Corporate Office Properties Trust 10-Q 2 Aug 16 2016 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Jul. 22, 2016
Entity Information [Line Items]
Entity Registrant Name	CORPORATE OFFICE PROPERTIES TRUST
Entity Central Index Key	860,546
Document Type	10-Q
Document Period End Date	Jun. 30, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		94,759,023
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2
Corporate Office Properties, L.P.
Entity Information [Line Items]
Entity Registrant Name	CORPORATE OFFICE PROPERTIES, L.P.
Entity Central Index Key	1,577,966
Document Type	10-Q
Document Period End Date	Jun. 30, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Properties, net:
Operating properties, net	$ 2,782,330	$ 2,920,529
Projects in development or held for future development	387,397	429,219
Total properties, net	3,169,727	3,349,748
Assets held for sale, net	300,584	96,782
Cash and cash equivalents	13,317	60,310
Restricted cash and marketable securities	8,302	7,716
Accounts receivable (net of allowance for doubtful accounts of $745 and $1,525, respectively)	32,505	29,167
Deferred rent receivable (net of allowance of $422 and $1,962, respectively)	92,316	105,484
Intangible assets on real estate acquisitions, net	88,788	98,338
Deferred leasing costs (net of accumulated amortization of $63,768 and $66,364, respectively)	42,632	53,868
Investing receivables	50,162	47,875
Prepaid expenses and other assets, net	43,359	60,024
Total assets	3,841,692	3,909,312
Liabilities:
Debt, net	2,094,486	2,077,752
Accounts payable and accrued expenses	92,848	91,755
Rents received in advance and security deposits	32,035	37,148
Dividends and distributions payable	30,219	30,178
Deferred revenue associated with operating leases	17,560	19,758
Interest rate derivatives	20,245	3,160
Other liabilities	31,123	13,779
Total liabilities	2,318,516	2,273,530
Commitments and contingencies (Note 15)
Redeemable noncontrolling interests	22,473	19,218
Corporate Office Properties Trust’s shareholders’ equity:
Preferred Shares of beneficial interest at liquidation preference ($0.01 par value; 25,000,000 shares authorized, shares issued and outstanding of 7,431,667 at June 30, 2016 and December 31, 2015)	199,083	199,083
Common Shares of beneficial interest	947	945
Additional paid-in capital	2,007,328	2,004,507
Cumulative distributions in excess of net income	(756,940)	(657,172)
Accumulated other comprehensive loss	(17,712)	(2,838)
Total Corporate Office Properties Trust’s shareholders’ equity	1,432,706	1,544,525
Noncontrolling interests in subsidiaries:
Common units in COPLP	47,550	52,359
Preferred units in COPLP	8,800	8,800
Other consolidated entities	11,647	10,880
Noncontrolling interests in subsidiaries	67,997	72,039
Total equity	1,500,703	1,616,564
Total liabilities, redeemable noncontrolling interest and equity	3,841,692	3,909,312
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,782,330	2,920,529
Projects in development or held for future development	387,397	429,219
Total properties, net	3,169,727	3,349,748
Assets held for sale, net	300,584	96,782
Cash and cash equivalents	13,317	60,310
Restricted cash and marketable securities	3,256	1,953
Accounts receivable (net of allowance for doubtful accounts of $745 and $1,525, respectively)	32,505	29,167
Deferred rent receivable (net of allowance of $422 and $1,962, respectively)	92,316	105,484
Intangible assets on real estate acquisitions, net	88,788	98,338
Deferred leasing costs (net of accumulated amortization of $63,768 and $66,364, respectively)	42,632	53,868
Investing receivables	50,162	47,875
Prepaid expenses and other assets, net	43,359	60,024
Total assets	3,836,646	3,903,549
Liabilities:
Debt, net	2,094,486	2,077,752
Accounts payable and accrued expenses	92,848	91,755
Rents received in advance and security deposits	32,035	37,148
Dividends and distributions payable	30,219	30,178
Deferred revenue associated with operating leases	17,560	19,758
Interest rate derivatives	20,245	3,160
Other liabilities	26,077	8,016
Total liabilities	2,313,470	2,267,767
Commitments and contingencies (Note 15)
Redeemable noncontrolling interests	22,473	19,218
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,299,571	1,400,745
Accumulated other comprehensive loss	(18,437)	(2,985)
Total Corporate Office Properties Trust’s shareholders’ equity	1,489,017	1,605,643
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	11,686	10,921
Total equity	1,500,703	1,616,564
Total liabilities, redeemable noncontrolling interest and equity	3,836,646	3,903,549
General Partner | Corporate Office Properties, L.P.
Corporate Office Properties Trust’s shareholders’ equity:
Preferred partners' capital accounts	199,083	199,083
Limited Partner | Corporate Office Properties, L.P.
Corporate Office Properties Trust’s shareholders’ equity:
Preferred partners' capital accounts	$ 8,800	$ 8,800

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Allowance for doubtful accounts - AR	$ 745	$ 1,525
Deferred rent receivable	422	1,962
Deferred leasing costs, accumulated amortization	$ 63,768	$ 66,364
Preferred Shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred Shares of beneficial interest, shares authorized	25,000,000	25,000,000
Preferred Shares of beneficial interest, shares issued	7,431,667	7,431,667
Preferred Shares of beneficial interest, shares outstanding	7,431,667	7,431,667
Common Shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common Shares of beneficial interest, shares authorized	125,000,000	125,000,000
Common Shares of beneficial interest, shares issued	94,699,359	94,531,512
Common Shares of beneficial interest, shares outstanding	94,699,359	94,531,512
Corporate Office Properties, L.P.
Allowance for doubtful accounts - AR	$ 745	$ 1,525
Deferred rent receivable	422	1,962
Deferred leasing costs, accumulated amortization	$ 63,768	$ 66,364
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	94,699,359	94,531,512
Preferred Units, Outstanding	7,431,667	7,431,667
Corporate Office Properties, L.P. | Limited Partner
Common Shares of beneficial interest, shares outstanding	3,650,633	3,677,391
Preferred Units, Outstanding	352,000	352,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2016		Jun. 30, 2015	Jun. 30, 2016		Jun. 30, 2015
Revenues
Rental revenue		$ 107,524		$ 105,508	$ 212,906		$ 203,746
Tenant recoveries and other real estate operations revenue		26,400		22,683	54,105		47,155
Construction contract and other service revenues		12,003		42,172	23,223		80,496
Total revenues		145,927		170,363	290,234		331,397
Expenses
Property operating expenses		48,141		46,418	100,016		97,099
Depreciation and amortization associated with real estate operations		33,248		33,786	67,775		65,385
Construction contract and other service expenses		11,478		41,293	22,172		78,791
Impairment losses		69,692		1,238	72,138		1,238
General, administrative and leasing expenses		8,026		7,534	19,909		15,425
Business development expenses and land carry costs		2,363		2,623	4,781		5,413
Total operating expenses		172,948		132,892	286,791		263,351
Operating (loss) income		(27,021)		37,471	3,443		68,046
Interest expense		(22,639)		(21,768)	(46,198)		(42,606)
Interest and other income		1,330		1,242	2,486		2,525
Gain (loss) on early extinguishment of debt		5		(65)	22		(68)
(Loss) income from continuing operations before equity in income of unconsolidated entities and income taxes		(48,325)		16,880	(40,247)		27,897
Equity in income of unconsolidated entities		10		9	20		34
Income tax (expense) benefit		(1)		(50)	7		(105)
(Loss) income from continuing operations		(48,316)		16,839	(40,220)		27,826
Discontinued operations		0		394	0		156
(Loss) income before gain on sales of real estate		(48,316)		17,233	(40,220)		27,982
Gain on sales of real estate		0		(1)	0		3,985
Net (loss) income		(48,316)		17,232	(40,220)		31,967
Net loss (income) attributable to noncontrolling interests:
Common units in COPLP		1,976		(476)	1,849		(874)
Preferred units in COPLP		(165)		(165)	(330)		(330)
Other consolidated entities		(914)		(810)	(1,892)		(1,627)
Net (loss) income attributable to COPT		(47,419)		15,781	(40,593)		29,136
Preferred share/unit dividends/distributions		(3,553)		(3,553)	(7,105)		(7,105)
Net (loss) income attributable to COPT common shareholders		(50,972)		12,228	(47,698)		22,031
Net (loss) income attributable to COPT:
(Loss) income from continuing operations		(47,419)		15,402	(40,593)		28,983
Discontinued operations, net		0		379	0		153
Net (loss) income attributable to COPT		$ (47,419)		$ 15,781	$ (40,593)		$ 29,136
Basic earnings per common share
(Loss) income from continuing operations (in dollars per share/unit)		$ (0.54)	[1]	$ 0.13	$ (0.51)	[1]	$ 0.23	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[1]	(0.54)		0.13	(0.51)		0.23
Diluted earnings per common share
(Loss) income from continuing operations (in dollars per share/unit)		(0.54)	[1]	0.13	(0.51)	[1]	0.23	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[1]	(0.54)		0.13	(0.51)		0.23
Dividends declared per common share/unit (in dollars per share		$ 0.2750		$ 0.275	$ 0.55		$ 0.55
Corporate Office Properties, L.P.
Revenues
Rental revenue		$ 107,524		$ 105,508	$ 212,906		$ 203,746
Tenant recoveries and other real estate operations revenue		26,400		22,683	54,105		47,155
Construction contract and other service revenues		12,003		42,172	23,223		80,496
Total revenues		145,927		170,363	290,234		331,397
Expenses
Property operating expenses		48,141		46,418	100,016		97,099
Depreciation and amortization associated with real estate operations		33,248		33,786	67,775		65,385
Construction contract and other service expenses		11,478		41,293	22,172		78,791
Impairment losses		69,692		1,238	72,138		1,238
General, administrative and leasing expenses		8,026		7,534	19,909		15,425
Business development expenses and land carry costs		2,363		2,623	4,781		5,413
Total operating expenses		172,948		132,892	286,791		263,351
Operating (loss) income		(27,021)		37,471	3,443		68,046
Interest expense		(22,639)		(21,768)	(46,198)		(42,606)
Interest and other income		1,330		1,242	2,486		2,525
Gain (loss) on early extinguishment of debt		5		(65)	22		(68)
(Loss) income from continuing operations before equity in income of unconsolidated entities and income taxes		(48,325)		16,880	(40,247)		27,897
Equity in income of unconsolidated entities		10		9	20		34
Income tax (expense) benefit		(1)		(50)	7		(105)
(Loss) income from continuing operations		(48,316)		16,839	(40,220)		27,826
Discontinued operations		0		394	0		156
(Loss) income before gain on sales of real estate		(48,316)		17,233	(40,220)		27,982
Gain on sales of real estate		0		(1)	0		3,985
Net (loss) income		(48,316)		17,232	(40,220)		31,967
Net loss (income) attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities		(911)		(812)	(1,890)		(1,630)
Net (loss) income attributable to COPT		(49,227)		16,420	(42,110)		30,337
Preferred share/unit dividends/distributions		(3,718)		(3,718)	(7,435)		(7,435)
Net (loss) income attributable to COPT common shareholders		(52,945)		12,702	(49,545)		22,902
Net (loss) income attributable to COPT:
(Loss) income from continuing operations		(49,227)		16,026	(42,110)		30,178
Discontinued operations, net		0		394	0		159
Net (loss) income attributable to COPT		$ (49,227)		$ 16,420	$ (42,110)		$ 30,337
Basic earnings per common share
(Loss) income from continuing operations (in dollars per share/unit)	[2]	$ (0.54)		$ 0.13	$ (0.51)		$ 0.23
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[2]	(0.54)		0.13	(0.51)		0.23
Diluted earnings per common share
(Loss) income from continuing operations (in dollars per share/unit)	[2]	(0.54)		0.13	(0.51)		0.23
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[2]	(0.54)		0.13	(0.51)		0.23
Dividends declared per common share/unit (in dollars per share		$ 0.275		$ 0.275	$ 0.55		$ 0.55
[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.
[2]	Basic and diluted earnings per common unit are calculated based on amounts attributable to common unitholders of Corporate Office Properties, L.P.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net (loss) income	$ (48,316)	$ 17,232	$ (40,220)	$ 31,967
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(5,704)	392	(16,988)	(3,082)
Losses on interest rate derivatives included in interest expense	850	769	1,720	1,542
Equity in other comprehensive loss of equity method investee	(184)	(264)	(184)	(264)
Other comprehensive (loss) income	(5,038)	897	(15,452)	(1,804)
Comprehensive (loss) income	(53,354)	18,129	(55,672)	30,163
Comprehensive loss (income) attributable to noncontrolling interests	1,085	(1,542)	205	(2,871)
Comprehensive (loss) income attributable to COPT	(52,269)	16,587	(55,467)	27,292
Corporate Office Properties, L.P.
Net (loss) income	(48,316)	17,232	(40,220)	31,967
Other comprehensive (loss) income
Unrealized (loss) gain on interest rate derivatives	(5,704)	392	(16,988)	(3,082)
Losses on interest rate derivatives included in interest expense	850	769	1,720	1,542
Equity in other comprehensive loss of equity method investee	(184)	(264)	(184)	(264)
Other comprehensive (loss) income	(5,038)	897	(15,452)	(1,804)
Comprehensive (loss) income	(53,354)	18,129	(55,672)	30,163
Comprehensive loss (income) attributable to noncontrolling interests	(911)	(872)	(1,890)	(1,745)
Comprehensive (loss) income attributable to COPT	$ (54,265)	$ 17,257	$ (57,562)	$ 28,418

