COPT Defense Properties (CDP) 10-Q 4 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 21, 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	Sep. 30, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		94,761,691
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
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	Sep. 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	Q3

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Properties, net:
Operating properties, net	$ 2,632,069	$ 2,920,529
Projects in development or held for future development	396,269	429,219
Total properties, net	3,028,338	3,349,748
Assets held for sale, net	161,454	96,782
Cash and cash equivalents	47,574	60,310
Restricted cash and marketable securities	7,583	7,716
Investment in unconsolidated real estate joint venture	25,721	0
Accounts receivable (net of allowance for doubtful accounts of $612 and $1,525, respectively)	25,790	29,167
Deferred rent receivable (net of allowance of $330 and $1,962, respectively)	87,526	105,484
Intangible assets on real estate acquisitions, net	84,081	98,338
Deferred leasing costs (net of accumulated amortization of $62,767 and $66,364, respectively)	41,470	53,868
Investing receivables	51,119	47,875
Prepaid expenses and other assets, net	73,538	60,024
Total assets	3,634,194	3,909,312
Liabilities:
Debt, net	1,873,836	2,077,752
Accounts payable and accrued expenses	112,306	91,755
Rents received in advance and security deposits	28,740	37,148
Dividends and distributions payable	30,225	30,178
Deferred revenue associated with operating leases	9,898	19,758
Interest rate derivatives	17,272	3,160
Other liabilities	38,282	13,779
Total liabilities	2,110,559	2,273,530
Commitments and contingencies (Note 15)
Redeemable noncontrolling interests	22,848	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 September 30, 2016 and December 31, 2015)	199,083	199,083
Common Shares of beneficial interest	948	945
Additional paid-in capital	2,008,787	2,004,507
Cumulative distributions in excess of net income	(759,262)	(657,172)
Accumulated other comprehensive loss	(16,314)	(2,838)
Total Corporate Office Properties Trust’s shareholders’ equity	1,433,242	1,544,525
Noncontrolling interests in subsidiaries:
Common units in COPLP	46,757	52,359
Preferred units in COPLP	8,800	8,800
Other consolidated entities	11,988	10,880
Noncontrolling interests in subsidiaries	67,545	72,039
Total equity	1,500,787	1,616,564
Total liabilities, redeemable noncontrolling interest and equity	3,634,194	3,909,312
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,632,069	2,920,529
Projects in development or held for future development	396,269	429,219
Total properties, net	3,028,338	3,349,748
Assets held for sale, net	161,454	96,782
Cash and cash equivalents	47,574	60,310
Restricted cash and marketable securities	2,333	1,953
Investment in unconsolidated real estate joint venture	25,721	0
Accounts receivable (net of allowance for doubtful accounts of $612 and $1,525, respectively)	25,790	29,167
Deferred rent receivable (net of allowance of $330 and $1,962, respectively)	87,526	105,484
Intangible assets on real estate acquisitions, net	84,081	98,338
Deferred leasing costs (net of accumulated amortization of $62,767 and $66,364, respectively)	41,470	53,868
Investing receivables	51,119	47,875
Prepaid expenses and other assets, net	73,538	60,024
Total assets	3,628,944	3,903,549
Liabilities:
Debt, net	1,873,836	2,077,752
Accounts payable and accrued expenses	112,306	91,755
Rents received in advance and security deposits	28,740	37,148
Dividends and distributions payable	30,225	30,178
Deferred revenue associated with operating leases	9,898	19,758
Interest rate derivatives	17,272	3,160
Other liabilities	33,032	8,016
Total liabilities	2,105,309	2,267,767
Commitments and contingencies (Note 15)
Redeemable noncontrolling interests	22,848	19,218
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,297,858	1,400,745
Accumulated other comprehensive loss	(16,987)	(2,985)
Total Corporate Office Properties Trust’s shareholders’ equity	1,488,754	1,605,643
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	12,033	10,921
Total equity	1,500,787	1,616,564
Total liabilities, redeemable noncontrolling interest and equity	3,628,944	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	Sep. 30, 2016	Dec. 31, 2015
Allowance for doubtful accounts - AR	$ 612	$ 1,525
Deferred rent receivable	330	1,962
Deferred leasing costs, accumulated amortization	$ 62,767	$ 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	94,764,786	94,531,512
Common Shares of beneficial interest, shares outstanding	94,764,786	94,531,512
Corporate Office Properties, L.P.
Allowance for doubtful accounts - AR	$ 612	$ 1,525
Deferred rent receivable	330	1,962
Deferred leasing costs, accumulated amortization	$ 62,767	$ 66,364
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	94,764,786	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	3,590,391	3,677,391
Preferred Units, Outstanding	352,000	352,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015
Revenues
Rental revenue		$ 103,956		$ 109,080	$ 316,862		$ 312,826
Tenant recoveries and other real estate operations revenue		26,998		24,606	81,103		71,761
Construction contract and other service revenues		11,149		17,058	34,372		97,554
Total revenues		142,103		150,744	432,337		482,141
Expenses
Property operating expenses		49,952		48,897	149,968		145,996
Depreciation and amortization associated with real estate operations		32,015		38,403	99,790		103,788
Construction contract and other service expenses		10,341		16,132	32,513		94,923
Impairment losses		27,699		2,307	99,837		3,545
General, administrative and leasing expenses		8,855		7,439	28,764		22,864
Business development expenses and land carry costs		1,716		5,573	6,497		10,986
Total operating expenses		130,578		118,751	417,369		382,102
Operating income		11,525		31,993	14,968		100,039
Interest expense		(18,301)		(24,121)	(64,499)		(66,727)
Interest and other income		1,391		692	3,877		3,217
(Loss) gain on early extinguishment of debt		(59)		85,745	(37)		85,677
(Loss) income from continuing operations before equity in income of unconsolidated entities and income taxes		(5,444)		94,309	(45,691)		122,206
Equity in income of unconsolidated entities		594		18	614		52
Income tax benefit (expense)		21		(48)	28		(153)
(Loss) income from continuing operations		(4,829)		94,279	(45,049)		122,105
Discontinued operations		0		0	0		156
(Loss) income before gain on sales of real estate		(4,829)		94,279	(45,049)		122,261
Gain on sales of real estate		34,101		15	34,101		4,000
Net income (loss)		29,272		94,294	(10,948)		126,261
Net (income) loss attributable to noncontrolling interests:
Common units in COPLP		(901)		(3,357)	948		(4,231)
Preferred units in COPLP		(165)		(165)	(495)		(495)
Other consolidated entities		(907)		(972)	(2,799)		(2,599)
Net income (loss) attributable to COPT		27,299		89,800	(13,294)		118,936
Preferred share/unit dividends/distributions		(3,552)		(3,552)	(10,657)		(10,657)
Net income (loss) attributable to COPT common shareholders		23,747		86,248	(23,951)		108,279
Net income (loss) attributable to COPT:
Income (loss) from continuing operations		27,299		89,800	(13,294)		118,783
Discontinued operations, net		0		0	0		153
Net income (loss) attributable to COPT		$ 27,299		$ 89,800	$ (13,294)		$ 118,936
Basic earnings per common share
Income (loss) from continuing operations (in dollars per share/unit)		$ 0.25	[1]	$ 0.91	$ (0.26)	[1]	$ 1.15	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[1]	0.25		0.91	(0.26)		1.15
Diluted earnings per common share
Income (loss) from continuing operations (in dollars per share/unit)		0.25	[1]	0.91	(0.26)	[1]	1.15	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[1]	0.25		0.91	(0.26)		1.15
Dividends declared per common share/unit (in dollars per share		$ 0.2750		$ 0.275	$ 0.825		$ 0.825
Corporate Office Properties, L.P.
Revenues
Rental revenue		$ 103,956		$ 109,080	$ 316,862		$ 312,826
Tenant recoveries and other real estate operations revenue		26,998		24,606	81,103		71,761
Construction contract and other service revenues		11,149		17,058	34,372		97,554
Total revenues		142,103		150,744	432,337		482,141
Expenses
Property operating expenses		49,952		48,897	149,968		145,996
Depreciation and amortization associated with real estate operations		32,015		38,403	99,790		103,788
Construction contract and other service expenses		10,341		16,132	32,513		94,923
Impairment losses		27,699		2,307	99,837		3,545
General, administrative and leasing expenses		8,855		7,439	28,764		22,864
Business development expenses and land carry costs		1,716		5,573	6,497		10,986
Total operating expenses		130,578		118,751	417,369		382,102
Operating income		11,525		31,993	14,968		100,039
Interest expense		(18,301)		(24,121)	(64,499)		(66,727)
Interest and other income		1,391		692	3,877		3,217
(Loss) gain on early extinguishment of debt		(59)		85,745	(37)		85,677
(Loss) income from continuing operations before equity in income of unconsolidated entities and income taxes		(5,444)		94,309	(45,691)		122,206
Equity in income of unconsolidated entities		594		18	614		52
Income tax benefit (expense)		21		(48)	28		(153)
(Loss) income from continuing operations		(4,829)		94,279	(45,049)		122,105
Discontinued operations		0		0	0		156
(Loss) income before gain on sales of real estate		(4,829)		94,279	(45,049)		122,261
Gain on sales of real estate		34,101		15	34,101		4,000
Net income (loss)		29,272		94,294	(10,948)		126,261
Net (income) loss attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities		(913)		(972)	(2,803)		(2,602)
Net income (loss) attributable to COPT		28,359		93,322	(13,751)		123,659
Preferred share/unit dividends/distributions		(3,717)		(3,717)	(11,152)		(11,152)
Net income (loss) attributable to COPT common shareholders		24,642		89,605	(24,903)		112,507
Net income (loss) attributable to COPT:
Income (loss) from continuing operations		28,359		93,322	(13,751)		123,500
Discontinued operations, net		0		0	0		159
Net income (loss) attributable to COPT		$ 28,359		$ 93,322	$ (13,751)		$ 123,659
Basic earnings per common share
Income (loss) from continuing operations (in dollars per share/unit)	[2]	$ 0.25		$ 0.91	$ (0.26)		$ 1.15
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[2]	0.25		0.91	(0.26)		1.15
Diluted earnings per common share
Income (loss) from continuing operations (in dollars per share/unit)	[2]	0.25		0.91	(0.26)		1.15
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[2]	0.25		0.91	(0.26)		1.15
Dividends declared per common share/unit (in dollars per share		$ 0.275		$ 0.275	$ 0.825		$ 0.825
[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.
[2]	Basic and diluted earnings per common unit are calculated based on amounts attributable to common unitholders of Corporate Office Properties, L.P.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income (loss)	$ 29,272	$ 94,294	$ (10,948)	$ 126,261
Other comprehensive income (loss)
Unrealized gain (loss) on interest rate derivatives	407	(3,638)	(16,581)	(6,720)
Losses on interest rate derivatives included in interest expense	1,043	915	2,763	2,457
Equity in other comprehensive loss of equity method investee	0	0	(184)	(264)
Other comprehensive income (loss)	1,450	(2,723)	(14,002)	(4,527)
Comprehensive income (loss)	30,722	91,571	(24,950)	121,734
Comprehensive income attributable to noncontrolling interests	(2,025)	(4,453)	(1,820)	(7,324)
Comprehensive income (loss) attributable to COPT	28,697	87,118	(26,770)	114,410
Corporate Office Properties, L.P.
Net income (loss)	29,272	94,294	(10,948)	126,261
Other comprehensive income (loss)
Unrealized gain (loss) on interest rate derivatives	407	(3,638)	(16,581)	(6,720)
Losses on interest rate derivatives included in interest expense	1,043	915	2,763	2,457
Equity in other comprehensive loss of equity method investee	0	0	(184)	(264)
Other comprehensive income (loss)	1,450	(2,723)	(14,002)	(4,527)
Comprehensive income (loss)	30,722	91,571	(24,950)	121,734
Comprehensive income attributable to noncontrolling interests	(913)	(1,035)	(2,803)	(2,780)
Comprehensive income (loss) attributable to COPT	$ 29,809	$ 90,536	$ (27,753)	$ 118,954

