COPT Defense Properties (CDP) 10-Q 1 Nov 19 2019 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2019	Oct. 25, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2019
Entity File Number	1-14023
Entity Registrant Name	Corporate Office Properties Trust
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	23-2947217
Entity Address, Address Line One	6711 Columbia Gateway Drive
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Columbia
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21046
City Area Code	443
Local Phone Number	285-5400
Title of 12(b) Security	Common Shares of beneficial interest, $0.01 par value
Trading Symbol	OFC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		112,058,925
Entity Central Index Key	0000860546
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Small Business	false
Entity Emerging Growth Company	false
Corporate Office Properties, L.P.
Entity Information [Line Items]
Entity File Number	333-189188
Entity Registrant Name	Corporate Office Properties, L.P.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	23-2930022
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Central Index Key	0001577966
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Small Business	false
Entity Emerging Growth Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Properties, net:
Operating properties, net	$ 2,713,900	$ 2,847,265
Projects in development or held for future development	544,923	403,361
Total properties, net	3,258,823	3,250,626
Property - finance right-of-use assets	41,660
Assets held for sale, net	61,728	0
Cash and cash equivalents	34,005	8,066
Investment in unconsolidated real estate joint ventures	49,408	39,845
Accounts receivable	37,623	26,277
Deferred rent receivable	88,001	89,350
Intangible assets on real estate acquisitions, net	29,454	43,470
Deferred leasing costs (net of accumulated amortization of $34,198 and $31,994, respectively)	55,839	50,191
Investing receivables	72,114	56,982
Prepaid expenses and other assets, net	100,582	91,198
Total assets	3,855,369	3,656,005
Liabilities:
Debt, net	1,862,301	1,823,909
Accounts payable and accrued expenses	141,242	92,855
Rents received in advance and security deposits	27,975	30,079
Dividends and distributions payable	31,345	30,856
Deferred revenue associated with operating leases	7,665	9,125
Property - operating lease liabilities	16,686
Interest rate derivatives	34,825	5,459
Other liabilities	8,706	10,414
Total liabilities	2,130,745	2,002,697
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	28,677	26,260
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,121	1,102
Additional paid-in capital	2,480,083	2,431,355
Cumulative distributions in excess of net income	(790,235)	(846,808)
Accumulated other comprehensive loss	(34,580)	(238)
Total Corporate Office Properties Trust’s shareholders’ equity	1,656,389	1,585,411
Noncontrolling interests in subsidiaries:
Common units in COPLP	19,365	19,168
Preferred units in COPLP	8,800	8,800
Other consolidated entities	11,393	13,669
Noncontrolling interests in subsidiaries	39,558	41,637
Total equity	1,695,947	1,627,048
Total liabilities, redeemable noncontrolling interests and equity	3,855,369	3,656,005
Properties
Properties, net:
Property - operating right-of-use assets	27,325	0
Property - finance right-of-use assets	40,467	0
Liabilities:
Property - operating lease liabilities	16,686	0
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,713,900	2,847,265
Projects in development or held for future development	544,923	403,361
Total properties, net	3,258,823	3,250,626
Assets held for sale, net	61,728	0
Cash and cash equivalents	34,005	8,066
Investment in unconsolidated real estate joint ventures	49,408	39,845
Accounts receivable	37,623	26,277
Deferred rent receivable	88,001	89,350
Intangible assets on real estate acquisitions, net	29,454	43,470
Deferred leasing costs (net of accumulated amortization of $34,198 and $31,994, respectively)	55,839	50,191
Investing receivables	72,114	56,982
Prepaid expenses and other assets, net	96,325	87,330
Total assets	3,851,112	3,652,137
Liabilities:
Debt, net	1,862,301	1,823,909
Accounts payable and accrued expenses	141,242	92,855
Rents received in advance and security deposits	27,975	30,079
Dividends and distributions payable	31,345	30,856
Deferred revenue associated with operating leases	7,665	9,125
Interest rate derivatives	34,825	5,459
Other liabilities	4,449	6,546
Total liabilities	2,126,488	1,998,829
Commitments and contingencies (Note 17)
Redeemable noncontrolling interests	28,677	26,260
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,710,600	1,604,655
Accumulated other comprehensive loss	(34,891)	(121)
Total Corporate Office Properties Trust’s shareholders’ equity	1,684,509	1,613,334
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	11,438	13,714
Total equity	1,695,947	1,627,048
Total liabilities, redeemable noncontrolling interests and equity	3,851,112	3,652,137
Corporate Office Properties, L.P. | Properties
Properties, net:
Property - operating right-of-use assets	27,325	0
Property - finance right-of-use assets	40,467	0
Liabilities:
Property - operating lease liabilities	16,686	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 September 30, 2019 and December 31, 2018	$ 8,800	$ 8,800

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accumulated amortization of deferred leasing costs	$ 34,198	$ 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	112,059,175	110,241,868
Common Shares of beneficial interest, shares outstanding	112,059,175	110,241,868
Corporate Office Properties, L.P.
Accumulated amortization of deferred leasing costs	$ 34,198	$ 31,994
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	112,059,175	110,241,868
Corporate Office Properties, L.P. | Limited Partner
Common Shares of beneficial interest, shares outstanding	1,484,425	1,332,886
Preferred Units, Outstanding	352,000	352,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues
Lease revenue		$ 129,461	$ 127,691	$ 391,779	$ 382,731
Construction contract and other service revenues		28,697	8,423	87,946	53,202
Total revenues		159,431	137,411	483,441	439,630
Operating expenses
Property operating expenses		49,714	49,340	147,045	149,737
Depreciation and amortization associated with real estate operations		34,692	34,195	104,290	100,897
Construction contract and other service expenses		27,802	8,058	85,130	51,215
Impairment losses		327	0	327	0
General, administrative and leasing expenses		7,929	6,899	26,066	21,819
Business development expenses and land carry costs		964	1,567	2,947	4,415
Total operating expenses		121,428	100,059	365,805	328,083
Interest expense		(17,126)	(19,181)	(54,275)	(56,910)
Interest and other income		1,842	1,486	5,977	4,284
Gain on sales of real estate		0	0	84,469	(27)
Income before equity in income of unconsolidated entities and income taxes		22,719	19,657	153,807	58,894
Equity in income of unconsolidated entities		396	374	1,207	1,120
Income tax benefit		131	291	113	173
Net income		23,246	20,322	155,127	60,187
Net income attributable to noncontrolling interests:
Common units in COPLP		(267)	(380)	(1,863)	(1,532)
Preferred units in COPLP		(157)	(165)	(487)	(495)
Other consolidated entities		(1,565)	(1,080)	(3,870)	(2,879)
Net income attributable to COPLP		21,257	18,697	148,907	55,281
Net income attributable to COPT common shareholders		$ 21,257	$ 18,697	$ 148,907	$ 55,281
Earnings per common share:
Net income attributable to COPT common shareholders - basic (in dollars per share/unit)	[1]	$ 0.19	$ 0.18	$ 1.34	$ 0.54
Net income attributable to COPT common shareholders - diluted (in dollars per share/unit)	[1]	$ 0.19	$ 0.18	$ 1.33	$ 0.54
Other Property Revenue
Revenues
Total revenues		$ 1,273	$ 1,297	$ 3,716	$ 3,697
Corporate Office Properties, L.P.
Revenues
Lease revenue		129,461	127,691	391,779	382,731
Construction contract and other service revenues		28,697	8,423	87,946	53,202
Total revenues		159,431	137,411	483,441	439,630
Operating expenses
Property operating expenses		49,714	49,340	147,045	149,737
Depreciation and amortization associated with real estate operations		34,692	34,195	104,290	100,897
Construction contract and other service expenses		27,802	8,058	85,130	51,215
Impairment losses		327	0	327	0
General, administrative and leasing expenses		7,929	6,899	26,066	21,819
Business development expenses and land carry costs		964	1,567	2,947	4,415
Total operating expenses		121,428	100,059	365,805	328,083
Interest expense		(17,126)	(19,181)	(54,275)	(56,910)
Interest and other income		1,842	1,486	5,977	4,284
Gain on sales of real estate		0	0	84,469	(27)
Income before equity in income of unconsolidated entities and income taxes		22,719	19,657	153,807	58,894
Equity in income of unconsolidated entities		396	374	1,207	1,120
Income tax benefit		131	291	113	173
Net income		23,246	20,322	155,127	60,187
Net income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities		(1,565)	(1,080)	(3,870)	(2,879)
Net income attributable to COPLP		21,681	19,242	151,257	57,308
Preferred unit distributions		(157)	(165)	(487)	(495)
Net income attributable to COPT common shareholders		$ 21,524	$ 19,077	$ 150,770	$ 56,813
Earnings per common share:
Net income attributable to COPT common shareholders - basic (in dollars per share/unit)	[2]	$ 0.19	$ 0.18	$ 1.34	$ 0.54
Net income attributable to COPT common shareholders - diluted (in dollars per share/unit)	[2]	$ 0.19	$ 0.18	$ 1.33	$ 0.54
Corporate Office Properties, L.P. | Other Property Revenue
Revenues
Total revenues		$ 1,273	$ 1,297	$ 3,716	$ 3,697
[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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 23,246	$ 20,322	$ 155,127	$ 60,187
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(11,047)	1,325	(33,437)	7,913
Gain on interest rate derivatives recognized in interest expense	(307)	(207)	(1,434)	(9)
Other comprehensive (loss) income	(11,354)	1,118	(34,871)	7,904
Comprehensive income	11,892	21,440	120,256	68,091
Comprehensive income attributable to noncontrolling interests	(1,750)	(1,647)	(5,691)	(5,145)
Comprehensive income attributable to COPT	10,142	19,793	114,565	62,946
Corporate Office Properties, L.P.
Net income	23,246	20,322	155,127	60,187
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(11,047)	1,325	(33,437)	7,913
Gain on interest rate derivatives recognized in interest expense	(307)	(207)	(1,434)	(9)
Other comprehensive (loss) income	(11,354)	1,118	(34,871)	7,904
Comprehensive income	11,892	21,440	120,256	68,091
Comprehensive income attributable to noncontrolling interests	(1,464)	(1,080)	(3,769)	(2,879)
Comprehensive income attributable to COPT	$ 10,428	$ 20,360	$ 116,487	$ 65,212

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Forward Equity Sale Agreement	Common Stock At-the-Market Program	Common Shares	Common SharesForward Equity Sale Agreement	Common SharesCommon Stock At-the-Market Program	Additional Paid-in Capital	Additional Paid-in CapitalForward Equity Sale Agreement	Additional Paid-in CapitalCommon Stock At-the-Market Program	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 Stock At-the-Market Program	Corporate Office Properties, L.P.Common Shares	Corporate Office Properties, L.P.Common SharesForward Equity Sale Agreement	Corporate Office Properties, L.P.Common SharesCommon Stock At-the-Market Program	Corporate Office Properties, L.P.Accumulated Other Comprehensive Income (Loss)	Corporate Office Properties, L.P.Noncontrolling Interests	Corporate Office Properties, L.P.Limited Partner	Corporate Office Properties, L.P.Limited PartnerPreferred Shares
Increase (Decrease) in Shareholders' Equity
Cumulative effect of accounting change for adoption of hedge accounting guidance										$ (276)	$ 276					$ (276)			$ 276
Balance, as adjusted	$ 1,468,307			$ 1,013			$ 2,201,047			(802,361)	2,443	$ 66,165	$ 1,468,307			1,444,746			2,449	$ 12,312		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Dec. 31, 2017	$ 1,468,307			1,013			2,201,047			(802,085)	2,167	66,165	1,468,307			$ 1,445,022			2,173	12,312		$ 8,800
Balance (preferred units) at Dec. 31, 2017																						352,000
Balance (in units/shares) at Dec. 31, 2017	101,292,299															104,543,177
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 1,841,810 and 97,539 shares for the three months ended September 30, 2018 and 2019 and 1,895,627 and 103,039 shares for the nine months ended September 30, 2018 and 2019, respectively)	$ 0			19			27,263					(27,282)
Common shares issued under sale agreements and programs	$ 132,330		$ 29,732		$ 45	$ 10		$ 132,285	$ 29,722					$ 132,330	$ 29,732		$ 132,330	$ 29,732
Common shares issued under sale agreements and programs (in units/shares)		4,527,000	991,664														4,527,000	991,664
Share-based compensation issuance, net of redemptions (in units/shares)	141,633															141,633
Share-based compensation issuance, net of redemptions (COPT: 4,254 and 11,749 shares for the three months ended September 30, 2018 and 2019 and 141,633 and 100,181 shares issued, net of redemptions for the nine months ended September 30, 2018 and 2019, respectively)	$ 5,179			1			5,178						5,179			$ 5,179
Redemption of vested equity awards	(1,611)						(1,611)						(1,611)			(1,611)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0						(2,069)					2,069
Comprehensive income	66,188									55,281	7,665	3,242	66,188			56,813			7,904	976		$ 495
Dividends/Distributions	(86,428)									(86,428)			(89,054)			(88,559)						$ (495)
Distributions to owners of common and preferred units in COPLP	(2,626)											(2,626)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(11)											(11)	(11)							(11)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (1,331)						(1,331)						(1,331)			$ (1,331)
Balance (in units/shares) at Sep. 30, 2018	108,848,223															110,203,474
Balance (preferred units) at Sep. 30, 2018																						352,000
Balance (COPT: 108,848,223 and 112,059,175 shares as of September 30, 2018 and 2019, respectively) at Sep. 30, 2018	$ 1,609,729			1,088			2,390,484			(833,508)	10,108	41,557	1,609,729			$ 1,577,299			10,353	13,277		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Jun. 30, 2018	$ 1,508,485			1,033			2,254,430			(822,270)	9,012	66,280	1,508,485			$ 1,477,575			9,235	12,875		$ 8,800
Balance (preferred units) at Jun. 30, 2018																						352,000
Balance (in units/shares) at Jun. 30, 2018	103,260,495															106,457,556
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 1,841,810 and 97,539 shares for the three months ended September 30, 2018 and 2019 and 1,895,627 and 103,039 shares for the nine months ended September 30, 2018 and 2019, respectively)	$ 0			18			26,503					(26,521)
Common shares issued under sale agreements and programs		$ 80,103	$ 29,732		27	$ 10		80,076	$ 29,722					80,103	$ 29,732		$ 80,103	$ 29,732
Common shares issued under sale agreements and programs (in units/shares)		2,750,000	991,664														2,750,000	991,664
Share-based compensation issuance, net of redemptions (in units/shares)	4,254															4,254
Share-based compensation issuance, net of redemptions (COPT: 4,254 and 11,749 shares for the three months ended September 30, 2018 and 2019 and 141,633 and 100,181 shares issued, net of redemptions for the nine months ended September 30, 2018 and 2019, respectively)	$ 1,779						1,779						1,779			$ 1,779
Redemption of vested equity awards	(86)						(86)						(86)			(86)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0						(1,367)					1,367
Comprehensive income	20,766									18,697	1,096	973	20,766			19,077			1,118	406		$ 165
Dividends/Distributions	(29,935)									(29,935)			(30,473)			(30,308)						$ (165)
Distributions to owners of common and preferred units in COPLP	(538)											(538)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(4)											(4)	(4)							(4)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (573)						(573)						(573)			$ (573)
Balance (in units/shares) at Sep. 30, 2018	108,848,223															110,203,474
Balance (preferred units) at Sep. 30, 2018																						352,000
Balance (COPT: 108,848,223 and 112,059,175 shares as of September 30, 2018 and 2019, respectively) at Sep. 30, 2018	$ 1,609,729			1,088			2,390,484			(833,508)	10,108	41,557	1,609,729			$ 1,577,299			10,353	13,277		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Dec. 31, 2018	$ 1,627,048			1,102			2,431,355			(846,808)	(238)	41,637	1,627,048			$ 1,604,655			(121)	13,714		$ 8,800
Balance (preferred units) at Dec. 31, 2018																					352,000	352,000
Balance (in units/shares) at Dec. 31, 2018	110,241,868															111,574,754					1,332,886
Increase (Decrease) in Shareholders' Equity
Redemption of common units	$ (25)											(25)	(25)			$ (25)
Redemption of common units (in units)																(924)
Conversion of common units to common shares (COPT: 1,841,810 and 97,539 shares for the three months ended September 30, 2018 and 2019 and 1,895,627 and 103,039 shares for the nine months ended September 30, 2018 and 2019, respectively)	$ 0			1			1,555					(1,556)
Common shares issued under sale agreements and programs		$ 46,454			$ 16			$ 46,438						$ 46,454			$ 46,454
Common shares issued under sale agreements and programs (in units/shares)		1,614,087															1,614,087
Share-based compensation issuance, net of redemptions (in units/shares)	100,181															355,683
Share-based compensation issuance, net of redemptions (COPT: 4,254 and 11,749 shares for the three months ended September 30, 2018 and 2019 and 141,633 and 100,181 shares issued, net of redemptions for the nine months ended September 30, 2018 and 2019, respectively)	$ 5,530			2			4,574					954	5,530			$ 5,530
Redemption of vested equity awards	(1,973)						(1,973)						(1,973)			(1,973)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0						(522)					522
Comprehensive income	117,527									148,907	(34,342)	2,962	117,527			150,770			(34,770)	1,040		$ 487
Dividends/Distributions	(92,334)									(92,334)			(93,954)			(93,467)						$ (487)
Contributions from noncontrolling interests in other consolidated entities	2,570											2,570	2,570							2,570
Distributions to owners of common and preferred units in COPLP	(1,620)											(1,620)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(5,886)											(5,886)	(5,886)							(5,886)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ (1,344)						(1,344)						(1,344)			$ (1,344)
Balance (in units/shares) at Sep. 30, 2019	112,059,175															113,543,600					1,484,425
Balance (preferred units) at Sep. 30, 2019																					352,000	352,000
Balance (COPT: 108,848,223 and 112,059,175 shares as of September 30, 2018 and 2019, respectively) at Sep. 30, 2019	$ 1,695,947			1,121			2,480,083			(790,235)	(34,580)	39,558	1,695,947			$ 1,710,600			(34,891)	11,438		$ 8,800
Balance (COPT: 101,292,299 and 110,241,868 shares as of December 31, 2017 and 2018 and 103,260,495 and 111,949,887 shares as of June 30, 2018 and 2019, respectively) at Jun. 30, 2019	$ 1,719,111			1,119			2,475,293			(780,667)	(23,465)	46,831	1,719,111			$ 1,716,912			(23,638)	17,037		$ 8,800
Balance (preferred units) at Jun. 30, 2019																						352,000
Balance (in units/shares) at Jun. 30, 2019	111,949,887															113,532,731
Increase (Decrease) in Shareholders' Equity
Redemption of common units	$ (24)											(24)	(24)			$ (24)
Redemption of common units (in units)																(880)
Conversion of common units to common shares (COPT: 1,841,810 and 97,539 shares for the three months ended September 30, 2018 and 2019 and 1,895,627 and 103,039 shares for the nine months ended September 30, 2018 and 2019, respectively)	$ 0			1			1,475					(1,476)
Share-based compensation issuance, net of redemptions (in units/shares)	11,749															11,749
Share-based compensation issuance, net of redemptions (COPT: 4,254 and 11,749 shares for the three months ended September 30, 2018 and 2019 and 141,633 and 100,181 shares issued, net of redemptions for the nine months ended September 30, 2018 and 2019, respectively)	$ 1,895			1			1,525					369	1,895			$ 1,895
Redemption of vested equity awards	(53)						(53)						(53)			(53)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0						312					(312)
Comprehensive income	10,707									21,257	(11,115)	565	10,707			21,524			(11,253)	279		$ 157
Dividends/Distributions	(30,825)									(30,825)			(31,342)			(31,185)						$ (157)
Distributions to owners of common and preferred units in COPLP	(517)											(517)
Distributions to noncontrolling interests in other consolidated entities/subsidiaries	(5,878)											(5,878)	(5,878)							(5,878)
Adjustment to arrive at fair value of redeemable noncontrolling interests	$ 1,531						1,531						1,531			$ 1,531
Balance (in units/shares) at Sep. 30, 2019	112,059,175															113,543,600					1,484,425
Balance (preferred units) at Sep. 30, 2019																					352,000	352,000
Balance (COPT: 108,848,223 and 112,059,175 shares as of September 30, 2018 and 2019, respectively) at Sep. 30, 2019	$ 1,695,947			$ 1,121			$ 2,480,083			$ (790,235)	$ (34,580)	$ 39,558	$ 1,695,947			$ 1,710,600			$ (34,891)	$ 11,438		$ 8,800