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Cumulative Distributions in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	Corporate Office Properties, L.P.	Corporate Office Properties, L.P.Common Shares	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	Corporate Office Properties, L.P.General Partner	Corporate Office Properties, L.P.General PartnerPreferred Shares
Balance (COPT: 93,255,284 shares and 94,531,512 shares as of December 31, 2014 and 2015, respectively) at Dec. 31, 2014	$ 1,520,884	$ 199,083	$ 933	$ 1,969,968	$ (717,264)	$ (1,297)	$ 69,461	$ 1,520,884	$ 1,305,219	$ (1,381)	$ 9,163		$ 8,800		$ 199,083
Balance (preferred units) at Dec. 31, 2014													352,000		7,431,667
Balance (in units/ shares) at Dec. 31, 2014	93,255,284								97,092,835
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 158,000 and 26,758 shares for the six months ended June 30, 2015 and 2016, respectively)	$ 0		2	2,120			(2,122)
Issuance of common units resulting from common shares issued under at-the-market program (in units)									890,241
Issuance of common units resulting from common shares issued under at-the-market program (COPT: 890,241 shares for the six months ended June 30, 2015)	$ 26,535		9	26,526				26,535	$ 26,535
Exercise of share options (in units/shares)	76,474								76,474
Exercise of share options (COPT: 76,474 shares for the six months ended June 30, 2015)	$ 2,008		0	2,008				2,008	$ 2,008
Share-based compensation issuance, net of redemptions (in units/shares)	149,619								149,619
Share-based compensation issuance, net of redemptions (COPT: 149,619 and 141,089 shares issued, net of redemptions for the six months ended June 30, 2015 and 2016, respectively)	$ 3,658		2	3,656				3,658	$ 3,658
Redemption of vested equity awards	(2,245)			(2,245)				(2,245)	(2,245)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0			(519)			519
Comprehensive income (loss)	29,020				29,136	(1,844)	1,728	29,020	22,902	(1,919)	602		$ 330		$ 7,105
Dividends / Distributions to owners of common and preferred units	(59,106)				(59,106)			(61,460)	(54,025)				$ (330)		$ (7,105)
Distributions to owners of common and preferred units in COPLP	(2,354)						(2,354)
Distributions to noncontrolling interests in subsidiaries	(28)						(28)	(28)			(28)
Adjustment to arrive at fair value of redeemable noncontrolling interest	$ (739)			(739)				(739)	$ (739)
Balance (in units/ shares) at Jun. 30, 2015	94,529,618								98,209,169
Balance (preferred units) at Jun. 30, 2015													352,000		7,431,667
Balance (COPT: 94,529,618 shares and 94,699,359 shares as of June 30, 2015 and 2016, respectively) at Jun. 30, 2015	$ 1,517,633	199,083	946	2,000,775	(747,234)	(3,141)	67,204	1,517,633	$ 1,303,313	(3,300)	9,737		$ 8,800		$ 199,083
Balance (COPT: 93,255,284 shares and 94,531,512 shares as of December 31, 2014 and 2015, respectively) at Dec. 31, 2015	$ 1,616,564	199,083	945	2,004,507	(657,172)	(2,838)	72,039	1,616,564	$ 1,400,745	(2,985)	10,921		$ 8,800		$ 199,083
Balance (preferred units) at Dec. 31, 2015												352,000	352,000	7,431,667	7,431,667
Balance (in units/ shares) at Dec. 31, 2015	94,531,512								98,208,903			3,677,391		94,531,512
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 158,000 and 26,758 shares for the six months ended June 30, 2015 and 2016, respectively)	$ 0		0	371			(371)
Costs associated with common shares issued to the public	$ (5)			(5)				(5)	$ (5)
Share-based compensation issuance, net of redemptions (in units/shares)	141,089								141,089
Share-based compensation issuance, net of redemptions (COPT: 149,619 and 141,089 shares issued, net of redemptions for the six months ended June 30, 2015 and 2016, respectively)	$ 4,303		2	4,301				4,303	$ 4,303
Redemption of vested equity awards	(1,492)			(1,492)				(1,492)	(1,492)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0			(5)			5
Comprehensive income (loss)	(56,789)				(40,593)	(14,874)	(1,322)	(56,789)	(49,545)	(15,452)	773		$ 330		$ 7,105
Dividends / Distributions to owners of common and preferred units	(59,175)				(59,175)			(61,521)	(54,086)				$ (330)		$ (7,105)
Distributions to owners of common and preferred units in COPLP	(2,346)						(2,346)
Distributions to noncontrolling interests in subsidiaries	(8)						(8)	(8)			(8)
Adjustment to arrive at fair value of redeemable noncontrolling interest	$ (349)			(349)				(349)	$ (349)
Balance (in units/ shares) at Jun. 30, 2016	94,699,359								98,349,992			3,650,633		94,699,359
Balance (preferred units) at Jun. 30, 2016												352,000	352,000	7,431,667	7,431,667
Balance (COPT: 94,529,618 shares and 94,699,359 shares as of June 30, 2015 and 2016, respectively) at Jun. 30, 2016	$ 1,500,703	$ 199,083	$ 947	$ 2,007,328	$ (756,940)	$ (17,712)	$ 67,997	$ 1,500,703	$ 1,299,571	$ (18,437)	$ 11,686		$ 8,800		$ 199,083

Consolidated Statements of Equ7

Consolidated Statements of Equity (Parenthetical) - shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Balance (in units/ shares)	94,699,359	94,529,618	94,531,512	93,255,284
Conversion of common units to common shares (in units/ shares)	26,758	158,000
Exercise of share options (in units/shares)		76,474
Share-based compensation issuance, net of redemptions (in units/shares)	141,089	149,619
Common Shares
Issuance of common units resulting from common shares issued under at-the-market program (in units)		890,241

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities
Revenues from real estate operations received	$ 260,984	$ 240,538
Construction contract and other service revenues received	34,992	86,790
Property operating expenses paid	(87,005)	(79,667)
Construction contract and other service expenses paid	(24,303)	(76,355)
General, administrative, leasing, business development and land carry costs paid	(19,212)	(20,121)
Interest expense paid	(41,179)	(32,375)
Interest and other income received	128	4,055
Other	(5)	(26)
Net cash provided by operating activities	124,400	122,839
Cash flows from investing activities
Construction, development and redevelopment	(75,339)	(117,498)
Acquisitions of operating properties and related intangible assets	0	(137,125)
Tenant improvements on operating properties	(14,862)	(10,314)
Other capital improvements on operating properties	(16,007)	(8,372)
Proceeds from dispositions of properties	5,448	17,424
Investing receivables payments received	0	5,114
Leasing costs paid	(3,434)	(6,732)
Other	(13)	(3,538)
Net cash used in investing activities	(104,207)	(261,041)
Proceeds from debt
Revolving Credit Facility	133,500	294,000
Unsecured senior notes	0	296,580
Other debt proceeds	45,000	50,000
Repayments of debt
Revolving Credit Facility	(119,000)	(377,000)
Scheduled principal amortization	(3,532)	(3,319)
Other debt repayments	(40,498)	(50,630)
Deferred financing costs paid	(528)	(4,693)
Net proceeds from issuance of common shares/units	(5)	28,567
Common share/unit dividends/distributions paid	(52,021)	(51,642)
Preferred share/unit dividends/distributions paid	(7,105)	(7,105)
Distributions paid to noncontrolling interests in COPLP	(2,362)	(2,461)
Distributions paid to redeemable noncontrolling interests	(14,306)	0
Redemption of vested equity awards	(1,492)	(2,245)
Other	(4,837)	(853)
Net cash (used in) provided by financing activities	(67,186)	169,199
Net (decrease) increase in cash and cash equivalents	(46,993)	30,997
Cash and cash equivalents
Beginning of period	60,310	6,077
End of period	13,317	37,074
Reconciliation of net (loss) income to net cash provided by operating activities:
Net (loss) income	(40,220)	31,967
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and other amortization	68,901	66,404
Impairment losses	72,138	1,472
Losses on interest rate derivatives	1,870	0
Amortization of deferred financing costs and net debt discounts	2,998	2,618
Increase in deferred rent receivable	(1,276)	(5,956)
Gain on sales of real estate	0	(3,985)
Share-based compensation	3,839	3,210
Other	(1,725)	1,754
Operating changes in assets and liabilities:
(Increase) decrease in accounts receivable	(3,320)	10,655
Increase in restricted cash and marketable securities	(389)	(735)
Decrease in prepaid expenses and other assets, net	11,303	6,518
Increase in accounts payable, accrued expenses and other liabilities	15,394	12,557
Decrease in rents received in advance and security deposits	(5,113)	(3,640)
Net cash provided by operating activities	124,400	122,839
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	1,604	15,927
Increase in property and redeemable noncontrolling interests in connection with property contributed in a joint venture	22,600	0
Decrease in redeemable noncontrolling interests and increase in other liabilities in connection with distribution payable to redeemable noncontrolling interest	6,675	0
Other liabilities assumed on acquisition of operating properties	0	5,265
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(15,268)	(1,540)
Equity in other comprehensive loss of an equity method investee	(184)	(264)
Dividends/distributions payable	30,219	30,178
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	371	2,122
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	5	519
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	349	739
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	260,984	240,538
Construction contract and other service revenues received	34,992	86,790
Property operating expenses paid	(87,005)	(79,667)
Construction contract and other service expenses paid	(24,303)	(76,355)
General, administrative, leasing, business development and land carry costs paid	(19,212)	(20,121)
Interest expense paid	(41,179)	(32,375)
Interest and other income received	128	4,055
Other	(5)	(26)
Net cash provided by operating activities	124,400	122,839
Cash flows from investing activities
Construction, development and redevelopment	(75,339)	(117,498)
Acquisitions of operating properties and related intangible assets	0	(137,125)
Tenant improvements on operating properties	(14,862)	(10,314)
Other capital improvements on operating properties	(16,007)	(8,372)
Proceeds from dispositions of properties	5,448	17,424
Investing receivables payments received	0	5,114
Leasing costs paid	(3,434)	(6,732)
Other	(13)	(3,538)
Net cash used in investing activities	(104,207)	(261,041)
Proceeds from debt
Revolving Credit Facility	133,500	294,000
Unsecured senior notes	0	296,580
Other debt proceeds	45,000	50,000
Repayments of debt
Revolving Credit Facility	(119,000)	(377,000)
Scheduled principal amortization	(3,532)	(3,319)
Other debt repayments	(40,498)	(50,630)
Deferred financing costs paid	(528)	(4,693)
Net proceeds from issuance of common shares/units	(5)	28,567
Common share/unit dividends/distributions paid	(54,053)	(53,773)
Preferred share/unit dividends/distributions paid	(7,435)	(7,435)
Distributions paid to redeemable noncontrolling interests	(14,306)	0
Redemption of vested equity awards	(1,492)	(2,245)
Other	(4,837)	(853)
Net cash (used in) provided by financing activities	(67,186)	169,199
Net (decrease) increase in cash and cash equivalents	(46,993)	30,997
Cash and cash equivalents
Beginning of period	60,310	6,077
End of period	13,317	37,074
Reconciliation of net (loss) income to net cash provided by operating activities:
Net (loss) income	(40,220)	31,967
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and other amortization	68,901	66,404
Impairment losses	72,138	1,472
Losses on interest rate derivatives	1,870	0
Amortization of deferred financing costs and net debt discounts	2,998	2,618
Increase in deferred rent receivable	(1,276)	(5,956)
Gain on sales of real estate	0	(3,985)
Share-based compensation	3,839	3,210
Other	(1,725)	1,754
Operating changes in assets and liabilities:
(Increase) decrease in accounts receivable	(3,320)	10,655
Increase in restricted cash and marketable securities	(1,106)	(744)
Decrease in prepaid expenses and other assets, net	11,303	6,518
Increase in accounts payable, accrued expenses and other liabilities	16,111	12,566
Decrease in rents received in advance and security deposits	(5,113)	(3,640)
Net cash provided by operating activities	124,400	122,839
Supplemental schedule of non-cash investing and financing activities:
Increase in accrued capital improvements, leasing and other investing activity costs	1,604	15,927
Increase in property and redeemable noncontrolling interests in connection with property contributed in a joint venture	22,600	0
Decrease in redeemable noncontrolling interests and increase in other liabilities in connection with distribution payable to redeemable noncontrolling interest	6,675	0
Other liabilities assumed on acquisition of operating properties	0	5,265
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(15,268)	(1,540)
Equity in other comprehensive loss of an equity method investee	(184)	(264)
Dividends/distributions payable	30,219	30,178
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	$ 349	$ 739

Organization

Organization	6 Months Ended
	Jun. 30, 2016
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 United States Government agencies and their 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 complementary portfolio of traditional office properties located in select urban/urban-like submarkets within our regional footprint with durable Class-A office fundamentals and characteristics, as well as other properties supporting general commercial office tenants (“Regional Office”). As of June 30, 2016 , our properties included the following: • 181 operating office properties totaling 18.4 million square feet, including 11 triple-net leased, single-tenant data center properties; • 12 office properties under, or contractually committed for, construction or redevelopment that we estimate will total approximately 1.5 million square feet upon completion, including two partially operational properties included above and two properties completed but held for future lease to the United States Government; • 1,379 acres of land we control that we believe could be developed into approximately 16.7 million square feet; and • a wholesale data center with a critical load of 19.25 megawatts. COPLP owns real estate both directly and through subsidiary partnerships and limited liability companies (“LLCs”). In addition to owning real estate, COPLP also owns subsidiaries that provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. Some of these services are performed by a taxable REIT subsidiary (“TRS”). Equity interests in COPLP are in the form of common and preferred units. As of June 30, 2016 , COPT owned 96.3% of the outstanding COPLP common units (“common units”) and 95.5% of the outstanding COPLP preferred units (“preferred units”); the remaining common and preferred units in COPLP were owned by third parties. Common units in COPLP not owned by COPT carry certain redemption rights. The number of common units in COPLP owned by COPT is equivalent to the number of outstanding common shares of beneficial interest (“common shares”) of COPT, and the entitlement of all COPLP common units to quarterly distributions and payments in liquidation is substantially the same as those of COPT common shareholders. Similarly, in the case of each series of preferred units in COPLP held by COPT, there is a series of preferred shares of beneficial interest (“preferred shares”) in COPT that is equivalent in number and carries substantially the same terms as such series of COPLP preferred units. COPT’s common shares are publicly traded on the New York Stock Exchange (“NYSE”) under the ticker symbol “OFC”. Because COPLP is managed by COPT, and COPT conducts substantially all of its operations through COPLP, we refer to COPT’s executive officers as COPLP’s executive officers, and although, as a partnership, COPLP does not have a board of trustees, we refer to COPT’s Board of Trustees as COPLP’s Board of Trustees.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2016
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. We use the cost method of accounting when we own an interest in an entity and cannot exert significant influence over its operations. 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, 2015 included in our 2015 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly present 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 2015 Annual Report on Form 10-K. Recent Accounting Pronouncements We adopted guidance issued by the Financial Accounting Standards Board (“FASB”) effective January 1, 2016 regarding the presentation of extraordinary and unusual items in statements of operations. This guidance eliminates the concept of extraordinary items. However, the presentation and disclosure requirements for items that are either unusual in nature or infrequent in occurrence remain and will be expanded to include items that are both unusual in nature and infrequent in occurrence. Our adoption of this guidance did not affect on our reported consolidated financial statements. We adopted guidance issued by the FASB effective January 1, 2016 modifying the analysis that must be performed by us in determining whether we should consolidate certain types of legal entities. The guidance did not amend the existing disclosure requirements for VIEs or voting interest model entities. The guidance, however, modified the requirements to qualify under the voting interest model. Under the revised guidance, COPLP is considered a variable interest entity of COPT. As COPLP was already consolidated in the balance sheets of COPT, the identification of COPLP as a variable interest entity had no impact on the consolidated financial statements. There were no other legal entities qualifying under the scope of the revised guidance that were consolidated as a result of the adoption. In addition, there were no voting interest entities under prior existing guidance determined to be variable interest entities under the revised guidance. We adopted effective January 1, 2016 guidance that eliminates the requirement to restate prior period financial statements for measurement period adjustments following a business combination. The guidance requires that the cumulative impact of a measurement period adjustment (including the impact on prior periods) be recognized in the reporting period in which the adjustment is identified. The prior period impact of the adjustment should be either presented separately on the face of the statement of operations or disclosed in the notes. Our adoption of this guidance did not affect our reported consolidated financial statements. In May 2014, the FASB issued guidance regarding the recognition of revenue from contracts with customers. Under this guidance, an entity will recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Additionally, this guidance requires improved disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. We are required to adopt this guidance for our annual and interim periods beginning January 1, 2018 using one of two methods: retrospective restatement for each reporting period presented at the time of adoption, or retrospectively with the cumulative effect of initially applying this guidance recognized at the date of initial application. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In February 2016, the FASB issued guidance that sets 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. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. The guidance requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. This guidance is effective for reporting periods beginning after December 15, 2018, with early adoption permitted. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In March 2016, the FASB issued guidance intended to simplify certain aspects of the accounting for employee based share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the consolidated statement of cash flows. This guidance is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. We are currently assessing the financial impact of this guidance on our consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Recurring Fair Value Measurements COPT has a non-qualified elective deferred compensation plan for 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 sheet using quoted market prices, as are other marketable securities that we hold. The balance of the plan, which was fully funded, totaled $5.0 million as of June 30, 2016 , and is included in the accompanying COPT consolidated balance sheets in the line entitled restricted cash and marketable securities. The offsetting liability associated with the plan is adjusted to fair value at the end of each accounting period based on the fair value of the plan assets and reported in other liabilities on COPT’s consolidated balance sheets. The assets of the plan and other marketable securities that we hold are classified in Level 1 of the fair value hierarchy. The liability associated with the plan is classified in Level 2 of the fair value hierarchy. The fair values of our interest rate derivatives are determined using widely accepted valuation techniques, including a discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate market data and implied volatilities in such interest rates. While we determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our interest rate derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default. However, as of June 30, 2016 , 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. As discussed in Note 6, we estimated the fair values of our investing receivables 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 8, we estimated the fair value of our unsecured senior notes based on quoted market rates for publicly-traded debt (categorized within Level 2 of the fair value hierarchy) and estimated the fair value of our other debt based on the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximate current market rates for loans, or groups of loans, with similar maturities and credit quality, and the estimated future payments include scheduled principal and interest payments. Fair value estimates are made as of a specific point in time, are subjective in nature and involve uncertainties and matters of significant judgment. Settlement at such fair value amounts may not be possible and may not be a prudent management decision. For additional fair value information, please refer to Note 6 for investing receivables, Note 8 for debt and Note 9 for interest rate derivatives. COPT and Subsidiaries The table below sets forth financial assets and liabilities of COPT and its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2016 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 Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,954 $ — $ — $ 4,954 Other 92 — — 92 Total assets $ 5,046 $ — $ — $ 5,046 Liabilities: Deferred compensation plan liability (2) $ — $ 5,046 $ — $ 5,046 Interest rate derivatives — 20,245 — 20,245 Total liabilities $ — $ 25,291 $ — $ 25,291 (1) Included in the line entitled “restricted cash and marketable securities” 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 its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2016 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 Total Liabilities: Interest rate derivatives $ — $ 20,245 $ — $ 20,245 Nonrecurring Fair Value Measurements During the second quarter of 2016, as part of our closing process, we conducted our quarterly review of our portfolio for indicators of impairment considering the refined investment strategy of our newly-appointed Chief Executive Officer and concluded that we would: (1) not hold our operating properties in Aberdeen, Maryland for the long-term; (2) sell specific properties in our Northern Virginia Defense/IT and Fort Meade/BW Corridor sub-segments; (3) not develop commercial properties on land in Frederick, Maryland; and (4) sell the remaining operating property in Greater Philadelphia that had not previously been classified as held for sale. Accordingly, we performed recoverability analyses for each of these properties and recorded the following impairment losses resulting from nonrecurring fair value measurements: • $34.4 million on operating properties in Aberdeen, Maryland (included in our Other segment). After shortening our estimated holding period for these properties, we determined that the carrying amount of the properties would not likely be recovered from the operation and eventual dispositions of the properties during the shortened holding period. Accordingly, we adjusted the properties to their estimated fair value; • $14.1 million on operating properties in our Northern Virginia Defense/IT and Fort Meade/BW Corridor sub-segments that we reclassified to held for sale during the period whose carrying amounts exceeded their estimated fair values less cost to sell; • $8.2 million on land in Frederick, Maryland. We determined that the carrying amount of the land would not likely be recovered from the sale of this property. Accordingly, we adjusted the land to its estimated fair value; • $6.2 million on a property in Greater Philadelphia (included in our Regional Office segment) that we reclassified to held for sale during the period whose carrying amounts exceeded its estimated fair value less cost to sell; and • $4.4 million on land in Aberdeen, Maryland. In performing our analysis related to the operating properties in Aberdeen, we determined that the weakening leasing and overall commercial real estate conditions in that market indicated that our land holdings in the market may be impaired. As a result, we determined that the carrying amount of the land was not recoverable and, accordingly, adjusted the land to its estimated fair value. During the six months ended June 30, 2016, we also recognized the following impairment losses resulting from nonrecurring fair value measurements: • $3.4 million (primarily in the three months ended March 31, 2016) on land in Colorado Springs, Colorado, the carrying amount of which exceeded the estimated fair value less costs to sell. Most of these losses pertained to land we decided to sell during the three months ended March 31, 2016 that was reclassified as held for sale, and the remainder was attributable to further decreases in fair value of properties previously classified as held for sale based on recent bids from and negotiations with prospective buyers; and • $1.4 million (primarily in the three months ended March 31, 2016) primarily on operating properties in White Marsh, Maryland (included in our Regional Office segment) classified as held for sale whose carrying amounts exceeded their estimated fair values less costs to sell based on recent negotiations with prospective buyers. The table below sets forth the fair value hierarchy of the valuation technique we used to determine nonrecurring fair value measurements of these assets as of June 30, 2016 (dollars in thousands): Fair Values as of June 30, 2016 Quoted Prices in Significant Active Markets for Significant Other Unobservable Identical Assets Observable Inputs Inputs Description (Level 1) (Level 2) (Level 3) Total Assets: Operating properties, net (1) $ — $ — $ 13,700 $ 13,700 Projects in development or held for future development (2) — — 9,117 9,117 Assets held for sale, net (3) — — 55,322 55,322 (1) Valuations were determined using a discounted cash flow model. Refer to table below for quantitative information about significant unobservable inputs used in the model. (2) Valuation was determined using the comparable sales approach. (3) Represents fair value less estimated costs to sell using contract prices or bids that were deemed indicative of fair value. The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above for operating properties as of June 30, 2016 : Unobservable Input Range (Weighted Average) Discount rate 11.0% to 12.0% (11.6%) Capitalization rate 9.0% to 10.0% (9.5%)

