
Entity Central Index Key	0001577966
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Properties, net:
Operating properties, net	$ 2,865,829	$ 2,847,265
Projects in development or held for future development	437,173	403,361
Total properties, net	3,303,002	3,250,626
Property - finance right-of-use assets	41,685
Cash and cash equivalents	7,780	8,066
Investment in unconsolidated real estate joint venture	39,359	39,845
Accounts receivable	25,261	26,277
Deferred rent receivable	91,304	89,350
Intangible assets on real estate acquisitions, net	33,172	43,470
Deferred leasing costs (net of accumulated amortization of $34,666 and $31,994, respectively)	51,736	50,191
Investing receivables	69,390	56,982
Interest rate derivatives	2,602	5,617
Prepaid expenses and other assets, net	84,196	85,581
Total assets	3,775,859	3,656,005
Liabilities:
Debt, net	1,876,149	1,823,909
Accounts payable and accrued expenses	112,076	92,855
Rents received in advance and security deposits	25,635	30,079
Dividends and distributions payable	31,346	30,856
Deferred revenue associated with operating leases	8,415	9,125
Property - operating lease liabilities	16,619
Interest rate derivatives	11,894	5,459
Other liabilities	10,162	10,414
Total liabilities	2,092,296	2,002,697
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	27,385	26,260
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,119	1,102
Additional paid-in capital	2,475,497	2,431,355
Cumulative distributions in excess of net income	(856,703)	(846,808)
Accumulated other comprehensive loss	(9,538)	(238)
Total Corporate Office Properties Trust’s shareholders’ equity	1,610,375	1,585,411
Noncontrolling interests in subsidiaries:
Common units in COPLP	20,167	19,168
Preferred units in COPLP	8,800	8,800
Other consolidated entities	16,836	13,669
Noncontrolling interests in subsidiaries	45,803	41,637
Total equity	1,656,178	1,627,048
Total liabilities, redeemable noncontrolling interests and equity	3,775,859	3,656,005
Properties
Properties, net:
Property - operating right-of-use assets	27,569	0
Property - finance right-of-use assets	40,488	0
Liabilities:
Property - operating lease liabilities	16,619	0
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,865,829	2,847,265
Projects in development or held for future development	437,173	403,361
Total properties, net	3,303,002	3,250,626
Cash and cash equivalents	7,780	8,066
Investment in unconsolidated real estate joint venture	39,359	39,845
Accounts receivable	25,261	26,277
Deferred rent receivable	91,304	89,350
Intangible assets on real estate acquisitions, net	33,172	43,470
Deferred leasing costs (net of accumulated amortization of $34,666 and $31,994, respectively)	51,736	50,191
Investing receivables	69,390	56,982
Interest rate derivatives	2,602	5,617
Prepaid expenses and other assets, net	79,982	81,713
Total assets	3,771,645	3,652,137
Liabilities:
Debt, net	1,876,149	1,823,909
Accounts payable and accrued expenses	112,076	92,855
Rents received in advance and security deposits	25,635	30,079
Dividends and distributions payable	31,346	30,856
Deferred revenue associated with operating leases	8,415	9,125
Interest rate derivatives	11,894	5,459
Other liabilities	5,948	6,546
Total liabilities	2,088,082	1,998,829
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	27,385	26,260
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,640,272	1,604,655
Accumulated other comprehensive loss	(9,536)	(121)
Total Corporate Office Properties Trust’s shareholders’ equity	1,639,536	1,613,334
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	16,642	13,714
Total equity	1,656,178	1,627,048
Total liabilities, redeemable noncontrolling interests and equity	3,771,645	3,652,137
Corporate Office Properties, L.P. | Properties
Properties, net:
Property - operating right-of-use assets	27,569	0
Property - finance right-of-use assets	40,488	0
Liabilities:
Property - operating lease liabilities	16,619	0
Limited Partner | Corporate Office Properties, L.P.
Corporate Office Properties Trust’s shareholders’ equity:
Preferred units held by limited partner, 352,000 preferred units outstanding at March 31, 2019 and December 31, 2018	$ 8,800	$ 8,800

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accumulated amortization of deferred leasing costs	$ 34,666	$ 31,994
Common Shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common Shares of beneficial interest, shares authorized	150,000,000	150,000,000
Common Shares of beneficial interest, shares issued	111,939,790	110,241,868
Common Shares of beneficial interest, shares outstanding	111,939,790	110,241,868
Corporate Office Properties, L.P.
Accumulated amortization of deferred leasing costs	$ 34,666	$ 31,994
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	111,939,790	110,241,868
Corporate Office Properties, L.P. | Limited Partner
Common Shares of beneficial interest, shares outstanding	1,576,024	1,332,886
Preferred Units, Outstanding	352,000	352,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Revenues
Lease revenue		$ 130,903	$ 127,133
Construction contract and other service revenues		16,950	27,198
Total revenues		148,940	155,476
Operating expenses
Property operating expenses		49,445	50,951
Depreciation and amortization associated with real estate operations		34,796	33,512
Construction contract and other service expenses		16,326	26,216
General, administrative and leasing expenses		8,751	7,292
Business development expenses and land carry costs		1,113	1,614
Total operating expenses		110,431	119,585
Interest expense		(18,674)	(18,784)
Interest and other income		2,286	1,359
Gain on sales of real estate		0	(4)
Income before equity in income of unconsolidated entities and income taxes		22,121	18,462
Equity in income of unconsolidated entities		391	373
Income tax expense		(194)	(55)
Net income		22,318	18,780
Net income attributable to noncontrolling interests:
Common units in COPLP		(257)	(544)
Preferred units in COPLP		(165)	(165)
Other consolidated entities		(1,037)	(921)
Net income attributable to COPLP		20,859	17,150
Net income attributable to COPT common shareholders		$ 20,859	$ 17,150
Earnings per common share:
Net income attributable to COPT common shareholders - basic (in dollars per share/unit)	[1]	$ 0.19	$ 0.17
Net income attributable to COPT common shareholders - diluted (in dollars per share/unit)	[1]	$ 0.19	$ 0.17
Other Property Revenue
Revenues
Total revenues		$ 1,087	$ 1,145
Corporate Office Properties, L.P.
Revenues
Lease revenue		130,903	127,133
Construction contract and other service revenues		16,950	27,198
Total revenues		148,940	155,476
Operating expenses
Property operating expenses		49,445	50,951
Depreciation and amortization associated with real estate operations		34,796	33,512
Construction contract and other service expenses		16,326	26,216
General, administrative and leasing expenses		8,751	7,292
Business development expenses and land carry costs		1,113	1,614
Total operating expenses		110,431	119,585
Interest expense		(18,674)	(18,784)
Interest and other income		2,286	1,359
Gain on sales of real estate		0	(4)
Income before equity in income of unconsolidated entities and income taxes		22,121	18,462
Equity in income of unconsolidated entities		391	373
Income tax expense		(194)	(55)
Net income		22,318	18,780
Net income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities		(1,037)	(921)
Net income attributable to COPLP		21,281	17,859
Preferred unit distributions		(165)	(165)
Net income attributable to COPT common shareholders		$ 21,116	$ 17,694
Earnings per common share:
Net income attributable to COPT common shareholders - basic (in dollars per share/unit)	[2]	$ 0.19	$ 0.17
Net income attributable to COPT common shareholders - diluted (in dollars per share/unit)	[2]	$ 0.19	$ 0.17
Corporate Office Properties, L.P. | Other Property Revenue
Revenues
Total revenues		$ 1,087	$ 1,145
[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, 2019	Mar. 31, 2018
Net income	$ 22,318	$ 18,780
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(8,845)	4,676
(Gain) loss on interest rate derivatives recognized in interest expense	(570)	245
Other comprehensive (loss) income	(9,415)	4,921
Comprehensive income	12,903	23,701
Comprehensive income attributable to noncontrolling interests	(1,344)	(1,790)
Comprehensive income attributable to COPT	11,559	21,911
Corporate Office Properties, L.P.
Net income	22,318	18,780
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(8,845)	4,676
(Gain) loss on interest rate derivatives recognized in interest expense	(570)	245
Other comprehensive (loss) income	(9,415)	4,921
Comprehensive income	12,903	23,701
Comprehensive income attributable to noncontrolling interests	(1,037)	(921)
Comprehensive income attributable to COPT	$ 11,866	$ 22,780

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Forward Equity Sale Agreement	Common Shares	Common SharesForward Equity Sale Agreement	Additional Paid-in Capital	Additional Paid-in CapitalForward Equity Sale Agreement	Cumulative Distributions in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	Corporate Office Properties, L.P.	Corporate Office Properties, L.P.Forward Equity Sale Agreement	Corporate Office Properties, L.P.Common Shares	Corporate Office Properties, L.P.Common SharesForward Equity Sale Agreement	Corporate Office Properties, L.P.Accumulated Other Comprehensive Income (Loss)	Corporate Office Properties, L.P.Noncontrolling Interests	Corporate Office Properties, L.P.Limited Partner	Corporate Office Properties, L.P.Limited PartnerPreferred Shares
Increase (Decrease) in Shareholders' Equity
Cumulative effect of accounting change for adoption of hedge accounting guidance							$ (276)	$ 276				$ (276)		$ 276
Balance, as adjusted	$ 1,468,307		$ 1,013		$ 2,201,047		(802,361)	2,443	$ 66,165	$ 1,468,307		1,444,746		2,449	$ 12,312		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018, respectively) at Dec. 31, 2017	$ 1,468,307		1,013		2,201,047		(802,085)	2,167	66,165	1,468,307		$ 1,445,022		2,173	12,312		$ 8,800
Balance (preferred units) at Dec. 31, 2017																	352,000
Balance (in units/shares) at Dec. 31, 2017	101,292,299											104,543,177
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 53,817 and 5,500 shares for the three months ended March 31, 2018 and 2019, respectively)	$ 0		1		760				(761)
Common shares issued under forward equity sale agreements (COPT: 677,000 and 1,614,087 shares for the three months ended March 31, 2018 and 2019, respectively)		$ 19,976		$ 7		$ 19,969				19,976		$ 19,976
Common shares issued under forward equity sale agreements (in units/shares)		677,000										677,000
Share-based compensation issuance, net of redemptions (in units/shares)	127,242											127,242
Share-based compensation issuance, net of redemptions (COPT: 127,242 and 78,335 shares issued, net of redemptions for the three months ended March 31, 2018 and 2019, respectively)	$ 1,680		1		1,679					1,680		$ 1,680
Redemption of vested equity awards	(1,327)				(1,327)					(1,327)		(1,327)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0				(164)				164
Comprehensive income	23,063						17,150	4,761	1,152	23,063		17,694		4,921	283		$ 165
Dividends/Distributions	(28,091)						(28,091)			(29,135)		(28,970)					$ (165)
Distributions to owners of common and preferred units in COPLP	(1,044)								(1,044)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(3)								(3)	(3)					(3)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (537)				(537)					(537)		$ (537)
Balance (in units/shares) at Mar. 31, 2018	102,150,358											105,347,419
Balance (preferred units) at Mar. 31, 2018																	352,000
Balance (COPT: 102,150,358 and 111,939,790 shares as of March 31, 2018 and 2019, respectively) at Mar. 31, 2018	$ 1,482,024		1,022		2,221,427		(813,302)	7,204	65,673	1,482,024		$ 1,453,262		7,370	12,592		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018, respectively) at Dec. 31, 2018	$ 1,627,048		1,102		2,431,355		(846,808)	(238)	41,637	1,627,048		$ 1,604,655		(121)	13,714		$ 8,800
Balance (preferred units) at Dec. 31, 2018																352,000	352,000
Balance (in units/shares) at Dec. 31, 2018	110,241,868											111,574,754				1,332,886
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 53,817 and 5,500 shares for the three months ended March 31, 2018 and 2019, respectively)	$ 0		0		80				(80)
Common shares issued under forward equity sale agreements (COPT: 677,000 and 1,614,087 shares for the three months ended March 31, 2018 and 2019, respectively)		$ 46,454		$ 16		$ 46,438					$ 46,454		$ 46,454
Common shares issued under forward equity sale agreements (in units/shares)		1,614,087											1,614,087
Share-based compensation issuance, net of redemptions (in units/shares)	78,335											326,973
Share-based compensation issuance, net of redemptions (COPT: 127,242 and 78,335 shares issued, net of redemptions for the three months ended March 31, 2018 and 2019, respectively)	$ 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 (in units/shares) at Mar. 31, 2019	111,939,790											113,515,814				1,576,024
Balance (preferred units) at Mar. 31, 2019																352,000	352,000
Balance (COPT: 102,150,358 and 111,939,790 shares as of March 31, 2018 and 2019, respectively) at Mar. 31, 2019	$ 1,656,178		$ 1,119		$ 2,475,497		$ (856,703)	$ (9,538)	$ 45,803	$ 1,656,178		$ 1,640,272		$ (9,536)	$ 16,642		$ 8,800