Consolidated Statements of Eq_2

Consolidated Statements of Equity (Parenthetical) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Balance (in units/ shares)	112,059,175	108,848,223	112,059,175	108,848,223	111,949,887	110,241,868	103,260,495	101,292,299
Conversion of common units to common shares (in units/shares)	97,539	1,841,810	103,039	1,895,627
Share-based compensation issuance, net of redemptions (in units/shares)	11,749	4,254	100,181	141,633
Forward Equity Sale Agreement
Common shares issued during the period (in units/shares)		2,750,000	1,614,087	4,527,000
Common Stock At-the-Market Program
Common shares issued during the period (in units/shares)		991,664		991,664

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Revenues from real estate operations received	$ 391,758	$ 395,172
Construction contract and other service revenues received	65,813	27,450
Property operating expenses paid	(151,478)	(150,039)
Construction contract and other service expenses paid	(68,599)	(71,034)
General, administrative, leasing, business development and land carry costs paid	(23,806)	(20,858)
Interest expense paid	(52,818)	(55,611)
Lease incentives paid	(6,366)	(5,985)
Other	2,533	2,572
Net cash provided by operating activities	157,037	121,667
Cash flows from investing activities
Construction, development and redevelopment	(308,997)	(105,852)
Tenant improvements on operating properties	(16,466)	(27,962)
Other capital improvements on operating properties	(14,497)	(13,357)
Proceeds from property dispositions
Distribution from unconsolidated real estate joint venture following contribution of properties	129,783	0
Sale of properties	107,440	0
Distributions from unconsolidated real estate joint ventures	16,937	1,469
Investing receivables funded	(11,169)	0
Leasing costs paid	(13,502)	(6,277)
Other	1,558	(707)
Net cash used in investing activities	(108,913)	(152,686)
Proceeds from debt
Revolving Credit Facility	349,000	208,000
Other debt proceeds	32,002	11,267
Repayments of debt
Revolving Credit Facility	(342,000)	(235,000)
Scheduled principal amortization	(3,300)	(3,161)
Deferred financing costs paid	(405)	(3,413)
Payments on finance lease liabilities	(173)	(15,379)
Net proceeds from issuance of common shares/units	46,415	162,230
Common share/unit dividends/distributions paid	(91,835)	(84,349)
Redemption of vested equity awards	(1,973)	(1,611)
Other	(2,755)	(6,288)
Net cash (used in) provided by financing activities	(22,567)	29,120
Net increase (decrease) in cash and cash equivalents and restricted cash	25,557	(1,899)
Cash and cash equivalents and restricted cash
Beginning of period	11,950	14,831
End of period	37,507	12,932
Reconciliation of net income to net cash provided by operating activities:
Net income	155,127	60,187
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	105,686	102,440
Impairment losses	327	0
Amortization of deferred financing costs and net debt discounts	2,716	2,478
Increase in deferred rent receivable	(4,184)	(3,687)
Gain on sales of real estate	(84,469)	27
Share-based compensation	4,979	4,735
Other	(4,296)	(1,969)
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(9,483)	12,404
Increase in prepaid expenses and other assets, net	(26,878)	(3,810)
Increase (decrease) in accounts payable, accrued expenses and other liabilities	19,616	(48,649)
Decrease in rents received in advance and security deposits	(2,104)	(2,489)
Net cash provided by operating activities	157,037	121,667
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	29,457	3,550
Finance right-of-use asset contributed by noncontrolling interest in joint venture	2,570	0
Operating right-of-use assets obtained in exchange for operating lease liabilities	255	0
Non-cash changes from property dispositions
Contribution of properties to unconsolidated real estate joint venture	99,288	0
Investment in unconsolidated real estate joint venture retained in disposition	26,500	0
(Decrease) increase in fair value of derivatives applied to accumulated other comprehensive income and noncontrolling interests	(34,951)	7,802
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	1,556	27,282
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	522	2,069
Increase in redeemable noncontrolling interests and decrease in equity to carry redeemable noncontrolling interests at fair value	1,344	1,331
Other Consolidated Entities
Repayments of debt
Distributions paid to noncontrolling interests	(5,882)	(7)
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	391,758	395,172
Construction contract and other service revenues received	65,813	27,450
Property operating expenses paid	(151,478)	(150,039)
Construction contract and other service expenses paid	(68,599)	(71,034)
General, administrative, leasing, business development and land carry costs paid	(23,806)	(20,858)
Interest expense paid	(52,818)	(55,611)
Lease incentives paid	(6,366)	(5,985)
Other	2,533	2,572
Net cash provided by operating activities	157,037	121,667
Cash flows from investing activities
Construction, development and redevelopment	(308,997)	(105,852)
Tenant improvements on operating properties	(16,466)	(27,962)
Other capital improvements on operating properties	(14,497)	(13,357)
Proceeds from property dispositions
Distribution from unconsolidated real estate joint venture following contribution of properties	129,783	0
Sale of properties	107,440	0
Distributions from unconsolidated real estate joint ventures	16,937	1,469
Investing receivables funded	(11,169)	0
Leasing costs paid	(13,502)	(6,277)
Other	1,558	(707)
Net cash used in investing activities	(108,913)	(152,686)
Proceeds from debt
Revolving Credit Facility	349,000	208,000
Other debt proceeds	32,002	11,267
Repayments of debt
Revolving Credit Facility	(342,000)	(235,000)
Scheduled principal amortization	(3,300)	(3,161)
Deferred financing costs paid	(405)	(3,413)
Payments on finance lease liabilities	(173)	(15,379)
Net proceeds from issuance of common shares/units	46,415	162,230
Common share/unit dividends/distributions paid	(93,001)	(87,023)
Distributions paid to noncontrolling interests	(1,661)	(3,169)
Redemption of vested equity awards	(1,973)	(1,611)
Other	(3,250)	(6,783)
Net cash (used in) provided by financing activities	(22,567)	29,120
Net increase (decrease) in cash and cash equivalents and restricted cash	25,557	(1,899)
Cash and cash equivalents and restricted cash
Beginning of period	11,950	14,831
End of period	37,507	12,932
Reconciliation of net income to net cash provided by operating activities:
Net income	155,127	60,187
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	105,686	102,440
Impairment losses	327	0
Amortization of deferred financing costs and net debt discounts	2,716	2,478
Increase in deferred rent receivable	(4,184)	(3,687)
Gain on sales of real estate	(84,469)	27
Share-based compensation	4,979	4,735
Other	(4,296)	(1,969)
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(9,483)	12,404
Increase in prepaid expenses and other assets, net	(26,489)	(4,080)
Increase (decrease) in accounts payable, accrued expenses and other liabilities	19,227	(48,379)
Decrease in rents received in advance and security deposits	(2,104)	(2,489)
Net cash provided by operating activities	157,037	121,667
Reconciliation of cash and cash equivalents and restricted cash:
Cash and cash equivalents and restricted cash	37,507	12,932
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	29,457	3,550
Finance right-of-use asset contributed by noncontrolling interest in joint venture	2,570	0
Operating right-of-use assets obtained in exchange for operating lease liabilities	255	0
Non-cash changes from property dispositions
Contribution of properties to unconsolidated real estate joint venture	99,288	0
Investment in unconsolidated real estate joint venture retained in disposition	26,500	0
(Decrease) increase in fair value of derivatives applied to accumulated other comprehensive income and noncontrolling interests	(34,951)	7,802
Increase in redeemable noncontrolling interests and decrease in equity to carry redeemable noncontrolling interests at fair value	1,344	1,331
Corporate Office Properties, L.P. | Other Consolidated Entities
Repayments of debt
Distributions paid to noncontrolling interests	$ (5,882)	$ (7)

Organization

Organization	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Corporate Office Properties Trust (“COPT”) and subsidiaries (collectively, the “Company”) is a fully-integrated and self-managed real estate investment trust (“REIT”). Corporate Office Properties, L.P. (“COPLP”) and subsidiaries (collectively, the “Operating Partnership”) is the entity through which COPT, the sole general partner of COPLP, conducts almost all of its operations and owns almost all of its assets. Unless otherwise expressly stated or the context otherwise requires, “we”, “us” and “our” as used herein refer to each of the Company and the Operating Partnership. We own, manage, lease, develop and selectively acquire office and data center properties. The majority of our portfolio is in locations that support the United States Government and its contractors, most of whom are engaged in national security, defense and information technology (“IT”) related activities servicing what we believe are growing, durable, priority missions (“Defense/IT Locations”). We also own a portfolio of office properties located in select urban/urban-like submarkets in the Greater Washington, DC/Baltimore region with durable Class-A office fundamentals and characteristics (“Regional Office”). As of September 30, 2019 , our properties included the following: • 169 properties totaling 19.0 million square feet comprised of 15.3 million square feet in 147 office properties and 3.7 million square feet in 22 single-tenant data center shell properties (“data center shells”). We owned 13 of these data center shells through unconsolidated real estate joint ventures; • a wholesale data center with a critical load of 19.25 megawatts; • 15 properties under construction or redevelopment ( ten office properties and five data center shells) that we estimate will total approximately 2.6 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 11.2 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 September 30, 2019 , COPT owned 98.7% 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	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The COPT consolidated financial statements include the accounts of COPT, the Operating Partnership, their subsidiaries and other entities in which COPT has a majority voting interest and control. The COPLP consolidated financial statements include the accounts of COPLP, its subsidiaries and other entities in which COPLP has a majority voting interest and control. We also consolidate certain entities when control of such entities can be achieved through means other than voting rights (“variable interest entities” or “VIEs”) if we are deemed to be the primary beneficiary of such entities. We eliminate all intercompany balances and transactions in consolidation. We use the equity method of accounting when we own an interest in an entity and can exert significant influence over but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity. When we own an equity investment in an entity and cannot exert significant influence over its operations, we measure the investment at fair value, with changes recognized through net income. For an investment without a readily determinable fair value, we measure the investment at cost, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. These interim financial statements should be read together with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2018 included in our 2018 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2018 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below. Reclassification We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including reclassifications of our revenue from real estate operations in connection with our adoption of new lease guidance described below. Recent Accounting Pronouncements In February 2016, the FASB issued guidance setting forth principles for the recognition, measurement, presentation and disclosure of leases. This guidance requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. The resulting classification determines whether the lease expense is recognized based on an effective interest method or straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This guidance requires lessors of real estate to account for leases using an approach substantially equivalent to guidance previously in place for operating leases, direct financing leases and sales-type leases. We adopted this guidance on January 1, 2019 using a modified retrospective transition approach under which we elected to apply the guidance effective January 1, 2019 and not adjust prior comparative reporting periods (except for our presentation of lease revenue discussed below). We elected to apply a package of practical expedients that enabled us to carry forward upon adoption our historical assessments of: expired or existing leases regarding their lease classification and deferred recognition of non-incremental direct leasing costs; and whether any expired or existing contracts are, or contain, leases. We also elected a practical expedient that enabled us to avoid the need to assess whether expired or existing land easements not previously accounted for as leases are, or contain, a lease. In addition, we elected a practical expedient for our rental properties (as lessor) to avoid separating non-lease components that otherwise would need to be accounted for under the recently-adopted revenue accounting guidance (such as tenant reimbursements of property operating expenses) from the associated lease component since (1) the non-lease components have the same timing and pattern of transfer as the associated lease component and (2) the lease component, if accounted for separately, would be classified as an operating lease; this enables us to account for the combination of the lease component and non-lease components as an operating lease since the lease component is the predominant component of the combined components. Below is a summary of the primary changes in our accounting and reporting that resulted from our adoption of this guidance: • Property leases in which we are the lessor: ◦ Deferral of non-incremental leasing costs: For new or extended tenant leases, we no longer defer recognition of non-incremental leasing costs that we would have deferred under prior accounting guidance (refer to our 2018 Annual Report on Form 10-K in which we reported amounts deferred in 2018 , 2017 and 2016 ). ◦ Change in presentation of revenue: Due to our adoption of the practical expedient discussed above to not separate non-lease component revenue from the associated lease component, we are aggregating revenue from our lease components and non-lease components (comprised predominantly of tenant operating expense reimbursements) into the line entitled “lease revenue.” We are reporting other revenue from our properties in the line entitled “other property revenue.” We recast prior periods for these changes in presentation. ◦ Changes in assessment of lease revenue collectability: Changes in our assessment of lease revenue collectability that previously would have resulted in charges to bad debt expense under prior guidance are being recognized as an adjustment to rental revenue under the new guidance. Such amounts recognized by us in prior periods were not significant. ◦ Operating expenses paid directly by tenants to third parties: Operating expenses paid directly by tenants to third parties (primarily for real estate taxes) and revenue associated with such tenant payments that would have been recognized under prior guidance will no longer be reported on our Statement of Operations. Such amounts recognized by us in prior periods were not significant. • Leases (the most significant of which are ground leases) in which we are the lessee: ◦ Balance sheet presentation of property operating lease right-of-use assets: Upon adoption on January 1, 2019, we recognized property right-of-use assets and offsetting lease liabilities for existing operating leases totaling $16 million for the present value of minimum lease payments under these leases, and also reclassified an additional $11 million in amounts previously presented elsewhere on our balance sheet in connection with these leases to the right-of-use assets. We will recognize additional right-of-use assets and lease liabilities as we enter into new operating leases. ◦ Balance sheet presentation of property finance lease right-of-use assets: Property right-of-use assets of finance leases that previously were presented as properties under prior guidance are being presented as property finance right-of-use assets under the new guidance. As a result, we reclassified $38 million in assets from properties to property finance right-of-use assets upon adoption on January 1, 2019. ◦ Segment assets: We changed our definition of segment assets used for our reportable segments to include property right-of-use assets associated with operating properties, net of related lease liabilities. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance will apply to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables, loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments). Under the new guidance, an entity will recognize its estimate of expected credit losses as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and to be presented at the net amount expected to be collected. The guidance is effective for us beginning January 1, 2020, with early adoption permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2018, the FASB issued guidance that modifies disclosure requirements for fair value measurements. This guidance is effective for us beginning January 1, 2020. Early adoption is permitted for this guidance, and entities are permitted to early adopt with respect to any removed or modified disclosures while delaying adoption of additional disclosure requirements until the effective date. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. In August 2018, the FASB issued guidance that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. FASB guidance did not previously address the accounting for such implementation costs. The guidance is effective for us beginning January 1, 2020, with early adoption permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Recurring Fair Value Measurements COPT has a non-qualified elective deferred compensation plan for Trustees and certain members of our management team that permits participants to defer up to 100% of their compensation on a pre-tax basis and receive a tax-deferred return on such deferrals. The assets held in the plan (comprised primarily of mutual funds and equity securities) and the corresponding liability to the participants are measured at fair value on a recurring basis on COPT’s consolidated balance sheets using quoted market prices, as are other marketable securities that we hold. The balance of the plan, which was fully funded, totaled $4.3 million as of September 30, 2019 , and is included in the line entitled “prepaid expenses and other assets, net” on COPT’s consolidated balance sheets. The offsetting liability associated with the plan is adjusted to fair value at the end of each accounting period based on the fair value of the plan assets and included in the line entitled “other liabilities” on COPT’s consolidated balance sheets. The assets of the plan are classified in Level 1 of the fair value hierarchy, while the offsetting liability is classified in Level 2 of the fair value hierarchy. The fair values of our interest rate derivatives are determined using widely accepted valuation techniques, including a discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate market data and implied volatilities in such interest rates. While we determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our interest rate derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default. However, as of September 30, 2019 , we assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivatives and determined that these adjustments are not significant. As a result, we determined that our interest rate derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. The carrying values of cash and cash equivalents, restricted cash, accounts receivable, other assets (excluding investing receivables) and accounts payable and accrued expenses are reasonable estimates of their fair values because of the short maturities of these instruments. The fair values of our investing receivables, as disclosed in Note 7, were based on the discounted estimated future cash flows of the loans (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans with similar maturities and credit quality, and the estimated cash payments include scheduled principal and interest payments. For our disclosure of debt fair values in Note 9, we estimated the fair values of our unsecured senior notes based on quoted market rates for publicly-traded debt (categorized within Level 2 of the fair value hierarchy) and estimated the fair value of our other debt based on the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans, or groups of loans, with similar maturities and credit quality, and the estimated future payments include scheduled principal and interest payments. Fair value estimates are made as of a specific point in time, are subjective in nature and involve uncertainties and matters of significant judgment. Settlement at such fair value amounts may not be possible and may not be a prudent management decision. For additional fair value information, please refer to Note 7 for investing receivables, Note 9 for debt and Note 10 for interest rate derivatives. COPT and Subsidiaries The table below sets forth financial assets and liabilities of COPT and subsidiaries that are accounted for at fair value on a recurring basis as of September 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other (Level 2) Significant Inputs (Level 3) Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,232 $ — $ — $ 4,232 Other 25 — — 25 Interest rate derivatives (1) — 32 — 32 Total assets $ 4,257 $ 32 $ — $ 4,289 Liabilities: Deferred compensation plan liability (2) $ — $ 4,257 $ — $ 4,257 Interest rate derivatives — 34,825 — 34,825 Total liabilities $ — $ 39,082 $ — $ 39,082 (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 September 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other Significant Inputs (Level 3) Total Assets: Interest rate derivatives (1) $ — $ 32 $ — $ 32 Liabilities: Interest rate derivatives $ — $ 34,825 $ — $ 34,825 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPLP’s consolidated balance sheet. Nonrecurring Fair Value Measurements In the third quarter of 2019, we determined that the carrying amount of land held in Frederick, Maryland would not be recovered from its eventual disposition. As a result, we recognized an impairment loss of $327,000 in order to adjust the land to its estimated fair value.