Properties, Net

Properties, Net	6 Months Ended
	Jun. 30, 2016
Real Estate [Abstract]
Properties, Net	Properties, Net Operating properties, net consisted of the following (in thousands): June 30, December 31, Land $ 455,355 $ 463,305 Buildings and improvements 3,005,802 3,157,587 Less: Accumulated depreciation (678,827 ) (700,363 ) Operating properties, net $ 2,782,330 $ 2,920,529 Projects in development or held for future development consisted of the following (in thousands): June 30, December 31, Land $ 209,202 $ 207,774 Development in progress, excluding land 178,195 221,445 Projects in development or held for future development $ 387,397 $ 429,219 Our properties held for sale included: • as of June 30, 2016 : 13 operating properties in White Marsh, Maryland (included in our Regional Office segment); four operating properties in Greater Philadelphia (included in our Regional Office segment); ten operating properties in our Fort Meade/BW Corridor sub-segment; two operating properties in San Antonio (included in our Other segment); one operating property in our Northern Virginia Defense/IT sub-segment; and land in Northern Virginia, Colorado Springs and Greater Philadelphia; and • as of December 31, 2015: 13 operating properties in White Marsh, Maryland (included in our Regional Office segment); two operating properties in San Antonio (included in our Other segment); and land in Northern Virginia and Colorado Springs. The table below sets forth the components of assets held for sale on our consolidated balance sheet for these properties (in thousands): June 30, 2016 December 31, 2015 Properties, net $ 269,008 $ 90,188 Deferred rent receivable 15,765 2,891 Intangible assets on real estate acquisitions, net 1,591 1,591 Deferred leasing costs, net 10,869 1,391 Lease incentives, net 3,351 721 Assets held for sale, net $ 300,584 $ 96,782 Acquisitions We acquired the following operating properties in 2015: • 250 W. Pratt Street, a 367,000 square foot office property in Baltimore, Maryland that was 96.2% leased, for $61.8 million on March 19, 2015; • 2600 Park Tower Drive, a 237,000 square foot office property in Vienna, Virginia (in the Northern Virginia region) that was 100% leased, for $80.5 million on April 15, 2015; and • 100 Light Street, a 558,000 square foot office property in Baltimore, Maryland that was 93.5% leased, and its structured parking garage, 30 Light Street, for $121.2 million on August 7, 2015. In connection with that acquisition, we assumed a $55.0 million mortgage loan with a fair value at assumption of $55.5 million . These properties contributed: • revenues of $9.2 million for the three months ended June 30, 2016, $4.0 million for the three months ended June 30, 2015, $18.4 million for the six months ended June 30, 2016 and $4.3 million for the six months ended June 30, 2015; and • net income from continuing operations of $1.1 million for the three months ended June 30, 2016, $40,000 for the three months ended June 30, 2015, $2.0 million for the six months ended June 30, 2016 and $210,000 for the six months ended June 30, 2015. We accounted for these acquisitions as business combinations. We included the results of operations for the acquisitions in our consolidated statements of operations from their respective purchase dates through June 30, 2016 . The following table presents pro forma information for COPT and subsidiaries as if these acquisitions had occurred on January 1, 2014. This pro forma information also includes adjustments to reclassify operating property acquisition costs to the six months ended June 30, 2014 from the 2015 periods in which they were actually incurred. The pro forma financial information was prepared for comparative purposes only and is not necessarily indicative of what would have occurred had these acquisitions been made at that time or of results which may occur in the future (in thousands, except per share amounts). For the Three Months Ended June 30, 2015 For the Six Months Ended June 30, 2015 (Unaudited) Pro forma total revenues $ 175,996 $ 345,921 Pro forma net income attributable to COPT common shareholders $ 13,259 $ 24,106 Pro forma EPS: Basic $ 0.14 $ 0.25 Diluted $ 0.14 $ 0.25 2016 Dispositions We sold land in the six months ended June 30, 2016 for $5.7 million , with no gain recognized. 2016 Construction Activities During the six months ended June 30, 2016 , we placed into service 298,000 square feet in two newly constructed office properties and 55,000 square feet in two redeveloped properties (including a partially operational property). As of June 30, 2016 , we had nine office properties under construction, or for which we were contractually committed to construct, that we estimate will total 1.4 million square feet upon completion (including two properties completed but held for future lease to the United States Government) and three office properties under redevelopment that we estimate will total 104,000 square feet upon completion.

Real Estate Joint Ventures

Real Estate Joint Ventures	6 Months Ended
	Jun. 30, 2016
Equity Method Investments and Joint Ventures [Abstract]
Real Estate Joint Ventures	Real Estate Joint Ventures The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of June 30, 2016 (dollars in thousands): Nominal Ownership June 30, 2016 (1) Date % as of Total Encumbered Total Acquired 6/30/2016 Nature of Activity Assets Assets Liabilities LW Redstone Company, LLC 3/23/2010 85% Development and operation of real estate (2) $ 151,416 $ 81,094 $ 52,362 M Square Associates, LLC 6/26/2007 50% Development and operation of real estate (3) 65,788 47,399 46,205 Stevens Investors, LLC 8/11/2015 95% Development of real estate (4) 38,859 — 7,446 $ 256,063 $ 128,493 $ 106,013 (1) Excludes amounts eliminated in consolidation. (2) This joint venture’s properties are in Huntsville, Alabama. (3) This joint venture’s properties are in College Park, Maryland. (4) This joint venture’s property is in Washington, DC. In January 2016, our partner in Stevens Investors, LLC contributed to the joint venture, for a value of $22.6 million , interests in contracts controlling land to be developed (including a purchase agreement and a ground lease). Our partner subsequently received a cash distribution from the joint venture of $13.4 million , which was funded by us. Our partner is also entitled to receive an additional distribution from the joint venture of $6.7 million to be funded by us (expected later in 2016 or 2017) that was reported in other liabilities on our consolidated balance sheet as of June 30, 2016 .

Investing Receivables

Investing Receivables	6 Months Ended
	Jun. 30, 2016
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables, including accrued interest thereon, consisted of the following (in thousands): June 30, December 31, Notes receivable from the City of Huntsville $ 47,142 $ 44,875 Other investing loans receivable 3,020 3,000 $ 50,162 $ 47,875 Our notes receivable from the City of Huntsville funded infrastructure costs in connection with our LW Redstone Company, LLC joint venture (see Note 5) and carry an interest rate of 9.95% . We did not have an allowance for credit losses in connection with our investing receivables as of June 30, 2016 or December 31, 2015 . The fair value of these receivables approximated their carrying amounts as of June 30, 2016 and December 31, 2015 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	6 Months Ended
	Jun. 30, 2016
Prepaid Expense and Other Assets [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets consisted of the following (in thousands): June 30, December 31, Prepaid expenses $ 10,301 $ 23,009 Lease incentives, net 7,873 11,133 Furniture, fixtures and equipment, net 5,686 6,004 Construction contract costs incurred in excess of billings 5,281 3,261 Deferred financing costs, net (1) 4,497 5,867 Deferred tax asset, net (2) 3,589 3,467 Other assets 6,132 7,283 Prepaid expenses and other assets, net $ 43,359 $ 60,024 (1) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (2) Includes a valuation allowance of $2.1 million .

Debt, Net

Debt, Net	6 Months Ended
	Jun. 30, 2016
Debt Disclosure [Abstract]
Debt, Net	Debt, Net Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of Scheduled Maturity June 30, December 31, Stated Interest Rates as of as of June 30, 2016 June 30, 2016 Mortgage and Other Secured Loans: Fixed rate mortgage loans (2) $ 318,243 $ 281,208 3.82% - 7.87% (3) 2016-2026 Variable rate secured loans 13,608 49,792 LIBOR + 1.85% (4) 2016-2020 Total mortgage and other secured loans 331,851 331,000 Revolving Credit Facility 58,000 43,500 LIBOR + 0.875% to 1.60% (5) May 2019 Term Loan Facilities (6) 516,508 515,902 LIBOR + 0.90% to 2.60% (7) 2019-2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 346,920 346,714 3.60% (8) May 2023 5.250%, $250,000 aggregate principal 245,951 245,731 5.25% (9) February 2024 3.700%, $300,000 aggregate principal 297,609 297,378 3.70% (10) June 2021 5.000%, $300,000 aggregate principal 296,192 296,019 5.00% (11) July 2025 Unsecured notes payable 1,455 1,508 0% (12) 2026 Total debt, net $ 2,094,486 $ 2,077,752 (1) The carrying values of our loans other than the Revolving Credit Facility reflect net deferred financing costs of $7.4 million as of June 30, 2016 and $8.0 million as of December 31, 2015 . (2) Several of the fixed rate mortgages carry interest rates that were above or below market rates upon assumption 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 $459,000 as of June 30, 2016 and $514,000 as of December 31, 2015 . (3) The weighted average interest rate on our fixed rate mortgage loans was 5.75% as of June 30, 2016 . (4) The interest rate on our variable rate secured loan as of June 30, 2016 was 2.31% . (5) The weighted average interest rate on the Revolving Credit Facility was 1.62% as of June 30, 2016 . (6) An additional $150 million in borrowings is available to be drawn under a term loan. In addition, we have the ability to borrow an additional $430.0 million in the aggregate under these term loan facilities, provided that there is no default under the facilities and subject to the approval of the lenders. (7) The weighted average interest rate on these loans was 2.10% as of June 30, 2016 . (8) The carrying value of these notes reflects an unamortized discount totaling $2.1 million as of June 30, 2016 and $2.2 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (9) The carrying value of these notes reflects an unamortized discount totaling $3.6 million as of June 30, 2016 and $3.8 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (10) The carrying value of these notes reflects an unamortized discount totaling $1.9 million as of June 30, 2016 and $2.1 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (11) The carrying value of these notes reflects an unamortized discount totaling $3.2 million as of June 30, 2016 and $3.3 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (12) These notes carry interest rates that were below market rates upon assumption and therefore were recorded at their fair value based on applicable effective interest rates. The carrying value of these notes reflects an unamortized discount totaling $506,000 as of June 30, 2016 and $554,000 as of December 31, 2015 . All debt is owed by the Operating Partnership. While COPT is not directly obligated by any debt, it has guaranteed the Operating Partnership’s Revolving Credit Facility, Term Loan Facilities and Unsecured Senior Notes. Certain of our debt instruments require that we comply with a number of restrictive financial covenants. As of June 30, 2016 , we were within the compliance requirements of these financial covenants. We capitalized interest costs of $1.3 million in the three months ended June 30, 2016 , $2.0 million in the three months ended June 30, 2015 , $3.1 million in the six months ended June 30, 2016 and $4.1 million in the six months ended June 30, 2015 . The following table sets forth information pertaining to the fair value of our debt (in thousands): June 30, 2016 December 31, 2015 Carrying Estimated Carrying Estimated Amount Fair Value Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,186,672 $ 1,227,235 $ 1,185,842 $ 1,211,658 Other fixed-rate debt 319,698 329,066 282,716 291,991 Variable-rate debt 588,116 592,032 609,194 610,987 $ 2,094,486 $ 2,148,333 $ 2,077,752 $ 2,114,636