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Balance (in units/ shares)	111,939,790	102,150,358	110,241,868	101,292,299
Conversion of common units to common shares (in units/shares)	5,500	53,817
Share-based compensation issuance, net of redemptions (in units/shares)	78,335	127,242
Forward Equity Sale Agreement
Common shares issued during the period (in units/shares)	1,614,087	677,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Revenues from real estate operations received	$ 126,569	$ 135,027
Construction contract and other service revenues received	5,904	9,268
Property operating expenses paid	(42,974)	(43,212)
Construction contract and other service expenses paid	(4,614)	(41,128)
General, administrative, leasing, business development and land carry costs paid	(11,703)	(10,900)
Interest expense paid	(18,282)	(19,092)
Lease incentives paid	(1,158)	(4,204)
Other	910	436
Net cash provided by operating activities	54,652	26,195
Cash flows from investing activities
Construction, development and redevelopment	(100,212)	(17,540)
Tenant improvements on operating properties	(4,174)	(9,077)
Other capital improvements on operating properties	(4,476)	(5,198)
Investing receivables funded	(11,051)	0
Leasing costs paid	(2,539)	(2,015)
Other	1,297	(974)
Net cash used in investing activities	(121,155)	(34,804)
Proceeds from debt
Revolving Credit Facility	123,000	82,000
Other debt proceeds	3,350	0
Repayments of debt
Revolving Credit Facility	(74,000)	(55,000)
Scheduled principal amortization	(1,098)	(1,052)
Payments on finance lease liabilities	(52)	(4,202)
Net proceeds from issuance of common shares/units	46,415	19,989
Common share/unit dividends/distributions paid	(30,287)	(27,855)
Distributions paid to noncontrolling interests in COPLP	(553)	(1,059)
Redemption of vested equity awards	(1,817)	(1,327)
Other	1,370	(5,183)
Net cash provided by financing activities	66,328	6,311
Net decrease in cash and cash equivalents and restricted cash	(175)	(2,298)
Cash and cash equivalents and restricted cash
Beginning of period	11,950	14,831
End of period	11,775	12,533
Reconciliation of net income to net cash provided by operating activities:
Net income	22,318	18,780
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	35,229	34,035
Amortization of deferred financing costs and net debt discounts	898	822
Increase in deferred rent receivable	(2,539)	(1,512)
Gain on sales of real estate	0	4
Share-based compensation	1,659	1,545
Other	(1,572)	(907)
Changes in operating assets and liabilities:
Decrease in accounts receivable	1,033	7,877
(Increase) decrease in prepaid expenses and other assets, net	(6,752)	8,533
Increase (decrease) in accounts payable, accrued expenses and other liabilities	8,822	(43,903)
(Decrease) increase in rents received in advance and security deposits	(4,444)	921
Net cash provided by operating activities	54,652	26,195
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	11,950	14,831
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	11,329	12,232
Finance right-of-use asset contributed by noncontrolling interest in joint venture	2,570	0
Operating right-of-use assets obtained in exchange for operating lease liabilities	276	0
(Decrease) increase in fair value of derivatives applied to accumulated other comprehensive income and noncontrolling interests	(9,450)	4,887
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	80	761
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	1,322	164
Increase in redeemable noncontrolling interests and decrease in equity to carry redeemable noncontrolling interests at fair value	799	537
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	126,569	135,027
Construction contract and other service revenues received	5,904	9,268
Property operating expenses paid	(42,974)	(43,212)
Construction contract and other service expenses paid	(4,614)	(41,128)
General, administrative, leasing, business development and land carry costs paid	(11,703)	(10,900)
Interest expense paid	(18,282)	(19,092)
Lease incentives paid	(1,158)	(4,204)
Other	910	436
Net cash provided by operating activities	54,652	26,195
Cash flows from investing activities
Construction, development and redevelopment	(100,212)	(17,540)
Tenant improvements on operating properties	(4,174)	(9,077)
Other capital improvements on operating properties	(4,476)	(5,198)
Investing receivables funded	(11,051)	0
Leasing costs paid	(2,539)	(2,015)
Other	1,297	(974)
Net cash used in investing activities	(121,155)	(34,804)
Proceeds from debt
Revolving Credit Facility	123,000	82,000
Other debt proceeds	3,350	0
Repayments of debt
Revolving Credit Facility	(74,000)	(55,000)
Scheduled principal amortization	(1,098)	(1,052)
Payments on finance lease liabilities	(52)	(4,202)
Net proceeds from issuance of common shares/units	46,415	19,989
Common share/unit dividends/distributions paid	(30,675)	(28,749)
Preferred share/unit dividends/distributions paid	(165)	(165)
Redemption of vested equity awards	(1,817)	(1,327)
Other	1,370	(5,183)
Net cash provided by financing activities	66,328	6,311
Net decrease in cash and cash equivalents and restricted cash	(175)	(2,298)
Cash and cash equivalents and restricted cash
Beginning of period	11,950	14,831
End of period	11,775	12,533
Reconciliation of net income to net cash provided by operating activities:
Net income	22,318	18,780
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	35,229	34,035
Amortization of deferred financing costs and net debt discounts	898	822
Increase in deferred rent receivable	(2,539)	(1,512)
Gain on sales of real estate	0	4
Share-based compensation	1,659	1,545
Other	(1,572)	(907)
Changes in operating assets and liabilities:
Decrease in accounts receivable	1,033	7,877
(Increase) decrease in prepaid expenses and other assets, net	(6,406)	8,398
Increase (decrease) in accounts payable, accrued expenses and other liabilities	8,476	(43,768)
(Decrease) increase in rents received in advance and security deposits	(4,444)	921
Net cash provided by operating activities	54,652	26,195
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	11,950	14,831
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	11,329	12,232
Finance right-of-use asset contributed by noncontrolling interest in joint venture	2,570	0
Operating right-of-use assets obtained in exchange for operating lease liabilities	276	0
(Decrease) increase in fair value of derivatives applied to accumulated other comprehensive income and noncontrolling interests	(9,450)	4,887
Increase in redeemable noncontrolling interests and decrease in equity to carry redeemable noncontrolling interests at fair value	$ 799	$ 537

Organization

Organization	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Corporate Office Properties Trust (“COPT”) and subsidiaries (collectively, the “Company”) is a fully-integrated and self-managed real estate investment trust (“REIT”). Corporate Office Properties, L.P. (“COPLP”) and subsidiaries (collectively, the “Operating Partnership”) is the entity through which COPT, the sole general partner of COPLP, conducts almost all of its operations and owns almost all of its assets. Unless otherwise expressly stated or the context otherwise requires, “we”, “us” and “our” as used herein refer to each of the Company and the Operating Partnership. We own, manage, lease, develop and selectively acquire office and data center properties. The majority of our portfolio is in locations that support the United States Government and its contractors, most of whom are engaged in national security, defense and information technology (“IT”) related activities servicing what we believe are growing, durable, priority missions (“Defense/IT Locations”). We also own a portfolio of office properties located in select urban/urban-like submarkets in the Greater Washington, DC/Baltimore region with durable Class-A office fundamentals and characteristics (“Regional Office”). As of March 31, 2019 , our properties included the following: • 165 properties totaling 18.3 million square feet comprised of 15.2 million square feet in 146 office properties and 3.1 million square feet in 19 single-tenant data center shell properties (“data center shells”). We owned six of these data center shells through an unconsolidated real estate joint venture; • a wholesale data center with a critical load of 19.25 megawatts; • 15 properties under construction or redevelopment ( ten office properties and five data center shells) that we estimate will total approximately 2.0 million square feet upon completion, including two partially-operational properties; and • approximately 900 acres of land controlled for future development that we believe could be developed into approximately 11.6 million square feet and 150 acres of other land. COPLP owns real estate directly and through subsidiary partnerships and limited liability companies (“LLCs”). In addition to owning real estate, COPLP also owns subsidiaries that provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. Some of these services are performed by a taxable REIT subsidiary (“TRS”). Equity interests in COPLP are in the form of common and preferred units. As of March 31, 2019 , COPT owned 98.6% of the outstanding COPLP common units (“common units”); the remaining common units and all of the outstanding COPLP preferred units (“preferred units”) were owned by third parties. Common units not owned by COPT carry certain redemption rights. The number of common units owned by COPT is equivalent to the number of outstanding common shares of beneficial interest (“common shares”) of COPT, and the entitlement of common units to quarterly distributions and payments in liquidation is substantially the same as those of COPT common shareholders. However, COPLP’s common units include a special class of unit referred to as profit interest units (“PIUs”) originating from certain share-based compensation awards issued to executives (described further in Note 15) that are subject to vesting and certain tax event criteria, and accordingly may carry different rights to redemption and distributions than non-PIU common units. COPT’s common shares are publicly traded on the New York Stock Exchange (“NYSE”) under the ticker symbol “OFC”. Because COPLP is managed by COPT, and COPT conducts substantially all of its operations through COPLP, we refer to COPT’s executive officers as COPLP’s executive officers; similarly, although COPLP does not have a board of trustees, we refer to COPT’s Board of Trustees as COPLP’s Board of Trustees.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The COPT consolidated financial statements include the accounts of COPT, the Operating Partnership, their subsidiaries and other entities in which COPT has a majority voting interest and control. The COPLP consolidated financial statements include the accounts of COPLP, its subsidiaries and other entities in which COPLP has a majority voting interest and control. We also consolidate certain entities when control of such entities can be achieved through means other than voting rights (“variable interest entities” or “VIEs”) if we are deemed to be the primary beneficiary of such entities. We eliminate all intercompany balances and transactions in consolidation. We use the equity method of accounting when we own an interest in an entity and can exert significant influence over but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity. When we own an equity investment in an entity and cannot exert significant influence over its operations, we measure the investment at fair value, with changes recognized through net income. For an investment without a readily determinable fair value, we measure the investment at cost, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. These interim financial statements should be read together with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2018 included in our 2018 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2018 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below. Reclassification We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including reclassifications of our revenue from real estate operations in connection with our adoption of new lease guidance described below. Recent Accounting Pronouncements In February 2016, the FASB issued guidance setting forth principles for the recognition, measurement, presentation and disclosure of leases. This guidance requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. The resulting classification determines whether the lease expense is recognized based on an effective interest method or straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This guidance requires lessors of real estate to account for leases using an approach substantially equivalent to guidance previously in place for operating leases, direct financing leases and sales-type leases. We adopted this guidance on January 1, 2019 using a modified retrospective transition approach under which we elected to apply the guidance effective January 1, 2019 and not adjust prior comparative reporting periods (except for our presentation of lease revenue discussed below). We elected to apply a package of practical expedients that enabled us to carry forward upon adoption our historical assessments of: expired or existing leases regarding their lease classification and deferred recognition of non-incremental direct leasing costs; and whether any expired or existing contracts are, or contain, leases. We also elected a practical expedient that enabled us to avoid the need to assess whether expired or existing land easements not previously accounted for as leases are, or contain, a lease. In addition, we elected a practical expedient for our rental properties (as lessor) to avoid separating non-lease components that otherwise would need to be accounted for under the recently-adopted revenue accounting guidance (such as tenant reimbursements of property operating expenses) from the associated lease component since (1) the non-lease components have the same timing and pattern of transfer as the associated lease component and (2) the lease component, if accounted for separately, would be classified as an operating lease; this enables us to account for the combination of the lease component and non-lease components as an operating lease since the lease component is the predominant component of the combined components. Below is a summary of the primary changes in our accounting and reporting that resulted from our adoption of this guidance: • Property leases in which we are the lessor: ◦ Deferral of non-incremental leasing costs: For new or extended tenant leases, we no longer defer recognition of non-incremental leasing costs that we would have deferred under prior accounting guidance (refer to our 2018 Annual Report on Form 10-K in which we reported amounts deferred in 2018 , 2017 and 2016 ). ◦ Change in presentation of revenue: Due to our adoption of the practical expedient discussed above to not separate non-lease component revenue from the associated lease component, we are aggregating revenue from our lease components and non-lease components (comprised predominantly of tenant operating expense reimbursements) into the line entitled “lease revenue.” We are reporting other revenue from our properties in the line entitled “other property revenue.” We recast prior periods for these changes in presentation. ◦ Changes in assessment of lease revenue collectability: Changes in our assessment of lease revenue collectability that previously would have resulted in charges to bad debt expense under prior guidance are being recognized as an adjustment to rental revenue under the new guidance. Such amounts recognized by us in prior periods were not significant. ◦ Operating expenses paid directly by tenants to third parties: Operating expenses paid directly by tenants to third parties (primarily for real estate taxes) and revenue associated with such tenant payments that would have been recognized under prior guidance will no longer be reported on our Statement of Operations. Such amounts recognized by us in prior periods were not significant. • Leases (the most significant of which are ground leases) in which we are the lessee: ◦ Balance sheet presentation of property operating lease right-of-use assets: Upon adoption on January 1, 2019, we recognized property right-of-use assets and offsetting lease liabilities for existing operating leases totaling $16 million for the present value of minimum lease payments under these leases, and also reclassified an additional $11 million in amounts previously presented elsewhere on our balance sheet in connection with these leases to the right-of-use assets. We will recognize additional right-of-use assets and lease liabilities as we enter into new operating leases. ◦ Balance sheet presentation of property finance lease right-of-use assets: Property right-of-use assets of finance leases that previously were presented as properties under prior guidance are being presented as property finance right-of-use assets under the new guidance. As a result, we reclassified $38 million in assets from properties to property finance right-of-use assets upon adoption on January 1, 2019. ◦ Segment assets: We changed our definition of segment assets used for our reportable segments to include property right-of-use assets associated with operating properties, net of related lease liabilities. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance will apply to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables, loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments). Under the new guidance, an entity will recognize its estimate of expected credit losses as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and to be presented at the net amount expected to be collected. The guidance is effective for us beginning January 1, 2020, with early adoption permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2018, the FASB issued guidance that modifies disclosure requirements for fair value measurements. This guidance is effective for us beginning January 1, 2020. Early adoption is permitted for this guidance, and entities are permitted to early adopt with respect to any removed or modified disclosures while delaying adoption of additional disclosure requirements until the effective date. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. In August 2018, the FASB issued guidance that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. FASB guidance did not previously address the accounting for such implementation costs. The guidance is effective for us beginning January 1, 2020, with early adoption permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Recurring Fair Value Measurements COPT has a non-qualified elective deferred compensation plan for Trustees and certain members of our management team that permits participants to defer up to 100% of their compensation on a pre-tax basis and receive a tax-deferred return on such deferrals. The assets held in the plan (comprised primarily of mutual funds and equity securities) and the corresponding liability to the participants are measured at fair value on a recurring basis on COPT’s consolidated balance sheets using quoted market prices, as are other marketable securities that we hold. The balance of the plan, which was fully funded, totaled $4.2 million as of March 31, 2019 , and is included in the line entitled “prepaid expenses and other assets, net” on COPT’s consolidated balance sheets. The offsetting liability associated with the plan is adjusted to fair value at the end of each accounting period based on the fair value of the plan assets and reported in other liabilities on COPT’s consolidated balance sheets. The assets of the plan are classified in Level 1 of the fair value hierarchy, while the offsetting liability is classified in Level 2 of the fair value hierarchy. The fair values of our interest rate derivatives are determined using widely accepted valuation techniques, including a discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate market data and implied volatilities in such interest rates. While we determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our interest rate derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default. However, as of March 31, 2019 , we assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivatives and determined that these adjustments are not significant. As a result, we determined that our interest rate derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. The carrying values of cash and cash equivalents, restricted cash, accounts receivable, other assets (excluding investing receivables) and accounts payable and accrued expenses are reasonable estimates of their fair values because of the short maturities of these instruments. The fair values of our investing receivables, as disclosed in Note 7, were based on the discounted estimated future cash flows of the loans (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans with similar maturities and credit quality, and the estimated cash payments include scheduled principal and interest payments. For our disclosure of debt fair values in Note 9, we estimated the fair values of our unsecured senior notes based on quoted market rates for publicly-traded debt (categorized within Level 2 of the fair value hierarchy) and estimated the fair value of our other debt based on the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans, or groups of loans, with similar maturities and credit quality, and the estimated future payments include scheduled principal and interest payments. Fair value estimates are made as of a specific point in time, are subjective in nature and involve uncertainties and matters of significant judgment. Settlement at such fair value amounts may not be possible and may not be a prudent management decision. For additional fair value information, please refer to Note 7 for investing receivables, Note 9 for debt and Note 10 for interest rate derivatives. COPT and Subsidiaries The table below sets forth financial assets and liabilities of COPT and subsidiaries that are accounted for at fair value on a recurring basis as of March 31, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other (Level 2) Significant Inputs (Level 3) Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,171 $ — $ — $ 4,171 Other 43 — — 43 Interest rate derivatives — 2,602 — 2,602 Total assets $ 4,214 $ 2,602 $ — $ 6,816 Liabilities: Deferred compensation plan liability (2) $ — $ 4,214 $ — $ 4,214 Interest rate derivatives — 11,894 — 11,894 Total liabilities $ — $ 16,108 $ — $ 16,108 (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, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other Significant Inputs (Level 3) Total Assets: Interest rate derivatives $ — $ 2,602 $ — $ 2,602 Liabilities: Interest rate derivatives $ — $ 11,894 $ — $ 11,894