Properties, Net

Properties, Net	9 Months Ended
	Sep. 30, 2019
Real Estate [Abstract]
Properties, Net	Properties, Net Operating properties, net consisted of the following (in thousands): September 30, December 31, Land $ 460,110 $ 503,274 Buildings and improvements 3,233,143 3,241,894 Less: Accumulated depreciation (979,353 ) (897,903 ) Operating properties, net $ 2,713,900 $ 2,847,265 As of September 30, 2019 , we were under contract to sell controlling interests in two data center shell properties in Virginia; we expect this sale to occur in the fourth quarter of 2019. The table below sets forth the components of assets held for sale on our consolidated balance sheet as of September 30, 2019 for these properties (in thousands): Properties, net $ 60,566 Deferred rent receivable 1,128 Deferred leasing costs, net 34 Assets held for sale, net $ 61,728 2019 Dispositions On June 20, 2019, through a series of transactions, we sold a 90% interest in seven data center shell properties in Virginia based on an aggregate property value of $265.0 million and retained a 10% interest in the properties through BREIT COPT DC JV LLC (“BREIT-COPT”), a newly-formed joint venture. Our partner in the joint venture acquired the 90% interest from us for $238.5 million . We account for our interest in the joint venture using the equity method of accounting as described further in Note 6. We recognized a gain on sale of $84.5 million . 2019 Construction Activities During the nine months ended September 30, 2019 , we placed into service 794,000 square feet in seven newly-constructed properties (including one partially-operational property) and 10,000 in one partially-operational property under redevelopment. As of September 30, 2019 , we had 14 properties under construction (including one partially-operational property), or which we were contractually committed to construct, that we estimate will total 2.5 million square feet upon completion and one partially-operational property under redevelopment that we estimate will total 106,000 square feet upon completion.

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases Lessor arrangements We lease real estate properties, comprised primarily of office properties and data center shells, to third parties. As of September 30, 2019 , these leases, which may encompass all, or a portion of, a property, had remaining terms spanning from one month to 15 years and averaging approximately five years . These leases usually include options under which the tenant may renew its lease based on market rates at the time of renewal, which are then typically subject to further negotiation. These leases occasionally provide the tenant with an option to terminate its lease early usually for a defined termination fee. While a significant portion of our portfolio is leased to the United States Government, and the majority of those leases consist of a series of one -year renewal options, or provide for early termination rights, we have concluded that exercise of existing renewal options, or continuation of such leases without exercising early termination rights, is reasonably assured for virtually all of these leases. Most of our lease revenue is from fixed contractual payments defined under the lease that, in most cases, escalate annually over the term of the lease. Our lease revenue also includes variable lease payments predominantly for tenant reimbursements of property operating expenses and lease termination fees. Property operating expense reimbursement structures vary, with some tenants responsible for all of a property’s expenses, while others are responsible for their share of a property’s expense only to the extent such expenses exceed amounts defined in the lease (which are derived from the property’s historical expense levels). Lease termination fees in most cases result from a tenant’s exercise of an existing right under a lease, and are usually equal to a defined percentage of the remaining rents due under the lease and/or the remaining unamortized lease origination costs (including tenant improvements and lease commissions). The table below sets forth our allocation of lease revenue recognized between fixed contractual payments and variable lease payments (in thousands): Lease revenue For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 Fixed contractual payments $ 102,389 $ 311,226 Variable lease payments 27,072 80,553 $ 129,461 $ 391,779 Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, September 30, 2019 December 31, 2018 2019 (1) $ 102,289 $ 400,617 2020 378,897 337,646 2021 322,194 280,369 2022 284,935 246,329 2023 231,613 194,888 Thereafter 605,681 523,932 $ 1,925,609 $ 1,983,781 (1) As of September 30, 2019 , represents the three months ending December 31, 2019 . Lessee arrangements We lease from third parties land underlying certain properties that we are operating or developing. These ground leases have long durations with remaining terms ranging from 30 years (excluding extension options) to 97 years . As of September 30, 2019 , our balance sheet included $67.8 million in right-of-use assets associated with ground leases that included: • $37.8 million for land on which we are developing an office property in Washington, DC through our Stevens Investors, LLC joint venture, virtually all of the rent on which was previously paid. This lease has a 97 -year remaining term, and we possess a bargain purchase option that we expect to exercise in 2020; • $10.3 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 29 years and an option to renew for an additional 49 years that was included in the term used in determining the asset balance; • $6.7 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 63 to 75 years ; • $4.2 million for land in a business park in Huntsville, Alabama under nine leases through our LW Redstone Company, LLC joint venture, with remaining terms ranging from 44 to 50 years and options to renew for an additional 25 years that were not included in the term used in determining the asset balance; and • $2.3 million for other land in our Fort Meade/BW Corridor sub-segment under two leases with remaining terms of approximately 49 years all of the rent on which was previously paid. As of September 30, 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 September 30, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,325 Finance leases Property Property - finance right-of-use assets 40,467 Vehicles and office equipment Prepaid expenses and other assets, net 1,193 Total finance lease right-of-use assets 41,660 Total right-of-use assets $ 68,985 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location September 30, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 16,686 Finance leases Other liabilities 1,165 Total lease liabilities $ 17,851 The table below sets forth the weighted average terms and discount rates of our leases as of September 30, 2019 : Weighted average remaining lease term Operating leases 69 years Finance leases 1 year Weighted average discount rate Operating leases 7.35 % Finance leases 3.11 % The table below presents our total lease cost (in thousands): Lease cost Statement of Operations Location For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 Operating lease cost Property leases Property operating expenses $ 413 $ 1,239 Vehicles and office equipment General, administrative and leasing expenses 18 53 Finance lease cost Amortization of vehicles and office equipment right-of-use assets General, administrative and leasing expenses 114 343 Amortization of property right-of-use assets Property operating expenses 9 21 Interest on lease liabilities Interest expense 3 10 $ 557 $ 1,666 The table below presents the effect of lease payments on our consolidated statement of cash flows (in thousands): Supplemental cash flow information For the Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 804 Operating cash flows for financing leases $ 10 Financing cash flows for financing leases $ 173 Payments on leases as of September 30, 2019 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 (1) $ 279 $ 52 $ 331 2020 1,126 862 1,988 2021 1,111 202 1,313 2022 1,129 64 1,193 2023 1,134 — 1,134 Thereafter 99,187 — 99,187 Total lease payments 103,966 1,180 105,146 Less: Amount representing interest (87,280 ) (15 ) (87,295 ) Lease liability $ 16,686 $ 1,165 $ 17,851 (1) Represents the three 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	9 Months Ended
	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Real Estate Joint Ventures	Real Estate Joint Ventures Consolidated Real Estate Joint Ventures The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of September 30, 2019 (dollars in thousands): September 30, 2019 (1) Date Acquired Nominal Ownership % Total Assets Encumbered Assets Total Liabilities Entity Location LW Redstone Company, LLC 3/23/2010 85% Huntsville, Alabama $ 219,914 $ 74,333 $ 69,519 M Square Associates, LLC 6/26/2007 50% College Park, Maryland 84,662 64,539 57,315 Stevens Investors, LLC 8/11/2015 95% Washington, DC 111,994 111,467 42,464 $ 416,570 $ 250,339 $ 169,298 (1) Excludes amounts eliminated in consolidation. Unconsolidated Real Estate Joint Ventures The table below sets forth information pertaining to our investments in unconsolidated real estate joint ventures accounted for using the equity method of accounting (dollars in thousands): Date Acquired Nominal Ownership % Number of Properties Carrying Value of Investment (1) Entity September 30, 2019 December 31, 2018 GI-COPT DC Partnership LLC 7/21/2016 50% 6 $ 38,273 $ 39,845 BREIT COPT DC JV LLC 6/20/2019 10% 7 11,135 — 13 $ 49,408 $ 39,845 (1) Included in the line entitled “investment in unconsolidated real estate joint ventures” on our consolidated balance sheets. These joint ventures operate triple-net leased, single-tenant data center shell properties in Virginia. As described further in Note 4, on June 20, 2019, we sold a 90% interest in seven triple-net leased, single-tenant data center shell properties in Virginia and retained a 10%

Investing Receivables

Investing Receivables	9 Months Ended
	Sep. 30, 2019
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables, including accrued interest thereon, consisted of the following (in thousands): September 30, December 31, Notes receivable from the City of Huntsville $ 58,021 $ 53,961 Other investing loans receivable 14,093 3,021 $ 72,114 $ 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 September 30, 2019 or December 31, 2018 . The fair value of these receivables was approximately $74 million as of September 30, 2019 and $58 million as of December 31, 2018 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	9 Months Ended
	Sep. 30, 2019
Prepaid Expense and Other Assets [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets, net consisted of the following (in thousands): September 30, December 31, Lease incentives, net $ 26,179 $ 21,258 Prepaid expenses 25,158 25,658 Construction contract costs incurred in excess of billings 16,743 3,189 Furniture, fixtures and equipment, net (1) 7,931 8,630 Non-real estate equity investments 6,153 5,940 Deferred financing costs, net (2) 3,914 4,733 Restricted cash 3,502 3,884 Deferred tax asset, net (3) 2,294 2,084 Interest rate derivatives 32 5,617 Other assets 4,419 6,337 Total for COPLP and subsidiaries 96,325 87,330 Marketable securities in deferred compensation plan 4,257 3,868 Total for COPT and subsidiaries $ 100,582 $ 91,198 (1) Includes $1.2 million in finance right-of-use assets as of September 30, 2019 . (2) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (3) Includes a valuation allowance of $2.0 million as of September 30, 2019 and $2.7 million as of December 31, 2018 .

Debt, Net

Debt, Net	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt, Net	Debt, Net Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of September 30, December 31, September 30, 2019 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 144,270 $ 147,141 3.82% - 4.62% (3) 2023-2026 Variable rate secured debt (4) 55,923 23,282 LIBOR + 1.45% to 2.35% (5) 2020-2026 Total mortgage and other secured debt 200,193 170,423 Revolving Credit Facility 220,000 213,000 LIBOR + 0.775% to 1.45% (6) March 2023 (7) Term Loan Facility (8) 248,598 248,273 LIBOR + 0.85% to 1.65% (9) 2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 348,319 347,986 3.60% (10) May 2023 5.250%, $250,000 aggregate principal 247,521 247,136 5.25% (11) February 2024 3.700%, $300,000 aggregate principal 299,196 298,815 3.70% (12) June 2021 5.000%, $300,000 aggregate principal 297,403 297,109 5.00% (13) July 2025 Unsecured note payable 1,071 1,167 0% (14) May 2026 Total debt, net $ 1,862,301 $ 1,823,909 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.3 million as of September 30, 2019 and $7.2 million as of December 31, 2018 . (2) Certain of the fixed rate mortgages carry interest rates that, upon assumption, were above or below market rates and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $233,000 as of September 30, 2019 and $281,000 as of December 31, 2018 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.16% as of September 30, 2019 . (4) Includes a construction loan with $76.9 million in remaining borrowing capacity as of September 30, 2019 . (5) The weighted average interest rate on our variable rate secured debt was 4.18% as of September 30, 2019 . (6) The weighted average interest rate on the Revolving Credit Facility was 3.05% as of September 30, 2019 . (7) The facility matures in March 2023, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee of 0.075% of the total availability under the facility for each extension period. (8) As of September 30, 2019 , we have the ability to borrow an additional $150.0 million in the aggregate under this facility, provided that there is no default under the facility and subject to the approval of the lenders. In addition, in connection with our Revolving Credit Facility, we have the ability to borrow up to $500.0 million under new term loans from the facility’s lender group provided that there is no default under the facility and subject to the approval of the lenders. (9) The interest rate on this loan was 3.35% as of September 30, 2019 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.2 million as of September 30, 2019 and $1.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (11) The carrying value of these notes reflects an unamortized discount totaling $2.2 million as of September 30, 2019 and $2.6 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (12) The carrying value of these notes reflects an unamortized discount totaling $638,000 as of September 30, 2019 and $943,000 as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (13) The carrying value of these notes reflects an unamortized discount totaling $2.2 million as of September 30, 2019 and $2.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (14) This note carries an interest rate that, upon assumption, was below market rates and it therefore was recorded at its fair value based on applicable effective interest rates. The carrying value of this note reflects an unamortized discount totaling $240,000 as of September 30, 2019 and $294,000 as of December 31, 2018 . All debt is owed by COPLP. While COPT is not directly obligated by any debt, it has guaranteed COPLP’s Revolving Credit Facility, Term Loan Facilities and Unsecured Senior Notes. Certain of our debt instruments require that we comply with a number of restrictive financial covenants. As of September 30, 2019 , we were within the compliance requirements of these financial covenants. We capitalized interest costs of $2.9 million in the three months ended September 30, 2019 , $1.4 million in the three months ended September 30, 2018 , $7.3 million in the nine months ended September 30, 2019 and $4.2 million in the nine months ended September 30, 2018 . The following table sets forth information pertaining to the fair value of our debt (in thousands): September 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,192,439 $ 1,226,437 $ 1,191,046 $ 1,219,603 Other fixed-rate debt 145,341 150,500 148,308 147,106 Variable-rate debt 524,521 532,161 484,555 486,497 $ 1,862,301 $ 1,909,098 $ 1,823,909 $ 1,853,206

Interest Rate Derivatives

Interest Rate Derivatives	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest Rate Derivatives	Interest Rate Derivatives The following table sets forth the key terms and fair values of our interest rate swap derivatives, each of which was designated as a cash flow hedge of interest rate risk (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date September 30, December 31, $ 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 $ — $ 472 12,538 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 32 239 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (1,547 ) 1,968 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (1,558 ) 1,967 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (784 ) 971 11,200 (2) 1.6780% One-Month LIBOR 8/1/2019 8/1/2026 (202 ) — 75,000 3.1760% Three-Month LIBOR 6/30/2020 6/30/2030 (11,204 ) (2,676 ) 75,000 3.1920% Three-Month LIBOR 6/30/2020 6/30/2030 (11,315 ) (2,783 ) 75,000 2.7440% Three-Month LIBOR 6/30/2020 6/30/2030 (8,215 ) — $ (34,793 ) $ 158 (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . (2) The notional amount of this instrument is scheduled to amortize to $10.0 million . 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 September 30, December 31, 2018 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets, net $ 32 $ 5,617 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (34,825 ) $ (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 Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended September 30, For the Nine Months Ended September 30, For the Three Months Ended September 30, For the Nine Months Ended September 30, Derivatives in Hedging Relationships 2019 2018 2019 2018 2019 2018 2019 2018 Interest rate derivatives $ (11,047 ) $ 1,325 $ (33,437 ) $ 7,913 $ 307 $ 207 $ 1,434 $ 9 Over the next 12 months, we estimate that approximately $612,000 in losses will be reclassified from accumulated other comprehensive loss (“AOCL”) as an increase to interest expense. We have agreements with each of our interest rate derivative counterparties that contain provisions under which, if we default or are capable of being declared in default on defined levels of our indebtedness, we could also be declared in default on our derivative obligations. Failure to comply with the loan covenant provisions could result in our being declared in default on any derivative instrument obligations covered by the agreements. As of September 30, 2019 , we are not in default with any of these provisions. As of September 30, 2019 , the fair value of interest rate derivatives in a liability position related to these agreements was $34.9 million , excluding the effects of accrued interest and credit valuation adjustments. As of September 30, 2019 , we had not posted any collateral related to these agreements. If we breach any of these provisions, we could be required to settle our obligations under the agreements at their termination value, which was $34.9 million as of September 30, 2019 .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	9 Months Ended
	Sep. 30, 2019
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests Our partners in two real estate joint ventures, LW Redstone Company, LLC and Stevens Investors, LLC (discussed further in Note 6), have the right to require us to acquire their respective interests at fair value; accordingly, we classify the fair value of our partners’ interests as redeemable noncontrolling interests in the mezzanine section of our consolidated balance sheets. The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Nine Months Ended September 30, 2019 2018 Beginning balance $ 26,260 $ 23,125 Contributions from noncontrolling interests — 186 Distributions to noncontrolling interests (1,656 ) (1,114 ) Net income attributable to noncontrolling interests 2,729 1,903 Adjustment to arrive at fair value of interests 1,344 1,331 Ending balance $ 28,677 $ 25,431

Equity

Equity	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Equity	Equity COPLP Limited Partner Preferred Units COPLP has 352,000 Series I Preferred Units outstanding to an unrelated party with an aggregate liquidation preference of $8.8 million ( $25.00 per unit), plus any accrued and unpaid distributions of return thereon. On July 31, 2019, we amended the terms of these units to: • reduce the priority annual cumulative return from 7.5% of the units’ liquidation preference to 3.5% effective September 23, 2019, and eliminate provisions for future increases previously in place; • extend the earliest date that COPLP may redeem the units. As amended, the units may be redeemed for cash by COPLP at COPLP’s option on or after January 1, 2020, provided that COPLP provides notice to the unit holder six months prior to the effective date of the redemption; and • establish that COPLP provide notice to the unit holder for defined periods of time in advance of the sale of certain property or repayment or refinancing of certain debt, after which, in certain instances, the unit holder would have the ability to require COPLP to redeem the units at their liquidation preference. Common Shares/Units COPT issued 1.6 million common shares under its forward equity sale agreements for net proceeds of $46.5 million on March 27, 2019, after which it had no remaining capacity under the agreements. COPT contributed the net proceeds from this issuance to COPLP in exchange for an equal number of units in COPLP. As of September 30, 2019 , COPT had remaining capacity under its at-the-market stock offering program equal to an aggregate gross sales price of $300 million in common share sales. During the nine months ended September 30, 2019 , certain COPLP limited partners converted 103,039 common units in COPLP for an equal number of common shares in COPT. We declared dividends per COPT common share and distributions per COPLP common unit of $0.275 in the three months ended September 30, 2019 and 2018 and $0.825 in the nine months ended September 30, 2019 and 2018 . See Note 15 for disclosure of COPT common share and COPLP common unit activity pertaining to our share-based compensation plans.

