COPT Defense Properties (CDP) 10-Q 3 Aug 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 17, 2015
Entity Information [Line Items]
Entity Registrant Name	CORPORATE OFFICE PROPERTIES TRUST
Entity Central Index Key	860,546
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		94,528,982
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Corporate Office Properties, L.P.
Entity Information [Line Items]
Entity Registrant Name	CORPORATE OFFICE PROPERTIES, L.P.
Entity Central Index Key	1,577,966
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Properties, net:
Operating properties, net	$ 2,896,809	$ 2,751,488
Projects in development or held for future development	521,991	545,426
Total properties, net	3,418,800	3,296,914
Assets held for sale, net	77,013	14,339
Cash and cash equivalents	37,074	6,077
Restricted cash and marketable securities	10,121	9,069
Accounts receivable (net of allowance for doubtful accounts of $1,135 and $717, respectively)	16,181	26,901
Deferred rent receivable (net of allowance of $2,203 and $1,418, respectively)	101,488	95,910
Intangible assets on real estate acquisitions, net	81,728	43,854
Deferred leasing and financing costs, net	67,613	64,797
Investing receivables	45,766	52,147
Prepaid expenses and other assets, net	55,137	60,249
Total assets	3,910,921	3,670,257
Liabilities:
Debt, net	2,130,170	1,920,057
Accounts payable and accrued expenses	155,989	123,035
Rents received in advance and security deposits	27,371	31,011
Dividends and distributions payable	30,178	29,862
Deferred revenue associated with operating leases	15,179	13,031
Interest rate derivatives	3,121	1,855
Other liabilities	11,866	12,105
Total liabilities	$ 2,373,874	$ 2,130,956
Commitments and contingencies
Redeemable noncontrolling interest	$ 19,414	$ 18,417
Corporate Office Properties Trust’s shareholders’ equity:
Preferred Shares of beneficial interest at liquidation preference ($0.01 par value; 25,000,000 shares authorized; issued and outstanding of 7,431,667 at June 30, 2015 and December 31, 2014)	199,083	199,083
Common Shares of beneficial interest	946	933
Additional paid-in capital	2,000,775	1,969,968
Cumulative distributions in excess of net income	(747,234)	(717,264)
Accumulated other comprehensive loss	(3,141)	(1,297)
Total Corporate Office Properties Trust’s shareholders’ equity	1,450,429	1,451,423
Noncontrolling interests in subsidiaries:
Common units in COPLP	48,707	51,534
Preferred units in COPLP	8,800	8,800
Other consolidated entities	9,697	9,127
Noncontrolling interests in subsidiaries	67,204	69,461
Total equity	1,517,633	1,520,884
Total liabilities, redeemable noncontrolling interest and equity	3,910,921	3,670,257
Corporate Office Properties, L.P.
Properties, net:
Operating properties, net	2,896,809	2,751,488
Projects in development or held for future development	521,991	545,426
Total properties, net	3,418,800	3,296,914
Assets held for sale, net	77,013	14,339
Cash and cash equivalents	37,074	6,077
Restricted cash and marketable securities	4,248	3,187
Accounts receivable (net of allowance for doubtful accounts of $1,135 and $717, respectively)	16,181	26,901
Deferred rent receivable (net of allowance of $2,203 and $1,418, respectively)	101,488	95,910
Intangible assets on real estate acquisitions, net	81,728	43,854
Deferred leasing and financing costs, net	67,613	64,797
Investing receivables	45,766	52,147
Prepaid expenses and other assets, net	55,137	60,249
Total assets	3,905,048	3,664,375
Liabilities:
Debt, net	2,130,170	1,920,057
Accounts payable and accrued expenses	155,989	123,035
Rents received in advance and security deposits	27,371	31,011
Dividends and distributions payable	30,178	29,862
Deferred revenue associated with operating leases	15,179	13,031
Interest rate derivatives	3,121	1,855
Other liabilities	5,993	6,223
Total liabilities	$ 2,368,001	$ 2,125,074
Commitments and contingencies
Redeemable noncontrolling interest	$ 19,414	$ 18,417
Corporate Office Properties Trust’s shareholders’ equity:
Common Shares of beneficial interest	1,303,313	1,305,219
Accumulated other comprehensive loss	(3,300)	(1,381)
Total Corporate Office Properties Trust’s shareholders’ equity	1,507,896	1,511,721
Noncontrolling interests in subsidiaries:
Noncontrolling interests in subsidiaries	9,737	9,163
Total equity	1,517,633	1,520,884
Total liabilities, redeemable noncontrolling interest and equity	3,905,048	3,664,375
General Partner | Corporate Office Properties, L.P.