Properties, Net

Properties, Net	3 Months Ended
	Mar. 31, 2019
Real Estate [Abstract]
Properties, Net	Properties, Net Operating properties, net consisted of the following (in thousands): March 31, December 31, Land $ 505,062 $ 503,274 Buildings and improvements 3,288,033 3,241,894 Less: Accumulated depreciation (927,266 ) (897,903 ) Operating properties, net $ 2,865,829 $ 2,847,265 Properties we had in development or held for future development consisted of the following (in thousands): March 31, December 31, Land $ 227,852 $ 207,760 Development in progress, excluding land 209,321 195,601 Projects in development or held for future development $ 437,173 $ 403,361 2019 Construction Activities During the three months ended March 31, 2019 , we placed into service 181,000 square feet in three newly-constructed properties (including one partially-operational property). As of March 31, 2019 , we had 14 properties under construction (including two partially-operational properties), or which we were contractually committed to construct, that we estimate will total 1.9 million square feet upon completion and one property under redevelopment that we estimate will total 106,000 square feet upon completion.

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Leases Lessor arrangements We lease real estate properties, comprised primarily of office properties and data center shells, to third parties. As of March 31, 2019 , these leases, which may encompass all, or a portion of, a property, had remaining lease terms spanning from one month to 15 years and averaging approximately five years. These leases usually include options under which the tenant may renew its lease based on market rates at the time of renewal, which are then typically subject to further negotiation. These leases occasionally provide the tenant with an option to terminate its lease early usually for a defined termination fee. While a significant portion of our portfolio is leased to the United States Government, and the majority of those leases consist of a series of one -year renewal options, or provide for early termination rights, we have concluded that exercise of existing renewal options, or continuation of such leases without exercising early termination rights, is reasonably assured for virtually all of these leases. Most of our lease revenue is from fixed contractual payments defined under the lease that, in most cases, escalate annually over the term of the lease. Our lease revenue also includes variable lease payments predominantly for tenant reimbursements of property operating expenses and lease termination fees. Property operating expense reimbursement structures vary, with some tenants responsible for all of a property’s expenses, while others are responsible for their share of a property’s expense only to the extent such expenses exceed amounts defined in the lease (which are derived from the property’s historical expense levels). Lease termination fees in most cases result from a tenant’s exercise of an existing right under a lease, and are usually equal to a defined percentage of the remaining rents due under the lease and/or the remaining unamortized lease origination costs (including tenant improvements and lease commissions). The table below sets forth our allocation of lease revenue recognized between fixed contractual payments and variable lease payments (in thousands): Lease revenue For the Three Months Ended Fixed contractual payments $ 105,335 Variable lease payments 25,568 $ 130,903 Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, March 31, 2019 December 31, 2018 2019 (1) $ 305,864 $ 400,617 2020 347,477 337,646 2021 293,546 280,369 2022 258,502 246,329 2023 206,833 194,888 Thereafter 562,614 523,932 $ 1,974,836 $ 1,983,781 (1) As of March 31, 2019 , represents the nine months ending December 31, 2019 . Lessee arrangements We lease from third parties land underlying properties that we are operating or developing. These ground leases have long durations with remaining terms ranging from 30 years (excluding extension options) to 97 years. As of March 31, 2019 , our balance sheet included $68.1 million in right-of-use assets associated with ground leases that included: • $37.8 million for land on which we are developing an office property in Washington, DC through our Stevens Investors, LLC joint venture, virtually all of the rent on which was previously paid. This lease has a 97 -year remaining lease term, and we possess a bargain purchase option that we expect to exercise in 2020; • $10.4 million for land underlying office properties in Washington, DC under two leases with remaining terms of approximately 80 years; • $6.5 million for land underlying a parking garage in Baltimore, Maryland under a lease with a remaining term of 30 years and an option to renew for an additional 49 years that was included in the lease term used in determining the asset balance; • $6.7 million for land in a research park in College Park, Maryland under four leases through our M Square Associates, LLC joint venture all of the rent on which was previously paid. These leases had remaining terms ranging from 64 to 75 years; • $4.3 million for land in a business park in Huntsville, Alabama under nine leases through our LW Redstone Company, LLC joint venture, with remaining terms ranging from 44 to 50 years and options to renew for an additional 25 years that were not included in the lease term used in determining the asset balance; and • $2.3 million for other land in our Fort Meade/BW Corridor sub-segment under two leases with remaining terms of approximately 49 years all of the rent on which was previously paid. As of March 31, 2019 , our balance sheet also included right-of-use lease assets totaling $1.2 million in connection with vehicles and office equipment that we lease from third parties. In determining operating right-of-use assets and lease liabilities for our existing operating leases upon our adoption of the new lease guidance discussed further in Note 2, as well as for new operating leases in the current period, we were required to estimate an appropriate incremental borrowing rate on a fully-collateralized basis for the terms of the leases. Since the terms under our ground leases are significantly longer than the terms of borrowings available to us on a fully-collateralized basis, our estimate of this rate required significant judgment, and considered factors such as interest rates available to us on a fully-collateralized basis for shorter-termed debt and U.S. Treasury rates. Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,569 Finance leases Property Property - finance right-of-use assets 40,488 Vehicles and office equipment Prepaid expenses and other assets, net 1,197 Total finance lease right-of-use assets 41,685 Total right-of-use assets $ 69,254 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 16,619 Finance leases Other liabilities 1,275 Total lease liabilities $ 17,894 The table below sets forth the weighted average lease terms and discount rates of our leases as of March 31, 2019 : Weighted average remaining lease term Operating leases 70 years Finance leases 2 years Weighted average discount rate Operating leases 7.35 % Finance leases 3.10 % The table below presents our total lease cost (in thousands): Lease cost Statement of Operations Location For the Three Months Ended Operating lease cost Property leases Property operating expense $ 413 Vehicles and office equipment General, administrative and leasing expense 17 Finance lease cost Amortization of vehicles and office equipment right-of-use assets General, administrative and leasing expense 113 Interest on lease liabilities Interest expense 4 $ 547 The table below presents the effect of lease payments on our consolidated statement of cash flows (in thousands): Supplemental cash flow information For the Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 228 Operating cash flows for financing leases $ 4 Financing cash flows for financing leases $ 52 Payments on leases as of March 31, 2019 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 (1) $ 830 $ 179 $ 1,009 2020 1,128 862 1,990 2021 1,111 202 1,313 2022 1,129 64 1,193 2023 1,135 — 1,135 Thereafter 99,185 — 99,185 Total lease payments 104,518 1,307 105,825 Less: Amount representing interest (87,899 ) (32 ) (87,931 ) Lease liability $ 16,619 $ 1,275 $ 17,894 (1) Represents the nine months ending December 31, 2019 . Future minimum rental payments on leases as of December 31, 2018 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 $ 1,101 $ 219 $ 1,320 2020 1,110 844 1,954 2021 1,094 184 1,278 2022 1,115 49 1,164 2023 1,119 — 1,119 Thereafter 83,373 — 83,373 Total lease payments $ 88,912 1,296 90,208 Less: Amount representing interest N/A (24 ) (24 ) Total N/A $ 1,272 $ 90,184

Real Estate Joint Ventures

Real Estate Joint Ventures	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Real Estate Joint Ventures	Real Estate Joint Ventures Consolidated Real Estate Joint Ventures The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of March 31, 2019 (dollars in thousands): Nominal ownership % as of 3/31/19 March 31, 2019 (1) Date Acquired Total Assets Encumbered Assets Total Liabilities Nature of Activity LW Redstone Company, LLC 3/23/2010 85% Development and operation of real estate (2) $ 178,227 $ 75,542 $ 55,472 M Square Associates, LLC 6/26/2007 50% Development and operation of real estate (3) 79,257 46,180 44,554 Stevens Investors, LLC 8/11/2015 95% Development of real estate (4) 88,628 88,073 20,742 $ 346,112 $ 209,795 $ 120,768 (1) Excludes amounts eliminated in consolidation. (2) This joint venture’s properties are in Huntsville, Alabama. (3) This joint venture’s properties are in College Park, Maryland. (4) This joint venture’s property is in Washington, DC. Unconsolidated Real Estate Joint Venture As of March 31, 2019 , we owned a 50% interest in GI-COPT DC Partnership LLC (“GI-COPT”), a joint venture owning six triple-net leased, single-tenant data center shell properties in Virginia, that we account for using the equity method of accounting. As of March 31, 2019 , we had an investment balance in GI-COPT of $39.4 million .

Investing Receivables

Investing Receivables	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables, including accrued interest thereon, consisted of the following (in thousands): March 31, December 31, Notes receivable from the City of Huntsville $ 55,293 $ 53,961 Other investing loans receivable 14,097 3,021 $ 69,390 $ 56,982 Our notes receivable from the City of Huntsville funded infrastructure costs in connection with our LW Redstone Company, LLC joint venture (see Note 6) and carry an interest rate of 9.95% . Our other investing loans receivable carry an interest rate of 8.0% . We did not have an allowance for credit losses in connection with our investing receivables as of March 31, 2019 or December 31, 2018 . The fair value of these receivables was approximately $74 million as of March 31, 2019 and $58 million as of December 31, 2018 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	3 Months Ended
	Mar. 31, 2019
Prepaid Expense and Other Assets [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets, net consisted of the following (in thousands): March 31, December 31, Lease incentives, net $ 22,981 $ 21,258 Construction contract costs incurred in excess of billings 14,834 3,189 Prepaid expenses 10,749 25,658 Furniture, fixtures and equipment, net (1) 8,453 8,630 Non-real estate equity investments 5,792 5,940 Deferred financing costs, net (2) 4,473 4,733 Restricted cash 3,995 3,884 Deferred tax asset, net (3) 1,890 2,084 Other assets 6,815 6,337 Total for COPLP and subsidiaries 79,982 81,713 Marketable securities in deferred compensation plan 4,214 3,868 Total for COPT and subsidiaries $ 84,196 $ 85,581 (1) Includes $1.2 million in finance right-of-use assets as of March 31, 2019 . (2) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (3) Includes a valuation allowance of $2.4 million as of March 31, 2019 and $2.7 million as of December 31, 2018 .

Debt, Net

Debt, Net	3 Months Ended
	Mar. 31, 2019
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, 2019 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 146,212 $ 147,141 3.82% - 7.87% (3) 2019-2026 Variable rate secured debt (4) 26,915 23,282 LIBOR + 1.85% to 2.35% (5) 2020-2022 Total mortgage and other secured debt 173,127 170,423 Revolving Credit Facility 262,000 213,000 LIBOR + 0.775% to 1.45% (6) March 2023 (7) Term Loan Facility (8) 248,381 248,273 LIBOR + 0.85% to 1.65% (9) 2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 348,096 347,986 3.60% (10) May 2023 5.250%, $250,000 aggregate principal 247,263 247,136 5.25% (11) February 2024 3.700%, $300,000 aggregate principal 298,941 298,815 3.70% (12) June 2021 5.000%, $300,000 aggregate principal 297,206 297,109 5.00% (13) July 2025 Unsecured note payable 1,135 1,167 0% (14) May 2026 Total debt, net $ 1,876,149 $ 1,823,909 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.8 million as of March 31, 2019 and $7.2 million as of December 31, 2018 . (2) Certain of the fixed rate mortgages carry interest rates that, upon assumption, were above or below market rates and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $264,000 as of March 31, 2019 and $281,000 as of December 31, 2018 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.17% as of March 31, 2019 . (4) Includes a construction loan with $94.9 million in remaining borrowing capacity as of March 31, 2019 . (5) The weighted average interest rate on our variable rate secured debt was 4.63% as of March 31, 2019 . (6) The weighted average interest rate on the Revolving Credit Facility was 3.54% as of March 31, 2019 . (7) The facility matures in March 2023, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee of 0.075% of the total availability under the facility for each extension period. (8) As of March 31, 2019 , we have the ability to borrow an additional $150.0 million in the aggregate under this facility, provided that there is no default under the facility and subject to the approval of the lenders. In addition, in connection with our Revolving Credit Facility, we have the ability to borrow up to $500.0 million under new term loans from the facility’s lender group provided that there is no default under the facility and subject to the approval of the lenders. (9) The interest rate on this loan was 3.74% as of March 31, 2019 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.3 million as of March 31, 2019 and $1.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (11) The carrying value of these notes reflects an unamortized discount totaling $2.5 million as of March 31, 2019 and $2.6 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (12) The carrying value of these notes reflects an unamortized discount totaling $842,000 as of March 31, 2019 and $943,000 as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (13) The carrying value of these notes reflects an unamortized discount totaling $2.3 million as of March 31, 2019 and $2.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (14) This note carries an interest rate that, upon assumption, was below market rates and it therefore was recorded at its fair value based on applicable effective interest rates. The carrying value of this note reflects an unamortized discount totaling $276,000 as of March 31, 2019 and $294,000 as of December 31, 2018 . All debt is owed by COPLP. While COPT is not directly obligated by any debt, it has guaranteed COPLP’s Revolving Credit Facility, Term Loan Facilities and Unsecured Senior Notes. Certain of our debt instruments require that we comply with a number of restrictive financial covenants. As of March 31, 2019 , we were within the compliance requirements of these financial covenants. We capitalized interest costs of $2.0 million in the three months ended March 31, 2019 and $1.4 million in the three months ended March 31, 2018 . The following table sets forth information pertaining to the fair value of our debt (in thousands): March 31, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,191,506 $ 1,222,637 $ 1,191,046 $ 1,219,603 Other fixed-rate debt 147,347 146,585 148,308 147,106 Variable-rate debt 537,296 540,915 484,555 486,497 $ 1,876,149 $ 1,910,137 $ 1,823,909 $ 1,853,206