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: 160,160 and 87,000 shares for the nine months ended September 30, 2015 and 2016, respectively)	$ 0		2	2,149			(2,151)
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 nine months ended September 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 nine months ended September 30, 2015)	$ 2,008		0	2,008				2,008	$ 2,008
Share-based compensation issuance, net of redemptions (in units/shares)	151,511								151,511
Share-based compensation issuance, net of redemptions (COPT: 151,511 and 146,274 shares issued, net of redemptions for the nine months ended September 30, 2015 and 2016, respectively)	$ 5,600		1	5,599				5,600	$ 5,600
Redemption of vested equity awards	(2,330)			(2,330)				(2,330)	(2,330)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0			(591)			591
Comprehensive income (loss)	120,044				118,936	(4,526)	5,634	120,044	112,507	(4,705)	1,090		$ 495		$ 10,657
Dividends / Distributions to owners of common and preferred units	(88,658)				(88,658)			(92,188)	(81,036)				$ (495)		$ (10,657)
Distributions to owners of common and preferred units in COPLP	(3,530)						(3,530)
Distributions to noncontrolling interests in subsidiaries	(47)						(47)	(47)			(47)
Adjustment to arrive at fair value of redeemable noncontrolling interest	$ (599)			(599)				(599)	$ (599)
Balance (in units/ shares) at Sep. 30, 2015	94,533,670								98,211,061
Balance (preferred units) at Sep. 30, 2015													352,000		7,431,667
Balance (COPT: 94,533,670 shares and 94,764,786 shares as of September 30, 2015 and 2016, respectively) at Sep. 30, 2015	$ 1,579,907	199,083	945	2,002,730	(686,986)	(5,823)	69,958	1,579,907	$ 1,367,904	(6,086)	10,206		$ 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: 160,160 and 87,000 shares for the nine months ended September 30, 2015 and 2016, respectively)	$ 0		1	1,166			(1,167)
Costs associated with common shares issued to the public	$ (5)			(5)				(5)	$ (5)
Share-based compensation issuance, net of redemptions (in units/shares)	146,274								146,274
Share-based compensation issuance, net of redemptions (COPT: 151,511 and 146,274 shares issued, net of redemptions for the nine months ended September 30, 2015 and 2016, respectively)	$ 6,177		2	6,175				6,177	$ 6,177
Redemption of vested equity awards	(2,179)			(2,179)				(2,179)	(2,179)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0			(42)			42
Comprehensive income (loss)	(26,629)				(13,294)	(13,476)	141	(26,629)	(24,903)	(14,002)	1,124		$ 495		$ 10,657
Dividends / Distributions to owners of common and preferred units	(88,796)				(88,796)			(92,294)	(81,142)				$ (495)		$ (10,657)
Distributions to owners of common and preferred units in COPLP	(3,498)						(3,498)
Distributions to noncontrolling interests in subsidiaries	(12)						(12)	(12)			(12)
Adjustment to arrive at fair value of redeemable noncontrolling interest	(516)			(516)				(516)	(516)
Tax loss from share-based compensation	$ (319)			(319)				(319)	$ (319)
Balance (in units/ shares) at Sep. 30, 2016	94,764,786								98,355,177			3,590,391		94,764,786
Balance (preferred units) at Sep. 30, 2016												352,000	352,000	7,431,667	7,431,667
Balance (COPT: 94,533,670 shares and 94,764,786 shares as of September 30, 2015 and 2016, respectively) at Sep. 30, 2016	$ 1,500,787	$ 199,083	$ 948	$ 2,008,787	$ (759,262)	$ (16,314)	$ 67,545	$ 1,500,787	$ 1,297,858	$ (16,987)	$ 12,033		$ 8,800		$ 199,083

Consolidated Statements of Equ7

Consolidated Statements of Equity (Parenthetical) - shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Balance (in units/ shares)	94,764,786	94,533,670	94,531,512	93,255,284
Conversion of common units to common shares (in units/ shares)	87,000	160,160
Exercise of share options (in units/shares)		76,474
Share-based compensation issuance, net of redemptions (in units/shares)	146,274	151,511
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	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities
Revenues from real estate operations received	$ 391,511	$ 373,607
Construction contract and other service revenues received	54,399	104,817
Property operating expenses paid	(154,203)	(146,274)
Construction contract and other service expenses paid	(33,169)	(112,614)
General, administrative, leasing, business development and land carry costs paid	(27,879)	(29,620)
Interest expense paid	(61,662)	(46,278)
Interest and other income received	472	4,130
Other	504	(26)
Net cash provided by operating activities	169,973	147,742
Cash flows from investing activities
Construction, development and redevelopment	(121,297)	(174,434)
Acquisitions of operating properties and related intangible assets	0	(202,866)
Tenant improvements on operating properties	(26,055)	(18,129)
Other capital improvements on operating properties	(22,063)	(12,610)
Proceeds from dispositions of properties	210,661	45,066
Proceeds from partial sale of properties, net of related debt	43,686	0
Investing receivables payments received	0	5,114
Leasing costs paid	(6,024)	(8,603)
Other	(991)	(4,827)
Net cash provided by (used in) investing activities	77,917	(371,289)
Proceeds from debt
Revolving Credit Facility	362,500	422,000
Unsecured senior notes	0	296,580
Other debt proceeds	105,000	50,000
Repayments of debt
Revolving Credit Facility	(406,000)	(418,000)
Scheduled principal amortization	(4,454)	(5,011)
Other debt repayments	(203,056)	(50,681)
Deferred financing costs paid	(825)	(5,377)
Net proceeds from issuance of common shares/units	(46)	28,567
Common share/unit dividends/distributions paid	(78,072)	(77,641)
Preferred share/unit dividends/distributions paid	(10,657)	(10,657)
Distributions paid to noncontrolling interests in COPLP	(3,476)	(3,581)
Distributions paid to redeemable noncontrolling interests	(14,329)	0
Redemption of vested equity awards	(2,179)	(2,330)
Other	(5,032)	(2,559)
Net cash (used in) provided by financing activities	(260,626)	221,310
Net decrease in cash and cash equivalents	(12,736)	(2,237)
Cash and cash equivalents
Beginning of period	60,310	6,077
End of period	47,574	3,840
Reconciliation of net (loss) income to net cash provided by operating activities:
Net (loss) income	(10,948)	126,261
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and other amortization	101,429	105,397
Impairment losses	99,797	3,779
Losses on interest rate derivatives	347	0
Amortization of deferred financing costs and net debt discounts	4,456	4,144
Increase in deferred rent receivable	(930)	(11,939)
Gain on sales of real estate	(34,101)	(4,000)
Share-based compensation	5,637	4,949
Loss (gain) on early extinguishment of debt	34	(86,075)
Other	(2,761)	1,922
Operating changes in assets and liabilities:
Decrease in accounts receivable	3,658	6,526
Decrease (increase) in restricted cash and marketable securities	18	(1,102)
Increase in prepaid expenses and other assets, net	(19,778)	(5,228)
Increase (decrease) in accounts payable, accrued expenses and other liabilities	31,523	(655)
(Decrease) increase in rents received in advance and security deposits	(8,408)	3,763
Net cash provided by operating activities	169,973	147,742
Supplemental schedule of non-cash investing and financing activities:
Increase (decrease) in accrued capital improvements, leasing and other investing activity costs	9,963	(11,722)
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	6,683	0
Decrease in properties, net	(114,597)	0
Increase in investment in unconsolidated real estate joint venture	25,680	0
Decrease in debt	59,534	0
Other net decreases in assets and liabilities	3,619	0
Debt assumed on acquisition of operating property	0	55,490
Other liabilities assumed on acquisition of operating properties	0	5,265
Decrease in property in connection with surrender of property in settlement of debt	0	(82,738)
Decrease in debt in connection with surrender of property in settlement of debt	0	(150,000)
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(13,817)	(4,263)
Equity in other comprehensive loss of an equity method investee	(184)	(264)
Dividends/distributions payable	30,225	30,182
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	1,167	2,151
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	42	591
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	516	599
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	391,511	373,607
Construction contract and other service revenues received	54,399	104,817
Property operating expenses paid	(154,203)	(146,274)
Construction contract and other service expenses paid	(33,169)	(112,614)
General, administrative, leasing, business development and land carry costs paid	(27,879)	(29,620)
Interest expense paid	(61,662)	(46,278)
Interest and other income received	472	4,130
Other	504	(26)
Net cash provided by operating activities	169,973	147,742
Cash flows from investing activities
Construction, development and redevelopment	(121,297)	(174,434)
Acquisitions of operating properties and related intangible assets	0	(202,866)
Tenant improvements on operating properties	(26,055)	(18,129)
Other capital improvements on operating properties	(22,063)	(12,610)
Proceeds from dispositions of properties	210,661	45,066
Proceeds from partial sale of properties, net of related debt	43,686	0
Investing receivables payments received	0	5,114
Leasing costs paid	(6,024)	(8,603)
Other	(991)	(4,827)
Net cash provided by (used in) investing activities	77,917	(371,289)
Proceeds from debt
Revolving Credit Facility	362,500	422,000
Unsecured senior notes	0	296,580
Other debt proceeds	105,000	50,000
Repayments of debt
Revolving Credit Facility	(406,000)	(418,000)
Scheduled principal amortization	(4,454)	(5,011)
Other debt repayments	(203,056)	(50,681)
Deferred financing costs paid	(825)	(5,377)
Net proceeds from issuance of common shares/units	(46)	28,567
Common share/unit dividends/distributions paid	(81,053)	(80,727)
Preferred share/unit dividends/distributions paid	(11,152)	(11,152)
Distributions paid to redeemable noncontrolling interests	(14,329)	0
Redemption of vested equity awards	(2,179)	(2,330)
Other	(5,032)	(2,559)
Net cash (used in) provided by financing activities	(260,626)	221,310
Net decrease in cash and cash equivalents	(12,736)	(2,237)
Cash and cash equivalents
Beginning of period	60,310	6,077
End of period	47,574	3,840
Reconciliation of net (loss) income to net cash provided by operating activities:
Net (loss) income	(10,948)	126,261
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and other amortization	101,429	105,397
Impairment losses	99,797	3,779
Losses on interest rate derivatives	347	0
Amortization of deferred financing costs and net debt discounts	4,456	4,144
Increase in deferred rent receivable	(930)	(11,939)
Gain on sales of real estate	(34,101)	(4,000)
Share-based compensation	5,637	4,949
Loss (gain) on early extinguishment of debt	34	(86,075)
Other	(2,761)	1,922
Operating changes in assets and liabilities:
Decrease in accounts receivable	3,658	6,526
Decrease (increase) in restricted cash and marketable securities	(495)	(1,485)
Increase in prepaid expenses and other assets, net	(19,778)	(5,228)
Increase (decrease) in accounts payable, accrued expenses and other liabilities	32,036	(272)
(Decrease) increase in rents received in advance and security deposits	(8,408)	3,763
Net cash provided by operating activities	169,973	147,742
Supplemental schedule of non-cash investing and financing activities:
Increase (decrease) in accrued capital improvements, leasing and other investing activity costs	9,963	(11,722)
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	6,683	0
Decrease in properties, net	(114,597)	0
Increase in investment in unconsolidated real estate joint venture	25,680	0
Decrease in debt	59,534	0
Other net decreases in assets and liabilities	3,619	0
Debt assumed on acquisition of operating property	0	55,490
Other liabilities assumed on acquisition of operating properties	0	5,265
Decrease in property in connection with surrender of property in settlement of debt	0	(82,738)
Decrease in debt in connection with surrender of property in settlement of debt	0	(150,000)
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(13,817)	(4,263)
Equity in other comprehensive loss of an equity method investee	(184)	(264)
Dividends/distributions payable	30,225	30,182
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	$ 516	$ 599

Organization

Organization	9 Months Ended
	Sep. 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 September 30, 2016 , our properties included the following: • 168 operating office properties totaling 17.5 million square feet, including 12 triple-net leased, single-tenant data center properties. We owned six of these properties through an unconsolidated real estate joint venture; • 10 office properties under, or contractually committed for, construction or redevelopment that we estimate will total approximately 1.2 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; • 1,358 acres of land we control that we believe could be developed into approximately 16.2 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 September 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	9 Months Ended
	Sep. 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 state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 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. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2016, the FASB issued guidance that clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows with the objective of reducing the existing diversity in practice related to eight specific cash flow issues. The guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 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 $5.3 million as of September 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 September 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 September 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 $ 5,160 $ — $ — $ 5,160 Other 90 — — 90 Total assets $ 5,250 $ — $ — $ 5,250 Liabilities: Deferred compensation plan liability (2) $ — $ 5,250 $ — $ 5,250 Interest rate derivatives — 17,272 — 17,272 Total liabilities $ — $ 22,522 $ — $ 22,522 (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 September 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 $ — $ 17,272 $ — $ 17,272 Nonrecurring Fair Value Measurements In the first quarter of 2016, we set a goal to raise cash from sales of properties in 2016 considerably in excess of the $96.8 million in assets held for sale at December 31, 2015. The specific properties we would sell to achieve this goal had not been identified when the goal was established. Throughout 2016, we have been in the process of identifying properties we will sell. In the first quarter of 2016, we reclassified: most of our properties in Greater Philadelphia (included in our Regional Office segment); two properties in the Fort Meade/BW Corridor sub-segment; and our remaining land holdings in Colorado Springs, Colorado to held for sale and recognized $2.4 million of impairment losses. As of March 31, 2016, we had $225.9 million of assets held for sale. 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 then newly-appointed Chief Executive Officer and the goals of the asset sales program and concluded that we would: (1) not hold our operating properties in Aberdeen, Maryland (“Aberdeen”) for the long-term; (2) not develop commercial properties on land in Frederick, Maryland; (3) sell specific properties in our Northern Virginia Defense/IT and Fort Meade/BW Corridor sub-segments; 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: • $34.4 million on operating properties in Aberdeen (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 values; • $4.4 million on land in Aberdeen. 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 adjusted the land to its estimated fair value; • $8.2 million on land in Frederick, Maryland. We determined that the carrying amount of the land would not likely be recovered from its sale and adjusted the land to its estimated fair value; • $14.1 million on operating properties in our Northern Virginia 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 costs to sell; and • $6.2 million on the property in Greater Philadelphia (included in our Regional Office segment) that we reclassified to held for sale during the period and adjusted to fair value less costs to sell. There were no property sales in the second quarter of 2016 and as of June 30, 2016, we had $300.6 million of assets held for sale. During the third quarter of 2016, as part of our closing process, we conducted our quarterly review of our portfolio for indicators of impairment considering refinements to our disposition strategy made during the third quarter of 2016 to sell an additional operating property in our Northern Virginia Defense/IT sub-segment, an additional operating property in our Fort Meade/BW Corridor sub-segment and our remaining operating properties and land in White Marsh, Maryland (“White Marsh”) that had not previously been classified as held for sale. In connection with our determinations that we planned to sell these properties, we performed recoverability analyses for each of these properties and recorded the following impairment losses: • $13.3 million on the operating property in our Northern Virginia Defense/IT sub-segment. Communication with a major tenant in the building during the quarter led us to conclude that there was significant uncertainty with respect to the tenant renewing its lease expiring in 2019. As a result of this information and continuing sub-market weakness, we determined that this property no longer met our long-term hold strategy and we placed it into our asset sales program. Accordingly, we adjusted the carrying amount of the property to its estimated fair value less costs to sell; and • $2.9 million on the other properties that we reclassified as held for sale, primarily associated with a land parcel in White Marsh. As of June 30, 2016, this land was under a sales contract subject to a re-zoning contingency. During the third quarter, we were denied favorable re-zoning and the contract was canceled. As a result, we determined this property will be sold as is, reclassified it to held for sale and adjusted its carrying value to its estimated fair value less costs to sell. During our review we also recognized additional impairment losses of $11.5 million on properties previously classified as held for sale. Approximately $10 million of these losses pertained to properties in White Marsh due to our assessment that certain significant tenants will likely exercise lease termination rights and to reflect market conditions. The remainder of these losses pertained primarily to properties in San Antonio, Texas (in our Other segment), where prospective purchasers reduced offering prices late in the third quarter. We executed property sales of $210.7 million in the third quarter of 2016 (discussed further in Note 4), and had $161.5 million of assets held for sale at September 30, 2016. Changes in the expected future cash flows due to changes in our plans for specific properties (especially our expected holding period) could result in the recognition of additional impairment losses. In addition, because properties held for sale are carried at the lower of carrying value or estimated fair values less costs to sell, declines in their estimated fair values due to market conditions and other factors could result in the recognition of additional impairment losses. 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 September 30, 2016 (dollars in thousands): Fair Values as of September 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: Assets held for sale, net $ — $ — $ 127,128 $ 127,128 The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above as of September 30, 2016 (dollars in thousands): Valuation Technique Fair Values on Measurement Date Unobservable Input Range (Weighted Average) Contracts to sell $ 87,983 Contract amounts N/A Discounted cash flow $ 36,693 Discount rate 9.5% - 11.3% (10.5%) Terminal capitalization rate 8.3% - 9.5% (8.7%) Yield analyses $ 2,452 Investor yield requirement 9.0% (1) (1) Only one fair value applied for this unobservable input.