Information by Business Segment

Information by Business Segment	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Information by Business Segment	Information by Business Segment We have the following reportable segments: Defense/IT Locations; Regional Office; Wholesale Data Center; and Other. We also report on Defense/IT Locations sub-segments, which include the following: Fort George G. Meade and the Baltimore/Washington Corridor (referred to herein as “Fort Meade/BW Corridor”); Northern Virginia Defense/IT Locations; Lackland Air Force Base (in San Antonio); locations serving the U.S. Navy (“Navy Support Locations”), which included properties proximate to the Washington Navy Yard, the Naval Air Station Patuxent River in Maryland and the Naval Surface Warfare Center Dahlgren Division in Virginia; Redstone Arsenal (in Huntsville); and data center shells (properties leased to tenants to be operated as data centers in which the tenants generally fund the costs for the power, fiber connectivity and data center infrastructure). The table below reports segment financial information for our reportable segments (in thousands): Operating Property Segments Defense/Information Technology Locations Fort Meade/BW Corridor Northern Virginia Defense/IT Lackland Air Force Base Navy Support Locations Redstone Arsenal Data Center Shells Total Defense/IT Locations Regional Office Wholesale Other Total Three Months Ended September 30, 2019 Revenues from real estate operations $ 63,436 $ 13,551 $ 12,703 $ 8,183 $ 4,171 $ 5,913 $ 107,957 $ 15,508 $ 6,565 $ 704 $ 130,734 Property operating expenses (20,743 ) (4,965 ) (7,149 ) (3,581 ) (1,717 ) (518 ) (38,673 ) (7,343 ) (3,374 ) (324 ) (49,714 ) UJV NOI allocable to COPT — — — — — 1,601 1,601 — — — 1,601 NOI from real estate operations $ 42,693 $ 8,586 $ 5,554 $ 4,602 $ 2,454 $ 6,996 $ 70,885 $ 8,165 $ 3,191 $ 380 $ 82,621 Additions to long-lived assets $ 10,770 $ 2,922 $ — $ 2,003 $ 446 $ — $ 16,141 $ 6,339 $ 61 $ 19 $ 22,560 Transfers from non-operating properties $ 1,381 $ 118 $ 2,120 $ — $ 4,152 $ 9,483 $ 17,254 $ — $ (1,012 ) $ — $ 16,242 Three Months Ended September 30, 2018 Revenues from real estate operations $ 61,396 $ 13,960 $ 11,254 $ 7,899 $ 3,734 $ 6,689 $ 104,932 $ 15,272 $ 7,781 $ 1,003 $ 128,988 Property operating expenses (19,847 ) (5,518 ) (6,432 ) (3,208 ) (1,569 ) (574 ) (37,148 ) (7,425 ) (3,965 ) (802 ) (49,340 ) UJV NOI allocable to COPT — — — — — 1,206 1,206 — — — 1,206 NOI from real estate operations $ 41,549 $ 8,442 $ 4,822 $ 4,691 $ 2,165 $ 7,321 $ 68,990 $ 7,847 $ 3,816 $ 201 $ 80,854 Additions to long-lived assets $ 11,211 $ 2,305 $ — $ 1,758 $ 33 $ — $ 15,307 $ 5,670 $ 370 $ (88 ) $ 21,259 Transfers from non-operating properties $ 14,698 $ 1,550 $ — $ (17 ) $ 13 $ 30,286 $ 46,530 $ — $ 155 $ — $ 46,685 Nine Months Ended September 30, 2019 Revenues from real estate operations $ 187,778 $ 42,294 $ 36,368 $ 24,523 $ 12,078 $ 21,891 $ 324,932 $ 45,359 $ 22,996 $ 2,208 $ 395,495 Property operating expenses (62,422 ) (14,951 ) (19,756 ) (10,271 ) (4,855 ) (1,630 ) (113,885 ) (22,349 ) (9,830 ) (981 ) (147,045 ) UJV NOI allocable to COPT — — — — — 4,071 4,071 — — — 4,071 NOI from real estate operations $ 125,356 $ 27,343 $ 16,612 $ 14,252 $ 7,223 $ 24,332 $ 215,118 $ 23,010 $ 13,166 $ 1,227 $ 252,521 Additions to long-lived assets $ 22,204 $ 6,072 $ — $ 7,948 $ 1,282 $ — $ 37,506 $ 15,198 $ 312 $ 63 $ 53,079 Transfers from non-operating properties $ 7,759 $ 4,647 $ 10,456 $ — $ 13,363 $ 122,115 $ 158,340 $ — $ (1,012 ) $ — $ 157,328 Segment assets at September 30, 2019 $ 1,271,668 $ 398,137 $ 147,505 $ 186,243 $ 118,839 $ 298,675 $ 2,421,067 $ 393,747 $ 205,550 $ 3,708 $ 3,024,072 Nine Months Ended September 30, 2018 Revenues from real estate operations $ 186,171 $ 39,639 $ 35,079 $ 23,896 $ 11,019 $ 18,475 $ 314,279 $ 45,852 $ 23,963 $ 2,334 $ 386,428 Property operating expenses (61,550 ) (15,150 ) (20,524 ) (9,943 ) (4,518 ) (2,167 ) (113,852 ) (22,472 ) (12,373 ) (1,040 ) (149,737 ) UJV NOI allocable to COPT — — — — — 3,607 3,607 — — — 3,607 NOI from real estate operations $ 124,621 $ 24,489 $ 14,555 $ 13,953 $ 6,501 $ 19,915 $ 204,034 $ 23,380 $ 11,590 $ 1,294 $ 240,298 Additions to long-lived assets $ 26,483 $ 5,431 $ — $ 4,316 $ 463 $ — $ 36,693 $ 14,915 $ 487 $ 227 $ 52,322 Transfers from non-operating properties $ 34,919 $ 2,243 $ — $ (17 ) $ 483 $ 61,075 $ 98,703 $ — $ 2,300 $ — $ 101,003 Segment assets at September 30, 2018 $ 1,280,837 $ 394,066 $ 126,047 $ 189,406 $ 105,315 $ 359,653 $ 2,455,324 $ 396,624 $ 219,041 $ 3,997 $ 3,074,986 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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Segment revenues from real estate operations $ 130,734 $ 128,988 $ 395,495 $ 386,428 Construction contract and other service revenues 28,697 8,423 87,946 53,202 Total revenues $ 159,431 $ 137,411 $ 483,441 $ 439,630 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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 UJV NOI allocable to COPT $ 1,601 $ 1,206 $ 4,071 $ 3,607 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (1,202 ) (830 ) (2,859 ) (2,482 ) Add: Equity in loss of unconsolidated non-real estate entities (3 ) (2 ) (5 ) (5 ) Equity in income of unconsolidated entities $ 396 $ 374 $ 1,207 $ 1,120 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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Construction contract and other service revenues $ 28,697 $ 8,423 $ 87,946 $ 53,202 Construction contract and other service expenses (27,802 ) (8,058 ) (85,130 ) (51,215 ) NOI from service operations $ 895 $ 365 $ 2,816 $ 1,987 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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 NOI from real estate operations $ 82,621 $ 80,854 $ 252,521 $ 240,298 NOI from service operations 895 365 2,816 1,987 Interest and other income 1,842 1,486 5,977 4,284 Gain on sales of real estate — — 84,469 (27 ) Equity in income of unconsolidated entities 396 374 1,207 1,120 Income tax benefit 131 291 113 173 Depreciation and other amortization associated with real estate operations (34,692 ) (34,195 ) (104,290 ) (100,897 ) Impairment losses (327 ) — (327 ) — General, administrative and leasing expenses (7,929 ) (6,899 ) (26,066 ) (21,819 ) Business development expenses and land carry costs (964 ) (1,567 ) (2,947 ) (4,415 ) Interest expense (17,126 ) (19,181 ) (54,275 ) (56,910 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,601 ) (1,206 ) (4,071 ) (3,607 ) Net income $ 23,246 $ 20,322 $ 155,127 $ 60,187 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): September 30, September 30, Segment assets $ 3,024,072 $ 3,074,986 Operating properties lease liabilities included in segment assets 16,645 — Non-operating property assets 597,301 420,109 Other assets 217,351 155,271 Total COPT consolidated assets $ 3,855,369 $ 3,650,366 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	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Construction Contract and Other Service Revenues	Construction Contract and Other Service Revenues We disaggregate our construction contract and other service revenues by compensation arrangement and by service type as we believe it best depicts the nature, timing and uncertainty of our revenue. The table below reports construction contract and other service revenues by compensation arrangement (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Construction contract revenues: Guaranteed maximum price $ 16,217 $ 1,840 $ 54,365 $ 31,865 Firm fixed price 2,349 3,653 6,009 16,376 Cost-plus fee 9,906 2,719 26,935 4,273 Other 225 211 637 688 $ 28,697 $ 8,423 $ 87,946 $ 53,202 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Construction contract revenues: Construction $ 27,988 $ 8,160 $ 86,487 $ 50,743 Design 484 52 822 1,771 Other 225 211 637 688 $ 28,697 $ 8,423 $ 87,946 $ 53,202 We recognized a (decrease) increase in revenue from performance obligations satisfied (or partially satisfied) in previous periods of $(1,000) in the three months ended September 30, 2018 , and $18,000 and $318,000 in the nine months ended September 30, 2019 and 2018 , respectively. 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 Nine Months Ended September 30, 2019 2018 Beginning balance $ 6,701 $ 4,577 Ending balance $ 15,494 $ 5,571 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 Nine Months Ended September 30, 2019 2018 Beginning balance $ 3,189 $ 4,884 Ending balance $ 16,743 $ 2,821 Contract liabilities are included in other liabilities reported on our consolidated balance sheets. Changes in contract liabilities were as follows (in thousands): For the Nine Months Ended September 30, 2019 2018 Beginning balance $ 568 $ 27,402 Ending balance $ 725 $ 560 Portion of beginning balance recognized in revenue during: Three months ended September 30 $ — $ — Nine months ended September 30 $ 445 $ 27,296 The change in the contract liabilities balance reported above for the nine months ended September 30, 2018 was due primarily to our satisfaction of performance obligations during the period on a contract on which we previously received advance payments from a customer. Revenue allocated to the remaining performance obligations under existing contracts as of September 30, 2019 that will be recognized as revenue in future periods was $27.5 million , approximately $23 million of which we expect to recognize during the remainder of 2019. We have no deferred incremental costs incurred to obtain or fulfill our construction contracts or other service revenues and had no impairment losses on construction contracts receivable or unbilled construction revenue in the three or nine months ended September 30, 2019 and 2018

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation Restricted Shares During the nine months ended September 30, 2019 , certain employees and non-employee members of our Board of Trustees (“Trustees”) were granted a total of 185,095 restricted common shares with an aggregate grant date fair value of $4.9 million (weighted average of $26.41 per share). Restricted shares granted to employees vest based on increments and over periods of time set forth under the terms of the respective awards provided that the employee remains employed by us. Restricted shares granted to non-employee Trustees vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. During the nine months ended September 30, 2019 , forfeiture restrictions lapsed on 175,973 previously issued common shares; these shares had a weighted average grant date fair value of $28.05 per share, and the aggregate intrinsic value of the shares on the vesting dates was $4.6 million . Deferred Share Awards During the nine months ended September 30, 2019 , certain non-employee Trustees were granted a total of 3,432 deferred share awards with an aggregate grant date fair value of $95,000 ( $27.60 per share). Deferred share awards vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. We settle deferred share awards by issuing an equivalent number of common shares upon vesting of the awards or a later date elected by the Trustee (generally upon cessation of being a Trustee). During the nine months ended September 30, 2019 , we issued 3,097 common shares in settlement of deferred share awards; these shares had a grant date fair value of $26.77 per share, and the aggregate intrinsic value of the shares on the settlement date was $86,000 . Performance Share Awards (“PSUs”) We issued 44,757 common shares on January 18, 2019 to executives in settlement of PSUs granted in 2016, representing 157% of the target award for those PSUs. PIUs Commencing in 2019, we offered our executives and Trustees the opportunity to select PIUs as a form of long-term compensation in lieu of, or in combination with, other forms of share-based compensation awards (restricted shares, deferred share awards and PSUs). PIUs are a special class of common unit structured to qualify as “profit interests” for tax purposes. Our executives and certain of our Trustees selected PIUs as their form of share-based compensation for their 2019 grants. We granted two forms of PIUs: time-based PIUs (“TB-PIUs”); and performance-based PIUs (“PB-PIUs”). TB-PIUs are subject to forfeiture restrictions until the end of the requisite service period, at which time the TB-PIUs automatically convert into vested PIUs. PB-PIUs are subject to a market condition in that the number of earned awards are determined at the end of the performance period (as described further below) and then settled in vested PIUs. Vested PIUs carry substantially the same rights to redemption and distributions as non-PIU common units. TB-PIUs During the nine months ended September 30, 2019 , our executives and certain non-employee Trustees were granted a total of 61,820 TB-PIUs with an aggregate grant date fair value of $1.6 million (weighted average of $26.01 per TB-PIU). TB-PIUs granted to executives vest in equal one-third increments over a three -year period beginning on the first anniversary of the date of grant. TB-PIUs granted to non-employee Trustees vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. Prior to vesting, TB-PIUs carry substantially the same rights to distributions as non-PIU common units but carry no redemption rights. PB-PIUs On January 1, 2019 , we granted our executives 193,682 PB-PIUs with a three -year performance period concluding on the earlier of December 31, 2021 or the date of: (1) termination by us without cause, death or disability of the executive or constructive discharge of the executive (collectively, “qualified termination”); or (2) a sale event. The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT’s total shareholder return relative to a peer group of companies, as set forth in the following schedule: Percentile Rank Earned Awards Payout % 75th or greater 100% of PB-PIUs granted 50th (target) 50% of PB-PIUs granted 25th 25% of PB-PIUs granted Below 25th 0% of PB-PIUs granted If the percentile rank exceeds the 25th percentile and is between two of the percentile ranks set forth in the table above, then the percentage of the earned awards will be interpolated between the ranges set forth in the table above to reflect any performance between the listed percentiles. During the performance period, PB-PIUs carry rights to distributions equal to 10% of the distribution rights of non-PIU common units but carry no redemption rights. At the end of the performance period, we will settle the award by issuing vested PIUs equal to the number of earned awards in settlement of the award plan and paying cash equal to the excess, if any, of: the aggregate distributions that would have been paid with respect to vested PIUs issued in settlement of the earned awards through the date of settlement had such vested PIUs been issued on the grant date; over the aggregate distributions made on the PB-PIUs during the performance period. If a performance period ends due to a sale event or qualified termination, the number of earned awards is prorated based on the portion of the three -year performance period that has elapsed. If employment is terminated by the employee or by us for cause, all PB-PIUs are forfeited. These PB-PIUs had an aggregate grant date fair value of $2.4 million ( $12.47 per PB-PIU) which is being recognized over the performance period. The grant date fair value was computed using a Monte Carlo model that included the following assumptions: baseline common share value of $21.03 ; expected volatility for common shares of 21.0% ; and a risk-free interest rate of 2.51%