Interest Rate Derivatives

Interest Rate Derivatives	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest Rate Derivatives	Interest Rate Derivatives The following table sets forth the key terms and fair values of our interest rate swap derivatives, each of which was designated as a cash flow hedge of interest rate risk (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date March 31, December 31, $ 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 $ 255 $ 472 12,735 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 170 239 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 879 1,968 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 871 1,967 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 427 971 75,000 3.1760% Three-Month LIBOR 6/30/2020 6/30/2030 (4,869 ) (2,676 ) 75,000 3.1920% Three-Month LIBOR 6/30/2020 6/30/2030 (4,974 ) (2,783 ) 75,000 2.7440% Three-Month LIBOR 6/30/2020 6/30/2030 (2,051 ) — $ (9,292 ) $ 158 (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location March 31, December 31, 2018 Interest rate swaps designated as cash flow hedges Interest rate derivatives (assets) $ 2,602 $ 5,617 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (11,894 ) $ (5,459 ) The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): Amount of (Loss) Gain Recognized in AOCL on Derivatives Amount of Gain (Loss) Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended March 31, For the Three Months Ended March 31, Derivatives in Hedging Relationships 2019 2018 2019 2018 Interest rate derivatives $ (8,845 ) $ 4,676 $ 570 $ (245 ) Over the next 12 months, we estimate that approximately $817,000 of gains will be reclassified from accumulated other comprehensive loss (“AOCL”) as a decrease to interest expense. We have agreements with each of our interest rate derivative counterparties that contain provisions under which, if we default or are capable of being declared in default on defined levels of our indebtedness, we could also be declared in default on our derivative obligations. Failure to comply with the loan covenant provisions could result in our being declared in default on any derivative instrument obligations covered by the agreements. As of March 31, 2019 , we are not in default with any of these provisions. As of March 31, 2019 , the fair value of interest rate derivatives in a liability position related to these agreements was $12.0 million , excluding the effects of accrued interest and credit valuation adjustments. As of March 31, 2019 , we had not posted any collateral related to these agreements. If we breach any of these provisions, we could be required to settle our obligations under the agreements at their termination value, which was $12.0 million as of March 31, 2019 .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests Our partners in two real estate joint ventures, LW Redstone Company, LLC and Stevens Investors, LLC (discussed further in Note 6), have the right to require us to acquire their respective interests at fair value; accordingly, we classify the fair value of our partners’ interests as redeemable noncontrolling interests in the mezzanine section of our consolidated balance sheets. The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Three Months Ended March 31, 2019 2018 Beginning balance $ 26,260 $ 23,125 Distributions to noncontrolling interests (349 ) (452 ) Net income attributable to noncontrolling interests 675 638 Adjustment to arrive at fair value of interests 799 537 Ending balance $ 27,385 $ 23,848 We determine the fair value of the interests based on unobservable inputs after considering the assumptions that market participants would make in pricing the interest. We apply a discount rate to the estimated future cash flows allocable to our partners from the properties underlying the respective joint ventures. Estimated cash flows used in such analyses are based on our plans for the properties and our views of market and economic conditions, and consider items such as current and future rental rates, occupancy projections and estimated operating and development expenditures.

Equity

Equity	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Equity	Equity During the three months ended March 31, 2019 , COPT issued 1.6 million common shares under its forward equity sale agreements for net proceeds of $46.5 million . COPT contributed the net proceeds from these issuances to COPLP in exchange for an equal number of units in COPLP. COPT has no remaining capacity under the forward equity sale agreements as of March 31, 2019 . As of March 31, 2019, COPT had remaining capacity under its at-the-market stock offering program equal to an aggregate gross sales price of $300 million in common share sales. During the three months ended March 31, 2019 , certain COPLP limited partners converted 5,500 common units in COPLP for an equal number of common shares in COPT. We declared dividends per COPT common share and COPLP common unit of $0.275 in the three months ended March 31, 2019 and 2018 . See Note 15 for disclosure of COPT common share and COPLP common unit activity pertaining to our share-based compensation plans.

Information by Business Segment

Information by Business Segment	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Information by Business Segment	Information by Business Segment We have the following reportable segments: Defense/IT Locations; Regional Office; Wholesale Data Center; and Other. We also report on Defense/IT Locations sub-segments, which include the following: Fort George G. Meade and the Baltimore/Washington Corridor (referred to herein as “Fort Meade/BW Corridor”); Northern Virginia Defense/IT Locations; Lackland Air Force Base (in San Antonio); locations serving the U.S. Navy (“Navy Support Locations”), which included properties proximate to the Washington Navy Yard, the Naval Air Station Patuxent River in Maryland and the Naval Surface Warfare Center Dahlgren Division in Virginia; Redstone Arsenal (in Huntsville); and data center shells (properties leased to tenants to be operated as data centers in which the tenants generally fund the costs for the power, fiber connectivity and data center infrastructure). 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, 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 Three Months Ended March 31, 2018 Revenues from real estate operations $ 62,782 $ 12,561 $ 11,443 $ 7,870 $ 3,633 $ 5,831 $ 104,120 $ 15,284 $ 8,077 $ 797 $ 128,278 Property operating expenses (21,604 ) (4,723 ) (6,598 ) (3,304 ) (1,440 ) (794 ) (38,463 ) (7,878 ) (4,258 ) (352 ) (50,951 ) UJV NOI allocable to COPT — — — — — 1,199 1,199 — — — 1,199 NOI from real estate operations $ 41,178 $ 7,838 $ 4,845 $ 4,566 $ 2,193 $ 6,236 $ 66,856 $ 7,406 $ 3,819 $ 445 $ 78,526 Additions to long-lived assets $ 7,121 $ 1,940 $ — $ 1,108 $ 79 $ — $ 10,248 $ 3,884 $ 36 $ 127 $ 14,295 Transfers from non-operating properties $ 17,186 $ 341 $ — $ (3 ) $ 444 $ 1,114 $ 19,082 $ — $ 1,012 $ — $ 20,094 Segment assets at March 31, 2018 $ 1,273,359 $ 399,202 $ 127,855 $ 192,116 $ 107,096 $ 302,120 $ 2,401,748 $ 397,355 $ 222,738 $ 4,125 $ 3,025,966 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, 2019 2018 Segment revenues from real estate operations $ 131,990 $ 128,278 Construction contract and other service revenues 16,950 27,198 Total revenues $ 148,940 $ 155,476 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, 2019 2018 UJV NOI allocable to COPT $ 1,219 $ 1,199 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (827 ) (824 ) Add: Equity in loss of unconsolidated non-real estate entities (1 ) (2 ) Equity in income of unconsolidated entities $ 391 $ 373 As previously discussed, we provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. The primary manner in which we evaluate the operating performance of our service activities is through a measure we define as net operating income from service operations (“NOI from service operations”), which is based on the net of revenues and expenses from these activities. Construction contract and other service revenues and expenses consist primarily of subcontracted costs that are reimbursed to us by the customer along with a management fee. The operating margins from these activities are small relative to the revenue. We believe NOI from service operations is a useful measure in assessing both our level of activity and our profitability in conducting such operations. The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended March 31, 2019 2018 Construction contract and other service revenues $ 16,950 $ 27,198 Construction contract and other service expenses (16,326 ) (26,216 ) NOI from service operations $ 624 $ 982 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, 2019 2018 NOI from real estate operations $ 83,764 $ 78,526 NOI from service operations 624 982 Interest and other income 2,286 1,359 Gain on sales of real estate — (4 ) Equity in income of unconsolidated entities 391 373 Income tax expense (194 ) (55 ) Depreciation and other amortization associated with real estate operations (34,796 ) (33,512 ) General, administrative and leasing expenses (8,751 ) (7,292 ) Business development expenses and land carry costs (1,113 ) (1,614 ) Interest expense (18,674 ) (18,784 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,219 ) (1,199 ) Net income $ 22,318 $ 18,780 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): March 31, March 31, Segment assets $ 3,108,153 $ 3,025,966 Operating properties lease liabilities included in segment assets 16,342 — Non-operating property assets 485,911 425,951 Other assets 165,453 144,321 Total COPT consolidated assets $ 3,775,859 $ 3,596,238 The accounting policies of the segments are the same as those used to prepare our consolidated financial statements. In the segment reporting presented above, we did not allocate interest expense, depreciation and amortization, gain on sales of real estate and equity in income of unconsolidated entities not included in NOI to our real estate segments since they are not included in the measure of segment profit reviewed by management. We also did not allocate general, administrative and leasing expenses, business development expenses and land carry costs, interest and other income, income taxes and noncontrolling interests because these items represent general corporate or non-operating property items not attributable to segments.

Construction Contract and Other

Construction Contract and Other Service Revenues	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Construction Contract and Other Service Revenues	Construction Contract and Other Service Revenues We disaggregate our construction contract and other service revenues by compensation arrangement and by service type as we believe it best depicts the nature, timing and uncertainty of our revenue. The table below reports construction contract and other service revenues by compensation arrangement (in thousands): For the Three Months Ended March 31, 2019 2018 Construction contract revenues: Guaranteed maximum price $ 12,356 $ 20,486 Firm fixed price 2,325 6,435 Cost-plus fee 2,060 58 Other 209 219 $ 16,950 $ 27,198 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended March 31, 2019 2018 Construction contract revenues: Construction $ 16,489 $ 25,915 Design 252 1,064 Other 209 219 $ 16,950 $ 27,198 We recognized revenue of $32,000 and $309,000 in the three months ended March 31, 2019 and 2018 , respectively, from performance obligations satisfied (or partially satisfied) in previous periods. Accounts receivable related to our construction contract services is included in accounts receivable, net on our consolidated balance sheets. The beginning and ending balances of accounts receivable related to our construction contracts were as follows (in thousands): For the Three Months Ended March 31, 2019 2018 Beginning balance $ 6,701 $ 4,577 Ending balance $ 6,569 $ 4,021 Contract assets, which we refer to herein as construction costs in excess of billings, are included in prepaid expenses and other assets, net reported on our consolidated balance sheets. The beginning and ending balances of our contract assets were as follows (in thousands): For the Three Months Ended March 31, 2019 2018 Beginning balance $ 3,189 $ 4,884 Ending balance $ 14,834 $ 4,250 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, 2019 2018 Beginning balance $ 568 $ 27,402 Ending balance $ 1,005 $ 8,279 Revenue recognized included in beginning balance $ 439 $ 19,297 The change in the contract liabilities balance reported above for the three months ended March 31, 2018 was due primarily to our satisfaction of performance obligations during the period on a contract on which we previously received advance payments from a customer. Revenue allocated to the remaining performance obligations under existing contracts as of March 31, 2019 that will be recognized as revenue in future periods was $51.6 million , approximately $45 million of which we expect to recognize during the remainder of 2019. We have no deferred incremental costs incurred to obtain or fulfill our construction contracts or other service revenues and had no impairment losses on construction contracts receivable or unbilled construction revenue for the three months ended March 31, 2019 and 2018 .

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Restricted Shares During the three months ended March 31, 2019 , certain employees were granted a total of 135,396 restricted common shares with an aggregate grant date fair value of $3.5 million ( $25.81 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, 2019 , forfeiture restrictions lapsed on 151,252 previously issued common shares; these shares had a weighted average grant date fair value of $27.94 per share, and the aggregate intrinsic value of the shares on the vesting dates was $3.9 million . Performance Share Awards (“PSUs”) We issued 44,757 common shares on January 18, 2019 to executives in settlement of PSUs granted in 2016, representing 157% of the target award for those PSUs. PIUs Commencing in 2019, we offered our executives 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 and PSUs). PIUs are a special class of common unit structured to qualify as “profit interests” for tax purposes. Our executives selected PIUs as their form of share-based compensation for their 2019 grants. We granted the executives 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, 2019 , our executives were granted a total of 54,956 TB-PIUs with an aggregate grant date fair value of $1.4 million ( $25.81 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. PB-PIUs On January 1, 2019 , we granted our executives 193,682 PB-PIUs with a three -year performance period concluding on the earlier of December 31, 2021 or the date of: (1) termination by us without cause, death or disability of the executive or constructive discharge of the executive (collectively, “qualified termination”); or (2) a sale event. The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT’s total shareholder return relative to a peer group of companies, as set forth in the following schedule: Percentile Rank Earned Awards Payout % 75th or greater 100% of PB-PIUs granted 50th (target) 50% of PB-PIUs granted 25th 25% of PB-PIUs granted Below 25th 0% of PB-PIUs granted If the percentile rank exceeds the 25th percentile and is between two of the percentile ranks set forth in the table above, then the percentage of the earned awards will be interpolated between the ranges set forth in the table above to reflect any performance between the listed percentiles. During the performance period, PB-PIUs carry rights to distributions equal to 10% of the distribution rights of non-PIU common units but carry no redemption rights. At the end of the performance period, we will settle the award by issuing vested PIUs equal to the number of earned awards in settlement of the award plan and paying cash equal to the excess, if any, of: the aggregate distributions that would have been paid with respect to vested PIUs issued in settlement of the earned awards through the date of settlement had such vested PIUs been issued on the grant date; over the aggregate distributions made on the PB-PIUs during the performance period. If a performance period ends due to a sale event or qualified termination, the number of earned awards is prorated based on the portion of the three -year performance period that has elapsed. If employment is terminated by the employee or by us for cause, all PB-PIUs are forfeited. These PB-PIUs had an aggregate grant date fair value of $2.4 million ( $12.47 per PB-PIU) which is being recognized over the performance period. The grant date fair value was computed using a Monte Carlo model that included the following assumptions: baseline common share value of $21.03 ; expected volatility for common shares of 21.0% ; and a risk-free interest rate of 2.51% .