Properties, Net

Properties, Net	9 Months Ended
	Sep. 30, 2016
Real Estate [Abstract]
Properties, Net	Properties, Net Operating properties, net consisted of the following (in thousands): September 30, December 31, Land $ 424,627 $ 463,305 Buildings and improvements 2,888,918 3,157,587 Less: Accumulated depreciation (681,476 ) (700,363 ) Operating properties, net $ 2,632,069 $ 2,920,529 Projects in development or held for future development consisted of the following (in thousands): September 30, December 31, Land $ 199,038 $ 207,774 Development in progress, excluding land 197,231 221,445 Projects in development or held for future development $ 396,269 $ 429,219 Our properties held for sale included: • as of September 30, 2016 : nine operating properties in White Marsh (included primarily in our Regional Office segment); two operating properties in our Northern Virginia Defense/IT sub-segment; six operating properties in our Fort Meade/BW Corridor sub-segment; two operating properties in San Antonio, Texas (included in our Other segment); and land in White Marsh, Northern Virginia and Colorado Springs; and • as of December 31, 2015: 13 operating properties in White Marsh (included in our Regional Office segment); two operating properties in San Antonio, Texas (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): September 30, 2016 December 31, 2015 Properties, net $ 147,236 $ 90,188 Deferred rent receivable 6,642 2,891 Intangible assets on real estate acquisitions, net 1,540 1,591 Deferred leasing costs, net 4,901 1,391 Lease incentives, net 1,135 721 Assets held for sale, net $ 161,454 $ 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 September 30, 2016 , $6.9 million for the three months ended September 30, 2015, $27.6 million for the nine months ended September 30, 2016 and $11.2 million for the nine months ended September 30, 2015; and • net income from continuing operations of $432,000 for the three months ended September 30, 2016 , $487,000 for the three months ended September 30, 2015, $2.4 million for the nine months ended September 30, 2016 and $697,000 for the nine months ended September 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 September 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 nine months ended September 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 September 30, 2015 For the Nine Months Ended September 30, 2015 (Unaudited) Pro forma total revenues $ 152,736 $ 498,657 Pro forma net income attributable to COPT common shareholders $ 88,836 $ 112,941 Pro forma EPS: Basic $ 0.94 $ 1.20 Diluted $ 0.94 $ 1.20 2016 Dispositions During the nine months ended September 30, 2016, we completed dispositions of the following operating properties (dollars in thousands): Project Name City, State Segment Date of Disposition Number of Buildings Total Rentable Square Feet Transaction Value Gain on Disposition Arborcrest Corporate Campus (1) Philadelphia, PA Regional Office 8/4/2016 4 654,000 $ 142,800 $ 4,742 8003 Corporate Drive White Marsh, MD Regional Office 8/17/2016 1 18,000 2,400 — 1341 & 1343 Ashton Road Hanover, MD Fort Meade/BW Corridor 9/9/2016 2 25,000 2,900 848 8007, 8013, 8015, 8019 and 8023-8027 Corporate Drive (1) White Marsh, MD Regional Office 9/21/2016 5 130,000 14,513 1,906 1302, 1304 and 1306 Concourse Drive Linthicum, MD Fort Meade/BW Corridor 9/29/2016 3 299,000 48,100 8,683 15 1,126,000 $ 210,713 $ 16,179 (1) This disposition also included land. We also sold: • a 50% interest in six triple-net leased, single-tenant data center properties in Virginia by contributing them into a newly-formed joint venture, GI-COPT DC Partnership LLC (“GI-COPT”), for an aggregate property value of $147.6 million on July 21, 2016. We obtained $60.0 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 $44.3 million . We account for our 50% interest in the joint venture using the equity method of accounting as described further in Note 5. We recognized a partial gain on the sale of our interest of $17.9 million ; and • other land for $5.7 million , with no gain recognized. 2016 Construction Activities During the nine months ended September 30, 2016 , we placed into service 490,000 square feet in five newly constructed office properties (including a partially operational property) and 55,000 square feet in two redeveloped properties (including a partially operational property). As of September 30, 2016 , we had seven office properties under construction, or for which we were contractually committed to construct, that we estimate will total 1.1 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	9 Months Ended
	Sep. 30, 2016
Equity Method Investments and Joint Ventures [Abstract]
Real Estate Joint Ventures	Real Estate Joint Ventures Consolidated Joint Ventures The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of September 30, 2016 (dollars in thousands): Nominal Ownership September 30, 2016 (1) Date % as of Total Encumbered Total Acquired 9/30/2016 Nature of Activity Assets Assets Liabilities LW Redstone Company, LLC 3/23/2010 85% Development and operation of real estate (2) $ 157,168 $ 80,154 $ 53,056 M Square Associates, LLC 6/26/2007 50% Development and operation of real estate (3) 66,053 47,006 45,807 Stevens Investors, LLC 8/11/2015 95% Development of real estate (4) 40,282 — 7,680 $ 263,503 $ 127,160 $ 106,543 (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 in 2017) that was reported in other liabilities on our consolidated balance sheet as of September 30, 2016 . Unconsolidated Joint Venture As described further in Note 4, on July 21, 2016, we sold a 50% interest in six triple-net leased, single-tenant data center properties in Virginia by contributing them into GI-COPT, a newly-formed joint venture. We account for our 50% interest in the joint venture using the equity method of accounting. As of September 30, 2016 , we had an investment balance in GI-COPT of $25.7 million . Our balance is $18.5 million lower than our share of the joint venture’s equity due to a difference between our cost basis and our share of the underlying equity in the net assets upon formation of the joint venture; we are amortizing this basis difference into equity in income from unconsolidated entities over the lives of the underlying assets. Under the terms of the joint venture agreement, we and our partner receive returns in proportion to our investments in the joint venture.

Investing Receivables

Investing Receivables	9 Months Ended
	Sep. 30, 2016
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables, including accrued interest thereon, consisted of the following (in thousands): September 30, December 31, Notes receivable from the City of Huntsville $ 48,098 $ 44,875 Other investing loans receivable 3,021 3,000 $ 51,119 $ 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 September 30, 2016 or December 31, 2015 . The fair value of these receivables approximated their carrying amounts as of September 30, 2016 and December 31, 2015 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	9 Months Ended
	Sep. 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): September 30, December 31, Prepaid expenses $ 28,752 $ 23,009 Lease incentives, net 19,106 11,133 Construction contract costs incurred in excess of billings 6,367 3,261 Furniture, fixtures and equipment, net 5,492 6,004 Deferred financing costs, net (1) 3,812 5,867 Deferred tax asset, net (2) 3,282 3,467 Other assets 6,727 7,283 Prepaid expenses and other assets, net $ 73,538 $ 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	9 Months Ended
	Sep. 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 September 30, December 31, Stated Interest Rates as of as of September 30, 2016 September 30, 2016 Mortgage and Other Secured Loans: Fixed rate mortgage loans (2) $ 154,976 $ 281,208 3.82% - 7.87% (3) 2019-2026 Variable rate secured loans 13,529 49,792 LIBOR + 1.85% (4) October 2020 Total mortgage and other secured loans 168,505 331,000 Revolving Credit Facility — 43,500 LIBOR + 0.875% to 1.60% May 2019 Term Loan Facilities (5) 516,812 515,902 LIBOR + 0.90% to 2.60% (6) 2019-2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 347,024 346,714 3.60% (7) May 2023 5.250%, $250,000 aggregate principal 246,063 245,731 5.25% (8) February 2024 3.700%, $300,000 aggregate principal 297,725 297,378 3.70% (9) June 2021 5.000%, $300,000 aggregate principal 296,279 296,019 5.00% (10) July 2025 Unsecured notes payable 1,428 1,508 0% (11) 2026 Total debt, net $ 1,873,836 $ 2,077,752 (1) The carrying values of our loans other than the Revolving Credit Facility reflect net deferred financing costs of $6.9 million as of September 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 $440,000 as of September 30, 2016 and $514,000 as of December 31, 2015 . (3) The weighted average interest rate on our fixed rate mortgage loans was 4.20% as of September 30, 2016 . (4) The interest rate on our variable rate secured loan as of September 30, 2016 was 2.37% . (5) As of September 30, 2016, we had an additional $150 million in borrowings available to be drawn under a term loan. In addition, we had 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. On October 12, 2016, we repaid a $120.0 million term loan that was scheduled to mature in August 2019. (6) The weighted average interest rate on these loans was 2.17% as of September 30, 2016 . (7) The carrying value of these notes reflects an unamortized discount totaling $2.0 million as of September 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% . (8) The carrying value of these notes reflects an unamortized discount totaling $3.5 million as of September 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% . (9) The carrying value of these notes reflects an unamortized discount totaling $1.8 million as of September 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% . (10) The carrying value of these notes reflects an unamortized discount totaling $3.1 million as of September 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% . (11) 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 $483,000 as of September 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 September 30, 2016 , we were within the compliance requirements of these financial covenants. We capitalized interest costs of $1.2 million in the three months ended September 30, 2016 , $1.5 million in the three months ended September 30, 2015 , $4.3 million in the nine months ended September 30, 2016 and $5.6 million in the nine months ended September 30, 2015 . The following table sets forth information pertaining to the fair value of our debt (in thousands): September 30, 2016 December 31, 2015 Carrying Estimated Carrying Estimated Amount Fair Value Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,187,091 $ 1,233,860 $ 1,185,842 $ 1,211,658 Other fixed-rate debt 156,404 162,974 282,716 291,991 Variable-rate debt 530,341 533,079 609,194 610,987 $ 1,873,836 $ 1,929,913 $ 2,077,752 $ 2,114,636

Interest Rate Derivatives

Interest Rate Derivatives	9 Months Ended
	Sep. 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 September 30, December 31, $ 100,000 1.6730% One-Month LIBOR 9/1/2015 8/1/2019 $ (2,339 ) $ (1,217 ) 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 (2,500 ) (1,429 ) 13,676 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 (236 ) 53 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (4,879 ) (138 ) 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (4,872 ) (45 ) 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (2,446 ) (32 ) 100,000 0.8055% One-Month LIBOR 9/2/2014 9/1/2016 — (148 ) 100,000 0.8100% One-Month LIBOR 9/2/2014 9/1/2016 — (151 ) $ (17,272 ) $ (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 September 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 (17,272 ) (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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Amount of gain (loss) recognized in accumulated other comprehensive loss (“AOCL”) (effective portion) $ 407 $ (3,638 ) $ (16,581 ) $ (6,720 ) Amount of losses reclassified from AOCL into interest expense (effective portion) 1,043 915 2,763 2,457 Amount of gain (loss) recognized in interest expense (ineffective portion) 1,523 — (347 ) — Over the next 12 months, we estimate that approximately $5.2 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 September 30, 2016 , the fair value of interest rate derivatives in a liability position related to these agreements was $17.9 million , excluding the effects of accrued interest and credit valuation adjustments. As of September 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 $18.4 million .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	9 Months Ended
	Sep. 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 Nine Months Ended September 30, 2016 2015 Beginning balance $ 19,218 $ 18,417 Contributions from noncontrolling interests 22,779 — Distributions to noncontrolling interests (21,344 ) (1,098 ) Net income attributable to noncontrolling interests 1,679 1,690 Adjustment to arrive at fair value of interests 516 599 Ending balance $ 22,848 $ 19,608