Corporate Office Properties Trust’s shareholders’ equity:
Preferred partners' capital accounts	199,083	199,083
Limited Partner | Corporate Office Properties, L.P.
Corporate Office Properties Trust’s shareholders’ equity:
Preferred partners' capital accounts	$ 8,800	$ 8,800

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Allowance for doubtful accounts - AR	$ 1,135	$ 717
Allowance - Deferred rent receivable	$ 2,203	$ 1,418
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 Stock, Shares, Issued	94,529,618	93,255,284
Common Shares of beneficial interest, shares outstanding	94,529,618	93,255,284
Corporate Office Properties, L.P.
Allowance for doubtful accounts - AR	$ 1,135	$ 717
Allowance - Deferred rent receivable	$ 2,203	$ 1,418
Corporate Office Properties, L.P. | General Partner
Common Shares of beneficial interest, shares outstanding	94,529,618	93,255,284
Preferred Units, Outstanding	7,431,667	7,431,667
Corporate Office Properties, L.P. | Limited Partner
Common Shares of beneficial interest, shares outstanding	3,679,551	3,837,551
Preferred Units, Outstanding	352,000	352,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues
Rental revenue		$ 105,508	$ 94,332	$ 203,746	$ 192,367
Tenant recoveries and other real estate operations revenue		22,683	21,627	47,155	48,469
Construction contract and other service revenues		42,172	23,861	80,496	45,651
Total revenues		170,363	139,820	331,397	286,487
Expenses
Property operating expenses		46,418	43,772	97,099	93,544
Depreciation and amortization associated with real estate operations		33,786	30,895	65,385	74,491
Construction contract and other service expenses		41,293	23,136	78,791	41,760
Impairment losses		1,238	1,302	1,238	1,302
General, administrative and leasing expenses		7,534	7,528	15,425	15,671
Business development expenses and land carry costs		2,623	1,351	5,413	2,677
Total operating expenses		132,892	107,984	263,351	229,445
Operating income		37,471	31,836	68,046	57,042
Interest expense		(21,768)	(23,478)	(42,606)	(44,305)
Interest and other income		1,242	1,299	2,525	2,584
Loss on early extinguishment of debt		(65)	(270)	(68)	(270)
Income from continuing operations before equity in income (loss) of unconsolidated entities and income taxes		16,880	9,387	27,897	15,051
Equity in income (loss) of unconsolidated entities		9	(47)	34	13
Income tax expense		(50)	(92)	(105)	(156)
Income from continuing operations		16,839	9,248	27,826	14,908
Discontinued operations		394	(198)	156	(187)
Income before gain on sales of real estate		17,233	9,050	27,982	14,721
Gain on sales of real estate		(1)	0	3,985	0
Net income		17,232	9,050	31,967	14,721
Net income attributable to noncontrolling interests:
Common units in COPLP		(476)	(158)	(874)	(174)
Preferred units in COPLP		(165)	(165)	(330)	(330)
Other consolidated entities		(810)	(837)	(1,627)	(1,586)
Net income attributable to COPT		15,781	7,890	29,136	12,631
Preferred share/unit dividends/distributions		(3,553)	(4,344)	(7,105)	(8,834)
Issuance costs associated with redeemed preferred shares/unit		0	(1,769)	0	(1,769)
Net income attributable to COPT common shareholders		12,228	1,777	22,031	2,028
Net income attributable to COPT:
Income from continuing operations		15,402	8,077	28,983	12,805
Discontinued operations, net		379	(187)	153	(174)
Net income attributable to COPT		$ 15,781	$ 7,890	$ 29,136	$ 12,631
Basic earnings per common share
Income from continuing operations (in dollars per share/unit)	[1]	$ 0.13	$ 0.02	$ 0.23	$ 0.02
Discontinued operations (in dollars per share/unit)	[1]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[1]	0.13	0.02	0.23	0.02
Diluted earnings per common share
Income from continuing operations (in dollars per share/unit)	[1]	0.13	0.02	0.23	0.02
Discontinued operations (in dollars per share/unit)	[1]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[1]	0.13	0.02	0.23	0.02
Dividends declared per common share/unit		$ 0.2750	$ 0.2750	$ 0.55	$ 0.55
Corporate Office Properties, L.P.