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”)	Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”) COPT and Subsidiaries EPS We present both basic and diluted EPS. We compute basic EPS by dividing net income available to common shareholders allocable to unrestricted common shares under the two-class method by the weighted average number of unrestricted common shares outstanding during the period. Our computation of diluted EPS is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common shares that would have been outstanding if securities that are convertible into common shares were converted; and (2) the effect of dilutive potential common shares outstanding during the period attributable to COPT’s forward equity sale agreements, redeemable noncontrolling interests and our share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common shares that we add to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended March 31, 2019 2018 Numerator: Net income attributable to COPT $ 20,859 $ 17,150 Income attributable to share-based compensation awards (86 ) (117 ) Numerator for basic and diluted EPS on net income attributable to COPT common shareholders $ 20,773 $ 17,033 Denominator (all weighted averages): Denominator for basic EPS (common shares) 109,951 100,999 Dilutive effect of share-based compensation awards 267 144 Denominator for diluted EPS (common shares) 110,218 101,143 Basic EPS $ 0.19 $ 0.17 Diluted EPS $ 0.19 $ 0.17 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, 2019 2018 Conversion of common units 1,331 3,221 Conversion of redeemable noncontrolling interests 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 and 2018 of 1.5 million and 7.5 million , respectively; • weighted average restricted shares and deferred share awards for the three months ended March 31, 2019 and 2018 of 463,000 and 444,000 , respectively; • weighted average options for the three months ended March 31, 2019 and 2018 of 30,000 and 60,000 , respectively; and • weighted average unvested PIUs of 19,000 for the three months ended March 31, 2019 . 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, 2019 2018 Numerator: Net income attributable to COPLP $ 21,281 $ 17,859 Preferred unit distributions (165 ) (165 ) Income attributable to share-based compensation awards (93 ) (117 ) Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ 21,023 $ 17,577 Denominator (all weighted averages): Denominator for basic EPU (common units) 111,282 104,220 Dilutive effect of share-based compensation awards 267 144 Denominator for diluted EPU (common units) 111,549 104,364 Basic EPU $ 0.19 $ 0.17 Diluted EPU $ 0.19 $ 0.17 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 Units Excluded from Denominator For the Three Months Ended March 31, 2019 2018 Conversion of redeemable noncontrolling interests 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 and 2018 of 1.5 million and 7.5 million , respectively; • weighted average restricted units and deferred share awards for the three months ended March 31, 2019 and 2018 of 463,000 and 444,000 , respectively; • weighted average options for the three months ended March 31, 2019 and 2018 of 30,000 and 60,000 , respectively; and • weighted average unvested PIUs of 19,000 for the three months ended March 31, 2019 .

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation and Claims In the normal course of business, we are subject to legal actions and other claims. We record losses for specific legal proceedings and claims when we determine that a loss is probable and the amount of loss can be reasonably estimated. Management believes that it is reasonably possible that we could incur losses pursuant to such claims but do not believe such losses would materially affect our financial position, liquidity or results of operations. Our assessment of the potential outcomes of these matters involves significant judgment and is subject to change based on future developments. Environmental We are subject to various Federal, state and local environmental regulations related to our property ownership and operation. We have performed environmental assessments of our properties, the results of which have not revealed any environmental liability that we believe would have a materially adverse effect on our financial position, operations or liquidity. In connection with a lease and subsequent sale in 2008 and 2010 of three properties in Dayton, New Jersey, we agreed to provide certain environmental indemnifications limited to $19 million in the aggregate. We have insurance coverage in place to mitigate much of any potential future losses that may result from these indemnification agreements. Tax Incremental Financing Obligation In August 2010, Anne Arundel County, Maryland issued $30 million in tax incremental financing bonds to third-party investors in order to finance public improvements needed in connection with our project known as National Business Park North. The real estate taxes on increases in assessed value of a development district encompassing National Business Park North are to be 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, 2019 , we do not expect any such future fundings will be required. Contractual Obligations We had amounts remaining to be incurred under various contractual obligations as of March 31, 2019 that included the following (excluding amounts incurred and therefore reflected as liabilities reported on our consolidated balance sheets): • development and redevelopment obligations of $184.3 million ; • tenant and other capital improvements of $45.3 million ; • third party construction obligations of $32.6 million ; and • other obligations of $1.7 million .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The COPT consolidated financial statements include the accounts of COPT, the Operating Partnership, their subsidiaries and other entities in which COPT has a majority voting interest and control. The COPLP consolidated financial statements include the accounts of COPLP, its subsidiaries and other entities in which COPLP has a majority voting interest and control. We also consolidate certain entities when control of such entities can be achieved through means other than voting rights (“variable interest entities” or “VIEs”) if we are deemed to be the primary beneficiary of such entities. We eliminate all intercompany balances and transactions in consolidation. We use the equity method of accounting when we own an interest in an entity and can exert significant influence over but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity. When we own an equity investment in an entity and cannot exert significant influence over its operations, we measure the investment at fair value, with changes recognized through net income. For an investment without a readily determinable fair value, we measure the investment at cost, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. These interim financial statements should be read together with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2018 included in our 2018 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2018 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below.
Reclassification	Reclassification We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including reclassifications of our revenue from real estate operations in connection with our adoption of new lease guidance described below.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued guidance setting forth principles for the recognition, measurement, presentation and disclosure of leases. This guidance requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. The resulting classification determines whether the lease expense is recognized based on an effective interest method or straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This guidance requires lessors of real estate to account for leases using an approach substantially equivalent to guidance previously in place for operating leases, direct financing leases and sales-type leases. We adopted this guidance on January 1, 2019 using a modified retrospective transition approach under which we elected to apply the guidance effective January 1, 2019 and not adjust prior comparative reporting periods (except for our presentation of lease revenue discussed below). We elected to apply a package of practical expedients that enabled us to carry forward upon adoption our historical assessments of: expired or existing leases regarding their lease classification and deferred recognition of non-incremental direct leasing costs; and whether any expired or existing contracts are, or contain, leases. We also elected a practical expedient that enabled us to avoid the need to assess whether expired or existing land easements not previously accounted for as leases are, or contain, a lease. In addition, we elected a practical expedient for our rental properties (as lessor) to avoid separating non-lease components that otherwise would need to be accounted for under the recently-adopted revenue accounting guidance (such as tenant reimbursements of property operating expenses) from the associated lease component since (1) the non-lease components have the same timing and pattern of transfer as the associated lease component and (2) the lease component, if accounted for separately, would be classified as an operating lease; this enables us to account for the combination of the lease component and non-lease components as an operating lease since the lease component is the predominant component of the combined components. Below is a summary of the primary changes in our accounting and reporting that resulted from our adoption of this guidance: • Property leases in which we are the lessor: ◦ Deferral of non-incremental leasing costs: For new or extended tenant leases, we no longer defer recognition of non-incremental leasing costs that we would have deferred under prior accounting guidance (refer to our 2018 Annual Report on Form 10-K in which we reported amounts deferred in 2018 , 2017 and 2016 ). ◦ Change in presentation of revenue: Due to our adoption of the practical expedient discussed above to not separate non-lease component revenue from the associated lease component, we are aggregating revenue from our lease components and non-lease components (comprised predominantly of tenant operating expense reimbursements) into the line entitled “lease revenue.” We are reporting other revenue from our properties in the line entitled “other property revenue.” We recast prior periods for these changes in presentation. ◦ Changes in assessment of lease revenue collectability: Changes in our assessment of lease revenue collectability that previously would have resulted in charges to bad debt expense under prior guidance are being recognized as an adjustment to rental revenue under the new guidance. Such amounts recognized by us in prior periods were not significant. ◦ Operating expenses paid directly by tenants to third parties: Operating expenses paid directly by tenants to third parties (primarily for real estate taxes) and revenue associated with such tenant payments that would have been recognized under prior guidance will no longer be reported on our Statement of Operations. Such amounts recognized by us in prior periods were not significant. • Leases (the most significant of which are ground leases) in which we are the lessee: ◦ Balance sheet presentation of property operating lease right-of-use assets: Upon adoption on January 1, 2019, we recognized property right-of-use assets and offsetting lease liabilities for existing operating leases totaling $16 million for the present value of minimum lease payments under these leases, and also reclassified an additional $11 million in amounts previously presented elsewhere on our balance sheet in connection with these leases to the right-of-use assets. We will recognize additional right-of-use assets and lease liabilities as we enter into new operating leases. ◦ Balance sheet presentation of property finance lease right-of-use assets: Property right-of-use assets of finance leases that previously were presented as properties under prior guidance are being presented as property finance right-of-use assets under the new guidance. As a result, we reclassified $38 million in assets from properties to property finance right-of-use assets upon adoption on January 1, 2019. ◦ Segment assets: We changed our definition of segment assets used for our reportable segments to include property right-of-use assets associated with operating properties, net of related lease liabilities. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance will apply to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables, loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments). Under the new guidance, an entity will recognize its estimate of expected credit losses as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and to be presented at the net amount expected to be collected. The guidance is effective for us beginning January 1, 2020, with early adoption permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2018, the FASB issued guidance that modifies disclosure requirements for fair value measurements. This guidance is effective for us beginning January 1, 2020. Early adoption is permitted for this guidance, and entities are permitted to early adopt with respect to any removed or modified disclosures while delaying adoption of additional disclosure requirements until the effective date. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. In August 2018, the FASB issued guidance that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. FASB guidance did not previously address the accounting for such implementation costs. The guidance is effective for us beginning January 1, 2020, with early adoption permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of fair value assets and liabilities measured on recurring basis	The table below sets forth financial assets and liabilities of COPLP and subsidiaries that are accounted for at fair value on a recurring basis as of March 31, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other Significant Inputs (Level 3) Total Assets: Interest rate derivatives $ — $ 2,602 $ — $ 2,602 Liabilities: Interest rate derivatives $ — $ 11,894 $ — $ 11,894 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, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other (Level 2) Significant Inputs (Level 3) Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,171 $ — $ — $ 4,171 Other 43 — — 43 Interest rate derivatives — 2,602 — 2,602 Total assets $ 4,214 $ 2,602 $ — $ 6,816 Liabilities: Deferred compensation plan liability (2) $ — $ 4,214 $ — $ 4,214 Interest rate derivatives — 11,894 — 11,894 Total liabilities $ — $ 16,108 $ — $ 16,108 (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.

Properties, Net (Tables)

Properties, Net (Tables)	3 Months Ended
	Mar. 31, 2019
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): March 31, December 31, Land $ 505,062 $ 503,274 Buildings and improvements 3,288,033 3,241,894 Less: Accumulated depreciation (927,266 ) (897,903 ) Operating properties, net $ 2,865,829 $ 2,847,265
Schedule of projects in development or held for future development	Properties we had in development or held for future development consisted of the following (in thousands): March 31, December 31, Land $ 227,852 $ 207,760 Development in progress, excluding land 209,321 195,601 Projects in development or held for future development $ 437,173 $ 403,361

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Operating Lease Revenue Recognized	The table below sets forth our allocation of lease revenue recognized between fixed contractual payments and variable lease payments (in thousands): Lease revenue For the Three Months Ended Fixed contractual payments $ 105,335 Variable lease payments 25,568 $ 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, 2019 December 31, 2018 2019 (1) $ 305,864 $ 400,617 2020 347,477 337,646 2021 293,546 280,369 2022 258,502 246,329 2023 206,833 194,888 Thereafter 562,614 523,932 $ 1,974,836 $ 1,983,781 (1) As of March 31, 2019 , represents the nine months ending December 31, 2019
Right-of-Use Assets and Lease Liabilities	Our right-of-use assets consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,569 Finance leases Property Property - finance right-of-use assets 40,488 Vehicles and office equipment Prepaid expenses and other assets, net 1,197 Total finance lease right-of-use assets 41,685 Total right-of-use assets $ 69,254 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location March 31, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 16,619 Finance leases Other liabilities 1,275 Total lease liabilities $ 17,894
Lease Costs	The table below sets forth the weighted average lease terms and discount rates of our leases as of March 31, 2019 : Weighted average remaining lease term Operating leases 70 years Finance leases 2 years Weighted average discount rate Operating leases 7.35 % Finance leases 3.10 % The table below presents our total lease cost (in thousands): Lease cost Statement of Operations Location For the Three Months Ended Operating lease cost Property leases Property operating expense $ 413 Vehicles and office equipment General, administrative and leasing expense 17 Finance lease cost Amortization of vehicles and office equipment right-of-use assets General, administrative and leasing expense 113 Interest on lease liabilities Interest expense 4 $ 547 The table below presents the effect of lease payments on our consolidated statement of cash flows (in thousands): Supplemental cash flow information For the Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 228 Operating cash flows for financing leases $ 4 Financing cash flows for financing leases $ 52
Maturity of Lease Liabilities	Payments on leases as of March 31, 2019 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 (1) $ 830 $ 179 $ 1,009 2020 1,128 862 1,990 2021 1,111 202 1,313 2022 1,129 64 1,193 2023 1,135 — 1,135 Thereafter 99,185 — 99,185 Total lease payments 104,518 1,307 105,825 Less: Amount representing interest (87,899 ) (32 ) (87,931 ) Lease liability $ 16,619 $ 1,275 $ 17,894 (1) Represents the nine months ending December 31, 2019 . Future minimum rental payments on leases as of December 31, 2018 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 $ 1,101 $ 219 $ 1,320 2020 1,110 844 1,954 2021 1,094 184 1,278 2022 1,115 49 1,164 2023 1,119 — 1,119 Thereafter 83,373 — 83,373 Total lease payments $ 88,912 1,296 90,208 Less: Amount representing interest N/A (24 ) (24 ) Total N/A $ 1,272 $ 90,184

Real Estate Joint Ventures (Tab

Real Estate Joint Ventures (Tables)	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of information related to investments in consolidated real estate joint ventures	The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of March 31, 2019 (dollars in thousands): Nominal ownership % as of 3/31/19 March 31, 2019 (1) Date Acquired Total Assets Encumbered Assets Total Liabilities Nature of Activity LW Redstone Company, LLC 3/23/2010 85% Development and operation of real estate (2) $ 178,227 $ 75,542 $ 55,472 M Square Associates, LLC 6/26/2007 50% Development and operation of real estate (3) 79,257 46,180 44,554 Stevens Investors, LLC 8/11/2015 95% Development of real estate (4) 88,628 88,073 20,742 $ 346,112 $ 209,795 $ 120,768 (1) Excludes amounts eliminated in consolidation. (2) This joint venture’s properties are in Huntsville, Alabama. (3) This joint venture’s properties are in College Park, Maryland. (4) This joint venture’s property is in Washington, DC.