Interest Rate Derivatives

Interest Rate Derivatives	6 Months Ended
	Jun. 30, 2016
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 (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date June 30, December 31, $ 100,000 0.8055% One-Month LIBOR 9/2/2014 9/1/2016 $ (58 ) $ (148 ) 100,000 0.8100% One-Month LIBOR 9/2/2014 9/1/2016 (59 ) (151 ) 100,000 1.6730% One-Month LIBOR 9/1/2015 8/1/2019 (3,117 ) (1,217 ) 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 (3,293 ) (1,429 ) 13,765 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 (337 ) 53 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (5,367 ) (138 ) 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (5,336 ) (45 ) 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (2,678 ) (32 ) $ (20,245 ) $ (3,107 ) (1) The notional amount of this instrument is scheduled to amortize to $12.1 million . Each of the interest rate swaps set forth in the table above was designated as a cash flow hedge of interest rate risk. The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location June 30, December 31, 2015 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets $ — $ 53 Interest rate swaps designated as cash flow hedges Interest rate derivatives (20,245 ) (3,160 ) The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Amount of (loss) gain recognized in accumulated other comprehensive loss (“AOCL”) (effective portion) $ (5,704 ) $ 392 $ (16,988 ) $ (3,082 ) Amount of losses reclassified from AOCL into interest expense (effective portion) 850 769 1,720 1,542 Amount of loss recognized in interest expense (ineffective portion) 319 — 1,870 — Over the next 12 months, we estimate that approximately $5.6 million of losses will be reclassified from 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. These agreements also incorporate the loan covenant provisions of our indebtedness with a lender affiliate of the derivative counterparties. Failure to comply with the loan covenant provisions could result in our being declared in default on any derivative instrument obligations covered by the agreements. As of June 30, 2016 , the fair value of interest rate derivatives in a liability position related to these agreements was $21.1 million , excluding the effects of accrued interest and credit valuation adjustments. As of June 30, 2016 , we had not posted any collateral related to these agreements. We are not in default with any of these provisions. If we breached any of these provisions, we could be required to settle our obligations under the agreements at their termination value of $21.4 million .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	6 Months Ended
	Jun. 30, 2016
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 5), 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 sheet. We determine the fair value of the interests based on unobservable inputs after considering the assumptions that market participants would make in pricing the interest. We apply a discount rate to the estimated future cash flows allocable to our partners from the properties underlying the respective joint ventures. Estimated cash flows used in such analyses are based on our plans for the properties and our views of market and economic conditions, and consider items such as current and future rental rates, occupancies for the properties and comparable properties and estimated operating and capital expenditures. The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Six Months Ended June 30, 2016 2015 Beginning balance $ 19,218 $ 18,417 Contributions from noncontrolling interests 22,778 — Distributions to noncontrolling interests (20,989 ) (885 ) Net income attributable to noncontrolling interests 1,117 1,143 Adjustment to arrive at fair value of interests 349 739 Ending balance $ 22,473 $ 19,414

Equity

Equity	6 Months Ended
	Jun. 30, 2016
Equity [Abstract]
Equity	Equity During the six months ended June 30, 2016 , certain COPLP limited partners redeemed 26,758 common units in COPLP for an equal number of common shares in COPT. See Note 13 for disclosure of COPT common share and COPLP common unit activity pertaining to our share-based compensation plans.

Information by Business Segment

Information by Business Segment	6 Months Ended
	Jun. 30, 2016
Segment Reporting [Abstract]
Information by Business Segment	Information by Business Segment Our segment reporting includes the following segments: Defense/IT Locations; Regional Office; our operating wholesale data center; and other. Our segment reporting also includes reporting for 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). We measure the performance of our segments through the measure we define as NOI from real estate operations, which is derived by subtracting property operating expenses from revenues from real estate operations. Operating Office 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 Operating Other Total Three Months Ended June 30, 2016 Revenues from real estate operations $ 60,912 $ 12,057 $ 11,651 $ 6,998 $ 3,191 $ 7,288 $ 102,097 $ 23,283 $ 6,804 $ 1,740 $ 133,924 Property operating expenses 20,378 4,307 6,844 2,675 960 826 35,990 8,721 2,651 779 48,141 NOI from real estate operations $ 40,534 $ 7,750 $ 4,807 $ 4,323 $ 2,231 $ 6,462 $ 66,107 $ 14,562 $ 4,153 $ 961 $ 85,783 Additions to long-lived assets $ 7,096 $ 3,059 $ — $ 2,233 $ 301 $ — $ 12,689 $ 2,180 $ — $ 153 $ 15,022 Transfers from non-operating properties $ 768 $ 27,944 $ 231 $ — $ 4 $ 29,857 $ 58,804 $ 26 $ (482 ) $ — $ 58,348 Three Months Ended June 30, 2015 — Revenues from real estate operations $ 60,007 $ 13,462 $ 9,743 $ 7,186 $ 2,658 $ 5,037 $ 98,093 $ 24,400 $ 3,820 $ 1,882 $ 128,195 Property operating expenses 19,480 5,354 5,349 3,390 888 499 34,960 8,406 2,221 820 46,407 NOI from real estate operations $ 40,527 $ 8,108 $ 4,394 $ 3,796 $ 1,770 $ 4,538 $ 63,133 $ 15,994 $ 1,599 $ 1,062 $ 81,788 Additions to long-lived assets $ 5,141 $ 83,913 $ — $ 1,769 $ 208 $ — $ 91,031 $ 3,396 $ 78 $ 210 $ 94,715 Transfers from non-operating properties $ 6,098 $ 7,735 $ 468 $ — $ 8,980 $ 911 $ 24,192 $ 5,218 $ 15,202 $ 12 $ 44,624 Six Months Ended June 30, 2016 Revenues from real estate operations $ 123,421 $ 24,173 $ 21,876 $ 13,932 $ 6,307 $ 13,618 $ 203,327 $ 46,785 $ 13,297 $ 3,602 $ 267,011 Property operating expenses 43,624 8,848 12,264 6,199 1,938 1,636 74,509 18,552 5,312 1,643 100,016 NOI from real estate operations $ 79,797 $ 15,325 $ 9,612 $ 7,733 $ 4,369 $ 11,982 $ 128,818 $ 28,233 $ 7,985 $ 1,959 $ 166,995 Additions to long-lived assets $ 13,615 $ 6,137 $ — $ 3,503 $ 919 $ — $ 24,174 $ 4,939 $ — $ 310 $ 29,423 Transfers from non-operating properties $ 36,519 $ 27,850 $ 237 $ — $ 215 $ 55,954 $ 120,775 $ 108 $ (431 ) $ (11 ) $ 120,441 Segment assets at June 30, 2016 $ 1,305,769 $ 424,441 $ 133,359 $ 195,195 $ 106,810 $ 256,276 $ 2,421,850 $ 594,750 $ 237,226 $ 35,291 $ 3,289,117 Six Months Ended June 30, 2015 Revenues from real estate operations $ 121,191 $ 24,508 $ 18,408 $ 14,451 $ 5,104 $ 10,151 $ 193,813 $ 46,360 $ 6,855 $ 3,877 $ 250,905 Property operating expenses 42,996 10,970 10,112 6,788 1,717 1,194 73,777 17,154 4,433 1,729 97,093 NOI from real estate operations $ 78,195 $ 13,538 $ 8,296 $ 7,663 $ 3,387 $ 8,957 $ 120,036 $ 29,206 $ 2,422 $ 2,148 $ 153,812 Additions to long-lived assets $ 8,586 $ 84,700 $ — $ 3,362 $ 291 $ — $ 96,939 $ 69,330 $ 108 $ 309 $ 166,686 Transfers from non-operating properties $ 19,028 $ 51,208 $ 31,559 $ — $ 11,977 $ 16,008 $ 129,780 $ 16,725 $ 15,379 $ 12 $ 161,896 Segment assets at June 30, 2015 $ 1,266,632 $ 499,601 $ 134,127 $ 194,764 $ 107,677 $ 170,006 $ 2,372,807 $ 598,030 $ 175,563 $ 72,257 $ 3,218,657 The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Segment revenues from real estate operations $ 133,924 $ 128,195 $ 267,011 $ 250,905 Construction contract and other service revenues 12,003 42,172 23,223 80,496 Less: Revenues from discontinued operations — (4 ) — (4 ) Total revenues $ 145,927 $ 170,363 $ 290,234 $ 331,397 The following table reconciles our segment property operating expenses to property operating expenses as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Segment property operating expenses $ 48,141 $ 46,407 $ 100,016 $ 97,093 Less: Property operating expenses from discontinued operations — 11 — 6 Total property operating expenses $ 48,141 $ 46,418 $ 100,016 $ 97,099 As previously discussed, we provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. The primary manner in which we evaluate the operating performance of our service activities is through a measure we define as net operating income from service operations (“NOI from service operations”), which is based on the net of revenues and expenses from these activities. Construction contract and other service revenues and expenses consist primarily of subcontracted costs that are reimbursed to us by the customer along with a management fee. The operating margins from these activities are small relative to the revenue. We believe NOI from service operations is a useful measure in assessing both our level of activity and our profitability in conducting such operations. The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Construction contract and other service revenues $ 12,003 $ 42,172 $ 23,223 $ 80,496 Construction contract and other service expenses (11,478 ) (41,293 ) (22,172 ) (78,791 ) NOI from service operations $ 525 $ 879 $ 1,051 $ 1,705 The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to income from continuing operations as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 NOI from real estate operations $ 85,783 $ 81,788 $ 166,995 $ 153,812 NOI from service operations 525 879 1,051 1,705 Interest and other income 1,330 1,242 2,486 2,525 Equity in income of unconsolidated entities 10 9 20 34 Income tax (expense) benefit (1 ) (50 ) 7 (105 ) Other adjustments: — — Depreciation and other amortization associated with real estate operations (33,248 ) (33,786 ) (67,775 ) (65,385 ) Impairment losses (69,692 ) (1,238 ) (72,138 ) (1,238 ) General, administrative and leasing expenses (8,026 ) (7,534 ) (19,909 ) (15,425 ) Business development expenses and land carry costs (2,363 ) (2,623 ) (4,781 ) (5,413 ) Interest expense (22,639 ) (21,768 ) (46,198 ) (42,606 ) NOI from discontinued operations — (15 ) — (10 ) Gain (loss) on early extinguishment of debt 5 (65 ) 22 (68 ) (Loss) income from continuing operations $ (48,316 ) $ 16,839 $ (40,220 ) $ 27,826 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): June 30, June 30, Segment assets $ 3,289,117 $ 3,218,657 Non-operating property assets 413,597 527,742 Other assets 138,978 157,660 Total COPT consolidated assets $ 3,841,692 $ 3,904,059 The accounting policies of the segments are the same as those used to prepare our consolidated financial statements, except that discontinued operations are not presented separately for segment purposes. In the segment reporting presented above, we did not allocate interest expense, depreciation and amortization, impairment losses, gain (loss) on early extinguishment of debt and gain on sales of real estate 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, equity in income of unconsolidated entities, income taxes and noncontrolling interests because these items represent general corporate or non-operating property items not attributable to segments.

Share-Based Compensation and Ot

Share-Based Compensation and Other Compensation Matters	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation and Other Compensation Matters	Share-Based Compensation and Other Compensation Matters Performance Share Units (“PSUs”) On March 1, 2016, our Board of Trustees granted 26,299 PSUs with an aggregate grant date fair value of $1.0 million to executives. The PSUs have a performance period beginning on January 1, 2016 and concluding on the earlier of December 31, 2018 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 PSUs earned (“earned PSUs”) 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 PSUs Payout % 75th or greater 200% of PSUs granted 50th or greater 100% of PSUs granted 25th 50% of PSUs granted Below 25th 0% of PSUs 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 PSUs will be interpolated between the ranges set forth in the table above to reflect any performance between the listed percentiles. At the end of the performance period, we, in settlement of the award, will issue a number of fully-vested COPT common shares equal to the sum of: • the number of earned PSUs in settlement of the award plan; plus • the aggregate dividends that would have been paid with respect to the common shares issued in settlement of the earned PSUs through the date of settlement had such shares been issued on the grant date, divided by the share price on such settlement date, as defined under the terms of the agreement. If a performance period ends due to a sale event or qualified termination, the number of earned PSUs 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 PSUs are forfeited. PSUs do not carry voting rights. We computed a grant date fair value of $38.21 per PSU using a Monte Carlo model, which included assumptions of, among other things, the following: baseline common share value of $23.90 ; expected volatility for COPT common shares of 20.4% ; and a risk-free interest rate of 0.96% . We are recognizing the grant date fair value in connection with these PSU awards over the period commencing on March 1, 2016 and ending on December 31, 2018. Based on COPT’s total shareholder return relative to its peer group of companies, for PSUs issued in 2014 and 2015 to Mr. Wayne H. Lingafelter, our former Executive Vice President, Development & Construction Services, who departed on March 31, 2016, we issued 10,326 common shares on May 30, 2016 in settlement of such PSUs. Restricted Shares During the six months ended June 30, 2016 , certain employees were granted a total of 197,087 restricted common shares with an aggregate grant date fair value of $4.8 million (weighted average of $24.11 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 employees remain employed by us. During the six months ended June 30, 2016 , forfeiture restrictions lapsed on 159,171 previously issued common shares; these shares had a weighted average grant date fair value of $27.62 per share, and the aggregate intrinsic value of the shares on the vesting dates was $3.8 million . Deferred Share Awards During the six months ended June 30, 2016 , nonemployee members of our Board of Trustees were granted a total of 24,944 deferred share awards with an aggregate grant date fair value of $671,000 ( $26.89 per share). Deferred share awards vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. We settle deferred share awards by issuing an equivalent number of common shares upon vesting of the awards or a later date elected by the Trustee (generally upon cessation of being a Trustee). During the six months ended June 30, 2016 , we issued 12,028 common shares in settlement of deferred share awards granted in 2015; these shares had a grant date fair value of $26.70 per share, and the aggregate intrinsic value of the shares on the settlement date was $322,000 . Executive Transition Costs Our Board of Trustees appointed Stephen E. Budorick, our Executive Vice President and Chief Operating Officer since September 2011, to become our President and Chief Executive Officer effective May 12, 2016, the date of the Company’s 2016 Annual Meeting of Shareholders. On that date, Roger A. Waesche, Jr., our current President and Chief Executive Officer, left the Company to pursue other interests, and he was not nominated for reelection as a Trustee. The Board appointed Mr. Budorick to our Board of Trustees after the 2016 Annual Meeting of Shareholders. In addition, our Executive Vice President, Development & Construction Services, Wayne H. Lingafelter, departed the Company to pursue other interests effective March 31, 2016. We recognized executive transition costs of approximately $4.4 million in the six months ended June 30, 2016 primarily in connection with the departure of Mr. Waesche and Mr. Lingafelter.