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”)	Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”) COPT and Subsidiaries EPS We present both basic and diluted EPS. We compute basic EPS by dividing net income available to common shareholders allocable to unrestricted common shares under the two-class method by the weighted average number of unrestricted common shares outstanding during the period. Our computation of diluted EPS is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common shares that would have been outstanding if securities that are convertible into common shares were converted; and (2) the effect of dilutive potential common shares outstanding during the period attributable to COPT’s forward equity sale agreements, redeemable noncontrolling interests and our share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common shares that we add to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPT $ 21,257 $ 18,697 $ 148,907 $ 55,281 Income attributable to share-based compensation awards (123 ) (114 ) (495 ) (348 ) Numerator for basic EPS on net income attributable to COPT common shareholders 21,134 18,583 148,412 54,933 Redeemable noncontrolling interests — — 100 — Income attributable to share-based compensation awards 5 — 26 — Numerator for diluted EPS on net income attributable to COPT common shareholders $ 21,139 $ 18,583 $ 148,538 $ 54,933 Denominator (all weighted averages): Denominator for basic EPS (common shares) 111,582 104,379 111,036 102,401 Dilutive effect of share-based compensation awards 361 231 313 165 Dilutive effect of redeemable noncontrolling interests — — 123 — Dilutive effect of forward equity sale agreements — 178 — 60 Denominator for diluted EPS (common shares) 111,943 104,788 111,472 102,626 Basic EPS $ 0.19 $ 0.18 $ 1.34 $ 0.54 Diluted EPS $ 0.19 $ 0.18 $ 1.33 $ 0.54 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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Conversion of common units 1,312 2,135 1,323 2,847 Conversion of redeemable noncontrolling interests 975 — 893 — Conversion of Series I preferred units 176 176 176 176 The following securities were also excluded from the computation of diluted EPS because their effect was antidilutive: • weighted average shares related to COPT’s forward equity sale agreements for the nine months ended September 30, 2019 of 503,000 ; • weighted average restricted shares and deferred share awards for the three months ended September 30, 2019 and 2018 of 436,000 and 455,000 , respectively, and for the nine months ended September 30, 2019 and 2018 of 441,000 and 452,000 , respectively; • weighted average options for the three months ended September 30, 2019 and 2018 of 3,000 and 30,000 , respectively, and for the nine months ended September 30, 2019 and 2018 of 16,000 and 45,000 , respectively; and • weighted average unvested PIUs for the three and nine months ended September 30, 2019 of 62,000 and 47,000 , respectively. COPLP and Subsidiaries EPU We present both basic and diluted EPU. We compute basic EPU by dividing net income available to common unitholders allocable to unrestricted common units under the two-class method by the weighted average number of unrestricted common units outstanding during the period. Our computation of diluted EPU is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common units that would have been outstanding if securities that are convertible into our common units were converted; and (2) the effect of dilutive potential common units outstanding during the period attributable to COPT’s forward equity sale agreements, redeemable noncontrolling interests and our share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common units that we add to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPLP $ 21,681 $ 19,242 $ 151,257 $ 57,308 Preferred unit distributions (157 ) (165 ) (487 ) (495 ) Income attributable to share-based compensation awards (139 ) (114 ) (592 ) (348 ) Numerator for basic EPU on net income attributable to COPLP common unitholders 21,385 18,963 150,178 56,465 Redeemable noncontrolling interests — 100 — Income attributable to share-based compensation awards 5 — 26 — Numerator for diluted EPU on net income attributable to COPLP common unitholders $ 21,390 $ 18,963 $ 150,304 $ 56,465 Denominator (all weighted averages): Denominator for basic EPU (common units) 112,894 106,514 112,359 105,248 Dilutive effect of redeemable noncontrolling interests — — 123 — Dilutive effect of share-based compensation awards 361 231 313 165 Dilutive effect of forward equity sale agreements — 178 — 60 Denominator for diluted EPU (common units) 113,255 106,923 112,795 105,473 Basic EPU $ 0.19 $ 0.18 $ 1.34 $ 0.54 Diluted EPU $ 0.19 $ 0.18 $ 1.33 $ 0.54 Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Conversion of redeemable noncontrolling interests 975 — 893 — Conversion of Series I preferred units 176 176 176 176 The following securities were also excluded from the computation of diluted EPU because their effect was antidilutive: • weighted average shares related to COPT’s forward equity sale agreements for the nine months ended September 30, 2019 of 503,000 ; • weighted average restricted units and deferred share awards for the three months ended September 30, 2019 and 2018 of 436,000 and 455,000 , respectively, and for the nine months ended September 30, 2019 and 2018 of 441,000 and 452,000 , respectively; • weighted average options for the three months ended September 30, 2019 and 2018 of 3,000 and 30,000 , respectively, and for the nine months ended September 30, 2019 and 2018 of 16,000 and 45,000 , respectively; and • weighted average unvested PIUs for the three and nine months ended September 30, 2019 of 62,000 and 47,000 , respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation and Claims In the normal course of business, we are subject to legal actions and other claims. We record losses for specific legal proceedings and claims when we determine that a loss is probable and the amount of loss can be reasonably estimated. Management believes that it is reasonably possible that we could incur losses pursuant to such claims but do not believe such losses would materially affect our financial position, liquidity or results of operations. Our assessment of the potential outcomes of these matters involves significant judgment and is subject to change based on future developments. Environmental We are subject to various Federal, state and local environmental regulations related to our property ownership and operation. We have performed environmental assessments of our properties, the results of which have not revealed any environmental liability that we believe would have a materially adverse effect on our financial position, operations or liquidity. In connection with a lease and subsequent sale in 2008 and 2010 of three properties in Dayton, New Jersey, we agreed to provide certain environmental indemnifications limited to $19 million in the aggregate. We have insurance coverage in place to mitigate much of any potential future losses that may result from these indemnification agreements. Tax Incremental Financing Obligation Anne Arundel County, Maryland issued tax incremental financing bonds to third-party investors in order to finance public improvements needed in connection with our project known as the National Business Park. These bonds had a remaining principal balance of approximately $34 million as of September 30, 2019 . The real estate taxes on increases in assessed values post-bond issuance of properties in development districts encompassing the National Business Park are transferred to a special fund pledged to the repayment of the bonds. While we are obligated to fund, through a special tax, any future shortfalls between debt service of the bonds and real estate taxes available to repay the bonds, as of September 30, 2019 , we do not expect any such future fundings will be required. Contractual Obligations We had amounts remaining to be incurred under various contractual obligations as of September 30, 2019 that included the following (excluding amounts incurred and therefore reflected as liabilities reported on our consolidated balance sheets): • development and redevelopment obligations of $217.1 million ; • tenant and other capital improvements of $60.8 million ; • third party construction obligations of $13.5 million ; and • other obligations of $1.6 million .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The COPT consolidated financial statements include the accounts of COPT, the Operating Partnership, their subsidiaries and other entities in which COPT has a majority voting interest and control. The COPLP consolidated financial statements include the accounts of COPLP, its subsidiaries and other entities in which COPLP has a majority voting interest and control. We also consolidate certain entities when control of such entities can be achieved through means other than voting rights (“variable interest entities” or “VIEs”) if we are deemed to be the primary beneficiary of such entities. We eliminate all intercompany balances and transactions in consolidation. We use the equity method of accounting when we own an interest in an entity and can exert significant influence over but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity. When we own an equity investment in an entity and cannot exert significant influence over its operations, we measure the investment at fair value, with changes recognized through net income. For an investment without a readily determinable fair value, we measure the investment at cost, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer. These interim financial statements should be read together with the consolidated financial statements and notes thereto as of and for the year ended December 31, 2018 included in our 2018 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2018 Annual Report on Form 10-K as updated for our adoption of recent accounting pronouncements discussed below.
Reclassification	Reclassification We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including reclassifications of our revenue from real estate operations in connection with our adoption of new lease guidance described below.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued guidance setting forth principles for the recognition, measurement, presentation and disclosure of leases. This guidance requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase of the leased asset by the lessee. The resulting classification determines whether the lease expense is recognized based on an effective interest method or straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. This guidance requires lessors of real estate to account for leases using an approach substantially equivalent to guidance previously in place for operating leases, direct financing leases and sales-type leases. We adopted this guidance on January 1, 2019 using a modified retrospective transition approach under which we elected to apply the guidance effective January 1, 2019 and not adjust prior comparative reporting periods (except for our presentation of lease revenue discussed below). We elected to apply a package of practical expedients that enabled us to carry forward upon adoption our historical assessments of: expired or existing leases regarding their lease classification and deferred recognition of non-incremental direct leasing costs; and whether any expired or existing contracts are, or contain, leases. We also elected a practical expedient that enabled us to avoid the need to assess whether expired or existing land easements not previously accounted for as leases are, or contain, a lease. In addition, we elected a practical expedient for our rental properties (as lessor) to avoid separating non-lease components that otherwise would need to be accounted for under the recently-adopted revenue accounting guidance (such as tenant reimbursements of property operating expenses) from the associated lease component since (1) the non-lease components have the same timing and pattern of transfer as the associated lease component and (2) the lease component, if accounted for separately, would be classified as an operating lease; this enables us to account for the combination of the lease component and non-lease components as an operating lease since the lease component is the predominant component of the combined components. Below is a summary of the primary changes in our accounting and reporting that resulted from our adoption of this guidance: • Property leases in which we are the lessor: ◦ Deferral of non-incremental leasing costs: For new or extended tenant leases, we no longer defer recognition of non-incremental leasing costs that we would have deferred under prior accounting guidance (refer to our 2018 Annual Report on Form 10-K in which we reported amounts deferred in 2018 , 2017 and 2016 ). ◦ Change in presentation of revenue: Due to our adoption of the practical expedient discussed above to not separate non-lease component revenue from the associated lease component, we are aggregating revenue from our lease components and non-lease components (comprised predominantly of tenant operating expense reimbursements) into the line entitled “lease revenue.” We are reporting other revenue from our properties in the line entitled “other property revenue.” We recast prior periods for these changes in presentation. ◦ Changes in assessment of lease revenue collectability: Changes in our assessment of lease revenue collectability that previously would have resulted in charges to bad debt expense under prior guidance are being recognized as an adjustment to rental revenue under the new guidance. Such amounts recognized by us in prior periods were not significant. ◦ Operating expenses paid directly by tenants to third parties: Operating expenses paid directly by tenants to third parties (primarily for real estate taxes) and revenue associated with such tenant payments that would have been recognized under prior guidance will no longer be reported on our Statement of Operations. Such amounts recognized by us in prior periods were not significant. • Leases (the most significant of which are ground leases) in which we are the lessee: ◦ Balance sheet presentation of property operating lease right-of-use assets: Upon adoption on January 1, 2019, we recognized property right-of-use assets and offsetting lease liabilities for existing operating leases totaling $16 million for the present value of minimum lease payments under these leases, and also reclassified an additional $11 million in amounts previously presented elsewhere on our balance sheet in connection with these leases to the right-of-use assets. We will recognize additional right-of-use assets and lease liabilities as we enter into new operating leases. ◦ Balance sheet presentation of property finance lease right-of-use assets: Property right-of-use assets of finance leases that previously were presented as properties under prior guidance are being presented as property finance right-of-use assets under the new guidance. As a result, we reclassified $38 million in assets from properties to property finance right-of-use assets upon adoption on January 1, 2019. ◦ Segment assets: We changed our definition of segment assets used for our reportable segments to include property right-of-use assets associated with operating properties, net of related lease liabilities. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance will apply to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables, loans, held-to-maturity debt securities, net investments in leases and off-balance-sheet credit exposures (e.g. loan commitments). Under the new guidance, an entity will recognize its estimate of expected credit losses as an allowance, as the guidance requires that financial assets be measured on an amortized cost basis and to be presented at the net amount expected to be collected. The guidance is effective for us beginning January 1, 2020, with early adoption permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2018, the FASB issued guidance that modifies disclosure requirements for fair value measurements. This guidance is effective for us beginning January 1, 2020. Early adoption is permitted for this guidance, and entities are permitted to early adopt with respect to any removed or modified disclosures while delaying adoption of additional disclosure requirements until the effective date. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements. In August 2018, the FASB issued guidance that aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. FASB guidance did not previously address the accounting for such implementation costs. The guidance is effective for us beginning January 1, 2020, with early adoption permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of fair value assets and liabilities measured on recurring basis	The table below sets forth financial assets and liabilities of COPLP and subsidiaries that are accounted for at fair value on a recurring basis as of September 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other Significant Inputs (Level 3) Total Assets: Interest rate derivatives (1) $ — $ 32 $ — $ 32 Liabilities: Interest rate derivatives $ — $ 34,825 $ — $ 34,825 (1) Included in the line entitled “prepaid expenses and other assets, net” on COPLP’s consolidated balance sheet. 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 September 30, 2019 and the hierarchy level of inputs used in measuring their respective fair values under applicable accounting standards (in thousands): Description Quoted Prices in Significant Other (Level 2) Significant Inputs (Level 3) Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,232 $ — $ — $ 4,232 Other 25 — — 25 Interest rate derivatives (1) — 32 — 32 Total assets $ 4,257 $ 32 $ — $ 4,289 Liabilities: Deferred compensation plan liability (2) $ — $ 4,257 $ — $ 4,257 Interest rate derivatives — 34,825 — 34,825 Total liabilities $ — $ 39,082 $ — $ 39,082 (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)	9 Months Ended
	Sep. 30, 2019
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): September 30, December 31, Land $ 460,110 $ 503,274 Buildings and improvements 3,233,143 3,241,894 Less: Accumulated depreciation (979,353 ) (897,903 ) Operating properties, net $ 2,713,900 $ 2,847,265
Components of assets held for sale	The table below sets forth the components of assets held for sale on our consolidated balance sheet as of September 30, 2019 for these properties (in thousands): Properties, net $ 60,566 Deferred rent receivable 1,128 Deferred leasing costs, net 34 Assets held for sale, net $ 61,728

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Operating Lease Revenue Recognized	The table below sets forth our allocation of lease revenue recognized between fixed contractual payments and variable lease payments (in thousands): Lease revenue For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 Fixed contractual payments $ 102,389 $ 311,226 Variable lease payments 27,072 80,553 $ 129,461 $ 391,779
Fixed Contractual Payments Due	Fixed contractual payments due under our property leases were as follows (in thousands): Year Ending December 31, September 30, 2019 December 31, 2018 2019 (1) $ 102,289 $ 400,617 2020 378,897 337,646 2021 322,194 280,369 2022 284,935 246,329 2023 231,613 194,888 Thereafter 605,681 523,932 $ 1,925,609 $ 1,983,781 (1) As of September 30, 2019 , represents the three 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 September 30, 2019 Right-of-use assets Operating leases - Property Property - operating right-of-use assets $ 27,325 Finance leases Property Property - finance right-of-use assets 40,467 Vehicles and office equipment Prepaid expenses and other assets, net 1,193 Total finance lease right-of-use assets 41,660 Total right-of-use assets $ 68,985 Lease liabilities consisted of the following (in thousands): Leases Balance Sheet Location September 30, 2019 Lease liabilities Operating leases - Property Property - operating lease liabilities $ 16,686 Finance leases Other liabilities 1,165 Total lease liabilities $ 17,851
Lease Costs	The table below presents our total lease cost (in thousands): Lease cost Statement of Operations Location For the Three Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 Operating lease cost Property leases Property operating expenses $ 413 $ 1,239 Vehicles and office equipment General, administrative and leasing expenses 18 53 Finance lease cost Amortization of vehicles and office equipment right-of-use assets General, administrative and leasing expenses 114 343 Amortization of property right-of-use assets Property operating expenses 9 21 Interest on lease liabilities Interest expense 3 10 $ 557 $ 1,666 The table below presents the effect of lease payments on our consolidated statement of cash flows (in thousands): Supplemental cash flow information For the Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 804 Operating cash flows for financing leases $ 10 Financing cash flows for financing leases $ 173 The table below sets forth the weighted average terms and discount rates of our leases as of September 30, 2019 : Weighted average remaining lease term Operating leases 69 years Finance leases 1 year Weighted average discount rate Operating leases 7.35 % Finance leases 3.11 %
Maturity of Lease Liabilities	Payments on leases as of September 30, 2019 were due as follows (in thousands): Year Ending December 31, Operating leases Finance leases Total 2019 (1) $ 279 $ 52 $ 331 2020 1,126 862 1,988 2021 1,111 202 1,313 2022 1,129 64 1,193 2023 1,134 — 1,134 Thereafter 99,187 — 99,187 Total lease payments 103,966 1,180 105,146 Less: Amount representing interest (87,280 ) (15 ) (87,295 ) Lease liability $ 16,686 $ 1,165 $ 17,851 (1) Represents the three 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)	9 Months Ended
	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of information related to investments in consolidated real estate joint ventures	The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of September 30, 2019 (dollars in thousands): September 30, 2019 (1) Date Acquired Nominal Ownership % Total Assets Encumbered Assets Total Liabilities Entity Location LW Redstone Company, LLC 3/23/2010 85% Huntsville, Alabama $ 219,914 $ 74,333 $ 69,519 M Square Associates, LLC 6/26/2007 50% College Park, Maryland 84,662 64,539 57,315 Stevens Investors, LLC 8/11/2015 95% Washington, DC 111,994 111,467 42,464 $ 416,570 $ 250,339 $ 169,298 (1) Excludes amounts eliminated in consolidation.
Schedule of information related to investments in unconsolidated real estate joint ventures	The table below sets forth information pertaining to our investments in unconsolidated real estate joint ventures accounted for using the equity method of accounting (dollars in thousands): Date Acquired Nominal Ownership % Number of Properties Carrying Value of Investment (1) Entity September 30, 2019 December 31, 2018 GI-COPT DC Partnership LLC 7/21/2016 50% 6 $ 38,273 $ 39,845 BREIT COPT DC JV LLC 6/20/2019 10% 7 11,135 — 13 $ 49,408 $ 39,845 (1) Included in the line entitled “investment in unconsolidated real estate joint ventures” on our consolidated balance sheets.

Investing Receivables (Tables)

Investing Receivables (Tables)	9 Months Ended
	Sep. 30, 2019
Receivables [Abstract]
Schedule of investing receivables	Investing receivables, including accrued interest thereon, consisted of the following (in thousands): September 30, December 31, Notes receivable from the City of Huntsville $ 58,021 $ 53,961 Other investing loans receivable 14,093 3,021 $ 72,114 $ 56,982

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets, Net (Tables)	9 Months Ended
	Sep. 30, 2019
Prepaid Expense and Other Assets [Abstract]
Schedule of prepaid expenses and other assets	Prepaid expenses and other assets, net consisted of the following (in thousands): September 30, December 31, Lease incentives, net $ 26,179 $ 21,258 Prepaid expenses 25,158 25,658 Construction contract costs incurred in excess of billings 16,743 3,189 Furniture, fixtures and equipment, net (1) 7,931 8,630 Non-real estate equity investments 6,153 5,940 Deferred financing costs, net (2) 3,914 4,733 Restricted cash 3,502 3,884 Deferred tax asset, net (3) 2,294 2,084 Interest rate derivatives 32 5,617 Other assets 4,419 6,337 Total for COPLP and subsidiaries 96,325 87,330 Marketable securities in deferred compensation plan 4,257 3,868 Total for COPT and subsidiaries $ 100,582 $ 91,198 (1) Includes $1.2 million in finance right-of-use assets as of September 30, 2019 . (2) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (3) Includes a valuation allowance of $2.0 million as of September 30, 2019 and $2.7 million as of December 31, 2018 .