Investing Receivables (Tables)

Investing Receivables (Tables)	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Schedule of investing receivables	Investing receivables, including accrued interest thereon, consisted of the following (in thousands): March 31, December 31, Notes receivable from the City of Huntsville $ 55,293 $ 53,961 Other investing loans receivable 14,097 3,021 $ 69,390 $ 56,982

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets, Net (Tables)	3 Months Ended
	Mar. 31, 2019
Prepaid Expense and Other Assets [Abstract]
Schedule of prepaid expenses and other assets	Prepaid expenses and other assets, net consisted of the following (in thousands): March 31, December 31, Lease incentives, net $ 22,981 $ 21,258 Construction contract costs incurred in excess of billings 14,834 3,189 Prepaid expenses 10,749 25,658 Furniture, fixtures and equipment, net (1) 8,453 8,630 Non-real estate equity investments 5,792 5,940 Deferred financing costs, net (2) 4,473 4,733 Restricted cash 3,995 3,884 Deferred tax asset, net (3) 1,890 2,084 Other assets 6,815 6,337 Total for COPLP and subsidiaries 79,982 81,713 Marketable securities in deferred compensation plan 4,214 3,868 Total for COPT and subsidiaries $ 84,196 $ 85,581 (1) Includes $1.2 million in finance right-of-use assets as of March 31, 2019 . (2) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (3) Includes a valuation allowance of $2.4 million as of March 31, 2019 and $2.7 million as of December 31, 2018 .

Debt, Net (Tables)

Debt, Net (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 146,212 $ 147,141 3.82% - 7.87% (3) 2019-2026 Variable rate secured debt (4) 26,915 23,282 LIBOR + 1.85% to 2.35% (5) 2020-2022 Total mortgage and other secured debt 173,127 170,423 Revolving Credit Facility 262,000 213,000 LIBOR + 0.775% to 1.45% (6) March 2023 (7) Term Loan Facility (8) 248,381 248,273 LIBOR + 0.85% to 1.65% (9) 2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 348,096 347,986 3.60% (10) May 2023 5.250%, $250,000 aggregate principal 247,263 247,136 5.25% (11) February 2024 3.700%, $300,000 aggregate principal 298,941 298,815 3.70% (12) June 2021 5.000%, $300,000 aggregate principal 297,206 297,109 5.00% (13) July 2025 Unsecured note payable 1,135 1,167 0% (14) May 2026 Total debt, net $ 1,876,149 $ 1,823,909 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.8 million as of March 31, 2019 and $7.2 million as of December 31, 2018 . (2) Certain of the fixed rate mortgages carry interest rates that, upon assumption, were above or below market rates and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $264,000 as of March 31, 2019 and $281,000 as of December 31, 2018 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.17% as of March 31, 2019 . (4) Includes a construction loan with $94.9 million in remaining borrowing capacity as of March 31, 2019 . (5) The weighted average interest rate on our variable rate secured debt was 4.63% as of March 31, 2019 . (6) The weighted average interest rate on the Revolving Credit Facility was 3.54% as of March 31, 2019 . (7) The facility matures in March 2023, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee of 0.075% of the total availability under the facility for each extension period. (8) As of March 31, 2019 , we have the ability to borrow an additional $150.0 million in the aggregate under this facility, provided that there is no default under the facility and subject to the approval of the lenders. In addition, in connection with our Revolving Credit Facility, we have the ability to borrow up to $500.0 million under new term loans from the facility’s lender group provided that there is no default under the facility and subject to the approval of the lenders. (9) The interest rate on this loan was 3.74% as of March 31, 2019 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.3 million as of March 31, 2019 and $1.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (11) The carrying value of these notes reflects an unamortized discount totaling $2.5 million as of March 31, 2019 and $2.6 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (12) The carrying value of these notes reflects an unamortized discount totaling $842,000 as of March 31, 2019 and $943,000 as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (13) The carrying value of these notes reflects an unamortized discount totaling $2.3 million as of March 31, 2019 and $2.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (14) This note carries an interest rate that, upon assumption, was below market rates and it therefore was recorded at its fair value based on applicable effective interest rates. The carrying value of this note reflects an unamortized discount totaling $276,000 as of March 31, 2019 and $294,000 as of December 31, 2018 .
Schedule of the fair value of debt	The following table sets forth information pertaining to the fair value of our debt (in thousands): March 31, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,191,506 $ 1,222,637 $ 1,191,046 $ 1,219,603 Other fixed-rate debt 147,347 146,585 148,308 147,106 Variable-rate debt 537,296 540,915 484,555 486,497 $ 1,876,149 $ 1,910,137 $ 1,823,909 $ 1,853,206

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of key terms and fair values of interest rate swap derivatives	The following table sets forth the key terms and fair values of our interest rate swap derivatives, each of which was designated as a cash flow hedge of interest rate risk (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date March 31, December 31, $ 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 $ 255 $ 472 12,735 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 170 239 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 879 1,968 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 871 1,967 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 427 971 75,000 3.1760% Three-Month LIBOR 6/30/2020 6/30/2030 (4,869 ) (2,676 ) 75,000 3.1920% Three-Month LIBOR 6/30/2020 6/30/2030 (4,974 ) (2,783 ) 75,000 2.7440% Three-Month LIBOR 6/30/2020 6/30/2030 (2,051 ) — $ (9,292 ) $ 158 (1) The notional amount of this instrument is scheduled to amortize to $12.1 million .
Schedule of fair value and balance sheet classification of interest rate derivatives	The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location March 31, December 31, 2018 Interest rate swaps designated as cash flow hedges Interest rate derivatives (assets) $ 2,602 $ 5,617 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (11,894 ) $ (5,459 )
Schedule of effect of interest rate derivatives on consolidated statements of operations and comprehensive income	The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): Amount of (Loss) Gain Recognized in AOCL on Derivatives Amount of Gain (Loss) Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended March 31, For the Three Months Ended March 31, Derivatives in Hedging Relationships 2019 2018 2019 2018 Interest rate derivatives $ (8,845 ) $ 4,676 $ 570 $ (245 )

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Schedule of activity for redeemable noncontrolling interest	The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Three Months Ended March 31, 2019 2018 Beginning balance $ 26,260 $ 23,125 Distributions to noncontrolling interests (349 ) (452 ) Net income attributable to noncontrolling interests 675 638 Adjustment to arrive at fair value of interests 799 537 Ending balance $ 27,385 $ 23,848

Information by Business Segme_2

Information by Business Segment (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of segment financial information for real estate operations	The table below reports segment financial information for our reportable segments (in thousands): Operating Property Segments Defense/Information Technology Locations Fort Meade/BW Corridor Northern Virginia Defense/IT Lackland Air Force Base Navy Support Locations Redstone Arsenal Data Center Shells Total Defense/IT Locations Regional Office Wholesale Other Total Three Months Ended 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 Three Months Ended March 31, 2018 Revenues from real estate operations $ 62,782 $ 12,561 $ 11,443 $ 7,870 $ 3,633 $ 5,831 $ 104,120 $ 15,284 $ 8,077 $ 797 $ 128,278 Property operating expenses (21,604 ) (4,723 ) (6,598 ) (3,304 ) (1,440 ) (794 ) (38,463 ) (7,878 ) (4,258 ) (352 ) (50,951 ) UJV NOI allocable to COPT — — — — — 1,199 1,199 — — — 1,199 NOI from real estate operations $ 41,178 $ 7,838 $ 4,845 $ 4,566 $ 2,193 $ 6,236 $ 66,856 $ 7,406 $ 3,819 $ 445 $ 78,526 Additions to long-lived assets $ 7,121 $ 1,940 $ — $ 1,108 $ 79 $ — $ 10,248 $ 3,884 $ 36 $ 127 $ 14,295 Transfers from non-operating properties $ 17,186 $ 341 $ — $ (3 ) $ 444 $ 1,114 $ 19,082 $ — $ 1,012 $ — $ 20,094 Segment assets at March 31, 2018 $ 1,273,359 $ 399,202 $ 127,855 $ 192,116 $ 107,096 $ 302,120 $ 2,401,748 $ 397,355 $ 222,738 $ 4,125 $ 3,025,966
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, 2019 2018 Segment revenues from real estate operations $ 131,990 $ 128,278 Construction contract and other service revenues 16,950 27,198 Total revenues $ 148,940 $ 155,476
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, 2019 2018 UJV NOI allocable to COPT $ 1,219 $ 1,199 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (827 ) (824 ) Add: Equity in loss of unconsolidated non-real estate entities (1 ) (2 ) Equity in income of unconsolidated entities $ 391 $ 373
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, 2019 2018 Construction contract and other service revenues $ 16,950 $ 27,198 Construction contract and other service expenses (16,326 ) (26,216 ) NOI from service operations $ 624 $ 982
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, 2019 2018 NOI from real estate operations $ 83,764 $ 78,526 NOI from service operations 624 982 Interest and other income 2,286 1,359 Gain on sales of real estate — (4 ) Equity in income of unconsolidated entities 391 373 Income tax expense (194 ) (55 ) Depreciation and other amortization associated with real estate operations (34,796 ) (33,512 ) General, administrative and leasing expenses (8,751 ) (7,292 ) Business development expenses and land carry costs (1,113 ) (1,614 ) Interest expense (18,674 ) (18,784 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,219 ) (1,199 ) Net income $ 22,318 $ 18,780
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 $ 3,108,153 $ 3,025,966 Operating properties lease liabilities included in segment assets 16,342 — Non-operating property assets 485,911 425,951 Other assets 165,453 144,321 Total COPT consolidated assets $ 3,775,859 $ 3,596,238

Construction Contract and Oth_2

Construction Contract and Other Service Revenues (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The table below reports construction contract and other service revenues by compensation arrangement (in thousands): For the Three Months Ended March 31, 2019 2018 Construction contract revenues: Guaranteed maximum price $ 12,356 $ 20,486 Firm fixed price 2,325 6,435 Cost-plus fee 2,060 58 Other 209 219 $ 16,950 $ 27,198 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended March 31, 2019 2018 Construction contract revenues: Construction $ 16,489 $ 25,915 Design 252 1,064 Other 209 219 $ 16,950 $ 27,198
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, 2019 2018 Beginning balance $ 6,701 $ 4,577 Ending balance $ 6,569 $ 4,021
Contract with Customer, Asset and Liability	Changes in contract liabilities were as follows (in thousands): For the Three Months Ended March 31, 2019 2018 Beginning balance $ 568 $ 27,402 Ending balance $ 1,005 $ 8,279 Revenue recognized included in beginning balance $ 439 $ 19,297 The beginning and ending balances of our contract assets were as follows (in thousands): For the Three Months Ended March 31, 2019 2018 Beginning balance $ 3,189 $ 4,884 Ending balance $ 14,834 $ 4,250

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of payouts for defined performance under performance-based awards of share-based compensation	The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT’s total shareholder return relative to a peer group of companies, as set forth in the following schedule: Percentile Rank Earned Awards Payout % 75th or greater 100% of PB-PIUs granted 50th (target) 50% of PB-PIUs granted 25th 25% of PB-PIUs granted Below 25th 0% of PB-PIUs granted

Earnings Per Share ("EPS") an_2

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended March 31, 2019 2018 Numerator: Net income attributable to COPT $ 20,859 $ 17,150 Income attributable to share-based compensation awards (86 ) (117 ) Numerator for basic and diluted EPS on net income attributable to COPT common shareholders $ 20,773 $ 17,033 Denominator (all weighted averages): Denominator for basic EPS (common shares) 109,951 100,999 Dilutive effect of share-based compensation awards 267 144 Denominator for diluted EPS (common shares) 110,218 101,143 Basic EPS $ 0.19 $ 0.17 Diluted EPS $ 0.19 $ 0.17
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended March 31, 2019 2018 Conversion of common units 1,331 3,221 Conversion of redeemable noncontrolling interests 1,013 — Conversion of Series I preferred units 176 176
Corporate Office Properties, L.P.
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended March 31, 2019 2018 Numerator: Net income attributable to COPLP $ 21,281 $ 17,859 Preferred unit distributions (165 ) (165 ) Income attributable to share-based compensation awards (93 ) (117 ) Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ 21,023 $ 17,577 Denominator (all weighted averages): Denominator for basic EPU (common units) 111,282 104,220 Dilutive effect of share-based compensation awards 267 144 Denominator for diluted EPU (common units) 111,549 104,364 Basic EPU $ 0.19 $ 0.17 Diluted EPU $ 0.19 $ 0.17
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 Units Excluded from Denominator For the Three Months Ended March 31, 2019 2018 Conversion of redeemable noncontrolling interests 1,013 — Conversion of Series I preferred units 176 176

Organization (Details)

Organization (Details) - Mar. 31, 2019 ft² in Millions	Property	MW	ft²	a
Operating Properties
Investments in real estate
Number of real estate properties	165
Area of real estate property (in sq ft or acres) | ft²			18.3
Operating Properties | Office Properties
Investments in real estate
Number of real estate properties	146
Area of real estate property (in sq ft or acres) | ft²			15.2
Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties	19
Area of real estate property (in sq ft or acres) | ft²			3.1
Properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties	15
Area of real estate property (in sq ft or acres) | ft²			2
Properties under, or contractually committed for, construction or approved for redevelopment | Office Properties
Investments in real estate
Number of real estate properties	10
Properties under, or contractually committed for, construction or approved for redevelopment | Single-tenant data centers
Investments in real estate
Number of real estate properties	5
Properties under, or contractually committed for, construction or approved for redevelopment | Partially operational properties
Investments in real estate
Number of real estate properties	2
Land controlled for future development
Investments in real estate
Area of real estate property (in sq ft or acres)			11.6	900
Other Land
Investments in real estate
Area of real estate property (in sq ft or acres) | a				150
Operating wholesale data center
Investments in real estate
Critical load (in megawatts) | MW		19.25
GI-COPT | Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties	6