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	6 Months Ended
	Jun. 30, 2016
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 COPT common shares were converted; and (2) the effect of dilutive potential common shares outstanding during the period attributable to 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 added to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (48,316 ) $ 16,839 $ (40,220 ) $ 27,826 Gain on sales of real estate, net — (1 ) — 3,985 Preferred share dividends (3,553 ) (3,553 ) (7,105 ) (7,105 ) Loss (income) from continuing operations attributable to noncontrolling interests 897 (1,436 ) (373 ) (2,828 ) Income from continuing operations attributable to share-based compensation awards (96 ) (113 ) (214 ) (235 ) Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders $ (51,068 ) $ 11,736 $ (47,912 ) $ 21,643 Discontinued operations — 394 — 156 Discontinued operations attributable to noncontrolling interests — (15 ) — (3 ) Numerator for basic and diluted EPS on net income attributable to COPT common shareholders $ (51,068 ) $ 12,115 $ (47,912 ) $ 21,796 Denominator (all weighted averages): Denominator for basic EPS (common shares) 94,300 94,128 94,251 93,666 Dilutive effect of share-based compensation awards — 35 — 114 Denominator for diluted EPS (common shares) 94,300 94,163 94,251 93,780 Basic EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Diluted EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Conversion of common units 3,676 3,680 3,676 3,706 Conversion of Series I Preferred Units 176 176 176 176 Conversion of Series K Preferred Shares 434 434 434 434 The following share-based compensation securities were excluded from the computation of diluted EPS because their effects were antidilutive: • weighted average restricted shares and deferred share awards for the three months ended June 30, 2016 and 2015 of 403,000 and 426,000 , respectively, and for the six months ended June 30, 2016 and 2015 of 404,000 and 413,000 , respectively; and • weighted average options for the three months ended June 30, 2016 and 2015 of 309,000 and 473,000 , respectively, and for the six months ended June 30, 2016 and 2015 of 344,000 and 472,000 , respectively. We had outstanding senior notes, which we redeemed in April 2015, with an exchange settlement feature, but such notes did not affect our diluted EPS reported above since the weighted average closing price of COPT’s common shares during each of the periods was less than the exchange prices per common share applicable for such periods. 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 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 added to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (48,316 ) $ 16,839 $ (40,220 ) $ 27,826 Gain on sales of real estate, net — (1 ) — 3,985 Preferred unit distributions (3,718 ) (3,718 ) (7,435 ) (7,435 ) Income from continuing operations attributable to noncontrolling interests (911 ) (812 ) (1,890 ) (1,633 ) Income from continuing operations attributable to share-based compensation awards (96 ) (113 ) (214 ) (235 ) Numerator for basic and diluted EPU from continuing operations attributable to COPLP common unitholders $ (53,041 ) $ 12,195 $ (49,759 ) $ 22,508 Discontinued operations — 394 — 156 Discontinued operations attributable to noncontrolling interests — — — 3 Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ (53,041 ) $ 12,589 $ (49,759 ) $ 22,667 Denominator (all weighted averages): Denominator for basic EPU (common units) 97,976 97,808 97,927 97,372 Dilutive effect of share-based compensation awards — 35 — 114 Denominator for diluted EPU (common units) 97,976 97,843 97,927 97,486 Basic EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Diluted EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Units Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Conversion of Series I preferred units 176 176 176 176 Conversion of Series K preferred units 434 434 434 434 The following share-based compensation securities were excluded from the computation of diluted EPU because their effects were antidilutive: • weighted average restricted units and deferred share awards for the three months ended June 30, 2016 and 2015 of 403,000 and 426,000 , respectively, and for the six months ended June 30, 2016 and 2015 of 404,000 and 413,000 , respectively; and • weighted average options for the three months ended June 30, 2016 and 2015 of 309,000 and 473,000 , respectively, and for the six months ended June 30, 2016 and 2015 of 344,000 and 472,000 , respectively. We had outstanding senior notes, which we redeemed in April 2015, with an exchange settlement feature, but such notes did not affect our diluted EPU reported above since the weighted average closing price of COPT’s common shares during each of the periods was less than the exchange prices per common share applicable for such periods.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation In the normal course of business, we are involved in legal actions arising from our ownership and administration of properties. We establish reserves for specific legal proceedings when we determine that the likelihood of an unfavorable outcome is probable and the amount of loss can be reasonably estimated. Management does not anticipate that any liabilities that may result from such proceedings will have a materially adverse effect on our financial position, operations or liquidity. 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. Tax Incremental Financing Obligation In August 2010, Anne Arundel County, Maryland issued $30 million in tax incremental financing bonds to third-party investors in order to finance public improvements needed in connection with our project known as National Business Park North. The real estate taxes on increases in assessed value of a development district encompassing National Business Park North are to be transferred to a special fund pledged to the repayment of the bonds. We recognized a $1.9 million liability through June 30, 2016 representing our estimated obligation to fund through a special tax any future shortfalls between debt service on the bonds and real estate taxes available to repay the bonds. Operating Leases We are obligated as lessee under operating leases (mostly ground leases) with various expiration dates extending to the year 2100. Future minimum rental payments due under the terms of these operating leases as of June 30, 2016 follow (in thousands): Year Ending December 31, 2016 (1) $ 603 2017 1,139 2018 1,092 2019 1,067 2020 1,084 Thereafter 86,805 $ 91,790 (1) Represents six months ending December 31, 2016. Contractual Obligations We had amounts remaining to be incurred under various contractual obligations as of June 30, 2016 that included the following: • new development and redevelopment obligations of $78.8 million ; • capital expenditures for operating properties of $48.7 million ; • third party construction and development of $17.3 million ; and • purchase obligations of $2.5 million . Environmental Indemnity Agreement 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. The prior owner of the properties, a Fortune 100 company that is responsible for groundwater contamination at such properties, previously agreed to indemnify us for (1) direct losses incurred in connection with the contamination and (2) its failure to perform remediation activities required by the State of New Jersey, up to the point that the state declares the remediation to be complete. Under the environmental indemnification agreement, we agreed to the following: • to indemnify the tenant against losses covered under the prior owner’s indemnity agreement if the prior owner fails to indemnify the tenant for such losses. This indemnification is capped at $5.0 million in perpetuity after the State of New Jersey declares the remediation to be complete; • to indemnify the tenant for consequential damages (e.g., business interruption) at one of the buildings in perpetuity and another of the buildings through 2025. This indemnification is limited to $12.5 million ; and • to pay 50% of additional costs related to construction and environmental regulatory activities incurred by the tenant as a result of the indemnified environmental condition of the properties. This indemnification is limited to $300,000 annually and $1.5 million in the aggregate.

Subsequent Event

Subsequent Event	6 Months Ended
	Jun. 30, 2016
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event On July 21, 2016, we sold a 50% interest in six triple-net leased, single-tenant data center properties by contributing them into a newly-formed joint venture for a property value of $147.6 million . We obtained $60 million in non-recourse mortgage loans on the properties through the joint venture immediately prior to the sale of our interest and received the net proceeds. Our partner in the joint venture acquired the 50% interest in the joint venture from us for $44 million . We will account for our 50% interest in the joint venture using the equity method of accounting. Due to our continuing involvement in the properties through the joint venture, we recognized a partial gain on the sale of our interest of approximately $18 million .

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2016
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. We use the cost method of accounting when we own an interest in an entity and cannot exert significant influence over its operations. 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, 2015 included in our 2015 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly present 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 2015 Annual Report on Form 10-K.
Recent Accounting Pronouncement	Recent Accounting Pronouncements We adopted guidance issued by the Financial Accounting Standards Board (“FASB”) effective January 1, 2016 regarding the presentation of extraordinary and unusual items in statements of operations. This guidance eliminates the concept of extraordinary items. However, the presentation and disclosure requirements for items that are either unusual in nature or infrequent in occurrence remain and will be expanded to include items that are both unusual in nature and infrequent in occurrence. Our adoption of this guidance did not affect on our reported consolidated financial statements. We adopted guidance issued by the FASB effective January 1, 2016 modifying the analysis that must be performed by us in determining whether we should consolidate certain types of legal entities. The guidance did not amend the existing disclosure requirements for VIEs or voting interest model entities. The guidance, however, modified the requirements to qualify under the voting interest model. Under the revised guidance, COPLP is considered a variable interest entity of COPT. As COPLP was already consolidated in the balance sheets of COPT, the identification of COPLP as a variable interest entity had no impact on the consolidated financial statements. There were no other legal entities qualifying under the scope of the revised guidance that were consolidated as a result of the adoption. In addition, there were no voting interest entities under prior existing guidance determined to be variable interest entities under the revised guidance. We adopted effective January 1, 2016 guidance that eliminates the requirement to restate prior period financial statements for measurement period adjustments following a business combination. The guidance requires that the cumulative impact of a measurement period adjustment (including the impact on prior periods) be recognized in the reporting period in which the adjustment is identified. The prior period impact of the adjustment should be either presented separately on the face of the statement of operations or disclosed in the notes. Our adoption of this guidance did not affect our reported consolidated financial statements. In May 2014, the FASB issued guidance regarding the recognition of revenue from contracts with customers. Under this guidance, an entity will recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Additionally, this guidance requires improved disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. We are required to adopt this guidance for our annual and interim periods beginning January 1, 2018 using one of two methods: retrospective restatement for each reporting period presented at the time of adoption, or retrospectively with the cumulative effect of initially applying this guidance recognized at the date of initial application. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In February 2016, the FASB issued guidance that sets 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. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. The guidance requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. This guidance is effective for reporting periods beginning after December 15, 2018, with early adoption permitted. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In March 2016, the FASB issued guidance intended to simplify certain aspects of the accounting for employee based share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the consolidated statement of cash flows. This guidance is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. We are currently assessing the financial impact of this guidance on our consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2016
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 its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2016 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 Total Liabilities: Interest rate derivatives $ — $ 20,245 $ — $ 20,245 The table below sets forth financial assets and liabilities of COPT and its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2016 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 Total Assets: Marketable securities in deferred compensation plan (1) Mutual funds $ 4,954 $ — $ — $ 4,954 Other 92 — — 92 Total assets $ 5,046 $ — $ — $ 5,046 Liabilities: Deferred compensation plan liability (2) $ — $ 5,046 $ — $ 5,046 Interest rate derivatives — 20,245 — 20,245 Total liabilities $ — $ 25,291 $ — $ 25,291 (1) Included in the line entitled “restricted cash and marketable securities” on COPT’s consolidated balance sheet. (2) Included in the line entitled “other liabilities” on COPT’s consolidated balance sheet.
Schedule of fair value hierarchy of impaired properties and other assets associated with such properties	The table below sets forth the fair value hierarchy of the valuation technique we used to determine nonrecurring fair value measurements of these assets as of June 30, 2016 (dollars in thousands): Fair Values as of June 30, 2016 Quoted Prices in Significant Active Markets for Significant Other Unobservable Identical Assets Observable Inputs Inputs Description (Level 1) (Level 2) (Level 3) Total Assets: Operating properties, net (1) $ — $ — $ 13,700 $ 13,700 Projects in development or held for future development (2) — — 9,117 9,117 Assets held for sale, net (3) — — 55,322 55,322 (1) Valuations were determined using a discounted cash flow model. Refer to table below for quantitative information about significant unobservable inputs used in the model. (2) Valuation was determined using the comparable sales approach. (3) Represents fair value less estimated costs to sell using contract prices or bids that were deemed indicative of fair value.
Schedule of quantitative information about significant unobservable inputs used for Level 3 fair value measurements	The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above for operating properties as of June 30, 2016 : Unobservable Input Range (Weighted Average) Discount rate 11.0% to 12.0% (11.6%) Capitalization rate 9.0% to 10.0% (9.5%)

Properties, Net (Tables)

Properties, Net (Tables)	6 Months Ended
	Jun. 30, 2016
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): June 30, December 31, Land $ 455,355 $ 463,305 Buildings and improvements 3,005,802 3,157,587 Less: Accumulated depreciation (678,827 ) (700,363 ) Operating properties, net $ 2,782,330 $ 2,920,529
Schedule of projects in development or held for future development	Projects in development or held for future development consisted of the following (in thousands): June 30, December 31, Land $ 209,202 $ 207,774 Development in progress, excluding land 178,195 221,445 Projects in development or held for future development $ 387,397 $ 429,219
Components of assets held for sale	The table below sets forth the components of assets held for sale on our consolidated balance sheet for these properties (in thousands): June 30, 2016 December 31, 2015 Properties, net $ 269,008 $ 90,188 Deferred rent receivable 15,765 2,891 Intangible assets on real estate acquisitions, net 1,591 1,591 Deferred leasing costs, net 10,869 1,391 Lease incentives, net 3,351 721 Assets held for sale, net $ 300,584 $ 96,782
Pro Forma results	The pro forma financial information was prepared for comparative purposes only and is not necessarily indicative of what would have occurred had these acquisitions been made at that time or of results which may occur in the future (in thousands, except per share amounts). For the Three Months Ended June 30, 2015 For the Six Months Ended June 30, 2015 (Unaudited) Pro forma total revenues $ 175,996 $ 345,921 Pro forma net income attributable to COPT common shareholders $ 13,259 $ 24,106 Pro forma EPS: Basic $ 0.14 $ 0.25 Diluted $ 0.14 $ 0.25

Real Estate Joint Ventures (Tab

Real Estate Joint Ventures (Tables)	6 Months Ended
	Jun. 30, 2016
Equity Method Investments and Joint Ventures [Abstract]
Schedule of information related to investments in consolidated real estate joint ventures	The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of June 30, 2016 (dollars in thousands): Nominal Ownership June 30, 2016 (1) Date % as of Total Encumbered Total Acquired 6/30/2016 Nature of Activity Assets Assets Liabilities LW Redstone Company, LLC 3/23/2010 85% Development and operation of real estate (2) $ 151,416 $ 81,094 $ 52,362 M Square Associates, LLC 6/26/2007 50% Development and operation of real estate (3) 65,788 47,399 46,205 Stevens Investors, LLC 8/11/2015 95% Development of real estate (4) 38,859 — 7,446 $ 256,063 $ 128,493 $ 106,013 (1) Excludes amounts eliminated in consolidation. (2) This joint venture’s properties are in Huntsville, Alabama. (3) This joint venture’s properties are in College Park, Maryland. (4) This joint venture’s property is in Washington, DC.

Investing Receivables (Tables)

Investing Receivables (Tables)	6 Months Ended
	Jun. 30, 2016
Receivables [Abstract]
Schedule of investing receivables	Investing receivables, including accrued interest thereon, consisted of the following (in thousands): June 30, December 31, Notes receivable from the City of Huntsville $ 47,142 $ 44,875 Other investing loans receivable 3,020 3,000 $ 50,162 $ 47,875

Prepaid Expenses and Other As30

Prepaid Expenses and Other Assets, Net (Tables)	6 Months Ended
	Jun. 30, 2016
Prepaid Expense and Other Assets [Abstract]
Schedule of prepaid expenses and other assets	Prepaid expenses and other assets consisted of the following (in thousands): June 30, December 31, Prepaid expenses $ 10,301 $ 23,009 Lease incentives, net 7,873 11,133 Furniture, fixtures and equipment, net 5,686 6,004 Construction contract costs incurred in excess of billings 5,281 3,261 Deferred financing costs, net (1) 4,497 5,867 Deferred tax asset, net (2) 3,589 3,467 Other assets 6,132 7,283 Prepaid expenses and other assets, net $ 43,359 $ 60,024 (1) Represents deferred costs, net of accumulated amortization, attributable to our Revolving Credit Facility and interest rate derivatives. (2) Includes a valuation allowance of $2.1 million .