Equity

Equity	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Equity	Equity In September 2016, COPT established a new at-the-market (“ATM”) stock offering program under which it may, from time to time, offer and sell common shares in “at the market” stock offerings having an aggregate gross sales price of up to $200.0 million . This program replaced an ATM stock offering program that we previously had in place. During the nine months ended September 30, 2016 , certain COPLP limited partners redeemed 87,000 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	9 Months Ended
	Sep. 30, 2016
Segment Reporting [Abstract]
Information by Business Segment	Information by Business Segment We have the following reportable segments: Defense/IT Locations; Regional Office; our operating wholesale data center; and other. We also report on Defense/IT Locations sub-segments, which include the following: Fort George G. Meade and the Baltimore/Washington Corridor (referred to herein as “Fort Meade/BW Corridor”); Northern Virginia Defense/IT Locations; Lackland Air Force Base (in San Antonio); locations serving the U.S. Navy (“Navy Support Locations”), which included properties proximate to the Washington Navy Yard, the Naval Air Station Patuxent River in Maryland and the Naval Surface Warfare Center Dahlgren Division in Virginia; Redstone Arsenal (in Huntsville); and data center shells (properties leased to tenants to be operated as data centers in which the tenants generally fund the costs for the power, fiber connectivity and data center infrastructure). Effective in the quarter ended September 30, 2016, we changed our segment reporting measures to include certain amounts discussed below pertaining to investments in unconsolidated real estate joint ventures (“UJVs”); this change did not affect prior periods reported herein as we did not own any investments in UJVs during such periods prior to July 21, 2016 (see Note 5). We measure the performance of our segments through the measure we define as net operating income from real estate operations (“NOI from real estate operations”), which includes: real estate revenues and property operating expenses from continuing and discontinued operations; and the net of revenues and property operating expenses of real estate operations owned through UJVs that is allocable to COPT’s ownership interest (“UJV NOI allocable to COPT”). Amounts reported for segment assets represent long-lived assets associated with consolidated operating properties (including the carrying value of properties, intangible assets, deferred leasing costs, deferred rents receivable and lease incentives) and the carrying value of investments in UJVs owning operating properties. Amounts reported as additions to long-lived assets represent additions to existing consolidated operating properties, excluding transfers from non-operating properties, which we report separately. The table below reports segment financial information for our reportable segments (in thousands). Operating 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 September 30, 2016 Revenues from real estate operations $ 61,460 $ 12,231 $ 12,532 $ 7,232 $ 3,189 $ 5,175 $ 101,819 $ 20,499 $ 6,809 $ 1,827 $ 130,954 Property operating expenses 20,598 4,462 7,599 3,374 1,112 528 37,673 8,155 3,317 807 49,952 UJV NOI allocable to COPT — — — — — 1,008 1,008 — — — 1,008 NOI from real estate operations $ 40,862 $ 7,769 $ 4,933 $ 3,858 $ 2,077 $ 5,655 $ 65,154 $ 12,344 $ 3,492 $ 1,020 $ 82,010 Additions to long-lived assets $ 5,901 $ 7,153 $ — $ 2,207 $ 2,642 $ — $ 17,903 $ 4,168 $ 108 $ 53 $ 22,232 Transfers from non-operating properties $ 5,331 $ 308 $ 3 $ — $ 3,100 $ 25,513 $ 34,255 $ (4 ) $ 40 $ — $ 34,291 Three Months Ended September 30, 2015 Revenues from real estate operations $ 61,400 $ 12,875 $ 9,018 $ 6,886 $ 3,061 $ 5,665 $ 98,905 $ 26,782 $ 6,078 $ 1,921 $ 133,686 Property operating expenses 20,106 5,150 4,553 3,287 888 532 34,516 9,596 4,008 777 48,897 UJV NOI allocable to COPT — — — — — — — — — — — NOI from real estate operations $ 41,294 $ 7,725 $ 4,465 $ 3,599 $ 2,173 $ 5,133 $ 64,389 $ 17,186 $ 2,070 $ 1,144 $ 84,789 Additions to long-lived assets $ 7,943 $ 1,603 $ — $ 2,084 $ 175 $ — $ 11,805 $ 129,259 $ — $ (27 ) $ 141,037 Transfers from non-operating properties $ 25,184 $ (91 ) $ 591 $ 1,408 $ 1,207 $ 34,287 $ 62,586 $ 5,505 $ 73,804 $ 315 $ 142,210 Nine Months Ended September 30, 2016 Revenues from real estate operations $ 184,881 $ 36,404 $ 34,408 $ 21,164 $ 9,496 $ 18,793 $ 305,146 $ 67,284 $ 20,106 $ 5,429 $ 397,965 Property operating expenses 64,222 13,310 19,863 9,573 3,050 2,164 112,182 26,707 8,629 2,450 149,968 UJV NOI allocable to COPT — — — — — 1,008 1,008 — — — 1,008 NOI from real estate operations $ 120,659 $ 23,094 $ 14,545 $ 11,591 $ 6,446 $ 17,637 $ 193,972 $ 40,577 $ 11,477 $ 2,979 $ 249,005 Additions to long-lived assets $ 19,516 $ 13,290 $ — $ 5,710 $ 3,561 $ — $ 42,077 $ 9,107 $ 108 $ 363 $ 51,655 Transfers from non-operating properties $ 41,850 $ 28,158 $ 240 $ — $ 3,315 $ 81,467 $ 155,030 $ 104 $ (391 ) $ (11 ) $ 154,732 Segment assets at September 30, 2016 $ 1,261,337 $ 416,886 $ 132,722 $ 195,244 $ 111,310 $ 189,746 $ 2,307,245 $ 453,766 $ 234,551 $ 31,563 $ 3,027,125 Nine Months Ended September 30, 2015 Revenues from real estate operations $ 182,591 $ 37,383 $ 27,426 $ 21,337 $ 8,165 $ 15,816 $ 292,718 $ 73,142 $ 12,933 $ 5,798 $ 384,591 Property operating expenses 63,102 16,120 14,665 10,075 2,605 1,726 108,293 26,750 8,441 2,506 145,990 UJV NOI allocable to COPT — — — — — — — — — — — NOI from real estate operations $ 119,489 $ 21,263 $ 12,761 $ 11,262 $ 5,560 $ 14,090 $ 184,425 $ 46,392 $ 4,492 $ 3,292 $ 238,601 Additions to long-lived assets $ 16,529 $ 86,303 $ — $ 5,446 $ 466 $ — $ 108,744 $ 198,589 $ 108 $ 282 $ 307,723 Transfers from non-operating properties $ 44,212 $ 51,117 $ 32,150 $ 1,408 $ 13,184 $ 50,295 $ 192,366 $ 22,230 $ 89,183 $ 327 $ 304,106 Segment assets at September 30, 2015 $ 1,284,712 $ 413,321 $ 134,790 $ 196,105 $ 108,541 $ 203,090 $ 2,340,559 $ 695,490 $ 246,806 $ 71,907 $ 3,354,762 The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Segment revenues from real estate operations $ 130,954 $ 133,686 $ 397,965 $ 384,591 Construction contract and other service revenues 11,149 17,058 34,372 97,554 Less: Revenues from discontinued operations — — — (4 ) Total revenues $ 142,103 $ 150,744 $ 432,337 $ 482,141 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Segment property operating expenses $ 49,952 $ 48,897 $ 149,968 $ 145,990 Less: Property operating expenses from discontinued operations — — — 6 Total property operating expenses $ 49,952 $ 48,897 $ 149,968 $ 145,996 The following table reconciles UJV NOI allocable to COPT to equity in income of unconsolidated entities as reported on our consolidated statements of operations (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 UJV NOI allocable to COPT $ 1,008 $ — $ 1,008 $ — Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (415 ) — (415 ) — Add: Equity in income of unconsolidated non-real estate entities 1 18 21 52 Equity in income of unconsolidated entities $ 594 $ 18 $ 614 $ 52 As previously discussed, we provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. The primary manner in which we evaluate the operating performance of our service activities is through a measure we define as net operating income from service operations (“NOI from service operations”), which is based on the net of revenues and expenses from these activities. Construction contract and other service revenues and expenses consist primarily of subcontracted costs that are reimbursed to us by the customer along with a management fee. The operating margins from these activities are small relative to the revenue. We believe NOI from service operations is a useful measure in assessing both our level of activity and our profitability in conducting such operations. The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Construction contract and other service revenues $ 11,149 $ 17,058 $ 34,372 $ 97,554 Construction contract and other service expenses (10,341 ) (16,132 ) (32,513 ) (94,923 ) NOI from service operations $ 808 $ 926 $ 1,859 $ 2,631 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 NOI from real estate operations $ 82,010 $ 84,789 $ 249,005 $ 238,601 NOI from service operations 808 926 1,859 2,631 Interest and other income 1,391 692 3,877 3,217 Equity in income of unconsolidated entities 594 18 614 52 Income tax (expense) benefit 21 (48 ) 28 (153 ) Depreciation and other amortization associated with real estate operations (32,015 ) (38,403 ) (99,790 ) (103,788 ) Impairment losses (27,699 ) (2,307 ) (99,837 ) (3,545 ) General, administrative and leasing expenses (8,855 ) (7,439 ) (28,764 ) (22,864 ) Business development expenses and land carry costs (1,716 ) (5,573 ) (6,497 ) (10,986 ) Interest expense (18,301 ) (24,121 ) (64,499 ) (66,727 ) NOI from discontinued operations — — — (10 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,008 ) — (1,008 ) — (Loss) gain on early extinguishment of debt (59 ) 85,745 (37 ) 85,677 (Loss) income from continuing operations $ (4,829 ) $ 94,279 $ (45,049 ) $ 122,105 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): September 30, September 30, Segment assets $ 3,027,125 $ 3,354,762 Non-operating property assets 421,364 416,540 Other assets 185,705 140,790 Total COPT consolidated assets $ 3,634,194 $ 3,912,092 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, (loss) gain on early extinguishment of debt, gain on sales of real estate and equity in income of unconsolidated entities not included in NOI to our real estate segments since they are not included in the measure of segment profit reviewed by management. We also did not allocate general, administrative and leasing expenses, business development expenses and land carry costs, interest and other income, income taxes and noncontrolling interests because these items represent general corporate or non-operating property items not attributable to segments.

Share-Based Compensation and Ot

Share-Based Compensation and Other Compensation Matters	9 Months Ended
	Sep. 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, we made the following common share issuances in settlement of such PSUs during the nine months ended September 30, 2016: • 10,326 shares on May 30, 2016 to Mr. Wayne H. Lingafelter, our former Executive Vice President, Development & Construction Services, who departed on March 31, 2016; and • 20,569 shares on July 12, 2016 to Mr. Roger A. Waesche, Jr., our former Chief Executive Officer, who departed on May 12, 2016. Restricted Shares During the nine months ended September 30, 2016 , certain employees were granted a total of 206,487 restricted common shares with an aggregate grant date fair value of $5.0 million (weighted average of $24.31 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 nine months ended September 30, 2016 , forfeiture restrictions lapsed on 189,569 previously issued common shares; these shares had a weighted average grant date fair value of $27.52 per share, and the aggregate intrinsic value of the shares on the vesting dates was $4.7 million . Deferred Share Awards During the nine months ended September 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 nine months ended September 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, and our Senior Vice President, General Counsel and Secretary, Karen M. Singer, departed the Company to pursue other interests effective March 31, 2016 and August 31, 2016, respectively. We recognized executive transition costs of approximately $6.0 million in the nine months ended September 30, 2016 primarily for termination benefits in connection with the departures of Mr. Waesche, Mr. Lingafelter and Ms. Singer.

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	9 Months Ended
	Sep. 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (4,829 ) $ 94,279 $ (45,049 ) $ 122,105 Gain on sales of real estate, net 34,101 15 34,101 4,000 Preferred share dividends (3,552 ) (3,552 ) (10,657 ) (10,657 ) Income from continuing operations attributable to noncontrolling interests (1,973 ) (4,494 ) (2,346 ) (7,322 ) Income from continuing operations attributable to share-based compensation awards (105 ) (369 ) (319 ) (475 ) Numerator for basic EPS from continuing operations attributable to COPT common shareholders 23,642 85,879 (24,270 ) 107,651 Convertible preferred shares — 372 — — Dilutive effect of common units in COPLP on diluted EPS from continuing operations — — — 4,225 Numerator for diluted EPS from continuing operations attributable to COPT common shareholders $ 23,642 $ 86,251 $ (24,270 ) $ 111,876 Numerator for basic EPS from continuing operations attributable to COPT common shareholders $ 23,642 $ 85,879 $ (24,270 ) $ 107,651 Discontinued operations — — — 156 Discontinued operations attributable to noncontrolling interests — — — (3 ) Numerator for basic EPS on net income attributable to COPT common shareholders 23,642 85,879 (24,270 ) 107,804 Convertible preferred shares — 372 — — Dilutive effect of common units in COPLP — — — 4,231 Numerator for diluted EPS on net income attributable to COPT common shareholders $ 23,642 $ 86,251 $ (24,270 ) $ 112,035 Denominator (all weighted averages): Denominator for basic EPS (common shares) 94,433 94,153 94,312 93,830 Convertible preferred shares — 434 — — Dilutive effect of common units — — — 3,697 Dilutive effect of share-based compensation awards 81 21 — 82 Denominator for diluted EPS (common shares) 94,514 94,608 94,312 97,609 Basic EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Diluted EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Conversion of common units 3,591 3,679 3,648 — Conversion of Series I Preferred Units 176 176 176 176 Conversion of Series K Preferred Shares 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 September 30, 2016 and 2015 of 375,000 and 411,000 , respectively, and for the nine months ended September 30, 2016 and 2015 of 394,000 and 412,000 , respectively; and • weighted average options for the three months ended September 30, 2016 and 2015 of 233,000 and 440,000 , respectively, and for the nine months ended September 30, 2016 and 2015 of 307,000 and 480,000 , 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (4,829 ) $ 94,279 $ (45,049 ) $ 122,105 Gain on sales of real estate, net 34,101 15 34,101 4,000 Preferred unit distributions (3,717 ) (3,717 ) (11,152 ) (11,152 ) Income from continuing operations attributable to noncontrolling interests (913 ) (972 ) (2,803 ) (2,605 ) Income from continuing operations attributable to share-based compensation awards (105 ) (369 ) (319 ) (475 ) Numerator for basic EPU from continuing operations attributable to COPLP common unitholders 24,537 89,236 (25,222 ) 111,873 Convertible preferred units — 372 — — Numerator for diluted EPU from continuing operations attributable to COPLP common unitholders $ 24,537 $ 89,608 $ (25,222 ) $ 111,873 Numerator for basic EPU from continuing operations attributable to COPLP common unitholders $ 24,537 $ 89,236 $ (25,222 ) $ 111,873 Discontinued operations — — — 156 Discontinued operations attributable to noncontrolling interests — — — 3 Numerator for basic EPU on net income attributable to COPLP common unitholders 24,537 89,236 (25,222 ) 112,032 Convertible preferred units — 372 — — Numerator for diluted EPU on net income attributable to COPLP common unitholders $ 24,537 $ 89,608 $ (25,222 ) $ 112,032 Denominator (all weighted averages): Denominator for basic EPU (common units) 98,024 97,832 97,960 97,527 Convertible preferred shares — 434 — — Dilutive effect of share-based compensation awards 81 21 — 82 Denominator for diluted EPU (common units) 98,105 98,287 97,960 97,609 Basic EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Diluted EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Conversion of Series I preferred units 176 176 176 176 Conversion of Series K preferred units 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 September 30, 2016 and 2015 of 375,000 and 411,000 , respectively, and for the nine months ended September 30, 2016 and 2015 of 394,000 and 412,000 , respectively; and • weighted average options for the three months ended September 30, 2016 and 2015 of 233,000 and 440,000 , respectively, and for the nine months ended September 30, 2016 and 2015 of 307,000 and 480,000 , 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	9 Months Ended
	Sep. 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 $1.3 million liability through September 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 September 30, 2016 follow (in thousands): Year Ending December 31, 2016 (1) $ 307 2017 1,159 2018 1,113 2019 1,082 2020 1,089 Thereafter 86,806 $ 91,556 (1) Represents the three months ending December 31, 2016. Contractual Obligations We had amounts remaining to be incurred under various contractual obligations as of September 30, 2016 that included the following: • new development and redevelopment obligations of $77.6 million ; • capital expenditures for operating properties of $60.5 million ; • third party construction and development of $10.5 million ; and • purchase obligations of $1.8 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 limited to $19 million in the aggregate. We have insurance coverage in place to mitigate much of any potential future losses that may result from these indemnification agreements.