Organization (Details 2)

Organization (Details 2)	3 Months Ended
	Mar. 31, 2019
Corporate Office Properties, L.P. | Common Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	98.60%

Summary of Significant Accoun_3

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

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Assets and liabilities measured at fair value on a recurring basis
Marketable securities in deferred compensation plan	$ 4,214	$ 3,868
Fair value measurement on a recurring basis | Deferred compensation plan | Trustees and Management
Assets and liabilities measured at fair value on a recurring basis
Maximum percentage of participants' compensation which is deferrable (as a percent)	100.00%
Marketable securities in deferred compensation plan	$ 4,200

Fair Value Measurements (Deta_2

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Marketable securities in deferred compensation plan	$ 4,214	$ 3,868
Fair value measurement on a recurring basis
Assets:
Interest rate derivatives	2,602
Total assets	6,816
Liabilities:
Deferred compensation plan liability	4,214
Interest rate derivatives	11,894
Total liabilities	16,108
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,171
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	43
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total assets	4,214
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,171
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	43
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	2,602
Total assets	2,602
Liabilities:
Deferred compensation plan liability	4,214
Interest rate derivatives	11,894
Total liabilities	16,108
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Assets:
Interest rate derivatives	2,602
Liabilities:
Interest rate derivatives	11,894
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	2,602
Liabilities:
Interest rate derivatives	$ 11,894

Properties, Net (Details)

Properties, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investments in real estate
Operating properties, net	$ 2,865,829	$ 2,847,265
Operating Properties, net
Investments in real estate
Less: accumulated depreciation	(927,266)	(897,903)
Operating properties, net	2,865,829	2,847,265
Operating Properties, net | Land
Investments in real estate
Gross	505,062	503,274
Operating Properties, net | Buildings and improvements
Investments in real estate
Gross	$ 3,288,033	$ 3,241,894

Properties, Net (Details 2)

Properties, Net (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Properties
Projects in development or held for future development	$ 437,173	$ 403,361
Projects in development or held for future development
Properties
Projects in development or held for future development	437,173	403,361
Projects in development or held for future development | Land
Properties
Projects in development or held for future development	227,852	207,760
Projects in development or held for future development | Development in progress, excluding land
Properties
Projects in development or held for future development	$ 209,321	$ 195,601

Properties, Net (Details 3)

Properties, Net (Details 3) ft² in Thousands	Mar. 31, 2019ft²Property
Newly constructed properties placed in service
Construction Activities
Square footage of real estate properties (in square feet) | ft²	181
Number of real estate properties	3
Newly constructed properties partially operational
Construction Activities
Number of real estate properties	1
Properties under construction or contractually committed for construction
Construction Activities
Square footage of real estate properties (in square feet) | ft²	1,900
Number of real estate properties	14
Properties under construction or contractually committed, partially operational property
Construction Activities
Number of real estate properties	2
Properties under or approved for redevelopment
Construction Activities
Square footage of real estate properties (in square feet) | ft²	106
Number of real estate properties	1

Leases (Details)

Leases (Details)	3 Months Ended
	Mar. 31, 2019
Lessor, Lease, Description [Line Items]
Average term of contract	5 years
Minimum
Lessor, Lease, Description [Line Items]
Term of contract	1 month
Maximum
Lessor, Lease, Description [Line Items]
Term of contract	15 years
United States Government
Lessor, Lease, Description [Line Items]
Renewal term	1 year

Leases (Details 1)

Leases (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Fixed contractual payments	$ 105,335
Variable lease payments	25,568
Lease revenue	130,903
Lease Payments to be Received
2019	305,864
2019		$ 400,617
2020	347,477	337,646
2021	293,546	280,369
2022	258,502	246,329
2023	206,833	194,888
Thereafter	562,614	523,932
Operating Lease Payments to be Received	$ 1,974,836	$ 1,983,781

Leases (Details 2)

Leases (Details 2) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)Lease
Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 68.1
Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	30 years
Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	97 years
Vehicles and Office Equipment
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 1.2
Washington, DC | Land
Lessee, Lease, Description [Line Items]
Number of contracts | Lease	2
Remaining term of contract	80 years
Lessee right-of-use asset	$ 10.4
Baltimore, Maryland | Land
Lessee, Lease, Description [Line Items]
Renewal term	49 years
Remaining term of contract	30 years
Lessee right-of-use asset	$ 6.5
Stevens Investors, LLC | Washington, DC | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	97 years
Lessee right-of-use asset	$ 37.8
M Square Associates, LLC | College Park, Maryland | Land
Lessee, Lease, Description [Line Items]
Number of contracts | Lease	4
Lessee right-of-use asset	$ 6.7
M Square Associates, LLC | College Park, Maryland | Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	64 years
M Square Associates, LLC | College Park, Maryland | Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	75 years
LW Redstone Company, LLC | Huntsville, Alabama | Land
Lessee, Lease, Description [Line Items]
Renewal term	25 years
Number of contracts | Lease	9
Lessee right-of-use asset	$ 4.3
LW Redstone Company, LLC | Huntsville, Alabama | Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	44 years
LW Redstone Company, LLC | Huntsville, Alabama | Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	50 years
Fort Meade/BW Corridor | Land
Lessee, Lease, Description [Line Items]
Number of contracts | Lease	2
Remaining term of contract	49 years
Lessee right-of-use asset	$ 2.3

Leases (Details 3)

Leases (Details 3) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Property - finance right-of-use assets	$ 41,685
Total right-of-use assets	69,254
Property - operating lease liabilities	16,619
Property - finance lease liabilities	1,275	$ 1,272
Total lease liabilities	17,894	90,184
Properties
Lessee, Lease, Description [Line Items]
Property - operating right-of-use assets	27,569	0
Property - finance right-of-use assets	40,488	0
Property - operating lease liabilities	16,619	$ 0
Operating Right-of-Use Assets | Properties
Lessee, Lease, Description [Line Items]
Property - operating right-of-use assets	27,569
Finance Right-of-Use Assets | Properties
Lessee, Lease, Description [Line Items]
Property - finance right-of-use assets	40,488
Prepaid Expenses and Other Assets, Net | Vehicles and Office Equipment
Lessee, Lease, Description [Line Items]
Property - finance right-of-use assets	$ 1,197

Leases (Details 4)

Leases (Details 4)	Mar. 31, 2019
Leases [Abstract]
Operating leases, Weighted average remaining lease term	70 years
Finance leases, Weighted average remaining lease term	2 years
Operating lease, Weighted average discount rate	7.35%
Finance lease, Weighted average discount rate	3.10%

Leases (Details 5)

Leases (Details 5) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Lease costs	$ 547
Property Operating Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	413
General, Administrative and Leasing Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	17
Amortization of vehicles and office equipment right-of-use assets	113
Interest Expense
Lessee, Lease, Description [Line Items]
Interest on lease liabilities	$ 4

Leases (Details 6)

Leases (Details 6) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Operating cash flows for operating leases	$ 228
Operating cash flows for financing leases	4
Financing cash flows for financing leases	$ 52	$ 4,202

Leases (Details 7)

Leases (Details 7) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Operating leases
2019	$ 830
2019		$ 1,101
2020	1,128	1,110
2021	1,111	1,094
2022	1,129	1,115
2023	1,135	1,119
Thereafter	99,185	83,373
Total lease payments	104,518	88,912
Less: Amount representing interest	(87,899)
Lease liability	16,619
Finance leases
2019	179
2019		219
2020	862	844
2021	202	184
2022	64	49
2023	0	0
Thereafter	0	0
Total lease payments	1,307	1,296
Less: Amount representing interest	(32)	(24)
Lease liability	1,275	1,272
Total
2019	1,009
2019		1,320
2020	1,990	1,954
2021	1,313	1,278
2022	1,193	1,164
2023	1,135	1,119
Thereafter	99,185	83,373
Total lease payments	105,825	90,208
Less: Amount representing interest	(87,931)	(24)
Total lease liabilities	$ 17,894	$ 90,184

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Property
GI-COPT
Investments in consolidated real estate joint ventures
Real estate equity method investments	$ 39,400
Consolidated real estate joint ventures
Investments in consolidated real estate joint ventures
Total Assets	346,112
Encumbered Assets	209,795
Total Liabilities	$ 120,768
Variable Interest Entity, Primary Beneficiary | LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	85.00%
Total Assets	$ 178,227
Encumbered Assets	75,542
Total Liabilities	$ 55,472
Variable Interest Entity, Primary Beneficiary | M Square Associates, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	50.00%
Total Assets	$ 79,257
Encumbered Assets	46,180
Total Liabilities	$ 44,554
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	95.00%
Total Assets	$ 88,628
Encumbered Assets	88,073
Total Liabilities	$ 20,742
Operating Properties | Single-tenant data centers | GI-COPT
Investments in consolidated real estate joint ventures
Ownership percentage (percent)	50.00%
Data Center Shells | Operating Properties | Single-tenant data centers
Investments in consolidated real estate joint ventures
Number of real estate properties | Property	6

Investing Receivables (Details)

Investing Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 69,390	$ 56,982
Investing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of investing receivables	74,000	58,000
Notes Receivable from the City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 55,293	53,961
Notes Receivable from the City of Huntsville | LW Redstone Company, LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Stated interest rate (as a percent)	9.95%
Other investing loans receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 14,097	$ 3,021
Stated interest rate (as a percent)	8.00%

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Properties
Restricted cash	$ 3,995	$ 3,884	$ 3,645	$ 2,570
Marketable securities in deferred compensation plan	4,214	3,868
Total for COPT and subsidiaries	84,196	85,581
Finance right-of-use assets	41,685
Furniture, Fixtures and Equipment, Net
Properties
Finance right-of-use assets	1,200
Taxable REIT Subsidiary
Properties
Deferred tax assets, valuation allowance	2,400	2,700
Corporate Office Properties, L.P.
Properties
Lease incentives, net	22,981	21,258
Construction contract costs incurred in excess of billings	14,834	3,189
Prepaid expenses	10,749	25,658
Furniture, fixtures and equipment, net (1)	8,453	8,630
Non-real estate equity investments	5,792	5,940
Deferred financing costs, net	4,473	4,733
Restricted cash	3,995	3,884	$ 3,645	$ 2,570
Deferred tax asset, net	1,890	2,084
Other assets	6,815	6,337
Total for COPT and subsidiaries	$ 79,982	$ 81,713

Debt, Net (Details)

Debt, Net (Details)	3 Months Ended
	Mar. 31, 2019USD ($)extension	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Debt
Carrying Value	$ 1,876,149,000		$ 1,823,909,000
Interest costs capitalized	2,000,000	$ 1,400,000
Mortgage and other secured debt
Debt
Carrying Value	$ 173,127,000		170,423,000
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	$ 6,800,000		7,200,000
Fixed rate mortgage debt | Mortgage and other secured debt
Debt
Carrying Value	146,212,000		147,141,000
Unamortized premium included in carrying value	$ 264,000		281,000
Weighted average interest rate (as a percent)	4.17%
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)	7.87%
Variable-rate debt | Mortgage and other secured debt
Debt
Carrying Value	$ 26,915,000		23,282,000
Weighted average interest rate (as a percent)	4.63%
Variable-rate debt | Mortgage and other secured debt | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)	1.85%
Variable-rate debt | Mortgage and other secured debt | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)	2.35%
Construction Loan | Mortgage and other secured debt | London Interbank Offered Rate (LIBOR)
Debt
Remaining borrowing capacity	$ 94,900,000
Revolving Credit Facility
Debt
Carrying Value	$ 262,000,000		213,000,000
Weighted average interest rate (as a percent)	3.54%
Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)	0.775%
Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)	1.45%
Term Loan Facility
Debt
Carrying Value	$ 248,381,000		248,273,000
Interest rate (as a percent)	3.74%
Aggregate additional borrowing capacity available	$ 150,000,000
Maximum availability	$ 500,000,000
Term Loan Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)	0.85%
Term Loan Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)	1.65%
3.600% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 348,096,000		347,986,000
Debt instrument, face amount	$ 350,000,000
Interest rate (as a percent)	3.60%
Unamortized discount included in carrying value	$ 1,300,000		1,400,000
Effective interest rate on debt (as a percent)	3.70%
5.250% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 247,263,000		247,136,000
Debt instrument, face amount	$ 250,000,000
Interest rate (as a percent)	5.25%
Unamortized discount included in carrying value	$ 2,500,000		2,600,000
Effective interest rate on debt (as a percent)	5.49%
3.700% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 298,941,000		298,815,000
Debt instrument, face amount	$ 300,000,000
Interest rate (as a percent)	3.70%
Unamortized discount included in carrying value	$ 800,000		943,000
Effective interest rate on debt (as a percent)	3.85%
5.000% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 297,206,000		297,109,000
Debt instrument, face amount	$ 300,000,000
Interest rate (as a percent)	5.00%
Unamortized discount included in carrying value	$ 2,300,000		2,400,000
Effective interest rate on debt (as a percent)	5.15%
Unsecured notes payable
Debt
Carrying Value	$ 1,135,000		1,167,000
Interest rate (as a percent)	0.00%
Unamortized discount included in carrying value	$ 276,000		$ 294,000

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Carrying Amount
Carrying amount and estimated fair value of debt
Long-term debt	$ 1,876,149	$ 1,823,909
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,191,506	1,191,046
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	147,347	148,308
Carrying Amount | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	537,296	484,555
Estimated Fair Value
Carrying amount and estimated fair value of debt
Long-term debt	1,910,137	1,853,206
Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,222,637	1,219,603
Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	146,585	147,106
Estimated Fair Value | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	$ 540,915	$ 486,497