Debt, Net (Tables)

Debt, Net (Tables)	6 Months Ended
	Jun. 30, 2016
Debt Disclosure [Abstract]
Schedule of debt	Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of Scheduled Maturity June 30, December 31, Stated Interest Rates as of as of June 30, 2016 June 30, 2016 Mortgage and Other Secured Loans: Fixed rate mortgage loans (2) $ 318,243 $ 281,208 3.82% - 7.87% (3) 2016-2026 Variable rate secured loans 13,608 49,792 LIBOR + 1.85% (4) 2016-2020 Total mortgage and other secured loans 331,851 331,000 Revolving Credit Facility 58,000 43,500 LIBOR + 0.875% to 1.60% (5) May 2019 Term Loan Facilities (6) 516,508 515,902 LIBOR + 0.90% to 2.60% (7) 2019-2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 346,920 346,714 3.60% (8) May 2023 5.250%, $250,000 aggregate principal 245,951 245,731 5.25% (9) February 2024 3.700%, $300,000 aggregate principal 297,609 297,378 3.70% (10) June 2021 5.000%, $300,000 aggregate principal 296,192 296,019 5.00% (11) July 2025 Unsecured notes payable 1,455 1,508 0% (12) 2026 Total debt, net $ 2,094,486 $ 2,077,752 (1) The carrying values of our loans other than the Revolving Credit Facility reflect net deferred financing costs of $7.4 million as of June 30, 2016 and $8.0 million as of December 31, 2015 . (2) Several of the fixed rate mortgages carry interest rates that were above or below market rates upon assumption 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 $459,000 as of June 30, 2016 and $514,000 as of December 31, 2015 . (3) The weighted average interest rate on our fixed rate mortgage loans was 5.75% as of June 30, 2016 . (4) The interest rate on our variable rate secured loan as of June 30, 2016 was 2.31% . (5) The weighted average interest rate on the Revolving Credit Facility was 1.62% as of June 30, 2016 . (6) An additional $150 million in borrowings is available to be drawn under a term loan. In addition, we have the ability to borrow an additional $430.0 million in the aggregate under these term loan facilities, provided that there is no default under the facilities and subject to the approval of the lenders. (7) The weighted average interest rate on these loans was 2.10% as of June 30, 2016 . (8) The carrying value of these notes reflects an unamortized discount totaling $2.1 million as of June 30, 2016 and $2.2 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (9) The carrying value of these notes reflects an unamortized discount totaling $3.6 million as of June 30, 2016 and $3.8 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (10) The carrying value of these notes reflects an unamortized discount totaling $1.9 million as of June 30, 2016 and $2.1 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (11) The carrying value of these notes reflects an unamortized discount totaling $3.2 million as of June 30, 2016 and $3.3 million as of December 31, 2015 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . (12) These notes carry interest rates that were below market rates upon assumption and therefore were recorded at their fair value based on applicable effective interest rates. The carrying value of these notes reflects an unamortized discount totaling $506,000 as of June 30, 2016 and $554,000 as of December 31, 2015 .
Schedule of the fair value of debt	The following table sets forth information pertaining to the fair value of our debt (in thousands): June 30, 2016 December 31, 2015 Carrying Estimated Carrying Estimated Amount Fair Value Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,186,672 $ 1,227,235 $ 1,185,842 $ 1,211,658 Other fixed-rate debt 319,698 329,066 282,716 291,991 Variable-rate debt 588,116 592,032 609,194 610,987 $ 2,094,486 $ 2,148,333 $ 2,077,752 $ 2,114,636

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	6 Months Ended
	Jun. 30, 2016
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 (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date June 30, December 31, $ 100,000 0.8055% One-Month LIBOR 9/2/2014 9/1/2016 $ (58 ) $ (148 ) 100,000 0.8100% One-Month LIBOR 9/2/2014 9/1/2016 (59 ) (151 ) 100,000 1.6730% One-Month LIBOR 9/1/2015 8/1/2019 (3,117 ) (1,217 ) 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 (3,293 ) (1,429 ) 13,765 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 (337 ) 53 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (5,367 ) (138 ) 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (5,336 ) (45 ) 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (2,678 ) (32 ) $ (20,245 ) $ (3,107 ) (1) The notional amount of this instrument is scheduled to amortize to $12.1 million .
Schedule of fair value and balance sheet classification of interest rate derivatives	The table below sets forth the fair value of our interest rate derivatives as well as their classification on our consolidated balance sheets (in thousands): Fair Value at Derivatives Balance Sheet Location June 30, December 31, 2015 Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets $ — $ 53 Interest rate swaps designated as cash flow hedges Interest rate derivatives (20,245 ) (3,160 )
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): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Amount of (loss) gain recognized in accumulated other comprehensive loss (“AOCL”) (effective portion) $ (5,704 ) $ 392 $ (16,988 ) $ (3,082 ) Amount of losses reclassified from AOCL into interest expense (effective portion) 850 769 1,720 1,542 Amount of loss recognized in interest expense (ineffective portion) 319 — 1,870 —

Redeemable Noncontrolling Int33

Redeemable Noncontrolling Interests (Tables)	6 Months Ended
	Jun. 30, 2016
Noncontrolling Interest [Abstract]
Schedule of activity for redeemable noncontrolling interest	The table below sets forth the activity for these redeemable noncontrolling interests (in thousands): For the Six Months Ended June 30, 2016 2015 Beginning balance $ 19,218 $ 18,417 Contributions from noncontrolling interests 22,778 — Distributions to noncontrolling interests (20,989 ) (885 ) Net income attributable to noncontrolling interests 1,117 1,143 Adjustment to arrive at fair value of interests 349 739 Ending balance $ 22,473 $ 19,414

Information by Business Segme34

Information by Business Segment (Tables)	6 Months Ended
	Jun. 30, 2016
Segment Reporting [Abstract]
Schedule of segment financial information for real estate operations	Operating Office 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 Operating Other Total Three Months Ended June 30, 2016 Revenues from real estate operations $ 60,912 $ 12,057 $ 11,651 $ 6,998 $ 3,191 $ 7,288 $ 102,097 $ 23,283 $ 6,804 $ 1,740 $ 133,924 Property operating expenses 20,378 4,307 6,844 2,675 960 826 35,990 8,721 2,651 779 48,141 NOI from real estate operations $ 40,534 $ 7,750 $ 4,807 $ 4,323 $ 2,231 $ 6,462 $ 66,107 $ 14,562 $ 4,153 $ 961 $ 85,783 Additions to long-lived assets $ 7,096 $ 3,059 $ — $ 2,233 $ 301 $ — $ 12,689 $ 2,180 $ — $ 153 $ 15,022 Transfers from non-operating properties $ 768 $ 27,944 $ 231 $ — $ 4 $ 29,857 $ 58,804 $ 26 $ (482 ) $ — $ 58,348 Three Months Ended June 30, 2015 — Revenues from real estate operations $ 60,007 $ 13,462 $ 9,743 $ 7,186 $ 2,658 $ 5,037 $ 98,093 $ 24,400 $ 3,820 $ 1,882 $ 128,195 Property operating expenses 19,480 5,354 5,349 3,390 888 499 34,960 8,406 2,221 820 46,407 NOI from real estate operations $ 40,527 $ 8,108 $ 4,394 $ 3,796 $ 1,770 $ 4,538 $ 63,133 $ 15,994 $ 1,599 $ 1,062 $ 81,788 Additions to long-lived assets $ 5,141 $ 83,913 $ — $ 1,769 $ 208 $ — $ 91,031 $ 3,396 $ 78 $ 210 $ 94,715 Transfers from non-operating properties $ 6,098 $ 7,735 $ 468 $ — $ 8,980 $ 911 $ 24,192 $ 5,218 $ 15,202 $ 12 $ 44,624 Six Months Ended June 30, 2016 Revenues from real estate operations $ 123,421 $ 24,173 $ 21,876 $ 13,932 $ 6,307 $ 13,618 $ 203,327 $ 46,785 $ 13,297 $ 3,602 $ 267,011 Property operating expenses 43,624 8,848 12,264 6,199 1,938 1,636 74,509 18,552 5,312 1,643 100,016 NOI from real estate operations $ 79,797 $ 15,325 $ 9,612 $ 7,733 $ 4,369 $ 11,982 $ 128,818 $ 28,233 $ 7,985 $ 1,959 $ 166,995 Additions to long-lived assets $ 13,615 $ 6,137 $ — $ 3,503 $ 919 $ — $ 24,174 $ 4,939 $ — $ 310 $ 29,423 Transfers from non-operating properties $ 36,519 $ 27,850 $ 237 $ — $ 215 $ 55,954 $ 120,775 $ 108 $ (431 ) $ (11 ) $ 120,441 Segment assets at June 30, 2016 $ 1,305,769 $ 424,441 $ 133,359 $ 195,195 $ 106,810 $ 256,276 $ 2,421,850 $ 594,750 $ 237,226 $ 35,291 $ 3,289,117 Six Months Ended June 30, 2015 Revenues from real estate operations $ 121,191 $ 24,508 $ 18,408 $ 14,451 $ 5,104 $ 10,151 $ 193,813 $ 46,360 $ 6,855 $ 3,877 $ 250,905 Property operating expenses 42,996 10,970 10,112 6,788 1,717 1,194 73,777 17,154 4,433 1,729 97,093 NOI from real estate operations $ 78,195 $ 13,538 $ 8,296 $ 7,663 $ 3,387 $ 8,957 $ 120,036 $ 29,206 $ 2,422 $ 2,148 $ 153,812 Additions to long-lived assets $ 8,586 $ 84,700 $ — $ 3,362 $ 291 $ — $ 96,939 $ 69,330 $ 108 $ 309 $ 166,686 Transfers from non-operating properties $ 19,028 $ 51,208 $ 31,559 $ — $ 11,977 $ 16,008 $ 129,780 $ 16,725 $ 15,379 $ 12 $ 161,896 Segment assets at June 30, 2015 $ 1,266,632 $ 499,601 $ 134,127 $ 194,764 $ 107,677 $ 170,006 $ 2,372,807 $ 598,030 $ 175,563 $ 72,257 $ 3,218,657
Schedule of reconciliation of segment revenues to total revenues	The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Segment revenues from real estate operations $ 133,924 $ 128,195 $ 267,011 $ 250,905 Construction contract and other service revenues 12,003 42,172 23,223 80,496 Less: Revenues from discontinued operations — (4 ) — (4 ) Total revenues $ 145,927 $ 170,363 $ 290,234 $ 331,397
Schedule of reconciliation of segment property operating expenses to total property operating expenses	The following table reconciles our segment property operating expenses to property operating expenses as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Segment property operating expenses $ 48,141 $ 46,407 $ 100,016 $ 97,093 Less: Property operating expenses from discontinued operations — 11 — 6 Total property operating expenses $ 48,141 $ 46,418 $ 100,016 $ 97,099
Schedule of computation of net operating income from service operations	The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Construction contract and other service revenues $ 12,003 $ 42,172 $ 23,223 $ 80,496 Construction contract and other service expenses (11,478 ) (41,293 ) (22,172 ) (78,791 ) NOI from service operations $ 525 $ 879 $ 1,051 $ 1,705
Schedule of reconciliation of net operating income from real estate operations and service operations to (loss) income from continuing operations	The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to income from continuing operations as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 NOI from real estate operations $ 85,783 $ 81,788 $ 166,995 $ 153,812 NOI from service operations 525 879 1,051 1,705 Interest and other income 1,330 1,242 2,486 2,525 Equity in income of unconsolidated entities 10 9 20 34 Income tax (expense) benefit (1 ) (50 ) 7 (105 ) Other adjustments: — — Depreciation and other amortization associated with real estate operations (33,248 ) (33,786 ) (67,775 ) (65,385 ) Impairment losses (69,692 ) (1,238 ) (72,138 ) (1,238 ) General, administrative and leasing expenses (8,026 ) (7,534 ) (19,909 ) (15,425 ) Business development expenses and land carry costs (2,363 ) (2,623 ) (4,781 ) (5,413 ) Interest expense (22,639 ) (21,768 ) (46,198 ) (42,606 ) NOI from discontinued operations — (15 ) — (10 ) Gain (loss) on early extinguishment of debt 5 (65 ) 22 (68 ) (Loss) income from continuing operations $ (48,316 ) $ 16,839 $ (40,220 ) $ 27,826
Schedule of reconciliation of segment assets to total assets	The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): June 30, June 30, Segment assets $ 3,289,117 $ 3,218,657 Non-operating property assets 413,597 527,742 Other assets 138,978 157,660 Total COPT consolidated assets $ 3,841,692 $ 3,904,059

Share-Based Compensation and 35

Share-Based Compensation and Other Compensation Matters (Tables)	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of payouts for defined performance under performance-based awards of share-based compensation	The number of PSUs earned (“earned PSUs”) 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 PSUs Payout % 75th or greater 200% of PSUs granted 50th or greater 100% of PSUs granted 25th 50% of PSUs granted Below 25th 0% of PSUs granted

Earnings Per Share ("EPS") an36

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Tables)	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (48,316 ) $ 16,839 $ (40,220 ) $ 27,826 Gain on sales of real estate, net — (1 ) — 3,985 Preferred share dividends (3,553 ) (3,553 ) (7,105 ) (7,105 ) Loss (income) from continuing operations attributable to noncontrolling interests 897 (1,436 ) (373 ) (2,828 ) Income from continuing operations attributable to share-based compensation awards (96 ) (113 ) (214 ) (235 ) Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders $ (51,068 ) $ 11,736 $ (47,912 ) $ 21,643 Discontinued operations — 394 — 156 Discontinued operations attributable to noncontrolling interests — (15 ) — (3 ) Numerator for basic and diluted EPS on net income attributable to COPT common shareholders $ (51,068 ) $ 12,115 $ (47,912 ) $ 21,796 Denominator (all weighted averages): Denominator for basic EPS (common shares) 94,300 94,128 94,251 93,666 Dilutive effect of share-based compensation awards — 35 — 114 Denominator for diluted EPS (common shares) 94,300 94,163 94,251 93,780 Basic EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Diluted EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Conversion of common units 3,676 3,680 3,676 3,706 Conversion of Series I Preferred Units 176 176 176 176 Conversion of Series K Preferred Shares 434 434 434 434
Corporate Office Properties, L.P.
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (48,316 ) $ 16,839 $ (40,220 ) $ 27,826 Gain on sales of real estate, net — (1 ) — 3,985 Preferred unit distributions (3,718 ) (3,718 ) (7,435 ) (7,435 ) Income from continuing operations attributable to noncontrolling interests (911 ) (812 ) (1,890 ) (1,633 ) Income from continuing operations attributable to share-based compensation awards (96 ) (113 ) (214 ) (235 ) Numerator for basic and diluted EPU from continuing operations attributable to COPLP common unitholders $ (53,041 ) $ 12,195 $ (49,759 ) $ 22,508 Discontinued operations — 394 — 156 Discontinued operations attributable to noncontrolling interests — — — 3 Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ (53,041 ) $ 12,589 $ (49,759 ) $ 22,667 Denominator (all weighted averages): Denominator for basic EPU (common units) 97,976 97,808 97,927 97,372 Dilutive effect of share-based compensation awards — 35 — 114 Denominator for diluted EPU (common units) 97,976 97,843 97,927 97,486 Basic EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Diluted EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ (0.54 ) $ 0.13 $ (0.51 ) $ 0.23
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Units Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2016 2015 2016 2015 Conversion of Series I preferred units 176 176 176 176 Conversion of Series K preferred units 434 434 434 434

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Future minimum rental payments for operating leases	Future minimum rental payments due under the terms of these operating leases as of June 30, 2016 follow (in thousands): Year Ending December 31, 2016 (1) $ 603 2017 1,139 2018 1,092 2019 1,067 2020 1,084 Thereafter 86,805 $ 91,790 (1) Represents six months ending December 31, 2016.