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 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 state our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 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. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in a more timely recognition of such losses. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 2018. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In August 2016, the FASB issued guidance that clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows with the objective of reducing the existing diversity in practice related to eight specific cash flow issues. The guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 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 September 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 $ — $ 17,272 $ — $ 17,272 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 September 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 $ 5,160 $ — $ — $ 5,160 Other 90 — — 90 Total assets $ 5,250 $ — $ — $ 5,250 Liabilities: Deferred compensation plan liability (2) $ — $ 5,250 $ — $ 5,250 Interest rate derivatives — 17,272 — 17,272 Total liabilities $ — $ 22,522 $ — $ 22,522 (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 September 30, 2016 (dollars in thousands): Fair Values as of September 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: Assets held for sale, net $ — $ — $ 127,128 $ 127,128
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 as of September 30, 2016 (dollars in thousands): Valuation Technique Fair Values on Measurement Date Unobservable Input Range (Weighted Average) Contracts to sell $ 87,983 Contract amounts N/A Discounted cash flow $ 36,693 Discount rate 9.5% - 11.3% (10.5%) Terminal capitalization rate 8.3% - 9.5% (8.7%) Yield analyses $ 2,452 Investor yield requirement 9.0% (1) (1) Only one fair value applied for this unobservable input.

Properties, Net (Tables)

Properties, Net (Tables)	9 Months Ended
	Sep. 30, 2016
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): September 30, December 31, Land $ 424,627 $ 463,305 Buildings and improvements 2,888,918 3,157,587 Less: Accumulated depreciation (681,476 ) (700,363 ) Operating properties, net $ 2,632,069 $ 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): September 30, December 31, Land $ 199,038 $ 207,774 Development in progress, excluding land 197,231 221,445 Projects in development or held for future development $ 396,269 $ 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): September 30, 2016 December 31, 2015 Properties, net $ 147,236 $ 90,188 Deferred rent receivable 6,642 2,891 Intangible assets on real estate acquisitions, net 1,540 1,591 Deferred leasing costs, net 4,901 1,391 Lease incentives, net 1,135 721 Assets held for sale, net $ 161,454 $ 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 September 30, 2015 For the Nine Months Ended September 30, 2015 (Unaudited) Pro forma total revenues $ 152,736 $ 498,657 Pro forma net income attributable to COPT common shareholders $ 88,836 $ 112,941 Pro forma EPS: Basic $ 0.94 $ 1.20 Diluted $ 0.94 $ 1.20
Schedule of operating property dispositions	During the nine months ended September 30, 2016, we completed dispositions of the following operating properties (dollars in thousands): Project Name City, State Segment Date of Disposition Number of Buildings Total Rentable Square Feet Transaction Value Gain on Disposition Arborcrest Corporate Campus (1) Philadelphia, PA Regional Office 8/4/2016 4 654,000 $ 142,800 $ 4,742 8003 Corporate Drive White Marsh, MD Regional Office 8/17/2016 1 18,000 2,400 — 1341 & 1343 Ashton Road Hanover, MD Fort Meade/BW Corridor 9/9/2016 2 25,000 2,900 848 8007, 8013, 8015, 8019 and 8023-8027 Corporate Drive (1) White Marsh, MD Regional Office 9/21/2016 5 130,000 14,513 1,906 1302, 1304 and 1306 Concourse Drive Linthicum, MD Fort Meade/BW Corridor 9/29/2016 3 299,000 48,100 8,683 15 1,126,000 $ 210,713 $ 16,179 (1) This disposition also included land.

Real Estate Joint Ventures (Tab

Real Estate Joint Ventures (Tables)	9 Months Ended
	Sep. 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 September 30, 2016 (dollars in thousands): Nominal Ownership September 30, 2016 (1) Date % as of Total Encumbered Total Acquired 9/30/2016 Nature of Activity Assets Assets Liabilities LW Redstone Company, LLC 3/23/2010 85% Development and operation of real estate (2) $ 157,168 $ 80,154 $ 53,056 M Square Associates, LLC 6/26/2007 50% Development and operation of real estate (3) 66,053 47,006 45,807 Stevens Investors, LLC 8/11/2015 95% Development of real estate (4) 40,282 — 7,680 $ 263,503 $ 127,160 $ 106,543 (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)	9 Months Ended
	Sep. 30, 2016
Receivables [Abstract]
Schedule of investing receivables	Investing receivables, including accrued interest thereon, consisted of the following (in thousands): September 30, December 31, Notes receivable from the City of Huntsville $ 48,098 $ 44,875 Other investing loans receivable 3,021 3,000 $ 51,119 $ 47,875

Prepaid Expenses and Other As29

Prepaid Expenses and Other Assets, Net (Tables)	9 Months Ended
	Sep. 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): September 30, December 31, Prepaid expenses $ 28,752 $ 23,009 Lease incentives, net 19,106 11,133 Construction contract costs incurred in excess of billings 6,367 3,261 Furniture, fixtures and equipment, net 5,492 6,004 Deferred financing costs, net (1) 3,812 5,867 Deferred tax asset, net (2) 3,282 3,467 Other assets 6,727 7,283 Prepaid expenses and other assets, net $ 73,538 $ 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)	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Schedule of debt	Our debt consisted of the following (dollars in thousands): Carrying Value (1) as of Scheduled Maturity September 30, December 31, Stated Interest Rates as of as of September 30, 2016 September 30, 2016 Mortgage and Other Secured Loans: Fixed rate mortgage loans (2) $ 154,976 $ 281,208 3.82% - 7.87% (3) 2019-2026 Variable rate secured loans 13,529 49,792 LIBOR + 1.85% (4) October 2020 Total mortgage and other secured loans 168,505 331,000 Revolving Credit Facility — 43,500 LIBOR + 0.875% to 1.60% May 2019 Term Loan Facilities (5) 516,812 515,902 LIBOR + 0.90% to 2.60% (6) 2019-2022 Unsecured Senior Notes 3.600%, $350,000 aggregate principal 347,024 346,714 3.60% (7) May 2023 5.250%, $250,000 aggregate principal 246,063 245,731 5.25% (8) February 2024 3.700%, $300,000 aggregate principal 297,725 297,378 3.70% (9) June 2021 5.000%, $300,000 aggregate principal 296,279 296,019 5.00% (10) July 2025 Unsecured notes payable 1,428 1,508 0% (11) 2026 Total debt, net $ 1,873,836 $ 2,077,752 (1) The carrying values of our loans other than the Revolving Credit Facility reflect net deferred financing costs of $6.9 million as of September 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 $440,000 as of September 30, 2016 and $514,000 as of December 31, 2015 . (3) The weighted average interest rate on our fixed rate mortgage loans was 4.20% as of September 30, 2016 . (4) The interest rate on our variable rate secured loan as of September 30, 2016 was 2.37% . (5) As of September 30, 2016, we had an additional $150 million in borrowings available to be drawn under a term loan. In addition, we had 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. On October 12, 2016, we repaid a $120.0 million term loan that was scheduled to mature in August 2019. (6) The weighted average interest rate on these loans was 2.17% as of September 30, 2016 . (7) The carrying value of these notes reflects an unamortized discount totaling $2.0 million as of September 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% . (8) The carrying value of these notes reflects an unamortized discount totaling $3.5 million as of September 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% . (9) The carrying value of these notes reflects an unamortized discount totaling $1.8 million as of September 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% . (10) The carrying value of these notes reflects an unamortized discount totaling $3.1 million as of September 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% . (11) 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 $483,000 as of September 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): September 30, 2016 December 31, 2015 Carrying Estimated Carrying Estimated Amount Fair Value Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,187,091 $ 1,233,860 $ 1,185,842 $ 1,211,658 Other fixed-rate debt 156,404 162,974 282,716 291,991 Variable-rate debt 530,341 533,079 609,194 610,987 $ 1,873,836 $ 1,929,913 $ 2,077,752 $ 2,114,636

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	9 Months Ended
	Sep. 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 September 30, December 31, $ 100,000 1.6730% One-Month LIBOR 9/1/2015 8/1/2019 $ (2,339 ) $ (1,217 ) 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 (2,500 ) (1,429 ) 13,676 (1) 1.3900% One-Month LIBOR 10/13/2015 10/1/2020 (236 ) 53 100,000 1.9013% One-Month LIBOR 9/1/2016 12/1/2022 (4,879 ) (138 ) 100,000 1.9050% One-Month LIBOR 9/1/2016 12/1/2022 (4,872 ) (45 ) 50,000 1.9079% One-Month LIBOR 9/1/2016 12/1/2022 (2,446 ) (32 ) 100,000 0.8055% One-Month LIBOR 9/2/2014 9/1/2016 — (148 ) 100,000 0.8100% One-Month LIBOR 9/2/2014 9/1/2016 — (151 ) $ (17,272 ) $ (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 September 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 (17,272 ) (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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Amount of gain (loss) recognized in accumulated other comprehensive loss (“AOCL”) (effective portion) $ 407 $ (3,638 ) $ (16,581 ) $ (6,720 ) Amount of losses reclassified from AOCL into interest expense (effective portion) 1,043 915 2,763 2,457 Amount of gain (loss) recognized in interest expense (ineffective portion) 1,523 — (347 ) —

Redeemable Noncontrolling Int32

Redeemable Noncontrolling Interests (Tables)	9 Months Ended
	Sep. 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 Nine Months Ended September 30, 2016 2015 Beginning balance $ 19,218 $ 18,417 Contributions from noncontrolling interests 22,779 — Distributions to noncontrolling interests (21,344 ) (1,098 ) Net income attributable to noncontrolling interests 1,679 1,690 Adjustment to arrive at fair value of interests 516 599 Ending balance $ 22,848 $ 19,608