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (Loss) Gain Recognized in AOCL on Derivatives	$ (8,845)	$ 4,676
Interest rate swaps | Interest Expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of Gain (Loss) Reclassified from AOCL into Interest Expense on Statement of Operations	570	$ (245)
Interest rate swaps | Interest rate derivatives (assets)
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	2,602		$ 5,617
Interest rate swaps | Interest rate derivative (liabilities)
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	(11,894)		(5,459)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(9,292)		158
Designated | Interest rate swaps
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Approximate amount to be reclassified from AOCL to interest expense over the next 12 months	817
Fair value of derivative liability	12,000
Settlement amount of derivative obligation at termination value	12,000
Designated | Interest rate swap, effective date September 1, 2015, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000
Fixed rate (as a percent)	1.73%
Fair value of interest rate swaps	$ 255		472
Designated | Interest rate swap, effective October 13, 2015
Fair values of interest rate swap derivatives
Notional Amount	$ 12,735
Fixed rate (as a percent)	1.39%
Fair value of interest rate swaps	$ 170		239
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 (as a percent)	1.9013%
Fair value of interest rate swaps	$ 879		1,968
Designated | Interest rate swap, effective September 1, 2016, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000
Fixed rate (as a percent)	1.905%
Fair value of interest rate swaps	$ 871		1,967
Designated | Interest rate swap, effective September 1, 2016, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 50,000
Fixed rate (as a percent)	1.9079%
Fair value of interest rate swaps	$ 427		971
Designated | Interest rate swap, effective June 30, 2020, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000
Fixed rate (as a percent)	3.176%
Fair value of interest rate swaps	$ (4,869)		(2,676)
Designated | Interest rate swap, effective June 30, 2020, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000
Fixed rate (as a percent)	3.192%
Fair value of interest rate swaps	$ (4,974)		(2,783)
Designated | Interest rate swap, effective June 30, 2020, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000
Fixed rate (as a percent)	2.744%
Fair value of interest rate swaps	$ (2,051)		$ 0

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interests (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)joint_venture	Mar. 31, 2018USD ($)
Noncontrolling Interest [Abstract]
Number of joint ventures with redeemable noncontrolling interests | joint_venture	2
Redeemable Noncontrolling Interest [Roll Forward]
Beginning balance	$ 26,260	$ 23,125
Distributions to noncontrolling interests	(349)	(452)
Net income attributable to noncontrolling interests	675	638
Adjustment to arrive at fair value of interests	799	537
Ending balance	$ 27,385	$ 23,848

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Class of Stock [Line Items]
Conversion of common units to common shares (in units/shares)	5,500	53,817
Dividends declared per share (in usd per share)	$ 0.2750	$ 0.275
Common Shares | Forward Equity Sale Agreement
Class of Stock [Line Items]
Number of shares issued	1,600,000
Proceeds from common shares issued under forward equity sale agreements	$ 46.5
Remaining capacity under program	0
Common Shares | 2018 Common Stock Issued to Public Under At-the-Market Program
Class of Stock [Line Items]
Aggregate gross sales price	$ 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, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment financial information for real estate operations
Revenues from real estate operations	$ 148,940	$ 155,476
Property operating expenses	(49,445)	(50,951)
UJV NOI allocable to COPT	1,219	1,199
Segment assets	3,775,859	3,596,238	$ 3,656,005
Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	131,990	128,278
Property operating expenses	(49,445)	(50,951)
UJV NOI allocable to COPT	1,219	1,199
NOI from real estate operations	83,764	78,526
Additions to long-lived assets	14,854	14,295
Transfers from non-operating properties	39,475	20,094
Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	108,523	104,120
Property operating expenses	(38,882)	(38,463)
UJV NOI allocable to COPT	1,219	1,199
NOI from real estate operations	70,860	66,856
Additions to long-lived assets	10,699	10,248
Transfers from non-operating properties	39,475	19,082
Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	62,683	62,782
Property operating expenses	(22,335)	(21,604)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	40,348	41,178
Additions to long-lived assets	3,935	7,121
Transfers from non-operating properties	5,040	17,186
Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	14,831	12,561
Property operating expenses	(5,292)	(4,723)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	9,539	7,838
Additions to long-lived assets	1,447	1,940
Transfers from non-operating properties	4,509	341
Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	11,561	11,443
Property operating expenses	(5,959)	(6,598)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	5,602	4,845
Additions to long-lived assets	0	0
Transfers from non-operating properties	6,503	0
Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	8,155	7,870
Property operating expenses	(3,404)	(3,304)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	4,751	4,566
Additions to long-lived assets	5,017	1,108
Transfers from non-operating properties	0	(3)
Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	3,939	3,633
Property operating expenses	(1,539)	(1,440)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	2,400	2,193
Additions to long-lived assets	300	79
Transfers from non-operating properties	3,635	444
Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	7,354	5,831
Property operating expenses	(353)	(794)
UJV NOI allocable to COPT	1,219	1,199
NOI from real estate operations	8,220	6,236
Additions to long-lived assets	0	0
Transfers from non-operating properties	19,788	1,114
Regional Office | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	14,833	15,284
Property operating expenses	(7,416)	(7,878)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	7,417	7,406
Additions to long-lived assets	3,989	3,884
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	7,871	8,077
Property operating expenses	(2,838)	(4,258)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	5,033	3,819
Additions to long-lived assets	156	36
Transfers from non-operating properties	0	1,012
Other | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	763	797
Property operating expenses	(309)	(352)
UJV NOI allocable to COPT	0	0
NOI from real estate operations	454	445
Additions to long-lived assets	10	127
Transfers from non-operating properties	0	0
Segment assets
Segment financial information for real estate operations
Segment assets	3,108,153	3,025,966
Segment assets | Real estate operations
Segment financial information for real estate operations
Segment assets	3,108,153	3,025,966
Segment assets | Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	2,496,255	2,401,748
Segment assets | Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Segment assets	1,279,983	1,273,359
Segment assets | Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Segment assets	400,741	399,202
Segment assets | Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Segment assets	145,697	127,855
Segment assets | Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	189,192	192,116
Segment assets | Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Segment assets	110,195	107,096
Segment assets | Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Segment assets	370,447	302,120
Segment assets | Regional Office | Real estate operations
Segment financial information for real estate operations
Segment assets	394,001	397,355
Segment assets | Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Segment assets	213,993	222,738
Segment assets | Other | Real estate operations
Segment financial information for real estate operations
Segment assets	$ 3,904	$ 4,125

Information by Business Segme_4

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reconciliation of segment revenues to total revenues
Construction contract and other service revenues	$ 16,950	$ 27,198
Total revenues	148,940	155,476
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,219	1,199
Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense	(827)	(824)
Add: Equity in loss of unconsolidated non-real estate entities	(1)	(2)
Equity in income of unconsolidated entities	391	373
Computation of net operating income from service operations
Construction contract and other service revenues	16,950	27,198
Construction contract and other service expenses	(16,326)	(26,216)
Real estate operations
Reconciliation of segment revenues to total revenues
Total revenues	131,990	128,278
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,219	1,199
Service operations
Computation of net operating income from service operations
NOI from service operations	$ 624	$ 982

Information by Business Segme_5

Information by Business Segment (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
Interest and other income	$ 2,286	$ 1,359
Gain on sales of real estate	0	(4)
Equity in income of unconsolidated entities	391	373
Income tax expense	(194)	(55)
Depreciation and other amortization associated with real estate operations	(34,796)	(33,512)
General, administrative and leasing expenses	(8,751)	(7,292)
Business development expenses and land carry costs	(1,113)	(1,614)
Interest expense	(18,674)	(18,784)
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,219)	(1,199)
Net income	22,318	18,780
Real estate operations
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from real estate operations	83,764	78,526
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,219)	(1,199)
Service operations
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from service operations	$ 624	$ 982

Information by Business Segme_6

Information by Business Segment (Details 4) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 3,775,859	$ 3,656,005	$ 3,596,238
Operating properties lease liabilities included in segment assets	16,619
Segment assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	3,108,153		3,025,966
Operating properties lease liabilities included in segment assets	16,342		0
Non-operating property assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	485,911		425,951
Other assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 165,453		$ 144,321

Construction Contract and Oth_3

Construction Contract and Other Service Revenues (Details) - Construction Contract Revenue - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Performance obligations satisfied or already satisfied	$ 32	$ 309
Remaining performance obligations	51,600
Remaining performance obligation expected to be recognized during the remainder of year	$ 45,000

Construction Contract and Oth_4

Construction Contract and Other Service Revenues (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 16,950	$ 27,198
Construction
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	16,489	25,915
Design
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	252	1,064
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	209	219
Guaranteed Maximum Price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	12,356	20,486
Firm fixed price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	2,325	6,435
Cost-plus fee
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	2,060	58
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 209	$ 219

Construction Contract and Oth_5

Construction Contract and Other Service Revenues (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Change in Accounts Receivable
Beginning balance	$ 25,261		$ 26,277
Ending balance	25,261		26,277
Construction Contract Revenue
Change in Accounts Receivable
Beginning balance	6,569	$ 4,021	6,701	$ 4,577
Ending balance	6,569	4,021	6,701	4,577
Change in Contract with Customer, Asset
Beginning balance	14,834	4,250	3,189	4,884
Ending balance	14,834	4,250	3,189	4,884
Change in Contract with Customer, Liability
Beginning balance	1,005	8,279	568	27,402
Ending balance	1,005	8,279	$ 568	$ 27,402
Revenue recognized included in beginning balance	$ 439	$ 19,297

Share-Based Compensation (Detai

Share-Based Compensation (Details) $ / shares in Units, $ in Millions	Jan. 18, 2019shares	Jan. 01, 2019USD ($)$ / sharesshares	Mar. 31, 2019USD ($)Percentile_RankForm$ / sharesshares
PIUs
Share-Based Compensation
Number of forms of executive compensation | Form			2
Time-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units) | shares			54,956
Aggregate grant date fair value | $			$ 1.4
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 25.81
Annual award vesting rights (percent)			33.33%
Award vesting period			3 years
Restricted shares
Share-Based Compensation
Stock awards granted (in shares or units) | shares			135,396
Aggregate grant date fair value | $			$ 3.5
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 25.81
Shares vested (in shares) | shares			151,252
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 27.94
Aggregate intrinsic value of awards upon vesting | $			$ 3.9
2016 PSU Grants | Performance share units | Executives
Share-Based Compensation
Shares issued (in shares) | shares	44,757
Percentage of target	157.00%
2019 PIU Grants | Performance-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units) | shares		193,682
Aggregate grant date fair value | $		$ 2.4
Aggregate grant date fair value (in dollars per share) | $ / shares		$ 12.47
Award vesting period		3 years
Potential earned PSUs payout for defined levels of performance under awards
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 75th or greater percentile rank		100.00%
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 50th percentile rank		50.00%
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 25th percentile rank		25.00%
Earned PB-PIUs granted on percentile rank below 25th (as a percent)		0.00%
The number of percentile ranks to fall between to earn interpolated PB-PIUs between such percentile ranks, conditioned on the percentile rank exceeding 25% | Percentile_Rank			2
Assumptions used to value stock awards
Percent of award distribution rights			10.00%
Award performance period			3 years
Baseline value per common share (in dollars per share) | $ / shares		$ 21.03
Expected volatility of common shares (as a percent)		21.00%
Risk-free interest rate (as a percent)		2.51%

Earnings Per Share ("EPS") an_3

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income attributable to COPT/COPLP		$ 20,859	$ 17,150
Income attributable to share-based compensation awards		(86)	(117)
Numerator for basic and diluted EPS on net income attributable to COPT/COPLP common share/unit holders		$ 20,773	$ 17,033
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)		109,951	100,999
Dilutive effect of share-based compensation awards		267	144
Denominator for diluted EPS/EPU (common shares/units)		110,218	101,143
Basic EPS:
Basic earnings per common share (in dollars per share/unit)	[1]	$ 0.19	$ 0.17
Diluted EPS:
Diluted earnings per common share (in dollars per share/unit)	[1]	$ 0.19	$ 0.17
Corporate Office Properties, L.P.
Numerator:
Net income attributable to COPT/COPLP		$ 21,281	$ 17,859
Preferred share/unit dividends/distributions		(165)	(165)
Income attributable to share-based compensation awards		(93)	(117)
Numerator for basic and diluted EPS on net income attributable to COPT/COPLP common share/unit holders		$ 21,023	$ 17,577
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)		111,282	104,220
Dilutive effect of share-based compensation awards		267	144
Denominator for diluted EPS/EPU (common shares/units)		111,549	104,364
Basic EPS:
Basic earnings per common share (in dollars per share/unit)	[2]	$ 0.19	$ 0.17
Diluted EPS:
Diluted earnings per common share (in dollars per share/unit)	[2]	$ 0.19	$ 0.17
[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, 2019	Mar. 31, 2018
Conversion of common units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,331	3,221
Conversion of redeemable noncontrolling interests
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,013	0
Conversion of Series I preferred units
Antidilutive securities
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
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,500	7,500
Weighted average restricted shares/units and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	463	444
Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	30	60
Weighted average unvested PIUs
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	19
Corporate Office Properties, L.P. | Conversion of redeemable noncontrolling interests
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,013	0
Corporate Office Properties, L.P. | Conversion of Series I preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	176	176
Corporate Office Properties, L.P. | Weighted average shares related to forward equity sale agreements
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,500	7,500
Corporate Office Properties, L.P. | Weighted average restricted shares/units and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	463	444
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	30	60
Corporate Office Properties, L.P. | Weighted average unvested PIUs
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	19

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	Mar. 31, 2019USD ($)Property	Aug. 31, 2010USD ($)
Environmental Indemnity Agreement
Number of properties which were provided environmental indemnifications | Property	3
Maximum additional costs agreed to be paid by the entity under environmental indemnification agreement	$ 19,000,000
Development and Redevelopment Obligations
Environmental Indemnity Agreement
Purchase obligations	184,300,000
Tenant and Other Capital Improvements
Environmental Indemnity Agreement
Purchase obligations	45,300,000
Third Party Construction
Environmental Indemnity Agreement
Purchase obligations	32,600,000
Other Obligations
Environmental Indemnity Agreement
Purchase obligations	$ 1,700,000
Specialty Tax Guarantee | Anne Arundel County, Maryland | Tax Incremental Financing Bond
Environmental Indemnity Agreement
Loan amount		$ 30,000,000