Debt, Net (Tables)

Debt, Net (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Schedule of debt	Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of September 30, December 31, September 30, 2019 Stated Interest Rates Scheduled Maturity Mortgage and Other Secured Debt: Fixed rate mortgage debt (2) $ 144,270 $ 147,141 3.82% - 4.62% (3) 2023-2026 Variable rate secured debt (4) 55,923 23,282 LIBOR + 1.45% to 2.35% (5) 2020-2026 Total mortgage and other secured debt 200,193 170,423 Revolving Credit Facility 220,000 213,000 LIBOR + 0.775% to 1.45% (6) March 2023 (7) Term Loan Facility (8) 248,598 248,273 LIBOR + 0.85% to 1.65% (9) 2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 348,319 347,986 3.60% (10) May 2023 5.250%, $250,000 aggregate principal 247,521 247,136 5.25% (11) February 2024 3.700%, $300,000 aggregate principal 299,196 298,815 3.70% (12) June 2021 5.000%, $300,000 aggregate principal 297,403 297,109 5.00% (13) July 2025 Unsecured note payable 1,071 1,167 0% (14) May 2026 Total debt, net $ 1,862,301 $ 1,823,909 (1) The carrying values of our debt other than the Revolving Credit Facility reflect net deferred financing costs of $6.3 million as of September 30, 2019 and $7.2 million as of December 31, 2018 . (2) Certain of the fixed rate mortgages carry interest rates that, upon assumption, were above or below market rates and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $233,000 as of September 30, 2019 and $281,000 as of December 31, 2018 . (3) The weighted average interest rate on our fixed rate mortgage debt was 4.16% as of September 30, 2019 . (4) Includes a construction loan with $76.9 million in remaining borrowing capacity as of September 30, 2019 . (5) The weighted average interest rate on our variable rate secured debt was 4.18% as of September 30, 2019 . (6) The weighted average interest rate on the Revolving Credit Facility was 3.05% as of September 30, 2019 . (7) The facility matures in March 2023, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee of 0.075% of the total availability under the facility for each extension period. (8) As of September 30, 2019 , we have the ability to borrow an additional $150.0 million in the aggregate under this facility, provided that there is no default under the facility and subject to the approval of the lenders. In addition, in connection with our Revolving Credit Facility, we have the ability to borrow up to $500.0 million under new term loans from the facility’s lender group provided that there is no default under the facility and subject to the approval of the lenders. (9) The interest rate on this loan was 3.35% as of September 30, 2019 . (10) The carrying value of these notes reflects an unamortized discount totaling $1.2 million as of September 30, 2019 and $1.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (11) The carrying value of these notes reflects an unamortized discount totaling $2.2 million as of September 30, 2019 and $2.6 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (12) The carrying value of these notes reflects an unamortized discount totaling $638,000 as of September 30, 2019 and $943,000 as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (13) The carrying value of these notes reflects an unamortized discount totaling $2.2 million as of September 30, 2019 and $2.4 million as of December 31, 2018 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (14) This note carries an interest rate that, upon assumption, was below market rates and it therefore was recorded at its fair value based on applicable effective interest rates. The carrying value of this note reflects an unamortized discount totaling $240,000 as of September 30, 2019 and $294,000 as of December 31, 2018 .
Schedule of the fair value of debt	The following table sets forth information pertaining to the fair value of our debt (in thousands): September 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,192,439 $ 1,226,437 $ 1,191,046 $ 1,219,603 Other fixed-rate debt 145,341 150,500 148,308 147,106 Variable-rate debt 524,521 532,161 484,555 486,497 $ 1,862,301 $ 1,909,098 $ 1,823,909 $ 1,853,206

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of key terms and fair values of interest rate swap derivatives	The following table sets forth the key terms and fair values of our interest rate swap derivatives, each of which was designated as a cash flow hedge of interest rate risk (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date September 30, December 31, $ 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 $ — $ 472 12,538 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 32 239 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (1,547 ) 1,968 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (1,558 ) 1,967 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (784 ) 971 11,200 (2) 1.6780% One-Month LIBOR 8/1/2019 8/1/2026 (202 ) — 75,000 3.1760% Three-Month LIBOR 6/30/2020 6/30/2030 (11,204 ) (2,676 ) 75,000 3.1920% Three-Month LIBOR 6/30/2020 6/30/2030 (11,315 ) (2,783 ) 75,000 2.7440% Three-Month LIBOR 6/30/2020 6/30/2030 (8,215 ) — $ (34,793 ) $ 158 (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . (2) The notional amount of this instrument is scheduled to amortize to $10.0 million .
Schedule of fair value and balance sheet classification of interest rate derivatives	The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location September 30, December 31, 2018 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets, net $ 32 $ 5,617 Interest rate swaps designated as cash flow hedges Interest rate derivatives (liabilities) $ (34,825 ) $ (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 Reclassified from AOCL into Interest Expense on Statement of Operations For the Three Months Ended September 30, For the Nine Months Ended September 30, For the Three Months Ended September 30, For the Nine Months Ended September 30, Derivatives in Hedging Relationships 2019 2018 2019 2018 2019 2018 2019 2018 Interest rate derivatives $ (11,047 ) $ 1,325 $ (33,437 ) $ 7,913 $ 307 $ 207 $ 1,434 $ 9

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interests (Tables)	9 Months Ended
	Sep. 30, 2019
Noncontrolling Interest [Abstract]
Schedule of activity for redeemable noncontrolling interest	The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Nine Months Ended September 30, 2019 2018 Beginning balance $ 26,260 $ 23,125 Contributions from noncontrolling interests — 186 Distributions to noncontrolling interests (1,656 ) (1,114 ) Net income attributable to noncontrolling interests 2,729 1,903 Adjustment to arrive at fair value of interests 1,344 1,331 Ending balance $ 28,677 $ 25,431

Information by Business Segme_2

Information by Business Segment (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Schedule of segment financial information for real estate operations	The table below reports segment financial information for our reportable segments (in thousands): Operating Property Segments Defense/Information Technology Locations Fort Meade/BW Corridor Northern Virginia Defense/IT Lackland Air Force Base Navy Support Locations Redstone Arsenal Data Center Shells Total Defense/IT Locations Regional Office Wholesale Other Total Three Months Ended September 30, 2019 Revenues from real estate operations $ 63,436 $ 13,551 $ 12,703 $ 8,183 $ 4,171 $ 5,913 $ 107,957 $ 15,508 $ 6,565 $ 704 $ 130,734 Property operating expenses (20,743 ) (4,965 ) (7,149 ) (3,581 ) (1,717 ) (518 ) (38,673 ) (7,343 ) (3,374 ) (324 ) (49,714 ) UJV NOI allocable to COPT — — — — — 1,601 1,601 — — — 1,601 NOI from real estate operations $ 42,693 $ 8,586 $ 5,554 $ 4,602 $ 2,454 $ 6,996 $ 70,885 $ 8,165 $ 3,191 $ 380 $ 82,621 Additions to long-lived assets $ 10,770 $ 2,922 $ — $ 2,003 $ 446 $ — $ 16,141 $ 6,339 $ 61 $ 19 $ 22,560 Transfers from non-operating properties $ 1,381 $ 118 $ 2,120 $ — $ 4,152 $ 9,483 $ 17,254 $ — $ (1,012 ) $ — $ 16,242 Three Months Ended September 30, 2018 Revenues from real estate operations $ 61,396 $ 13,960 $ 11,254 $ 7,899 $ 3,734 $ 6,689 $ 104,932 $ 15,272 $ 7,781 $ 1,003 $ 128,988 Property operating expenses (19,847 ) (5,518 ) (6,432 ) (3,208 ) (1,569 ) (574 ) (37,148 ) (7,425 ) (3,965 ) (802 ) (49,340 ) UJV NOI allocable to COPT — — — — — 1,206 1,206 — — — 1,206 NOI from real estate operations $ 41,549 $ 8,442 $ 4,822 $ 4,691 $ 2,165 $ 7,321 $ 68,990 $ 7,847 $ 3,816 $ 201 $ 80,854 Additions to long-lived assets $ 11,211 $ 2,305 $ — $ 1,758 $ 33 $ — $ 15,307 $ 5,670 $ 370 $ (88 ) $ 21,259 Transfers from non-operating properties $ 14,698 $ 1,550 $ — $ (17 ) $ 13 $ 30,286 $ 46,530 $ — $ 155 $ — $ 46,685 Nine Months Ended September 30, 2019 Revenues from real estate operations $ 187,778 $ 42,294 $ 36,368 $ 24,523 $ 12,078 $ 21,891 $ 324,932 $ 45,359 $ 22,996 $ 2,208 $ 395,495 Property operating expenses (62,422 ) (14,951 ) (19,756 ) (10,271 ) (4,855 ) (1,630 ) (113,885 ) (22,349 ) (9,830 ) (981 ) (147,045 ) UJV NOI allocable to COPT — — — — — 4,071 4,071 — — — 4,071 NOI from real estate operations $ 125,356 $ 27,343 $ 16,612 $ 14,252 $ 7,223 $ 24,332 $ 215,118 $ 23,010 $ 13,166 $ 1,227 $ 252,521 Additions to long-lived assets $ 22,204 $ 6,072 $ — $ 7,948 $ 1,282 $ — $ 37,506 $ 15,198 $ 312 $ 63 $ 53,079 Transfers from non-operating properties $ 7,759 $ 4,647 $ 10,456 $ — $ 13,363 $ 122,115 $ 158,340 $ — $ (1,012 ) $ — $ 157,328 Segment assets at September 30, 2019 $ 1,271,668 $ 398,137 $ 147,505 $ 186,243 $ 118,839 $ 298,675 $ 2,421,067 $ 393,747 $ 205,550 $ 3,708 $ 3,024,072 Nine Months Ended September 30, 2018 Revenues from real estate operations $ 186,171 $ 39,639 $ 35,079 $ 23,896 $ 11,019 $ 18,475 $ 314,279 $ 45,852 $ 23,963 $ 2,334 $ 386,428 Property operating expenses (61,550 ) (15,150 ) (20,524 ) (9,943 ) (4,518 ) (2,167 ) (113,852 ) (22,472 ) (12,373 ) (1,040 ) (149,737 ) UJV NOI allocable to COPT — — — — — 3,607 3,607 — — — 3,607 NOI from real estate operations $ 124,621 $ 24,489 $ 14,555 $ 13,953 $ 6,501 $ 19,915 $ 204,034 $ 23,380 $ 11,590 $ 1,294 $ 240,298 Additions to long-lived assets $ 26,483 $ 5,431 $ — $ 4,316 $ 463 $ — $ 36,693 $ 14,915 $ 487 $ 227 $ 52,322 Transfers from non-operating properties $ 34,919 $ 2,243 $ — $ (17 ) $ 483 $ 61,075 $ 98,703 $ — $ 2,300 $ — $ 101,003 Segment assets at September 30, 2018 $ 1,280,837 $ 394,066 $ 126,047 $ 189,406 $ 105,315 $ 359,653 $ 2,455,324 $ 396,624 $ 219,041 $ 3,997 $ 3,074,986
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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Segment revenues from real estate operations $ 130,734 $ 128,988 $ 395,495 $ 386,428 Construction contract and other service revenues 28,697 8,423 87,946 53,202 Total revenues $ 159,431 $ 137,411 $ 483,441 $ 439,630
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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 UJV NOI allocable to COPT $ 1,601 $ 1,206 $ 4,071 $ 3,607 Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (1,202 ) (830 ) (2,859 ) (2,482 ) Add: Equity in loss of unconsolidated non-real estate entities (3 ) (2 ) (5 ) (5 ) Equity in income of unconsolidated entities $ 396 $ 374 $ 1,207 $ 1,120
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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Construction contract and other service revenues $ 28,697 $ 8,423 $ 87,946 $ 53,202 Construction contract and other service expenses (27,802 ) (8,058 ) (85,130 ) (51,215 ) NOI from service operations $ 895 $ 365 $ 2,816 $ 1,987
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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 NOI from real estate operations $ 82,621 $ 80,854 $ 252,521 $ 240,298 NOI from service operations 895 365 2,816 1,987 Interest and other income 1,842 1,486 5,977 4,284 Gain on sales of real estate — — 84,469 (27 ) Equity in income of unconsolidated entities 396 374 1,207 1,120 Income tax benefit 131 291 113 173 Depreciation and other amortization associated with real estate operations (34,692 ) (34,195 ) (104,290 ) (100,897 ) Impairment losses (327 ) — (327 ) — General, administrative and leasing expenses (7,929 ) (6,899 ) (26,066 ) (21,819 ) Business development expenses and land carry costs (964 ) (1,567 ) (2,947 ) (4,415 ) Interest expense (17,126 ) (19,181 ) (54,275 ) (56,910 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,601 ) (1,206 ) (4,071 ) (3,607 ) Net income $ 23,246 $ 20,322 $ 155,127 $ 60,187
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): September 30, September 30, Segment assets $ 3,024,072 $ 3,074,986 Operating properties lease liabilities included in segment assets 16,645 — Non-operating property assets 597,301 420,109 Other assets 217,351 155,271 Total COPT consolidated assets $ 3,855,369 $ 3,650,366

Construction Contract and Oth_2

Construction Contract and Other Service Revenues (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The table below reports construction contract and other service revenues by compensation arrangement (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Construction contract revenues: Guaranteed maximum price $ 16,217 $ 1,840 $ 54,365 $ 31,865 Firm fixed price 2,349 3,653 6,009 16,376 Cost-plus fee 9,906 2,719 26,935 4,273 Other 225 211 637 688 $ 28,697 $ 8,423 $ 87,946 $ 53,202 The table below reports construction contract and other service revenues by service type (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Construction contract revenues: Construction $ 27,988 $ 8,160 $ 86,487 $ 50,743 Design 484 52 822 1,771 Other 225 211 637 688 $ 28,697 $ 8,423 $ 87,946 $ 53,202
Schedule of Accounts Receivable	The beginning and ending balances of accounts receivable related to our construction contracts were as follows (in thousands): For the Nine Months Ended September 30, 2019 2018 Beginning balance $ 6,701 $ 4,577 Ending balance $ 15,494 $ 5,571
Contract with Customer, Asset and Liability	The beginning and ending balances of our contract assets were as follows (in thousands): For the Nine Months Ended September 30, 2019 2018 Beginning balance $ 3,189 $ 4,884 Ending balance $ 16,743 $ 2,821 For the Nine Months Ended September 30, 2019 2018 Beginning balance $ 568 $ 27,402 Ending balance $ 725 $ 560 Portion of beginning balance recognized in revenue during: Three months ended September 30 $ — $ — Nine months ended September 30 $ 445 $ 27,296

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Schedule of payouts for defined performance under performance-based awards of share-based compensation	The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT’s total shareholder return 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)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPT $ 21,257 $ 18,697 $ 148,907 $ 55,281 Income attributable to share-based compensation awards (123 ) (114 ) (495 ) (348 ) Numerator for basic EPS on net income attributable to COPT common shareholders 21,134 18,583 148,412 54,933 Redeemable noncontrolling interests — — 100 — Income attributable to share-based compensation awards 5 — 26 — Numerator for diluted EPS on net income attributable to COPT common shareholders $ 21,139 $ 18,583 $ 148,538 $ 54,933 Denominator (all weighted averages): Denominator for basic EPS (common shares) 111,582 104,379 111,036 102,401 Dilutive effect of share-based compensation awards 361 231 313 165 Dilutive effect of redeemable noncontrolling interests — — 123 — Dilutive effect of forward equity sale agreements — 178 — 60 Denominator for diluted EPS (common shares) 111,943 104,788 111,472 102,626 Basic EPS $ 0.19 $ 0.18 $ 1.34 $ 0.54 Diluted EPS $ 0.19 $ 0.18 $ 1.33 $ 0.54
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 September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Conversion of common units 1,312 2,135 1,323 2,847 Conversion of redeemable noncontrolling interests 975 — 893 — Conversion of Series I preferred units 176 176 176 176
Corporate Office Properties, L.P.
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Numerator: Net income attributable to COPLP $ 21,681 $ 19,242 $ 151,257 $ 57,308 Preferred unit distributions (157 ) (165 ) (487 ) (495 ) Income attributable to share-based compensation awards (139 ) (114 ) (592 ) (348 ) Numerator for basic EPU on net income attributable to COPLP common unitholders 21,385 18,963 150,178 56,465 Redeemable noncontrolling interests — 100 — Income attributable to share-based compensation awards 5 — 26 — Numerator for diluted EPU on net income attributable to COPLP common unitholders $ 21,390 $ 18,963 $ 150,304 $ 56,465 Denominator (all weighted averages): Denominator for basic EPU (common units) 112,894 106,514 112,359 105,248 Dilutive effect of redeemable noncontrolling interests — — 123 — Dilutive effect of share-based compensation awards 361 231 313 165 Dilutive effect of forward equity sale agreements — 178 — 60 Denominator for diluted EPU (common units) 113,255 106,923 112,795 105,473 Basic EPU $ 0.19 $ 0.18 $ 1.34 $ 0.54 Diluted EPU $ 0.19 $ 0.18 $ 1.33 $ 0.54
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Conversion of redeemable noncontrolling interests 975 — 893 — Conversion of Series I preferred units 176 176 176 176

Organization (Details)

Organization (Details) - Sep. 30, 2019 ft² in Millions	ft²	property	MW	a
Unconsolidated Real Estate Joint Ventures
Investments in real estate
Number of real estate properties		13
Operating Properties
Investments in real estate
Number of real estate properties		169
Area of real estate property (in sq ft or acres) | ft²	19
Operating Properties | Office Properties
Investments in real estate
Number of real estate properties		147
Area of real estate property (in sq ft or acres) | ft²	15.3
Operating Properties | Single-tenant data centers
Investments in real estate
Number of real estate properties		22
Area of real estate property (in sq ft or acres) | ft²	3.7
Operating Properties | Single-tenant data centers | Unconsolidated Real Estate Joint Ventures
Investments in real estate
Number of real estate properties		13
Operating wholesale data center
Investments in real estate
Critical load (in megawatts) | MW			19.25
Properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties		15
Area of real estate property (in sq ft or acres) | ft²	2.6
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)	11.2			900
Other Land
Investments in real estate
Area of real estate property (in sq ft or acres) | a				150

Organization (Details 2)

Organization (Details 2)	9 Months Ended
	Sep. 30, 2019
Corporate Office Properties, L.P. | Common Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	98.70%

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	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Assets and liabilities measured at fair value on a recurring basis
Marketable securities in deferred compensation plan	$ 4,257	$ 4,257		$ 3,868
Impairment losses		$ 327	$ 0
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	4,300	$ 4,300
Fair value measurement on a nonrecurring basis | Frederick, Maryland
Assets and liabilities measured at fair value on a recurring basis
Impairment losses	$ 327