Information by Business Segme33

Information by Business Segment (Tables)	9 Months Ended
	Sep. 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 September 30, 2016 Revenues from real estate operations $ 61,460 $ 12,231 $ 12,532 $ 7,232 $ 3,189 $ 5,175 $ 101,819 $ 20,499 $ 6,809 $ 1,827 $ 130,954 Property operating expenses 20,598 4,462 7,599 3,374 1,112 528 37,673 8,155 3,317 807 49,952 UJV NOI allocable to COPT — — — — — 1,008 1,008 — — — 1,008 NOI from real estate operations $ 40,862 $ 7,769 $ 4,933 $ 3,858 $ 2,077 $ 5,655 $ 65,154 $ 12,344 $ 3,492 $ 1,020 $ 82,010 Additions to long-lived assets $ 5,901 $ 7,153 $ — $ 2,207 $ 2,642 $ — $ 17,903 $ 4,168 $ 108 $ 53 $ 22,232 Transfers from non-operating properties $ 5,331 $ 308 $ 3 $ — $ 3,100 $ 25,513 $ 34,255 $ (4 ) $ 40 $ — $ 34,291 Three Months Ended September 30, 2015 Revenues from real estate operations $ 61,400 $ 12,875 $ 9,018 $ 6,886 $ 3,061 $ 5,665 $ 98,905 $ 26,782 $ 6,078 $ 1,921 $ 133,686 Property operating expenses 20,106 5,150 4,553 3,287 888 532 34,516 9,596 4,008 777 48,897 UJV NOI allocable to COPT — — — — — — — — — — — NOI from real estate operations $ 41,294 $ 7,725 $ 4,465 $ 3,599 $ 2,173 $ 5,133 $ 64,389 $ 17,186 $ 2,070 $ 1,144 $ 84,789 Additions to long-lived assets $ 7,943 $ 1,603 $ — $ 2,084 $ 175 $ — $ 11,805 $ 129,259 $ — $ (27 ) $ 141,037 Transfers from non-operating properties $ 25,184 $ (91 ) $ 591 $ 1,408 $ 1,207 $ 34,287 $ 62,586 $ 5,505 $ 73,804 $ 315 $ 142,210 Nine Months Ended September 30, 2016 Revenues from real estate operations $ 184,881 $ 36,404 $ 34,408 $ 21,164 $ 9,496 $ 18,793 $ 305,146 $ 67,284 $ 20,106 $ 5,429 $ 397,965 Property operating expenses 64,222 13,310 19,863 9,573 3,050 2,164 112,182 26,707 8,629 2,450 149,968 UJV NOI allocable to COPT — — — — — 1,008 1,008 — — — 1,008 NOI from real estate operations $ 120,659 $ 23,094 $ 14,545 $ 11,591 $ 6,446 $ 17,637 $ 193,972 $ 40,577 $ 11,477 $ 2,979 $ 249,005 Additions to long-lived assets $ 19,516 $ 13,290 $ — $ 5,710 $ 3,561 $ — $ 42,077 $ 9,107 $ 108 $ 363 $ 51,655 Transfers from non-operating properties $ 41,850 $ 28,158 $ 240 $ — $ 3,315 $ 81,467 $ 155,030 $ 104 $ (391 ) $ (11 ) $ 154,732 Segment assets at September 30, 2016 $ 1,261,337 $ 416,886 $ 132,722 $ 195,244 $ 111,310 $ 189,746 $ 2,307,245 $ 453,766 $ 234,551 $ 31,563 $ 3,027,125 Nine Months Ended September 30, 2015 Revenues from real estate operations $ 182,591 $ 37,383 $ 27,426 $ 21,337 $ 8,165 $ 15,816 $ 292,718 $ 73,142 $ 12,933 $ 5,798 $ 384,591 Property operating expenses 63,102 16,120 14,665 10,075 2,605 1,726 108,293 26,750 8,441 2,506 145,990 UJV NOI allocable to COPT — — — — — — — — — — — NOI from real estate operations $ 119,489 $ 21,263 $ 12,761 $ 11,262 $ 5,560 $ 14,090 $ 184,425 $ 46,392 $ 4,492 $ 3,292 $ 238,601 Additions to long-lived assets $ 16,529 $ 86,303 $ — $ 5,446 $ 466 $ — $ 108,744 $ 198,589 $ 108 $ 282 $ 307,723 Transfers from non-operating properties $ 44,212 $ 51,117 $ 32,150 $ 1,408 $ 13,184 $ 50,295 $ 192,366 $ 22,230 $ 89,183 $ 327 $ 304,106 Segment assets at September 30, 2015 $ 1,284,712 $ 413,321 $ 134,790 $ 196,105 $ 108,541 $ 203,090 $ 2,340,559 $ 695,490 $ 246,806 $ 71,907 $ 3,354,762
Schedule of reconciliation of segment revenues to total revenues	The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Segment revenues from real estate operations $ 130,954 $ 133,686 $ 397,965 $ 384,591 Construction contract and other service revenues 11,149 17,058 34,372 97,554 Less: Revenues from discontinued operations — — — (4 ) Total revenues $ 142,103 $ 150,744 $ 432,337 $ 482,141
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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Segment property operating expenses $ 49,952 $ 48,897 $ 149,968 $ 145,990 Less: Property operating expenses from discontinued operations — — — 6 Total property operating expenses $ 49,952 $ 48,897 $ 149,968 $ 145,996
Schedule of reconciliation of unconsolidated joint venture net operating income to equity in income of unconsolidated entities	The following table reconciles UJV NOI allocable to COPT to equity in income of unconsolidated entities as reported on our consolidated statements of operations (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 UJV NOI allocable to COPT $ 1,008 $ — $ 1,008 $ — Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense (415 ) — (415 ) — Add: Equity in income of unconsolidated non-real estate entities 1 18 21 52 Equity in income of unconsolidated entities $ 594 $ 18 $ 614 $ 52
Schedule of computation of net operating income from service operations	The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Construction contract and other service revenues $ 11,149 $ 17,058 $ 34,372 $ 97,554 Construction contract and other service expenses (10,341 ) (16,132 ) (32,513 ) (94,923 ) NOI from service operations $ 808 $ 926 $ 1,859 $ 2,631
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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 NOI from real estate operations $ 82,010 $ 84,789 $ 249,005 $ 238,601 NOI from service operations 808 926 1,859 2,631 Interest and other income 1,391 692 3,877 3,217 Equity in income of unconsolidated entities 594 18 614 52 Income tax (expense) benefit 21 (48 ) 28 (153 ) Depreciation and other amortization associated with real estate operations (32,015 ) (38,403 ) (99,790 ) (103,788 ) Impairment losses (27,699 ) (2,307 ) (99,837 ) (3,545 ) General, administrative and leasing expenses (8,855 ) (7,439 ) (28,764 ) (22,864 ) Business development expenses and land carry costs (1,716 ) (5,573 ) (6,497 ) (10,986 ) Interest expense (18,301 ) (24,121 ) (64,499 ) (66,727 ) NOI from discontinued operations — — — (10 ) Less: UJV NOI allocable to COPT included in equity in income of unconsolidated entities (1,008 ) — (1,008 ) — (Loss) gain on early extinguishment of debt (59 ) 85,745 (37 ) 85,677 (Loss) income from continuing operations $ (4,829 ) $ 94,279 $ (45,049 ) $ 122,105
Schedule of reconciliation of segment assets to total assets	The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): September 30, September 30, Segment assets $ 3,027,125 $ 3,354,762 Non-operating property assets 421,364 416,540 Other assets 185,705 140,790 Total COPT consolidated assets $ 3,634,194 $ 3,912,092

Share-Based Compensation and 34

Share-Based Compensation and Other Compensation Matters (Tables)	9 Months Ended
	Sep. 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") an35

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Tables)	9 Months Ended
	Sep. 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (4,829 ) $ 94,279 $ (45,049 ) $ 122,105 Gain on sales of real estate, net 34,101 15 34,101 4,000 Preferred share dividends (3,552 ) (3,552 ) (10,657 ) (10,657 ) Income from continuing operations attributable to noncontrolling interests (1,973 ) (4,494 ) (2,346 ) (7,322 ) Income from continuing operations attributable to share-based compensation awards (105 ) (369 ) (319 ) (475 ) Numerator for basic EPS from continuing operations attributable to COPT common shareholders 23,642 85,879 (24,270 ) 107,651 Convertible preferred shares — 372 — — Dilutive effect of common units in COPLP on diluted EPS from continuing operations — — — 4,225 Numerator for diluted EPS from continuing operations attributable to COPT common shareholders $ 23,642 $ 86,251 $ (24,270 ) $ 111,876 Numerator for basic EPS from continuing operations attributable to COPT common shareholders $ 23,642 $ 85,879 $ (24,270 ) $ 107,651 Discontinued operations — — — 156 Discontinued operations attributable to noncontrolling interests — — — (3 ) Numerator for basic EPS on net income attributable to COPT common shareholders 23,642 85,879 (24,270 ) 107,804 Convertible preferred shares — 372 — — Dilutive effect of common units in COPLP — — — 4,231 Numerator for diluted EPS on net income attributable to COPT common shareholders $ 23,642 $ 86,251 $ (24,270 ) $ 112,035 Denominator (all weighted averages): Denominator for basic EPS (common shares) 94,433 94,153 94,312 93,830 Convertible preferred shares — 434 — — Dilutive effect of common units — — — 3,697 Dilutive effect of share-based compensation awards 81 21 — 82 Denominator for diluted EPS (common shares) 94,514 94,608 94,312 97,609 Basic EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Diluted EPS: (Loss) income from continuing operations attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPT common shareholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Conversion of common units 3,591 3,679 3,648 — Conversion of Series I Preferred Units 176 176 176 176 Conversion of Series K Preferred Shares 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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: (Loss) income from continuing operations $ (4,829 ) $ 94,279 $ (45,049 ) $ 122,105 Gain on sales of real estate, net 34,101 15 34,101 4,000 Preferred unit distributions (3,717 ) (3,717 ) (11,152 ) (11,152 ) Income from continuing operations attributable to noncontrolling interests (913 ) (972 ) (2,803 ) (2,605 ) Income from continuing operations attributable to share-based compensation awards (105 ) (369 ) (319 ) (475 ) Numerator for basic EPU from continuing operations attributable to COPLP common unitholders 24,537 89,236 (25,222 ) 111,873 Convertible preferred units — 372 — — Numerator for diluted EPU from continuing operations attributable to COPLP common unitholders $ 24,537 $ 89,608 $ (25,222 ) $ 111,873 Numerator for basic EPU from continuing operations attributable to COPLP common unitholders $ 24,537 $ 89,236 $ (25,222 ) $ 111,873 Discontinued operations — — — 156 Discontinued operations attributable to noncontrolling interests — — — 3 Numerator for basic EPU on net income attributable to COPLP common unitholders 24,537 89,236 (25,222 ) 112,032 Convertible preferred units — 372 — — Numerator for diluted EPU on net income attributable to COPLP common unitholders $ 24,537 $ 89,608 $ (25,222 ) $ 112,032 Denominator (all weighted averages): Denominator for basic EPU (common units) 98,024 97,832 97,960 97,527 Convertible preferred shares — 434 — — Dilutive effect of share-based compensation awards 81 21 — 82 Denominator for diluted EPU (common units) 98,105 98,287 97,960 97,609 Basic EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Diluted EPU: (Loss) income from continuing operations attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net (loss) income attributable to COPLP common unitholders $ 0.25 $ 0.91 $ (0.26 ) $ 1.15
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 September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Conversion of Series I preferred units 176 176 176 176 Conversion of Series K preferred units 434 — 434 434

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 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 September 30, 2016 follow (in thousands): Year Ending December 31, 2016 (1) $ 307 2017 1,159 2018 1,113 2019 1,082 2020 1,089 Thereafter 86,806 $ 91,556 (1) Represents the three months ending December 31, 2016.

Organization (Details)

Organization (Details) ft² in Thousands	Sep. 30, 2016aft²PropertyMW
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	168
Area of real estate property (in square feet or acres) | ft²	17,500
Operating office properties | Single-tenant data centers
Investments in real estate
Number of real estate properties	12
Operating office properties | Single-tenant data centers | Unconsolidated Joint Venture
Investments in real estate
Number of real estate properties	6
Office properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties	10
Area of real estate property (in square feet or acres) | ft²	1,200
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	1,358
Developable square feet | ft²	16,200
Operating 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.	9 Months Ended
	Sep. 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	9 Months Ended
	Sep. 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	$ 5.3

Fair Value Measurements (Deta40

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Liabilities:
Interest rate derivatives	$ 17,272	$ 3,160
Corporate Office Properties, L.P.
Liabilities:
Interest rate derivatives	17,272	$ 3,160
Fair value measurement on a recurring basis
Assets:
Fair Values on Measurement Date	5,250
Liabilities:
Deferred compensation plan liability	5,250
Interest rate derivatives	17,272
Liabilities	22,522
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	5,160
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	90
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Fair Values on Measurement Date	5,250
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	5,160
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	90
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Liabilities:
Deferred compensation plan liability	5,250
Interest rate derivatives	17,272
Liabilities	22,522
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Liabilities:
Interest rate derivatives	17,272
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Liabilities:
Interest rate derivatives	$ 17,272

Fair Value Measurements (Deta41

Fair Value Measurements (Details 3) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)Property	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	$ 27,699			$ 2,307	$ 99,837	$ 3,545
Assets held for sale, net	161,454				161,454		$ 96,782
Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Assets held for sale, net	161,454				161,454		96,782
Fort Meade/BW Corridor
Assets and liabilities measured at fair value on a non-recurring basis
Number of properties | Property			2
Fair value measurement on a nonrecurring basis | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Properties held-for-sale							$ 96,800
Impairment losses	11,500		$ 2,400
Assets held for sale, net	161,454	$ 300,600	$ 225,900		161,454
Fair Values on Measurement Date	127,128				127,128
Fair value measurement on a nonrecurring basis | Assets held for sale, net | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value on a non-recurring basis
Fair Values on Measurement Date	127,128				$ 127,128
Fair value measurement on a nonrecurring basis | Assets disposed of by sale
Assets and liabilities measured at fair value on a non-recurring basis
Transaction Value	210,700
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 | Defense/Information Technology Locations | Fort Meade/BW Corridor | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	13,300
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 | White Marsh, Maryland | Assets held for sale, net
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	10,000
Fair value measurement on a nonrecurring basis | White Marsh, Maryland | Assets held for sale, net | Land in development or held for future development
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	$ 2,900

Fair Value Measurements (Deta42

Fair Value Measurements (Details 4) - Fair value measurement on a nonrecurring basis - Significant Unobservable Inputs (Level 3) $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Contracts to sell
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Values on Measurement Date	$ 87,983
Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Values on Measurement Date	36,693
Yield analyses
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Values on Measurement Date	$ 2,452
Investor yield requirement (percent)	9.00%
Minimum | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	9.50%
Terminal capitalization rate (percent)	8.30%
Maximum | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	11.30%
Terminal capitalization rate (percent)	9.50%
Weighted Average | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	10.50%
Terminal capitalization rate (percent)	8.70%

Properties, Net (Details)

Properties, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investments in real estate
Less: accumulated depreciation	$ (681,476)	$ (700,363)
Operating properties, net	2,632,069	2,920,529
Land
Investments in real estate
Gross	424,627	463,305
Buildings and improvements
Investments in real estate
Gross	$ 2,888,918	$ 3,157,587

Properties, Net (Details 2)

Properties, Net (Details 2) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Properties
Projects in development or held for future development	$ 396,269	$ 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	199,038	207,774
Projects in development or held for future development | Construction in progress, excluding land
Properties
Projects in development or held for future development	$ 197,231	$ 221,445

Properties, Net (Details 3)