Organization (Details)

Organization (Details) ft² in Thousands	Jun. 30, 2016ft²aPropertyMW
Properties under or approved for redevelopment
Investments in real estate
Number of real estate properties	3
Area of real estate property (in square feet or acres) | ft²	104
Operating office properties
Investments in real estate
Number of real estate properties	181
Area of real estate property (in square feet or acres) | ft²	18,400
Operating office properties | Single-tenant data centers
Investments in real estate
Number of real estate properties	11
Office properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties	12
Area of real estate property (in square feet or acres) | ft²	1,500
Office properties under, or contractually committed for, construction or approved for redevelopment | Properties completed Held-for-future lease
Investments in real estate
Number of real estate properties	2
Partially operational properties | Properties under or approved for redevelopment
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 square feet or acres) | a	1,379
Developable square feet | ft²	16,700
Wholesale data centers
Investments in real estate
Critical load (in megawatts) | MW	19.25

Organization (Details 2)

Organization (Details 2) - Corporate Office Properties, L.P.	6 Months Ended
	Jun. 30, 2016
Common Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	96.30%
Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	95.50%

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Deferred compensation plan - Management $ in Millions	6 Months Ended
	Jun. 30, 2016USD ($)
Assets and liabilities measured at fair value on a recurring basis
Maximum percentage of participants' compensation which is deferrable (as a percent)	100.00%
Balance of the plan which was fully funded	$ 5

Fair Value Measurements (Deta41

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Liabilities:
Interest rate derivatives	$ 20,245	$ 3,160
Corporate Office Properties, L.P.
Liabilities:
Interest rate derivatives	20,245	$ 3,160
Fair value measurement on a recurring basis
Assets:
Assets	5,046
Liabilities:
Deferred compensation plan liability	5,046
Interest rate derivatives	20,245
Liabilities	25,291
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	4,954
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	92
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Assets	5,046
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	4,954
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	92
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Assets	0
Liabilities:
Deferred compensation plan liability	5,046
Interest rate derivatives	20,245
Liabilities	25,291
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Liabilities:
Interest rate derivatives	20,245
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Liabilities:
Interest rate derivatives	$ 20,245

Fair Value Measurements (Deta42

Fair Value Measurements (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	$ 69,692	$ 1,238	$ 72,138	$ 1,238
Fair value measurement on a recurring basis
Assets and liabilities measured at fair value on a non-recurring basis
Assets	5,046		5,046
Fair value measurement on a nonrecurring basis | Projects in development or held for future development
Assets and liabilities measured at fair value on a non-recurring basis
Assets	9,117		9,117
Fair value measurement on a nonrecurring basis | Projects in development or held for future development | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value on a non-recurring basis
Assets	9,117		9,117
Fair value measurement on a nonrecurring basis | Northern Virginia Defense/IT and Fort Meade/BW Corridor | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	14,100
Fair value measurement on a nonrecurring basis | Aberdeen, Maryland | Land in development or held for future development
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	4,400
Fair value measurement on a nonrecurring basis | Aberdeen, Maryland | Other Segments | Operating properties, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	34,400
Fair value measurement on a nonrecurring basis | Frederick, Maryland | Land in development or held for future development
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	8,200
Fair value measurement on a nonrecurring basis | Greater Philadelphia, Pennsylvania | Regional Office | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	6,200
Fair value measurement on a nonrecurring basis | Colorado Springs | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses			3,400
Fair value measurement on a nonrecurring basis | White Marsh, Maryland | Regional Office | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses			1,400
Assets held for sale, net | Fair value measurement on a nonrecurring basis
Assets and liabilities measured at fair value on a non-recurring basis
Assets	55,322		55,322
Assets held for sale, net | Fair value measurement on a nonrecurring basis | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value on a non-recurring basis
Assets	55,322		55,322
Operating properties, net | Fair value measurement on a nonrecurring basis
Assets and liabilities measured at fair value on a non-recurring basis
Assets	13,700		13,700
Operating properties, net | Fair value measurement on a nonrecurring basis | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value on a non-recurring basis
Assets	$ 13,700		$ 13,700

Fair Value Measurements (Deta43

Fair Value Measurements (Details 4) - Fair value measurement on a nonrecurring basis - Significant Unobservable Inputs (Level 3) - Discounted Cash Flow	6 Months Ended
	Jun. 30, 2016
Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	11.00%
Capitalization rate (percent)	9.00%
Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	12.00%
Capitalization rate (percent)	10.00%
Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	11.60%
Capitalization rate (percent)	9.60%

Properties, Net (Details)

Properties, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Investments in real estate
Less: accumulated depreciation	$ (678,827)	$ (700,363)
Operating properties, net	2,782,330	2,920,529
Land
Investments in real estate
Gross	455,355	463,305
Buildings and improvements
Investments in real estate
Gross	$ 3,005,802	$ 3,157,587

Properties, Net (Details 2)

Properties, Net (Details 2) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Properties
Projects in development or held for future development	$ 387,397	$ 429,219
Projects in development or held for future development | Land in development or held for future development
Properties
Projects in development or held for future development	209,202	207,774
Projects in development or held for future development | Construction in progress, excluding land
Properties
Projects in development or held for future development	$ 178,195	$ 221,445

Properties, Net (Details 3)

Properties, Net (Details 3) $ in Thousands	Jun. 30, 2016USD ($)Property	Dec. 31, 2015USD ($)Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, net | $	$ 300,584	$ 96,782
Assets held for sale, net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties, net | $	269,008	90,188
Deferred rent receivable | $	15,765	2,891
Intangible assets on real estate acquisitions, net | $	1,591	1,591
Deferred leasing costs, net | $	10,869	1,391
Lease incentives, net | $	3,351	721
Assets held for sale, net | $	$ 300,584	$ 96,782
Fort Meade/BW Corridor | 2016 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	10
Regional Office | White Marsh, Maryland | 2016 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	13
Regional Office | White Marsh, Maryland | 2015 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property		13
Regional Office | Greater Philadelphia, Pennsylvania | 2016 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	4
Other Segments | San Antonio, Texas | 2016 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	2
Other Segments | San Antonio, Texas | 2015 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property		2
Defense/Information Technology Locations | Northern Virginia Defense/IT | 2016 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	1

Properties, Net (Details 4)

Properties, Net (Details 4) ft² in Thousands, $ in Thousands	Aug. 07, 2015USD ($)ft²	Apr. 15, 2015USD ($)ft²	Mar. 19, 2015USD ($)ft²	Jun. 30, 2016USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2015USD ($)
2015 Acquisitions
Business Acquisition [Line Items]
Contributed revenues				$ 9,200	$ 4,000	$ 18,400	$ 4,300
Contributed net income from continuing operations				$ 1,100	$ 40	$ 2,000	$ 210
250 W Pratt St | Baltimore, Maryland
Business Acquisition [Line Items]
Square footage of real estate properties (in square feet) | ft²			367
Acquired property percentage leased			96.20%
Total acquisition cost			$ 61,800
2600 Park Tower Drive | Northern Virginia
Business Acquisition [Line Items]
Square footage of real estate properties (in square feet) | ft²		237
Acquired property percentage leased		100.00%
Total acquisition cost		$ 80,500
100 and 30 Light Street | Baltimore, Maryland
Business Acquisition [Line Items]
Square footage of real estate properties (in square feet) | ft²	558
Acquired property percentage leased	93.50%
Total acquisition cost	$ 121,200
Business combination, liabilities assumed	55,000
Fair value assumption of debt	$ 55,500

Properties, Net (Details 5)

Properties, Net (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015
Real Estate [Abstract]
Pro forma total revenues	$ 175,996	$ 345,921
Pro forma net income attributable to COPT common shareholders	$ 13,259	$ 24,106
Pro Forma EPS, Basic (in dollars per share)	$ 0.14	$ 0.25
Pro Forma EPS, Diluted (in dollars per share)	$ 0.14	$ 0.25

Properties, Net (Details 6)

Properties, Net (Details 6) ft² in Thousands, $ in Millions	6 Months Ended
	Jun. 30, 2016USD ($)ft²Property
Construction and Redevelopment Activities
Sale price of land | $	$ 5.7
Office properties under, or contractually committed for, construction or approved for redevelopment
Construction and Redevelopment Activities
Number of real estate properties	12
Square footage of real estate properties (in square feet) | ft²	1,500
Newly constructed properties placed in service
Construction and Redevelopment Activities
Square feet of properties placed in service | ft²	298
Number of real estate properties	2
Newly redeveloped properties placed in service
Construction and Redevelopment Activities
Square feet of properties placed in service | ft²	55
Number of real estate properties	2
Properties under construction or contractually committed for construction
Construction and Redevelopment Activities
Number of real estate properties	9
Square footage of real estate properties (in square feet) | ft²	1,400
Properties completed Held-for-future lease | Office properties under, or contractually committed for, construction or approved for redevelopment
Construction and Redevelopment Activities
Number of real estate properties	2
Properties under or approved for redevelopment
Construction and Redevelopment Activities
Number of real estate properties	3
Square footage of real estate properties (in square feet) | ft²	104

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Jan. 31, 2016	Jun. 30, 2016	Jun. 30, 2015
Investments in consolidated real estate joint ventures
Value of properties contributed		$ 22,600	$ 0
Consolidated real estate joint ventures
Investments in consolidated real estate joint ventures
Total Assets		256,063
Encumbered Assets		128,493
Total Liabilities		$ 106,013
Variable Interest Entity, Primary Beneficiary | LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)		85.00%
Total Assets		$ 151,416
Encumbered Assets		81,094
Total Liabilities		$ 52,362
Variable Interest Entity, Primary Beneficiary | M Square Associates, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)		50.00%
Total Assets		$ 65,788
Encumbered Assets		47,399
Total Liabilities		$ 46,205
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)		95.00%
Total Assets		$ 38,859
Encumbered Assets		0
Total Liabilities		7,446
Value of properties contributed	$ 22,600
Distributions to joint venture	$ 13,400
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC | Other Liabilities
Investments in consolidated real estate joint ventures
Due to Affiliate		$ 6,700

Investing Receivables (Details)

Investing Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 50,162	$ 47,875
Notes Receivable from City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 47,142	44,875
Notes Receivable from 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	$ 3,020	$ 3,000

Prepaid Expenses and Other As52

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Prepaid Expense and Other Assets [Abstract]
Prepaid expenses	$ 10,301	$ 23,009
Lease incentives, net	7,873	11,133
Furniture, fixtures and equipment, net	5,686	6,004
Construction contract costs incurred in excess of billings	5,281	3,261
Deferred financing costs, net	4,497	5,867
Deferred tax asset, net	3,589	3,467
Other assets	6,132	7,283
Prepaid expenses and other assets, net	43,359	60,024
Taxable REIT Subsidiary
Mortgage and Other Investing Receivables [Line Items]
Deferred tax assets, valuation allowance	$ 2,100	$ 2,100

Debt, Net (Details)

Debt, Net (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Debt
Carrying Value	$ 2,094,486,000		$ 2,094,486,000		$ 2,077,752,000
Deferred financing costs, net	4,497,000		4,497,000		5,867,000
Interest costs capitalized	1,300,000	$ 2,000,000	3,100,000	$ 4,100,000
Loans payable
Debt
Deferred financing costs, net	7,400,000		7,400,000		8,000,000
Mortgage and Other Secured Loans:
Debt
Carrying Value	331,851,000		331,851,000		331,000,000
Fixed rate mortgage loans
Debt
Carrying Value	318,243,000		$ 318,243,000		281,208,000
Stated interest rates, low end of range (as a percent)			3.82%
Stated interest rates, high end of range (as a percent)			7.87%
Unamortized premium included in carrying value	$ 459,000		$ 459,000		514,000
Weighted average interest rate (as a percent)	5.75%		5.75%
Variable rate secured loans
Debt
Carrying Value	$ 13,608,000		$ 13,608,000		49,792,000
Description of variable rate basis			LIBOR
Stated interest rate (as a percent)	2.31%		2.31%
Variable rate secured loans | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.85%
Variable rate secured loans | Revolving Credit Facility
Debt
Weighted average interest rate (as a percent)	1.62%		1.62%
Revolving Credit Facility
Debt
Carrying Value	$ 58,000,000		$ 58,000,000		43,500,000
Description of variable rate basis			LIBOR
Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			0.875%
Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			1.60%
Term Loan Facilities
Debt
Carrying Value	516,508,000		$ 516,508,000		515,902,000
Increase to maximum borrowing capacity	150,000,000		150,000,000
Aggregate additional borrowing capacity available	$ 430,000,000		$ 430,000,000
Description of variable rate basis			LIBOR
Weighted average interest rate (as a percent)	2.10%		2.10%
Term Loan Facilities | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			0.90%
Term Loan Facilities | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)			2.60%
3.60% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 346,920,000		$ 346,920,000		346,714,000
Stated interest rate (as a percent)	3.60%		3.60%
Debt instrument, face amount	$ 350,000		$ 350,000
Unamortized discount included in carrying value	$ 2,100,000		$ 2,100,000		2,200,000
Interest rate on debt (as a percent)	3.70%		3.70%
5.250% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 245,951,000		$ 245,951,000		245,731,000
Stated interest rate (as a percent)	5.25%		5.25%
Debt instrument, face amount	$ 250,000		$ 250,000
Unamortized discount included in carrying value	$ 3,600,000		$ 3,600,000		3,800,000
Interest rate on debt (as a percent)	5.49%		5.49%
3.70% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 297,609,000		$ 297,609,000		297,378,000
Stated interest rate (as a percent)	3.70%		3.70%
Debt instrument, face amount	$ 300,000		$ 300,000
Unamortized discount included in carrying value	$ 1,900,000		$ 1,900,000		2,100,000
Interest rate on debt (as a percent)	3.85%		3.85%
5.000% Senior Notes | Unsecured senior notes
Debt
Carrying Value	$ 296,192,000		$ 296,192,000		296,019,000
Stated interest rate (as a percent)	5.00%		5.00%
Debt instrument, face amount	$ 300,000		$ 300,000
Unamortized discount included in carrying value	$ 3,200,000		$ 3,200,000		3,300,000
Interest rate on debt (as a percent)	5.15%		5.15%
Unsecured notes payable
Debt
Carrying Value	$ 1,455,000		$ 1,455,000		1,508,000
Stated interest rate (as a percent)	0.00%		0.00%
Unamortized discount included in carrying value	$ 506,000		$ 506,000		$ 554,000

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Carrying amount and estimated fair value of debt
Carrying Value	$ 2,094,486	$ 2,077,752
Carrying Amount
Carrying amount and estimated fair value of debt
Variable-rate debt	588,116	609,194
Carrying Value	2,094,486	2,077,752
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Fixed-rate debt	1,186,672	1,185,842
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Fixed-rate debt	319,698	282,716
Total Estimated Fair Value
Carrying amount and estimated fair value of debt
Variable-rate debt	592,032	610,987
Carrying Value	2,148,333	2,114,636
Total Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Fixed-rate debt	1,227,235	1,211,658
Total Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Fixed-rate debt	$ 329,066	$ 291,991

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of (loss) gain recognized in accumulated other comprehensive loss (“AOCL”) (effective portion)	$ (5,704)	$ 392	$ (16,988)	$ (3,082)
Amount of losses reclassified from AOCL into interest expense (effective portion)	850	769	1,720	1,542
Interest rate swaps
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Approximate loss amount to be reclassified from AOCI to interest expense over the next 12 months	5,600		5,600
Interest rate derivatives in liability position, fair value	21,100		21,100
Termination value to settle obligations under interest rate derivative agreements	21,400		21,400
Interest rate swaps | Interest Expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of loss recognized in interest expense (ineffective portion)	319	$ 0	1,870	$ 0
Interest rate swaps | Prepaid expenses and other current assets
Fair value of interest rate derivatives and balance sheet classification
Interest rate derivatives	0		0		$ 53
Interest rate swaps | Interest rate derivatives
Fair value of interest rate derivatives and balance sheet classification
Fair value of Interest rate swaps classified as interest rate derivatives	(20,245)		(20,245)		(3,160)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(20,245)		(20,245)		(3,107)
Designated | Interest rate swap, effective date September 2, 2014, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	0.8055%		0.8055%
Fair value of interest rate swaps	$ (58)		$ (58)		(148)
Designated | Interest rate swap, effective date September 2, 2014, swap two
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	0.81%		0.81%
Fair value of interest rate swaps	$ (59)		$ (59)		(151)
Designated | Interest rate swap, effective date September 1, 2015, swap one
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	1.673%		1.673%
Fair value of interest rate swaps	$ (3,117)		$ (3,117)		(1,217)
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	$ (3,293)		$ (3,293)		(1,429)
Designated | Interest rate swap, effective October 13, 2015
Fair values of interest rate swap derivatives
Notional Amount	$ 13,765		$ 13,765
Fixed rate (as a percent)	1.39%		1.39%
Fair value of interest rate swaps	$ (337)		$ (337)		53
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	$ (5,367)		$ (5,367)		(138)
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	$ (5,336)		$ (5,336)		(45)
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	$ (2,678)		$ (2,678)		$ (32)

Redeemable Noncontrolling Int56

Redeemable Noncontrolling Interests (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016USD ($)joint_venture	Jun. 30, 2015USD ($)
Noncontrolling Interest [Abstract]
Number of joint ventures with redeemable noncontrolling interests | joint_venture	2
Redeemable Noncontrolling Interest [Roll Forward]
Beginning balance	$ 19,218	$ 18,417
Contributions from noncontrolling interests	22,778	0
Distributions to noncontrolling interests	(20,989)	(885)
Net income attributable to noncontrolling interests	1,117	1,143
Adjustment to arrive at fair value of interests	349	739
Ending balance	$ 22,473	$ 19,414

Equity (Details)

Equity (Details) - shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Conversion of common units to common shares (in units/ shares)	26,758	158,000