Fair Value Measurements (Deta_2

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
Marketable securities in deferred compensation plan	$ 4,257	$ 3,868
Fair value measurement on a recurring basis
Assets:
Interest rate derivatives	32
Total assets	4,289
Liabilities:
Deferred compensation plan liability	4,257
Interest rate derivatives	34,825
Total liabilities	39,082
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,232
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	25
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate derivatives	0
Total assets	4,257
Liabilities:
Deferred compensation plan liability	0
Interest rate derivatives	0
Total liabilities	0
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,232
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Assets:
Marketable securities in deferred compensation plan	25
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	32
Total assets	32
Liabilities:
Deferred compensation plan liability	4,257
Interest rate derivatives	34,825
Total liabilities	39,082
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2) | Other
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate derivatives	0
Total assets	0
Liabilities:
Deferred compensation plan liability	0
Interest rate derivatives	0
Total liabilities	0
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3) | Mutual funds
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3) | Other
Assets:
Marketable securities in deferred compensation plan	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Assets:
Interest rate derivatives	32
Liabilities:
Interest rate derivatives	34,825
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate derivatives	0
Liabilities:
Interest rate derivatives	0
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate derivatives	32
Liabilities:
Interest rate derivatives	34,825
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate derivatives	0
Liabilities:
Interest rate derivatives	$ 0

Properties, Net (Details)

Properties, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments in real estate
Operating properties, net	$ 2,713,900	$ 2,847,265
Operating Properties, net
Investments in real estate
Less: accumulated depreciation	(979,353)	(897,903)
Operating properties, net	2,713,900	2,847,265
Operating Properties, net | Land
Investments in real estate
Gross	460,110	503,274
Operating Properties, net | Buildings and improvements
Investments in real estate
Gross	$ 3,233,143	$ 3,241,894

Properties, Net (Details 2)

Properties, Net (Details 2) $ in Thousands	Sep. 30, 2019USD ($)property	Dec. 31, 2018USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, net	$ 61,728	$ 0
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties, net	60,566
Deferred rent receivable	1,128
Deferred leasing costs, net	34
Assets held for sale, net	$ 61,728
Held-for-sale | Single-tenant data centers | Data Center Shells
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties | property	2

Properties, Net (Details 3)

Properties, Net (Details 3) - Single-tenant data centers $ in Millions	Jun. 20, 2019USD ($)property
Disposed of by sale
Investments in real estate
Ownership percentage sold	90.00%
Proceeds from Divestiture of Businesses	$ 238.5
Disposed of by sale | Data Center Shells
Investments in real estate
Ownership percentage sold	90.00%
Number of real estate properties | property	7
Consideration received from sale of ownership interest	$ 265
Gain on sale of ownership interest	$ 84.5
BREIT COPT | Operating Properties | Variable Interest Entity, Not Primary Beneficiary
Investments in real estate
Ownership percentage (percent)	10.00%

Properties, Net (Details 4)

Properties, Net (Details 4) ft² in Thousands	Sep. 30, 2019ft²property
Newly constructed properties placed in service
Construction Activities
Square footage of real estate properties (in square feet) | ft²	794
Number of real estate properties	7
Newly constructed properties partially operational
Construction Activities
Number of real estate properties	1
Redeveloped Property Placed in Service, Partially-Operational [Member]
Construction Activities
Square footage of real estate properties (in square feet) | ft²	10
Number of real estate properties	1
Properties under construction or contractually committed for construction
Construction Activities
Square footage of real estate properties (in square feet) | ft²	2,500
Number of real estate properties	14
Properties under construction or contractually committed, partially operational property
Construction Activities
Number of real estate properties	1
Properties under or approved for redevelopment partially-operational
Construction Activities
Square footage of real estate properties (in square feet) | ft²	106
Number of real estate properties	1

Leases (Details)

Leases (Details)	9 Months Ended
	Sep. 30, 2019
Lessor, Lease, Description [Line Items]
Average term of contract	5 years
Minimum
Lessor, Lease, Description [Line Items]
Term of contract	1 month
Maximum
Lessor, Lease, Description [Line Items]
Term of contract	15 years
United States Government
Lessor, Lease, Description [Line Items]
Renewal term	1 year

Leases (Details 1)

Leases (Details 1) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Fixed contractual payments	$ 102,389	$ 311,226
Variable lease payments	27,072	80,553
Lease revenue	129,461	391,779
Lease Payments to be Received
2019	102,289	102,289
2020	378,897	378,897
2021	322,194	322,194
2022	284,935	284,935
2023	231,613	231,613
Thereafter	605,681	605,681
Operating Lease Payments to be Received	$ 1,925,609	$ 1,925,609
2019			$ 400,617
2020			337,646
2021			280,369
2022			246,329
2023			194,888
Thereafter			523,932
Operating Leases, Future Minimum Payments Receivable			$ 1,983,781

Leases (Details 2)

Leases (Details 2) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)Lease
Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 67.8
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]
Remaining term of contract	80 years
Lessee right-of-use asset	$ 10.3
Number of contracts | Lease	2
Baltimore, Maryland | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	29 years
Lessee right-of-use asset	$ 6.5
Renewal term	49 years
Stevens Investors, LLC | Washington, DC | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	97 years
Lessee right-of-use asset	$ 37.8
M Square Associates, LLC | College Park, Maryland | Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 6.7
Number of contracts | Lease	4
M Square Associates, LLC | College Park, Maryland | Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	63 years
M Square Associates, LLC | College Park, Maryland | Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	75 years
LW Redstone Company, LLC | Huntsville, Alabama | Land
Lessee, Lease, Description [Line Items]
Lessee right-of-use asset	$ 4.2
Renewal term	25 years
Number of contracts | Lease	9
LW Redstone Company, LLC | Huntsville, Alabama | Land | Minimum
Lessee, Lease, Description [Line Items]
Remaining term of contract	44 years
LW Redstone Company, LLC | Huntsville, Alabama | Land | Maximum
Lessee, Lease, Description [Line Items]
Remaining term of contract	50 years
Fort Meade/BW Corridor | Land
Lessee, Lease, Description [Line Items]
Remaining term of contract	49 years
Lessee right-of-use asset	$ 2.3
Number of contracts | Lease	2

Leases (Details 3)

Leases (Details 3) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Finance right-of-use assets	$ 41,660
Total right-of-use assets	68,985
Property - operating lease liabilities	16,686
Property - finance lease liabilities	1,165
Total lease liabilities	17,851	$ 90,184
Properties
Lessee, Lease, Description [Line Items]
Property - operating right-of-use assets	27,325	0
Finance right-of-use assets	40,467	0
Property - operating lease liabilities	16,686	$ 0
Property - operating right-of-use assets | Properties
Lessee, Lease, Description [Line Items]
Property - operating right-of-use assets	27,325
Property - finance right-of-use assets | Properties
Lessee, Lease, Description [Line Items]
Finance right-of-use assets	40,467
Prepaid expenses and other assets, net | Vehicles and Office Equipment
Lessee, Lease, Description [Line Items]
Finance right-of-use assets	$ 1,193

Leases (Details 4)

Leases (Details 4)	Sep. 30, 2019
Leases [Abstract]
Operating leases, Weighted average remaining lease term	69 years
Finance leases, Weighted average remaining lease term	1 year
Operating lease, Weighted average discount rate	7.35%
Finance lease, Weighted average discount rate	3.11%

Leases (Details 5)

Leases (Details 5) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lessee, Lease, Description [Line Items]
Lease costs	$ 557	$ 1,666
Property Operating Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	413	1,239
Finance lease right-of use amortization	9	21
General, Administrative and Leasing Expense
Lessee, Lease, Description [Line Items]
Operating lease cost	18	53
Finance lease right-of use amortization	114	343
Interest Expense
Lessee, Lease, Description [Line Items]
Interest on lease liabilities	$ 3	$ 10

Leases (Details 6)

Leases (Details 6) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating cash flows for operating leases	$ 804
Operating cash flows for financing leases	10
Financing cash flows for financing leases	$ 173	$ 15,379

Leases (Details 7)

Leases (Details 7) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Operating leases
2019	$ 279
2019		$ 1,101
2020	1,126
2020		1,110
2021		1,094
2021	1,111
2022		1,115
2022	1,129
2023	1,134
2023		1,119
Thereafter		83,373
Thereafter	99,187
Total lease payments	103,966
Total lease payments		88,912
Less: Amount representing interest	(87,280)
Lease liability	16,686
Finance leases
2019	52
2019		219
2020	862
2020		844
2021	202
2021		184
2022	64
2022		49
2023		0
2023	0
Thereafter	0
Thereafter		0
Total lease payments		1,296
Total lease payments	1,180
Less: Amount representing interest	(15)
Less: Amount representing interest		(24)
Lease liability	1,165
Lease liability		1,272
Total
2019	331
2019		1,320
2020	1,988	1,954
2021	1,313	1,278
2022	1,193	1,164
2023	1,134	1,119
Thereafter	99,187	83,373
Total lease payments	105,146	90,208
Less: Amount representing interest	(87,295)	(24)
Total lease liabilities	$ 17,851	$ 90,184

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)	Jun. 20, 2019property
Consolidated real estate joint ventures
Investments in consolidated real estate joint ventures
Total Assets	$ 416,570
Encumbered Assets	250,339
Total Liabilities	$ 169,298
Variable Interest Entity, Primary Beneficiary | LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	85.00%
Total Assets	$ 219,914
Encumbered Assets	74,333
Total Liabilities	$ 69,519
Variable Interest Entity, Primary Beneficiary | M Square Associates, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	50.00%
Total Assets	$ 84,662
Encumbered Assets	64,539
Total Liabilities	$ 57,315
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)	95.00%
Total Assets	$ 111,994
Encumbered Assets	111,467
Total Liabilities	$ 42,464
Operating Properties | Single-tenant data centers | Variable Interest Entity, Not Primary Beneficiary | BREIT COPT
Investments in consolidated real estate joint ventures
Ownership percentage (percent)		10.00%
Disposed of by sale | Single-tenant data centers
Investments in consolidated real estate joint ventures
Ownership percentage sold		90.00%
Disposed of by sale | Data Center Shells | Single-tenant data centers
Investments in consolidated real estate joint ventures
Ownership percentage sold		90.00%
Number of real estate properties | property		7

Real Estate Joint Ventures (D_2

Real Estate Joint Ventures (Details 2) $ in Thousands	Sep. 30, 2019USD ($)property	Dec. 31, 2018USD ($)
Unconsolidated Real Estate Joint Ventures
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property	13
Equity method investments | $	$ 49,408	$ 39,845
GI-COPT DC Partnership LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage (percent)	50.00%
Number of real estate properties | property	6
Equity method investments | $	$ 38,273	39,845
Variable Interest Entity, Not Primary Beneficiary | BREIT COPT DC JV LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage (percent)	10.00%
Number of real estate properties | property	7
Equity method investments | $	$ 11,135	$ 0

Investing Receivables (Details)

Investing Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 72,114	$ 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	$ 58,021	53,961
Notes Receivable from the City of Huntsville | LW Redstone Company, LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Stated interest rate (as a percent)	9.95%
Other investing loans receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 14,093	$ 3,021
Stated interest rate (as a percent)	8.00%

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Properties
Restricted cash	$ 3,502	$ 3,884	$ 3,440	$ 2,570
Marketable securities in deferred compensation plan	4,257	3,868
Total for COPT and subsidiaries	100,582	91,198
Finance right-of-use assets	41,660
Furniture, Fixtures and Equipment, Net
Properties
Finance right-of-use assets	1,200
Taxable REIT Subsidiary
Properties
Deferred tax assets, valuation allowance	2,000	2,700
Corporate Office Properties, L.P.
Properties
Lease incentives, net	26,179	21,258
Prepaid expenses	25,158	25,658
Construction contract costs incurred in excess of billings	16,743	3,189
Furniture, fixtures and equipment, net	7,931	8,630
Non-real estate equity investments	6,153	5,940
Deferred financing costs, net	3,914	4,733
Restricted cash	3,502	3,884	$ 3,440	$ 2,570
Deferred tax asset, net	2,294	2,084
Interest rate derivatives	32	5,617
Other assets	4,419	6,337
Total for COPT and subsidiaries	$ 96,325	$ 87,330

Debt, Net (Details)

Debt, Net (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)extension	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)extension	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Debt
Carrying Value	$ 1,862,301,000		$ 1,862,301,000		$ 1,823,909,000
Interest costs capitalized	2,900,000	$ 1,400,000	7,300,000	$ 4,200,000
Mortgage and other secured debt
Debt
Carrying Value	$ 200,193,000		$ 200,193,000		170,423,000
Line of Credit | Revolving Credit Facility
Debt
Number of extensions | extension	2		2
Extension option period (in years)			6 months
Line of credit facility, extension fee percentage			0.075%
Loans payable
Debt
Deferred financing costs, net	$ 6,300,000		$ 6,300,000		7,200,000
Fixed rate mortgage debt | Mortgage and other secured debt
Debt
Carrying Value	144,270,000		144,270,000		147,141,000
Unamortized premium included in carrying value	$ 233,000		$ 233,000		281,000
Weighted average interest rate (as a percent)	4.16%		4.16%
Fixed rate mortgage debt | Mortgage and other secured debt | Minimum
Debt
Interest rate (as a percent)	3.82%		3.82%
Fixed rate mortgage debt | Mortgage and other secured debt | Maximum
Debt
Interest rate (as a percent)	4.62%		4.62%
Variable-rate debt | Mortgage and other secured debt
Debt
Carrying Value	$ 55,923,000		$ 55,923,000		23,282,000
Weighted average interest rate (as a percent)	4.18%		4.18%
Variable-rate debt | Mortgage and other secured debt | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.45%
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	$ 76,900,000		$ 76,900,000
Revolving Credit Facility
Debt
Carrying Value	$ 220,000,000		$ 220,000,000		213,000,000
Weighted average interest rate (as a percent)	3.05%		3.05%
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	$ 248,598,000		$ 248,598,000		248,273,000
Interest rate (as a percent)	3.35%		3.35%
Aggregate additional borrowing capacity available	$ 150,000,000		$ 150,000,000
Maximum availability	500,000,000		$ 500,000,000
Term Loan Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			0.85%
Term Loan Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.65%
3.600% Senior Notes | Unsecured senior notes
Debt
Carrying Value	348,319,000		$ 348,319,000		347,986,000
Debt instrument, face amount	$ 350,000,000		$ 350,000,000
Interest rate (as a percent)	3.60%		3.60%
Unamortized discount included in carrying value	$ 1,200,000		$ 1,200,000		1,400,000
Effective interest rate on debt (as a percent)	3.70%		3.70%
5.250% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 247,521,000		$ 247,521,000		247,136,000
Debt instrument, face amount	$ 250,000,000		$ 250,000,000
Interest rate (as a percent)	5.25%		5.25%
Unamortized discount included in carrying value	$ 2,200,000		$ 2,200,000		2,600,000
Effective interest rate on debt (as a percent)	5.49%		5.49%
3.700% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 299,196,000		$ 299,196,000		298,815,000
Debt instrument, face amount	$ 300,000,000		$ 300,000,000
Interest rate (as a percent)	3.70%		3.70%
Unamortized discount included in carrying value	$ 638,000		$ 638,000		943,000
Effective interest rate on debt (as a percent)	3.85%		3.85%
5.000% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 297,403,000		$ 297,403,000		297,109,000
Debt instrument, face amount	$ 300,000,000		$ 300,000,000
Interest rate (as a percent)	5.00%		5.00%
Unamortized discount included in carrying value	$ 2,200,000		$ 2,200,000		2,400,000
Effective interest rate on debt (as a percent)	5.15%		5.15%
Unsecured notes payable
Debt
Carrying Value	$ 1,071,000		$ 1,071,000		1,167,000
Interest rate (as a percent)	0.00%		0.00%
Unamortized discount included in carrying value	$ 240,000		$ 240,000		$ 294,000

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Carrying Amount
Carrying amount and estimated fair value of debt
Long-term debt	$ 1,862,301	$ 1,823,909
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,192,439	1,191,046
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	145,341	148,308
Carrying Amount | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	524,521	484,555
Estimated Fair Value
Carrying amount and estimated fair value of debt
Long-term debt	1,909,098	1,853,206
Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term debt	1,226,437	1,219,603
Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	150,500	147,106
Estimated Fair Value | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term debt	$ 532,161	$ 486,497

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (Loss) Gain Recognized in AOCL on Derivatives	$ (11,047)	$ 1,325	$ (33,437)	$ 7,913
Interest rate swaps | Interest Expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of Gain Reclassified from AOCL into Interest Expense on Statement of Operations	307	$ 207	1,434	$ 9
Interest rate swaps | Prepaid expenses and other assets, net
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	32		32		$ 5,617
Interest rate swaps | Interest rate derivatives (liabilities)
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	(34,825)		(34,825)		(5,459)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(34,793)		(34,793)		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	612		612
Fair value of derivative liability	34,900		34,900
Settlement amount of derivative obligation at termination value	34,900		34,900
Designated | Interest rate swap, effective date September 1, 2015, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.73%		1.73%
Fair value of interest rate swaps	$ 0		$ 0		472
Designated | Interest rate swap, effective October 13, 2015
Fair values of interest rate swap derivatives
Notional Amount	$ 12,538		$ 12,538
Fixed rate (as a percent)	1.39%		1.39%
Fair value of interest rate swaps	$ 32		$ 32		239
Notional amount of interest rate derivatives after scheduled amortization	12,100		12,100
Designated | Interest rate swap, effective September 1, 2016, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.9013%		1.9013%
Fair value of interest rate swaps	$ (1,547)		$ (1,547)		1,968
Designated | Interest rate swap, effective September 1, 2016, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.905%		1.905%
Fair value of interest rate swaps	$ (1,558)		$ (1,558)		1,967
Designated | Interest rate swap, effective September 1, 2016, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 50,000		$ 50,000
Fixed rate (as a percent)	1.9079%		1.9079%
Fair value of interest rate swaps	$ (784)		$ (784)		971
Designated | Interest rate swap, effective August 1, 2019
Fair values of interest rate swap derivatives
Notional Amount	$ 11,200		$ 11,200
Fixed rate (as a percent)	1.678%		1.678%
Fair value of interest rate swaps	$ (202)		$ (202)		0
Notional amount of interest rate derivatives after scheduled amortization	10,000		10,000
Designated | Interest rate swap, effective June 30, 2020, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000		$ 75,000
Fixed rate (as a percent)	3.176%		3.176%
Fair value of interest rate swaps	$ (11,204)		$ (11,204)		(2,676)
Designated | Interest rate swap, effective June 30, 2020, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000		$ 75,000
Fixed rate (as a percent)	3.192%		3.192%
Fair value of interest rate swaps	$ (11,315)		$ (11,315)		(2,783)
Designated | Interest rate swap, effective June 30, 2020, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 75,000		$ 75,000
Fixed rate (as a percent)	2.744%		2.744%
Fair value of interest rate swaps	$ (8,215)		$ (8,215)		$ 0