Properties, Net (Details 3) $ in Thousands	Sep. 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	$ 161,454	$ 96,782
Assets held for sale, net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties, net	147,236	90,188
Deferred rent receivable	6,642	2,891
Intangible assets on real estate acquisitions, net	1,540	1,591
Deferred leasing costs, net	4,901	1,391
Lease incentives, net	1,135	721
Assets held for sale, net	$ 161,454	$ 96,782
Fort Meade/BW Corridor | Assets held for sale, net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	6
Regional Office | White Marsh, Maryland | Assets held for sale, net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	9	13
Other Segments | San Antonio, Texas | Assets held for sale, net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	2	2
Defense/Information Technology Locations | Northern Virginia Defense/IT | Assets held for sale, net
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | Property	2

Properties, Net (Details 4)

Properties, Net (Details 4) ft² in Thousands, $ in Thousands	Aug. 07, 2015USD ($)ft²	Apr. 15, 2015USD ($)ft²	Mar. 19, 2015USD ($)ft²	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
2015 Acquisitions
Business Acquisition [Line Items]
Contributed revenues				$ 9,200	$ 6,900	$ 27,600	$ 11,200
Contributed net income from continuing operations				$ 432	$ 487	$ 2,400	$ 697
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	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Real Estate [Abstract]
Pro forma total revenues	$ 152,736	$ 498,657
Pro forma net income attributable to COPT common shareholders	$ 88,836	$ 112,941
Pro Forma EPS, Basic (in dollars per share)	$ 0.94	$ 1.20
Pro Forma EPS, Diluted (in dollars per share)	$ 0.94	$ 1.20

Properties, Net (Details 6)

Properties, Net (Details 6) ft² in Thousands, $ in Thousands	Jul. 21, 2016USD ($)Property	Sep. 30, 2016USD ($)ft²builldingProperty	Sep. 30, 2015USD ($)
Construction and Redevelopment Activities
Value of properties contributed		$ 22,600	$ 0
Sale price of land		$ 5,700
Operating office properties
Construction and Redevelopment Activities
Square footage of real estate properties (in square feet) | ft²		17,500
Number of real estate properties | Property		168
Office properties under, or contractually committed for, construction or approved for redevelopment
Construction and Redevelopment Activities
Square footage of real estate properties (in square feet) | ft²		1,200
Number of real estate properties | Property		10
Single-tenant data centers | Operating office properties
Construction and Redevelopment Activities
Transaction Value		$ 44,300
Ownership percentage sold (percent)	50.00%
Number of properties contributed | Property	6
Value of properties contributed	$ 147,600
Proceeds from issuance of debt		$ 60,000
Ownership percentage (percent)	50.00%
Number of real estate properties | Property		12
Newly constructed properties placed in service
Construction and Redevelopment Activities
Square feet of properties placed in service | ft²		490
Number of real estate properties | Property		5
Newly redeveloped properties placed in service
Construction and Redevelopment Activities
Square feet of properties placed in service | ft²		55
Number of real estate properties | Property		2
Properties under construction or contractually committed for construction
Construction and Redevelopment Activities
Square footage of real estate properties (in square feet) | ft²		1,100
Number of real estate properties | Property		7
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 | Property		2
Properties under or approved for redevelopment
Construction and Redevelopment Activities
Square footage of real estate properties (in square feet) | ft²		104
Number of real estate properties | Property		3
Operating Properties
Construction and Redevelopment Activities
Number of Buildings | buillding		15
Square footage of real estate properties (in square feet) | ft²		1,126
Transaction Value		$ 210,713
Gain on Disposition		16,179
Operating Properties | Data Center Shells | Single-tenant data centers | Operating office properties
Construction and Redevelopment Activities
Gain on Disposition		$ 17,900
Number of properties contributed | buillding		6
Operating Properties | Regional Office | Arborcrest Corporate Campus
Construction and Redevelopment Activities
Number of Buildings | buillding		4
Square footage of real estate properties (in square feet) | ft²		654
Transaction Value		$ 142,800
Gain on Disposition		$ 4,742
Operating Properties | Regional Office | 8003 Corporate Drive
Construction and Redevelopment Activities
Number of Buildings | buillding		1
Square footage of real estate properties (in square feet) | ft²		18
Transaction Value		$ 2,400
Gain on Disposition		$ 0
Operating Properties | Regional Office | 8007, 8013, 8015, 8019 and 8023-8027 Corporate Drive
Construction and Redevelopment Activities
Number of Buildings | buillding		5
Square footage of real estate properties (in square feet) | ft²		130
Transaction Value		$ 14,513
Gain on Disposition		$ 1,906
Operating Properties | Fort Meade/BW Corridor | 1341 and 1343 Ashton Road
Construction and Redevelopment Activities
Number of Buildings | buillding		2
Square footage of real estate properties (in square feet) | ft²		25
Transaction Value		$ 2,900
Gain on Disposition		$ 848
Operating Properties | Fort Meade/BW Corridor | 1302, 1304 & 1306 Concourse Drive
Construction and Redevelopment Activities
Number of Buildings | buillding		3
Square footage of real estate properties (in square feet) | ft²		299
Transaction Value		$ 48,100
Gain on Disposition		$ 8,683

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) $ in Thousands	Jul. 21, 2016USD ($)Property	Jan. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)
Investments in consolidated real estate joint ventures
Value of properties contributed			$ 22,600	$ 0
Investment balance			25,700
Maximum amount at risk			18,500
Consolidated real estate joint ventures
Investments in consolidated real estate joint ventures
Total Assets			263,503
Encumbered Assets			127,160
Total Liabilities			$ 106,543
Variable Interest Entity, Primary Beneficiary | LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)			85.00%
Total Assets			$ 157,168
Encumbered Assets			80,154
Total Liabilities			$ 53,056
Variable Interest Entity, Primary Beneficiary | M Square Associates, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)			50.00%
Total Assets			$ 66,053
Encumbered Assets			47,006
Total Liabilities			$ 45,807
Variable Interest Entity, Primary Beneficiary | Stevens Investors, LLC
Investments in consolidated real estate joint ventures
Ownership (as a percent)			95.00%
Total Assets			$ 40,282
Encumbered Assets			0
Total Liabilities			7,680
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
Single-tenant data centers | Operating office properties
Investments in consolidated real estate joint ventures
Value of properties contributed	$ 147,600
Ownership percentage sold (percent)	50.00%
Number of properties contributed | Property	6
Ownership percentage (percent)	50.00%

Investing Receivables (Details)

Investing Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 51,119	$ 47,875
Notes Receivable from City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 48,098	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	$ 3,021	$ 3,000

Prepaid Expenses and Other As51

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Prepaid Expense and Other Assets [Abstract]
Prepaid expenses	$ 28,752	$ 23,009
Lease incentives, net	19,106	11,133
Construction contract costs incurred in excess of billings	6,367	3,261
Furniture, fixtures and equipment, net	5,492	6,004
Deferred financing costs, net	3,812	5,867
Deferred tax asset, net	3,282	3,467
Other assets	6,727	7,283
Prepaid expenses and other assets, net	73,538	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 ($)	Oct. 12, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Debt
Carrying Value		$ 1,873,836,000		$ 1,873,836,000		$ 2,077,752,000
Deferred financing costs, net		3,812,000		3,812,000		5,867,000
Interest costs capitalized		1,200,000	$ 1,500,000	4,300,000	$ 5,600,000
Loans payable
Debt
Deferred financing costs, net		6,900,000		6,900,000		8,000,000
Mortgage and Other Secured Loans:
Debt
Carrying Value		168,505,000		168,505,000		331,000,000
Fixed rate mortgage loans
Debt
Carrying Value		154,976,000		$ 154,976,000		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		$ 440,000		$ 440,000		514,000
Weighted average interest rate (as a percent)		4.20%		4.20%
Variable rate secured loans
Debt
Carrying Value		$ 13,529,000		$ 13,529,000		49,792,000
Description of variable rate basis				LIBOR
Stated interest rate (as a percent)		2.37%		2.37%
Variable rate secured loans | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)				1.85%
Revolving Credit Facility
Debt
Carrying Value		$ 0		$ 0		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		$ 516,812,000		$ 516,812,000		515,902,000
Description of variable rate basis				LIBOR
Weighted average interest rate (as a percent)		2.17%		2.17%
Increase to maximum borrowing capacity		$ 150,000,000		$ 150,000,000
Aggregate additional borrowing capacity available		430,000,000		$ 430,000,000
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%
Term Loan Facilities | Subsequent Event
Debt
Repayments of term loan	$ 120,000,000
3.60% Senior Notes | Unsecured senior notes
Debt
Carrying Value		347,024,000		$ 347,024,000		346,714,000
Debt instrument, face amount		$ 350,000		$ 350,000
Stated interest rate (as a percent)		3.60%		3.60%
Unamortized discount included in carrying value		$ 2,000,000		$ 2,000,000		2,200,000
Interest rate on debt (as a percent)		3.70%		3.70%
5.250% Senior Notes | Unsecured senior notes
Debt
Carrying Value		$ 246,063,000		$ 246,063,000		245,731,000
Debt instrument, face amount		$ 250,000		$ 250,000
Stated interest rate (as a percent)		5.25%		5.25%
Unamortized discount included in carrying value		$ 3,500,000		$ 3,500,000		3,800,000
Interest rate on debt (as a percent)		5.49%		5.49%
3.70% Senior Notes | Unsecured senior notes
Debt
Carrying Value		$ 297,725,000		$ 297,725,000		297,378,000
Debt instrument, face amount		$ 300,000		$ 300,000
Stated interest rate (as a percent)		3.70%		3.70%
Unamortized discount included in carrying value		$ 1,800,000		$ 1,800,000		2,100,000
Interest rate on debt (as a percent)		3.85%		3.85%
5.000% Senior Notes | Unsecured senior notes
Debt
Carrying Value		$ 296,279,000		$ 296,279,000		296,019,000
Debt instrument, face amount		$ 300,000		$ 300,000
Stated interest rate (as a percent)		5.00%		5.00%
Unamortized discount included in carrying value		$ 3,100,000		$ 3,100,000		3,300,000
Interest rate on debt (as a percent)		5.15%		5.15%
Unsecured notes payable
Debt
Carrying Value		$ 1,428,000		$ 1,428,000		1,508,000
Stated interest rate (as a percent)		0.00%		0.00%
Unamortized discount included in carrying value		$ 483,000		$ 483,000		$ 554,000

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Carrying Amount
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	$ 1,873,836	$ 2,077,752
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	1,187,091	1,185,842
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	156,404	282,716
Carrying Amount | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	530,341	609,194
Estimated Fair Value
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	1,929,913	2,114,636
Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	1,233,860	1,211,658
Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	162,974	291,991
Estimated Fair Value | Variable-rate debt
Carrying amount and estimated fair value of debt
Long-term Debt, Fair Value	$ 533,079	$ 610,987

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of gain (loss) recognized in accumulated other comprehensive loss (“AOCL”) (effective portion)	$ 407	$ (3,638)	$ (16,581)	$ (6,720)
Amount of losses reclassified from AOCL into interest expense (effective portion)	1,043	915	2,763	2,457
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	5,200		5,200
Interest rate derivatives in liability position, fair value	17,900		17,900
Termination value to settle obligations under interest rate derivative agreements	18,400		18,400
Interest rate swaps | Interest Expense
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of gain (loss) recognized in interest expense (ineffective portion)	1,523	$ 0	(347)	$ 0
Interest rate swaps | Prepaid expenses and other current assets
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	0		0		$ 53
Interest rate swaps | Interest rate derivatives
Fair value of interest rate derivatives and balance sheet classification
Interest rate swaps designated as cash flow hedges	(17,272)		(17,272)		(3,160)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(17,272)		(17,272)		(3,107)
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	$ (2,339)		$ (2,339)		(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	$ (2,500)		$ (2,500)		(1,429)
Designated | Interest rate swap, effective October 13, 2015
Fair values of interest rate swap derivatives
Notional Amount	$ 13,676		$ 13,676
Fixed rate (as a percent)	1.39%		1.39%
Fair value of interest rate swaps	$ (236)		$ (236)		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	$ (4,879)		$ (4,879)		(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	$ (4,872)		$ (4,872)		(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	$ (2,446)		$ (2,446)		(32)
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	$ 0		$ 0		(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	$ 0		$ 0		$ (151)

Redeemable Noncontrolling Int55

Redeemable Noncontrolling Interests (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)joint_venture	Sep. 30, 2015USD ($)
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	22,779	0
Distributions to noncontrolling interests	(21,344)	(1,098)
Net income attributable to noncontrolling interests	1,679	1,690
Adjustment to arrive at fair value of interests	516	599
Ending balance	$ 22,848	$ 19,608

Equity (Details)

Equity (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Class of Stock [Line Items]
Conversion of common units to common shares (in units/ shares)		87,000	160,160
Common Stock Issued to Public Under At-the-Market Program
Class of Stock [Line Items]
At-market-stock aggregate gross sales price	$ 200