Information by Business Segme58

Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment financial information for real estate operations
Revenues from real estate operations	$ 133,924	$ 128,195	$ 267,011	$ 250,905
Property operating expenses	48,141	46,407	100,016	97,093
NOI from real estate operations	85,783	81,788	166,995	153,812
Segment assets	3,841,692	3,904,059	3,841,692	3,904,059	$ 3,909,312
Segment assets
Segment financial information for real estate operations
Revenues from real estate operations	133,924	128,195	267,011	250,905
Property operating expenses	48,141	46,407	100,016	97,093
NOI from real estate operations	85,783	81,788	166,995	153,812
Additions to long-lived assets	15,022	94,715	29,423	166,686
Transfers from non-operating properties	58,348	44,624	120,441	161,896
Segment assets	3,289,117	3,218,657	3,289,117	3,218,657
Segment assets | Defense/Information Technology Locations
Segment financial information for real estate operations
Revenues from real estate operations	102,097	98,093	203,327	193,813
Property operating expenses	35,990	34,960	74,509	73,777
NOI from real estate operations	66,107	63,133	128,818	120,036
Additions to long-lived assets	12,689	91,031	24,174	96,939
Transfers from non-operating properties	58,804	24,192	120,775	129,780
Segment assets	2,421,850	2,372,807	2,421,850	2,372,807
Segment assets | Defense/Information Technology Locations | Fort Meade/BW Corridor
Segment financial information for real estate operations
Revenues from real estate operations	60,912	60,007	123,421	121,191
Property operating expenses	20,378	19,480	43,624	42,996
NOI from real estate operations	40,534	40,527	79,797	78,195
Additions to long-lived assets	7,096	5,141	13,615	8,586
Transfers from non-operating properties	768	6,098	36,519	19,028
Segment assets	1,305,769	1,266,632	1,305,769	1,266,632
Segment assets | Defense/Information Technology Locations | Northern Virginia Defense/IT
Segment financial information for real estate operations
Revenues from real estate operations	12,057	13,462	24,173	24,508
Property operating expenses	4,307	5,354	8,848	10,970
NOI from real estate operations	7,750	8,108	15,325	13,538
Additions to long-lived assets	3,059	83,913	6,137	84,700
Transfers from non-operating properties	27,944	7,735	27,850	51,208
Segment assets	424,441	499,601	424,441	499,601
Segment assets | Defense/Information Technology Locations | Lackland Air Force Base
Segment financial information for real estate operations
Revenues from real estate operations	11,651	9,743	21,876	18,408
Property operating expenses	6,844	5,349	12,264	10,112
NOI from real estate operations	4,807	4,394	9,612	8,296
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	231	468	237	31,559
Segment assets	133,359	134,127	133,359	134,127
Segment assets | Defense/Information Technology Locations | Navy Support Locations
Segment financial information for real estate operations
Revenues from real estate operations	6,998	7,186	13,932	14,451
Property operating expenses	2,675	3,390	6,199	6,788
NOI from real estate operations	4,323	3,796	7,733	7,663
Additions to long-lived assets	2,233	1,769	3,503	3,362
Transfers from non-operating properties	0	0	0	0
Segment assets	195,195	194,764	195,195	194,764
Segment assets | Defense/Information Technology Locations | Redstone Arsenal
Segment financial information for real estate operations
Revenues from real estate operations	3,191	2,658	6,307	5,104
Property operating expenses	960	888	1,938	1,717
NOI from real estate operations	2,231	1,770	4,369	3,387
Additions to long-lived assets	301	208	919	291
Transfers from non-operating properties	4	8,980	215	11,977
Segment assets	106,810	107,677	106,810	107,677
Segment assets | Defense/Information Technology Locations | Data Center Shells
Segment financial information for real estate operations
Revenues from real estate operations	7,288	5,037	13,618	10,151
Property operating expenses	826	499	1,636	1,194
NOI from real estate operations	6,462	4,538	11,982	8,957
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	29,857	911	55,954	16,008
Segment assets	256,276	170,006	256,276	170,006
Segment assets | Regional Office
Segment financial information for real estate operations
Revenues from real estate operations	23,283	24,400	46,785	46,360
Property operating expenses	8,721	8,406	18,552	17,154
NOI from real estate operations	14,562	15,994	28,233	29,206
Additions to long-lived assets	2,180	3,396	4,939	69,330
Transfers from non-operating properties	26	5,218	108	16,725
Segment assets	594,750	598,030	594,750	598,030
Segment assets | Wholesale data centers
Segment financial information for real estate operations
Revenues from real estate operations	6,804	3,820	13,297	6,855
Property operating expenses	2,651	2,221	5,312	4,433
NOI from real estate operations	4,153	1,599	7,985	2,422
Additions to long-lived assets	0	78	0	108
Transfers from non-operating properties	(482)	15,202	(431)	15,379
Segment assets	237,226	175,563	237,226	175,563
Segment assets | Other Segments
Segment financial information for real estate operations
Revenues from real estate operations	1,740	1,882	3,602	3,877
Property operating expenses	779	820	1,643	1,729
NOI from real estate operations	961	1,062	1,959	2,148
Additions to long-lived assets	153	210	310	309
Transfers from non-operating properties	0	12	(11)	12
Segment assets	$ 35,291	$ 72,257	$ 35,291	$ 72,257

Information by Business Segme59

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reconciliation of segment revenues to total revenues
Segment revenues from real estate operations	$ 133,924	$ 128,195	$ 267,011	$ 250,905
Construction contract and other service revenues	12,003	42,172	23,223	80,496
Less: Revenues from discontinued operations	0	(4)	0	(4)
Total revenues	145,927	170,363	290,234	331,397
Reconciliation of segment property operating expenses to property operating expenses
Segment property operating expenses	48,141	46,407	100,016	97,093
Less: Property operating expenses from discontinued operations	0	11	0	6
Total property operating expenses	48,141	46,418	100,016	97,099
Computation of net operating income from service operations
Construction contract and other service revenues	12,003	42,172	23,223	80,496
Construction contract and other service expenses	(11,478)	(41,293)	(22,172)	(78,791)
NOI from service operations	525	879	1,051	1,705
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from real estate operations	85,783	81,788	166,995	153,812
NOI from service operations	525	879	1,051	1,705
Interest and other income	1,330	1,242	2,486	2,525
Equity in income of unconsolidated entities	10	9	20	34
Income tax (expense) benefit	(1)	(50)	7	(105)
Other adjustments:
Depreciation and other amortization associated with real estate operations	(33,248)	(33,786)	(67,775)	(65,385)
Impairment losses	(69,692)	(1,238)	(72,138)	(1,238)
General, administrative and leasing expenses	(8,026)	(7,534)	(19,909)	(15,425)
Business development expenses and land carry costs	(2,363)	(2,623)	(4,781)	(5,413)
Interest expense	(22,639)	(21,768)	(46,198)	(42,606)
NOI from discontinued operations	0	(15)	0	(10)
Gain (loss) on early extinguishment of debt	5	(65)	22	(68)
(Loss) income from continuing operations	$ (48,316)	$ 16,839	$ (40,220)	$ 27,826

Information by Business Segme60

Information by Business Segment (Details 3) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Reconciliation of segment assets to total assets
Assets	$ 3,841,692	$ 3,909,312	$ 3,904,059
Segment assets
Reconciliation of segment assets to total assets
Assets	3,289,117		3,218,657
Non-operating property assets
Reconciliation of segment assets to total assets
Assets	413,597		527,742
Other assets
Reconciliation of segment assets to total assets
Assets	$ 138,978		$ 157,660

Share-Based Compensation and 61

Share-Based Compensation and Other Compensation Matters (Details)	May 30, 2016shares	Mar. 01, 2016USD ($)shares	Jun. 30, 2016USD ($)Percentile_Rank$ / sharesshares
Chief Executive Officer and Executive Vice President
Other Share-based Compensation Additional Disclosures
Executive transition cost | $			$ 4,400,000
Performance share units
Share-Based Compensation
Stock awards granted (in shares or units) | shares		26,299
Aggregate grant date fair value | $		$ 1,000,000
Potential earned PSUs payout for defined levels of performance under awards
Earned PSUs payout (as a percent of PSUs granted) on 75th or greater percentile rank			200.00%
Earned PSUs payout (as a percent of PSUs granted) on 50th percentile rank			100.00%
Earned PSUs payout (as a percent of PSUs granted) on 25th percentile rank			50.00%
Performance share units granted on percentile rank below 25th (as a percent)			0.00%
The number of percentile ranks to fall between to earn interpolated PSUs between such percentile ranks, conditioned on the percentile rank exceeding 25% | Percentile_Rank			2
Assumptions used to value stock awards
Performance period of the award			3 years
Weighted average grant date fair value (in dollars per share) | $ / shares			$ 38.21
Baseline value per common share (in dollars per share) | $ / shares			$ 23.90
Expected volatility of common shares (as a percent)			20.40%
Risk-free interest rate (as a percent)			0.96%
Restricted shares
Share-Based Compensation
Stock awards granted (in shares or units) | shares			197,087
Aggregate grant date fair value | $			$ 4,800,000
Assumptions used to value stock awards
Weighted average grant date fair value (in dollars per share) | $ / shares			$ 24.11
Other Share-based Compensation Additional Disclosures
Shares vested (in shares) | shares			159,171
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 27.62
Aggregate intrinsic value of awards upon vesting | $			$ 3,800,000
Deferred share award
Share-Based Compensation
Stock awards granted (in shares or units) | shares			24,944
Aggregate grant date fair value | $			$ 671,000
Assumptions used to value stock awards
Weighted average grant date fair value (in dollars per share) | $ / shares			$ 26.89
Other Share-based Compensation Additional Disclosures
Shares vested (in shares) | shares			12,028
Weighted average fair value of shares vested (in dollars per share) | $ / shares			$ 26.70
Aggregate intrinsic value of awards upon vesting | $			$ 322,000
2014 and 2015 PSU Grants | Performance share units | Executive Vice President
Other Share-based Compensation Additional Disclosures
Shares issued (in shares) | shares	10,326

Earnings Per Share ("EPS") an62

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2016		Jun. 30, 2015	Jun. 30, 2016		Jun. 30, 2015
Numerator:
(Loss) income from continuing operations		$ (48,316)		$ 16,839	$ (40,220)		$ 27,826
Gain on sales of real estate, net		0		(1)	0		3,985
Preferred share/unit dividends/distributions		(3,553)		(3,553)	(7,105)		(7,105)
Income from continuing operations attributable to noncontrolling interests		897		(1,436)	(373)		(2,828)
Income from continuing operations attributable to share-based compensation awards		(96)		(113)	(214)		(235)
Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders		(51,068)		11,736	(47,912)		21,643
Discontinued operations		0		394	0		156
Discontinued operations attributable to noncontrolling interests		0		(15)	0		(3)
Numerator for basic and diluted EPS on net income attributable to COPT common shareholders		$ (51,068)		$ 12,115	$ (47,912)		$ 21,796
Denominator (all weighted averages):
Denominator for basic EPS (common shares)		94,300		94,128	94,251		93,666
Dilutive effect of share-based compensation awards (shares)		0		35	0		114
Denominator for diluted EPS (common shares)		94,300		94,163	94,251		93,780
Basic EPS:
(Loss) income from continuing operations (in dollars per share/unit)		$ (0.54)	[1]	$ 0.13	$ (0.51)	[1]	$ 0.23	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[1]	(0.54)		0.13	(0.51)		0.23
Diluted EPS:
(Loss) income from continuing operations (in dollars per share/unit)		(0.54)	[1]	0.13	(0.51)	[1]	0.23	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[1]	$ (0.54)		$ 0.13	$ (0.51)		$ 0.23
Corporate Office Properties, L.P.
Numerator:
(Loss) income from continuing operations		$ (48,316)		$ 16,839	$ (40,220)		$ 27,826
Gain on sales of real estate, net		0		(1)	0		3,985
Preferred share/unit dividends/distributions		(3,718)		(3,718)	(7,435)		(7,435)
Income from continuing operations attributable to noncontrolling interests		(911)		(812)	(1,890)		(1,633)
Income from continuing operations attributable to share-based compensation awards		(96)		(113)	(214)		(235)
Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders		(53,041)		12,195	(49,759)		22,508
Discontinued operations		0		394	0		156
Discontinued operations attributable to noncontrolling interests		0		0	0		3
Numerator for basic and diluted EPS on net income attributable to COPT common shareholders		$ (53,041)		$ 12,589	$ (49,759)		$ 22,667
Denominator (all weighted averages):
Denominator for basic EPS (common shares)		97,976		97,808	97,927		97,372
Dilutive effect of share-based compensation awards (shares)		0		35	0		114
Denominator for diluted EPS (common shares)		97,976		97,843	97,927		97,486
Basic EPS:
(Loss) income from continuing operations (in dollars per share/unit)	[2]	$ (0.54)		$ 0.13	$ (0.51)		$ 0.23
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[2]	(0.54)		0.13	(0.51)		0.23
Diluted EPS:
(Loss) income from continuing operations (in dollars per share/unit)	[2]	(0.54)		0.13	(0.51)		0.23
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net (loss) income attributable to COPT common shareholders (in dollars per share/unit)	[2]	$ (0.54)		$ 0.13	$ (0.51)		$ 0.23
[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") an63

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details 2) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Conversion of common units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	3,676,000	3,680,000	3,676,000	3,706,000
Conversion of Series I Preferred Units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	176,000	176,000	176,000	176,000
Conversion of Series K Preferred Shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	434,000	434,000	434,000	434,000
Weighted average restricted stock and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	403,000	426,000	404,000	413,000
Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	309,000	473,000	344,000	472,000
Corporate Office Properties, L.P. | Weighted average restricted stock and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	403,000	426,000	404,000	413,000
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	309,000	473,000	344,000	472,000
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)	176,000	176,000	176,000	176,000
Corporate Office Properties, L.P. | Conversion of Series K preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	434,000	434,000	434,000	434,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	Jun. 30, 2016USD ($)Property	Aug. 31, 2010USD ($)
Tax incremental financing obligation
Liability recognized with regard to tax incremental financing obligation at end of current period	$ 1,900,000
Environmental Indemnity Agreement
Number of lease properties which were provided environmental indemnifications | Property	3
Environmental indemnification to the tenant against losses covered under prior owner's indemnity agreement	$ 5,000,000
Maximum environmental indemnification to the tenant against consequential damages after acquisition of property	$ 12,500,000
Additional costs agreed to be paid by the entity related to construction and environmental regulatory activities (as a percent)	50.00%
Maximum annual additional costs agreed to be paid by the entity related to construction and environmental regulatory activities	$ 300,000
Maximum additional costs agreed to be paid by the entity related to construction and environmental regulatory activities	1,500,000
New Development and Redevelopment Obligations
Loss Contingencies [Line Items]
Purchase obligations	78,800,000
Capital Expenditures For Operating Properties
Loss Contingencies [Line Items]
Purchase obligations	48,700,000
Third Party Construction and Development
Loss Contingencies [Line Items]
Purchase obligations	17,300,000
Other Purchase Obligations
Loss Contingencies [Line Items]
Purchase obligations	$ 2,500,000
Anne Arundel County, Maryland | Tax Incremental Financing Bond
Tax incremental financing obligation
Debt instrument, face amount		$ 30,000,000

Commitments and Contingencies65

Commitments and Contingencies - Future Minimum Payments (Details) $ in Thousands	Jun. 30, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 603
2,017	1,139
2,018	1,092
2,019	1,067
2,020	1,084
Thereafter	86,805
Total	$ 91,790

Subsequent Event (Details)

Subsequent Event (Details) $ in Thousands	Jul. 21, 2016USD ($)Property	Jun. 30, 2016USD ($)	Jun. 30, 2015USD ($)
Subsequent Event [Line Items]
Value of properties contributed		$ 22,600	$ 0
Subsequent Event | Single-tenant data centers | Operating office properties
Subsequent Event [Line Items]
Ownership percentage sold (percent)	50.00%
Number of properties contributed | Property	6
Value of properties contributed	$ 147,600
Debt instrument, face amount	60,000
Transaction value of disposition of interest in properties	44,000
Gain on sale of interest in properties	$ 18,000