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interests (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)joint_venture	Sep. 30, 2018USD ($)
Noncontrolling Interest [Abstract]
Number of joint ventures with redeemable noncontrolling interests | joint_venture	2
Redeemable Noncontrolling Interest [Roll Forward]
Beginning balance	$ 26,260	$ 23,125
Contributions from noncontrolling interests	0	186
Distributions to noncontrolling interests	(1,656)	(1,114)
Net income attributable to noncontrolling interests	2,729	1,903
Adjustment to arrive at fair value of interests	1,344	1,331
Ending balance	$ 28,677	$ 25,431

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 23, 2019	Sep. 22, 2019	Jul. 31, 2019	Mar. 27, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Preferred units in COPLP					$ 8,800		$ 8,800		$ 8,800
Conversion of common units to common shares (in units/shares)					97,539	1,841,810	103,039	1,895,627
Dividends declared per share (in usd per share)					$ 0.275	$ 0.275	$ 0.825	$ 0.825
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				$ 46,500
Common Shares | 2018 Common Stock Issued to Public Under At-the-Market Program
Class of Stock [Line Items]
Aggregate gross sales price					$ 300,000		$ 300,000
Corporate Office Properties, L.P.
Class of Stock [Line Items]
Dividends declared per share (in usd per share)					$ 0.275	$ 0.275	$ 0.825	$ 0.825
Series I Preferred Units | Corporate Office Properties, L.P.
Class of Stock [Line Items]
Number of limited partners' preferred units outstanding (in units)					352,000		352,000
Preferred units in COPLP					$ 8,800		$ 8,800
Liquidation preference of preferred stock per share (in usd per share)					$ 25		$ 25
Preferred stock dividend rate (percent)	3.50%	7.50%
Preferred stock redemption notification period			6 months

Information by Business Segme_3

Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment financial information for real estate operations
Revenues from real estate operations	$ 159,431	$ 137,411	$ 483,441	$ 439,630
Property operating expenses	(49,714)	(49,340)	(147,045)	(149,737)
UJV NOI allocable to COPT	1,601	1,206	4,071	3,607
Segment assets	3,855,369	3,650,366	3,855,369	3,650,366	$ 3,656,005
Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	130,734	128,988	395,495	386,428
Property operating expenses	(49,714)	(49,340)	(147,045)	(149,737)
UJV NOI allocable to COPT	1,601	1,206	4,071	3,607
NOI from real estate operations	82,621	80,854	252,521	240,298
Additions to long-lived assets	22,560	21,259	53,079	52,322
Transfers from non-operating properties	16,242	46,685	157,328	101,003
Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	107,957	104,932	324,932	314,279
Property operating expenses	(38,673)	(37,148)	(113,885)	(113,852)
UJV NOI allocable to COPT	1,601	1,206	4,071	3,607
NOI from real estate operations	70,885	68,990	215,118	204,034
Additions to long-lived assets	16,141	15,307	37,506	36,693
Transfers from non-operating properties	17,254	46,530	158,340	98,703
Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	63,436	61,396	187,778	186,171
Property operating expenses	(20,743)	(19,847)	(62,422)	(61,550)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	42,693	41,549	125,356	124,621
Additions to long-lived assets	10,770	11,211	22,204	26,483
Transfers from non-operating properties	1,381	14,698	7,759	34,919
Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	13,551	13,960	42,294	39,639
Property operating expenses	(4,965)	(5,518)	(14,951)	(15,150)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	8,586	8,442	27,343	24,489
Additions to long-lived assets	2,922	2,305	6,072	5,431
Transfers from non-operating properties	118	1,550	4,647	2,243
Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	12,703	11,254	36,368	35,079
Property operating expenses	(7,149)	(6,432)	(19,756)	(20,524)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	5,554	4,822	16,612	14,555
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	2,120	0	10,456	0
Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	8,183	7,899	24,523	23,896
Property operating expenses	(3,581)	(3,208)	(10,271)	(9,943)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	4,602	4,691	14,252	13,953
Additions to long-lived assets	2,003	1,758	7,948	4,316
Transfers from non-operating properties	0	(17)	0	(17)
Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	4,171	3,734	12,078	11,019
Property operating expenses	(1,717)	(1,569)	(4,855)	(4,518)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	2,454	2,165	7,223	6,501
Additions to long-lived assets	446	33	1,282	463
Transfers from non-operating properties	4,152	13	13,363	483
Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	5,913	6,689	21,891	18,475
Property operating expenses	(518)	(574)	(1,630)	(2,167)
UJV NOI allocable to COPT	1,601	1,206	4,071	3,607
NOI from real estate operations	6,996	7,321	24,332	19,915
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	9,483	30,286	122,115	61,075
Regional Office | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	15,508	15,272	45,359	45,852
Property operating expenses	(7,343)	(7,425)	(22,349)	(22,472)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	8,165	7,847	23,010	23,380
Additions to long-lived assets	6,339	5,670	15,198	14,915
Transfers from non-operating properties	0	0	0	0
Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	6,565	7,781	22,996	23,963
Property operating expenses	(3,374)	(3,965)	(9,830)	(12,373)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	3,191	3,816	13,166	11,590
Additions to long-lived assets	61	370	312	487
Transfers from non-operating properties	(1,012)	155	(1,012)	2,300
Other | Real estate operations
Segment financial information for real estate operations
Revenues from real estate operations	704	1,003	2,208	2,334
Property operating expenses	(324)	(802)	(981)	(1,040)
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	380	201	1,227	1,294
Additions to long-lived assets	19	(88)	63	227
Transfers from non-operating properties	0	0	0	0
Segment assets
Segment financial information for real estate operations
Segment assets	3,024,072	3,074,986	3,024,072	3,074,986
Segment assets | Real estate operations
Segment financial information for real estate operations
Segment assets	3,024,072	3,074,986	3,024,072	3,074,986
Segment assets | Defense/Information Technology Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	2,421,067	2,455,324	2,421,067	2,455,324
Segment assets | Defense/Information Technology Locations | Fort Meade/BW Corridor | Real estate operations
Segment financial information for real estate operations
Segment assets	1,271,668	1,280,837	1,271,668	1,280,837
Segment assets | Defense/Information Technology Locations | Northern Virginia Defense/IT | Real estate operations
Segment financial information for real estate operations
Segment assets	398,137	394,066	398,137	394,066
Segment assets | Defense/Information Technology Locations | Lackland Air Force Base | Real estate operations
Segment financial information for real estate operations
Segment assets	147,505	126,047	147,505	126,047
Segment assets | Defense/Information Technology Locations | Navy Support Locations | Real estate operations
Segment financial information for real estate operations
Segment assets	186,243	189,406	186,243	189,406
Segment assets | Defense/Information Technology Locations | Redstone Arsenal | Real estate operations
Segment financial information for real estate operations
Segment assets	118,839	105,315	118,839	105,315
Segment assets | Defense/Information Technology Locations | Data Center Shells | Real estate operations
Segment financial information for real estate operations
Segment assets	298,675	359,653	298,675	359,653
Segment assets | Regional Office | Real estate operations
Segment financial information for real estate operations
Segment assets	393,747	396,624	393,747	396,624
Segment assets | Operating wholesale data center | Real estate operations
Segment financial information for real estate operations
Segment assets	205,550	219,041	205,550	219,041
Segment assets | Other | Real estate operations
Segment financial information for real estate operations
Segment assets	$ 3,708	$ 3,997	$ 3,708	$ 3,997

Information by Business Segme_4

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reconciliation of segment revenues to total revenues
Construction contract and other service revenues	$ 28,697	$ 8,423	$ 87,946	$ 53,202
Total revenues	159,431	137,411	483,441	439,630
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,601	1,206	4,071	3,607
Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense	(1,202)	(830)	(2,859)	(2,482)
Add: Equity in loss of unconsolidated non-real estate entities	(3)	(2)	(5)	(5)
Equity in income of unconsolidated entities	396	374	1,207	1,120
Computation of net operating income from service operations
Construction contract and other service revenues	28,697	8,423	87,946	53,202
Construction contract and other service expenses	(27,802)	(8,058)	(85,130)	(51,215)
Real estate operations
Reconciliation of segment revenues to total revenues
Total revenues	130,734	128,988	395,495	386,428
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,601	1,206	4,071	3,607
Service operations
Computation of net operating income from service operations
NOI from service operations	$ 895	$ 365	$ 2,816	$ 1,987

Information by Business Segme_5

Information by Business Segment (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
Interest and other income	$ 1,842	$ 1,486	$ 5,977	$ 4,284
Gain on sales of real estate	0	0	84,469	(27)
Equity in income of unconsolidated entities	396	374	1,207	1,120
Income tax benefit	131	291	113	173
Depreciation and other amortization associated with real estate operations	(34,692)	(34,195)	(104,290)	(100,897)
Impairment losses	327	0	327	0
General, administrative and leasing expenses	(7,929)	(6,899)	(26,066)	(21,819)
Business development expenses and land carry costs	(964)	(1,567)	(2,947)	(4,415)
Interest expense	(17,126)	(19,181)	(54,275)	(56,910)
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,601)	(1,206)	(4,071)	(3,607)
Net income	23,246	20,322	155,127	60,187
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	82,621	80,854	252,521	240,298
Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities	(1,601)	(1,206)	(4,071)	(3,607)
Service operations
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from service operations	$ 895	$ 365	$ 2,816	$ 1,987

Information by Business Segme_6

Information by Business Segment (Details 4) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 3,855,369	$ 3,656,005	$ 3,650,366
Operating properties lease liabilities included in segment assets	16,686
Segment assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	3,024,072		3,074,986
Operating properties lease liabilities included in segment assets	16,645		0
Non-operating property assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	597,301		420,109
Other assets
Reconciliation of segment assets to total assets
Total COPT consolidated assets	$ 217,351		$ 155,271

Construction Contract and Oth_3

Construction Contract and Other Service Revenues (Details) - Construction Contract Revenue - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Performance obligations satisfied or already satisfied	$ (1)	$ 18	$ 318
Remaining performance obligations		27,500
Remaining performance obligation expected to be recognized during the remainder of year		$ 23,000

Construction Contract and Oth_4

Construction Contract and Other Service Revenues (Details 1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 28,697	$ 8,423	$ 87,946	$ 53,202
Construction
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	27,988	8,160	86,487	50,743
Design
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	484	52	822	1,771
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	225	211	637	688
Guaranteed Maximum Price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	16,217	1,840	54,365	31,865
Firm fixed price
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	2,349	3,653	6,009	16,376
Cost-plus fee
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	9,906	2,719	26,935	4,273
Other
Disaggregation of Revenue [Line Items]
Construction contract and other service revenues	$ 225	$ 211	$ 637	$ 688

Construction Contract and Oth_5

Construction Contract and Other Service Revenues (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Change in Accounts Receivable
Beginning balance	$ 37,623		$ 37,623		$ 26,277
Ending balance	37,623		37,623		26,277
Construction Contract Revenue
Change in Accounts Receivable
Beginning balance	15,494	$ 5,571	15,494	$ 5,571	6,701	$ 4,577
Ending balance	15,494	5,571	15,494	5,571	6,701	4,577
Change in Contract with Customer, Asset
Beginning balance	16,743	2,821	16,743	2,821	3,189	4,884
Ending balance	16,743	2,821	16,743	2,821	3,189	4,884
Change in Contract with Customer, Liability
Beginning balance	725	560	725	560	568	27,402
Ending balance	725	560	725	560	$ 568	$ 27,402
Revenue recognized included in beginning balance	$ 0	$ 0	$ 445	$ 27,296

Share-Based Compensation (Detai

Share-Based Compensation (Details) $ / shares in Units, $ in Thousands	Jan. 18, 2019shares	Jan. 01, 2019USD ($)$ / sharesshares	Sep. 30, 2019USD ($)FormPercentile_Rank$ / sharesshares
PIUs
Share-Based Compensation
Number of forms of executive compensation | Form			2
Time-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units) | shares			61,820
Aggregate grant date fair value | $			$ 1,600
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 26.01
Annual award vesting rights (percent)			33.33%
Award vesting period			3 years
Restricted shares
Share-Based Compensation
Stock awards granted (in shares or units) | shares			185,095
Aggregate grant date fair value | $			$ 4,900
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 26.41
Shares vested (in shares) | shares			175,973
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 28.05
Aggregate intrinsic value of awards upon vesting | $			$ 4,600
Deferred share awards
Share-Based Compensation
Stock awards granted (in shares or units) | shares			3,432
Aggregate grant date fair value | $			$ 95
Aggregate grant date fair value (in dollars per share) | $ / shares			$ 27.60
Shares vested (in shares) | shares			3,097
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 26.77
Aggregate intrinsic value of awards upon vesting | $			$ 86
2016 PSU Grants | Performance share units | Executives
Share-Based Compensation
Shares issued (in shares) | shares	44,757
Percentage of target	157.00%
2019 PIU Grants | Performance-based PIU's
Share-Based Compensation
Stock awards granted (in shares or units) | shares		193,682
Aggregate grant date fair value | $		$ 2,400
Aggregate grant date fair value (in dollars per share) | $ / shares		$ 12.47
Award vesting period		3 years
Potential earned PSUs payout for defined levels of performance under awards
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 75th or greater percentile rank		100.00%
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 50th percentile rank		50.00%
Earned PB-PIUs payout (as a percent of PB-PIUs granted) on 25th percentile rank		25.00%
Earned PB-PIUs granted on percentile rank below 25th (as a percent)		0.00%
The number of percentile ranks to fall between to earn interpolated PB-PIUs between such percentile ranks, conditioned on the percentile rank exceeding 25% | Percentile_Rank			2
Assumptions used to value stock awards
Percent of award distribution rights			10.00%
Award performance period			3 years
Baseline value per common share (in dollars per share) | $ / shares		$ 21.03
Expected volatility of common shares (as a percent)		21.00%
Risk-free interest rate (as a percent)		2.51%

Earnings Per Share ("EPS") an_3

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income attributable to COPT/COPLP		$ 21,257	$ 18,697	$ 148,907	$ 55,281
Income attributable to share-based compensation awards		(123)	(114)	(495)	(348)
Numerator for basic EPS on net income attributable to COPT common shareholders		21,134	18,583	148,412	54,933
Redeemable noncontrolling interests		0	0	100	0
Income attributable to share-based compensation awards		5	0	26	0
Numerator for diluted EPS on net income attributable to COPT/COPLP common share/unit holders		$ 21,139	$ 18,583	$ 148,538	$ 54,933
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)		111,582	104,379	111,036	102,401
Dilutive effect of share-based compensation awards (in shares/units)		361	231	313	165
Dilutive effect of redeemable noncontrolling interests (in shares/units)		0	0	123	0
Dilutive effect of forward equity sale agreements (in shares/units)		0	178	0	60
Denominator for diluted EPS/EPU (common shares/units)		111,943	104,788	111,472	102,626
Basic EPS:
Basic earnings per common share (in dollars per share/unit)	[1]	$ 0.19	$ 0.18	$ 1.34	$ 0.54
Diluted EPS:
Diluted earnings per common share (in dollars per share/unit)	[1]	$ 0.19	$ 0.18	$ 1.33	$ 0.54
Corporate Office Properties, L.P.
Numerator:
Net income attributable to COPT/COPLP		$ 21,681	$ 19,242	$ 151,257	$ 57,308
Preferred share/unit dividends/distributions		(157)	(165)	(487)	(495)
Income attributable to share-based compensation awards		(139)	(114)	(592)	(348)
Numerator for basic EPS on net income attributable to COPT common shareholders		21,385	18,963	150,178	56,465
Redeemable noncontrolling interests		0		100	0
Income attributable to share-based compensation awards		5	0	26	0
Numerator for diluted EPS on net income attributable to COPT/COPLP common share/unit holders		$ 21,390	$ 18,963	$ 150,304	$ 56,465
Denominator (all weighted averages):
Denominator for basic EPS/EPU (common shares/units)		112,894	106,514	112,359	105,248
Dilutive effect of share-based compensation awards (in shares/units)		361	231	313	165
Dilutive effect of redeemable noncontrolling interests (in shares/units)		0	0	123	0
Dilutive effect of forward equity sale agreements (in shares/units)		0	178	0	60
Denominator for diluted EPS/EPU (common shares/units)		113,255	106,923	112,795	105,473
Basic EPS:
Basic earnings per common share (in dollars per share/unit)	[2]	$ 0.19	$ 0.18	$ 1.34	$ 0.54
Diluted EPS:
Diluted earnings per common share (in dollars per share/unit)	[2]	$ 0.19	$ 0.18	$ 1.33	$ 0.54
[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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Conversion of common units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1,312	2,135	1,323	2,847
Conversion of redeemable noncontrolling interests
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	975	0	893	0
Conversion of Series I preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	176	176	176	176
Weighted average shares related to forward equity sale agreements
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)			503
Weighted average restricted shares/units and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	436	455	441	452
Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	3	30	16	45
Weighted average unvested PIUs
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	62		47
Corporate Office Properties, L.P. | Conversion of redeemable noncontrolling interests
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	975	0	893	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	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)			503
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)	436	455	441	452
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	3	30	16	45
Corporate Office Properties, L.P. | Weighted average unvested PIUs
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	62		47

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	Sep. 30, 2019USD ($)property	Dec. 31, 2018USD ($)
Environmental Indemnity Agreement
Number of properties which were provided environmental indemnifications | property	3
Maximum additional costs agreed to be paid by the entity under environmental indemnification agreement	$ 19,000
Carrying Value	1,862,301	$ 1,823,909
Development and Redevelopment Obligations
Environmental Indemnity Agreement
Purchase obligations	217,100
Tenant and Other Capital Improvements
Environmental Indemnity Agreement
Purchase obligations	60,800
Third Party Construction
Environmental Indemnity Agreement
Purchase obligations	13,500
Other Obligations
Environmental Indemnity Agreement
Purchase obligations	1,600
Specialty Tax Guarantee | Anne Arundel County, Maryland | Tax Incremental Financing Bond
Environmental Indemnity Agreement
Carrying Value	$ 34,000