Information by Business Segme57

Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment financial information for real estate operations
Revenues from real estate operations	$ 130,954	$ 133,686	$ 397,965	$ 384,591
Property operating expenses	49,952	48,897	149,968	145,990
UJV NOI allocable to COPT	1,008	0	1,008	0
NOI from real estate operations	82,010	84,789	249,005	238,601
Additions to long-lived assets	22,232	141,037	51,655	307,723
Transfers from non-operating properties	34,291	142,210	154,732	304,106
Segment assets	3,634,194	3,912,092	3,634,194	3,912,092	$ 3,909,312
Defense/Information Technology Locations
Segment financial information for real estate operations
Revenues from real estate operations	101,819	98,905	305,146	292,718
Property operating expenses	37,673	34,516	112,182	108,293
UJV NOI allocable to COPT	1,008	0	1,008	0
NOI from real estate operations	65,154	64,389	193,972	184,425
Additions to long-lived assets	17,903	11,805	42,077	108,744
Transfers from non-operating properties	34,255	62,586	155,030	192,366
Segment assets	2,307,245	2,340,559	2,307,245	2,340,559
Defense/Information Technology Locations | Fort Meade/BW Corridor
Segment financial information for real estate operations
Revenues from real estate operations	61,460	61,400	184,881	182,591
Property operating expenses	20,598	20,106	64,222	63,102
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	40,862	41,294	120,659	119,489
Additions to long-lived assets	5,901	7,943	19,516	16,529
Transfers from non-operating properties	5,331	25,184	41,850	44,212
Segment assets	1,261,337	1,284,712	1,261,337	1,284,712
Defense/Information Technology Locations | Northern Virginia Defense/IT
Segment financial information for real estate operations
Revenues from real estate operations	12,231	12,875	36,404	37,383
Property operating expenses	4,462	5,150	13,310	16,120
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	7,769	7,725	23,094	21,263
Additions to long-lived assets	7,153	1,603	13,290	86,303
Transfers from non-operating properties	308	(91)	28,158	51,117
Segment assets	416,886	413,321	416,886	413,321
Defense/Information Technology Locations | Lackland Air Force Base
Segment financial information for real estate operations
Revenues from real estate operations	12,532	9,018	34,408	27,426
Property operating expenses	7,599	4,553	19,863	14,665
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	4,933	4,465	14,545	12,761
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	3	591	240	32,150
Segment assets	132,722	134,790	132,722	134,790
Defense/Information Technology Locations | Navy Support Locations
Segment financial information for real estate operations
Revenues from real estate operations	7,232	6,886	21,164	21,337
Property operating expenses	3,374	3,287	9,573	10,075
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	3,858	3,599	11,591	11,262
Additions to long-lived assets	2,207	2,084	5,710	5,446
Transfers from non-operating properties	0	1,408	0	1,408
Segment assets	195,244	196,105	195,244	196,105
Defense/Information Technology Locations | Redstone Arsenal
Segment financial information for real estate operations
Revenues from real estate operations	3,189	3,061	9,496	8,165
Property operating expenses	1,112	888	3,050	2,605
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	2,077	2,173	6,446	5,560
Additions to long-lived assets	2,642	175	3,561	466
Transfers from non-operating properties	3,100	1,207	3,315	13,184
Segment assets	111,310	108,541	111,310	108,541
Defense/Information Technology Locations | Data Center Shells
Segment financial information for real estate operations
Revenues from real estate operations	5,175	5,665	18,793	15,816
Property operating expenses	528	532	2,164	1,726
UJV NOI allocable to COPT	1,008	0	1,008	0
NOI from real estate operations	5,655	5,133	17,637	14,090
Additions to long-lived assets	0	0	0	0
Transfers from non-operating properties	25,513	34,287	81,467	50,295
Segment assets	189,746	203,090	189,746	203,090
Regional Office
Segment financial information for real estate operations
Revenues from real estate operations	20,499	26,782	67,284	73,142
Property operating expenses	8,155	9,596	26,707	26,750
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	12,344	17,186	40,577	46,392
Additions to long-lived assets	4,168	129,259	9,107	198,589
Transfers from non-operating properties	(4)	5,505	104	22,230
Segment assets	453,766	695,490	453,766	695,490
Operating wholesale data centers
Segment financial information for real estate operations
Revenues from real estate operations	6,809	6,078	20,106	12,933
Property operating expenses	3,317	4,008	8,629	8,441
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	3,492	2,070	11,477	4,492
Additions to long-lived assets	108	0	108	108
Transfers from non-operating properties	40	73,804	(391)	89,183
Segment assets	234,551	246,806	234,551	246,806
Other Segments
Segment financial information for real estate operations
Revenues from real estate operations	1,827	1,921	5,429	5,798
Property operating expenses	807	777	2,450	2,506
UJV NOI allocable to COPT	0	0	0	0
NOI from real estate operations	1,020	1,144	2,979	3,292
Additions to long-lived assets	53	(27)	363	282
Transfers from non-operating properties	0	315	(11)	327
Segment assets	31,563	71,907	31,563	71,907
Segment assets
Segment financial information for real estate operations
Segment assets	$ 3,027,125	$ 3,354,762	$ 3,027,125	$ 3,354,762

Information by Business Segme58

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reconciliation of segment revenues to total revenues
Segment revenues from real estate operations	$ 130,954	$ 133,686	$ 397,965	$ 384,591
Construction contract and other service revenues	11,149	17,058	34,372	97,554
Less: Revenues from discontinued operations	0	0	0	(4)
Total revenues	142,103	150,744	432,337	482,141
Reconciliation of segment property operating expenses to property operating expenses
Segment property operating expenses	49,952	48,897	149,968	145,990
Less: Property operating expenses from discontinued operations	0	0	0	6
Total property operating expenses	49,952	48,897	149,968	145,996
Reconciliation of UJV NOI allocable to COPT to Equity Income in Unconsolidated Entities
UJV NOI allocable to COPT	1,008	0	1,008	0
Less: Income from UJV allocable to COPT attributable to depreciation and amortization expense and interest expense	(415)	0	(415)	0
Add: Equity in income of unconsolidated non-real estate entities	1	18	21	52
Equity in income of unconsolidated entities	594	18	614	52
Computation of net operating income from service operations
Construction contract and other service revenues	11,149	17,058	34,372	97,554
Construction contract and other service expenses	(10,341)	(16,132)	(32,513)	(94,923)
NOI from service operations	$ 808	$ 926	$ 1,859	$ 2,631

Information by Business Segme59

Information by Business Segment (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from real estate operations	$ 82,010	$ 84,789	$ 249,005	$ 238,601
NOI from service operations	808	926	1,859	2,631
Interest and other income	1,391	692	3,877	3,217
Equity in income of unconsolidated entities	594	18	614	52
Income tax benefit (expense)	21	(48)	28	(153)
Depreciation and other amortization associated with real estate operations	(32,015)	(38,403)	(99,790)	(103,788)
Impairment losses	(27,699)	(2,307)	(99,837)	(3,545)
General, administrative and leasing expenses	(8,855)	(7,439)	(28,764)	(22,864)
Business development expenses and land carry costs	(1,716)	(5,573)	(6,497)	(10,986)
Interest expense	(18,301)	(24,121)	(64,499)	(66,727)
NOI from discontinued operations	0	0	0	(10)
UJV NOI allocable to COPT	(1,008)	0	(1,008)	0
(Loss) gain on early extinguishment of debt	(59)	85,745	(37)	85,677
(Loss) income from continuing operations	$ (4,829)	$ 94,279	$ (45,049)	$ 122,105

Information by Business Segme60

Information by Business Segment (Details 4) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Reconciliation of segment assets to total assets
Assets	$ 3,634,194	$ 3,909,312	$ 3,912,092
Segment assets
Reconciliation of segment assets to total assets
Assets	3,027,125		3,354,762
Non-operating property assets
Reconciliation of segment assets to total assets
Assets	421,364		416,540
Other assets
Reconciliation of segment assets to total assets
Assets	$ 185,705		$ 140,790

Share-Based Compensation and 61

Share-Based Compensation and Other Compensation Matters (Details)	Jul. 02, 2016shares	May 30, 2016shares	Mar. 01, 2016USD ($)shares	Sep. 30, 2016USD ($)Percentile_Rank$ / sharesshares
Other Share-based Compensation Additional Disclosures
Executive transition cost | $				$ 6,000,000
Performance share units
Share-Based Compensation
Stock awards granted (in shares or units)			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)				206,487
Aggregate grant date fair value | $				$ 5,000,000
Assumptions used to value stock awards
Weighted average grant date fair value (in dollars per share) | $ / shares				$ 24.31
Other Share-based Compensation Additional Disclosures
Shares vested (in shares)				189,569
Weighted average fair value of shares vested (in dollars per share) | $ / shares				$ 27.52
Aggregate intrinsic value of awards upon vesting | $				$ 4,700,000
Deferred share award
Share-Based Compensation
Stock awards granted (in shares or units)				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)				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)		10,326
2014 and 2015 PSU Grants | Performance share units | Chief Executive Officer
Other Share-based Compensation Additional Disclosures
Shares issued (in shares)	20,569

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			9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015
Numerator:
(Loss) income from continuing operations		$ (4,829)		$ 94,279	$ (45,049)		$ 122,105
Gain on sales of real estate, net		34,101		15	34,101		4,000
Preferred share/unit dividends/distributions		(3,552)		(3,552)	(10,657)		(10,657)
Income from continuing operations attributable to noncontrolling interests		(1,973)		(4,494)	(2,346)		(7,322)
Income from continuing operations attributable to share-based compensation awards		(105)		(369)	(319)		(475)
Numerator for basic EPS from continuing operations attributable to COPT common shareholders		23,642		85,879	(24,270)		107,651
Convertible preferred shares/units		0		372	0		0
Dilutive effect of common units in COPLP on diluted EPS from continuing operations		0		0	0		4,225
Numerator for diluted EPS from continuing operations attributable to COPT common shareholders		23,642		86,251	(24,270)		111,876
Numerator for basic EPS from continuing operations attributable to COPT common shareholders		23,642		85,879	(24,270)		107,651
Discontinued operations		0		0	0		156
Discontinued operations attributable to noncontrolling interests		0		0	0		(3)
Numerator for basic EPS on net income attributable to COPT common shareholders		23,642		85,879	(24,270)		107,804
Convertible preferred shares/units		0		372	0		0
Dilutive effect of common units in COPLP		0			0		4,231
Numerator for diluted EPS on net income attributable to COPT common shareholders		$ 23,642		$ 86,251	$ (24,270)		$ 112,035
Denominator (all weighted averages):
Denominator for basic EPS (common shares)		94,433		94,153	94,312		93,830
Convertible preferred shares (shares)		0		434	0		0
Dilutive effect of common units (shares)		0			0		3,697
Dilutive effect of share-based compensation awards (shares)		81		21	0		82
Denominator for diluted EPS (common shares)		94,514		94,608	94,312		97,609
Basic EPS:
(Loss) income from continuing operations (in dollars per share/unit)		$ 0.25	[1]	$ 0.91	$ (0.26)	[1]	$ 1.15	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[1]	0.25		0.91	(0.26)		1.15
Diluted EPS:
(Loss) income from continuing operations (in dollars per share/unit)		0.25	[1]	0.91	(0.26)	[1]	1.15	[1]
Discontinued operations (in dollars per share/unit)	[1]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[1]	$ 0.25		$ 0.91	$ (0.26)		$ 1.15
Corporate Office Properties, L.P.
Numerator:
(Loss) income from continuing operations		$ (4,829)		$ 94,279	$ (45,049)		$ 122,105
Gain on sales of real estate, net		34,101		15	34,101		4,000
Preferred share/unit dividends/distributions		(3,717)		(3,717)	(11,152)		(11,152)
Income from continuing operations attributable to noncontrolling interests		(913)		(972)	(2,803)		(2,605)
Income from continuing operations attributable to share-based compensation awards		(105)		(369)	(319)		(475)
Numerator for basic EPS from continuing operations attributable to COPT common shareholders		24,537		89,236	(25,222)		111,873
Convertible preferred shares/units		0		372	0		0
Numerator for diluted EPS from continuing operations attributable to COPT common shareholders		24,537		89,608	(25,222)		111,873
Numerator for basic EPS from continuing operations attributable to COPT common shareholders		24,537		89,236	(25,222)		111,873
Discontinued operations		0		0	0		156
Discontinued operations attributable to noncontrolling interests		0		0	0		3
Numerator for basic EPS on net income attributable to COPT common shareholders		24,537		89,236	(25,222)		112,032
Convertible preferred shares/units		0		372	0		0
Numerator for diluted EPS on net income attributable to COPT common shareholders		$ 24,537		$ 89,608	$ (25,222)		$ 112,032
Denominator (all weighted averages):
Denominator for basic EPS (common shares)		98,024		97,832	97,960		97,527
Convertible preferred shares (shares)		0		434	0		0
Dilutive effect of share-based compensation awards (shares)		81		21	0		82
Denominator for diluted EPS (common shares)		98,105		98,287	97,960		97,609
Basic EPS:
(Loss) income from continuing operations (in dollars per share/unit)	[2]	$ 0.25		$ 0.91	$ (0.26)		$ 1.15
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[2]	0.25		0.91	(0.26)		1.15
Diluted EPS:
(Loss) income from continuing operations (in dollars per share/unit)	[2]	0.25		0.91	(0.26)		1.15
Discontinued operations (in dollars per share/unit)	[2]	0		0	0		0
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit)	[2]	$ 0.25		$ 0.91	$ (0.26)		$ 1.15
[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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Conversion of common units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	3,591,000	3,679,000	3,648,000	0
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	0	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)	375,000	411,000	394,000	412,000
Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	233,000	440,000	307,000	480,000
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)	375,000	411,000	394,000	412,000
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	233,000	440,000	307,000	480,000
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	0	434,000	434,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	Sep. 30, 2016USD ($)Property	Aug. 31, 2010USD ($)
Tax incremental financing obligation
Liability recognized with regard to tax incremental financing obligation at end of current period	$ 1,300,000
Environmental Indemnity Agreement
Number of properties which were provided environmental indemnifications | Property	3
Maximum additional costs agreed to be paid by the entity under environmental indemnification agreement	$ 19,000,000
New Development and Redevelopment Obligations
Loss Contingencies [Line Items]
Purchase obligations	77,600,000
Capital Expenditures For Operating Properties
Loss Contingencies [Line Items]
Purchase obligations	60,500,000
Third Party Construction and Development
Loss Contingencies [Line Items]
Purchase obligations	10,500,000
Other Purchase Obligations
Loss Contingencies [Line Items]
Purchase obligations	$ 1,800,000
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	Sep. 30, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 307
2,017	1,159
2,018	1,113
2,019	1,082
2,020	1,089
Thereafter	86,806
Total	$ 91,556