Revenues
Rental revenue		$ 105,508	$ 94,332	$ 203,746	$ 192,367
Tenant recoveries and other real estate operations revenue		22,683	21,627	47,155	48,469
Construction contract and other service revenues		42,172	23,861	80,496	45,651
Total revenues		170,363	139,820	331,397	286,487
Expenses
Property operating expenses		46,418	43,772	97,099	93,544
Depreciation and amortization associated with real estate operations		33,786	30,895	65,385	74,491
Construction contract and other service expenses		41,293	23,136	78,791	41,760
Impairment losses		1,238	1,302	1,238	1,302
General, administrative and leasing expenses		7,534	7,528	15,425	15,671
Business development expenses and land carry costs		2,623	1,351	5,413	2,677
Total operating expenses		132,892	107,984	263,351	229,445
Operating income		37,471	31,836	68,046	57,042
Interest expense		(21,768)	(23,478)	(42,606)	(44,305)
Interest and other income		1,242	1,299	2,525	2,584
Loss on early extinguishment of debt		(65)	(270)	(68)	(270)
Income from continuing operations before equity in income (loss) of unconsolidated entities and income taxes		16,880	9,387	27,897	15,051
Equity in income (loss) of unconsolidated entities		9	(47)	34	13
Income tax expense		(50)	(92)	(105)	(156)
Income from continuing operations		16,839	9,248	27,826	14,908
Discontinued operations		394	(198)	156	(187)
Income before gain on sales of real estate		17,233	9,050	27,982	14,721
Gain on sales of real estate		(1)	0	3,985	0
Net income		17,232	9,050	31,967	14,721
Net income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests in consolidated entities		(812)	(837)	(1,630)	(1,574)
Net income attributable to COPT		16,420	8,213	30,337	13,147
Preferred share/unit dividends/distributions		(3,718)	(4,509)	(7,435)	(9,164)
Issuance costs associated with redeemed preferred shares/unit		0	(1,769)	0	(1,769)
Net income attributable to COPT common shareholders		12,702	1,935	22,902	2,214
Net income attributable to COPT:
Income from continuing operations		16,026	8,408	30,178	13,329
Discontinued operations, net		394	(195)	159	(182)
Net income attributable to COPT		$ 16,420	$ 8,213	$ 30,337	$ 13,147
Basic earnings per common share
Income from continuing operations (in dollars per share/unit)	[2]	$ 0.13	$ 0.02	$ 0.23	$ 0.02
Discontinued operations (in dollars per share/unit)	[2]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[2]	0.13	0.02	0.23	0.02
Diluted earnings per common share
Income from continuing operations (in dollars per share/unit)	[2]	0.13	0.02	0.23	0.02
Discontinued operations (in dollars per share/unit)	[2]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[2]	0.13	0.02	0.23	0.02
Dividends declared per common share/unit		$ 0.275	$ 0.275	$ 0.55	$ 0.55
[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.
[2]	Basic and diluted earnings per common unit are calculated based on amounts attributable to common unitholders of Corporate Office Properties, L.P.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income	$ 17,232	$ 9,050	$ 31,967	$ 14,721
Other comprehensive income (loss)
Unrealized gain (loss) on interest rate derivatives	392	(3,630)	(3,082)	(5,753)
Equity in other comprehensive loss of equity method investee	(264)	0	(264)	0
Other comprehensive income (loss)	897	(2,911)	(1,804)	(4,339)
Comprehensive income	18,129	6,139	30,163	10,382
Comprehensive income attributable to noncontrolling interests	(1,542)	(1,081)	(2,871)	(1,992)
Comprehensive income attributable to COPT	16,587	5,058	27,292	8,390
Interest Expense [Member]
Other comprehensive income (loss)
Losses on interest rate derivatives included in interest expense	769	719	1,542	1,414
Corporate Office Properties, L.P.
Net income	17,232	9,050	31,967	14,721
Other comprehensive income (loss)
Unrealized gain (loss) on interest rate derivatives	392	(3,630)	(3,082)	(5,753)
Equity in other comprehensive loss of equity method investee	(264)	0	(264)	0
Other comprehensive income (loss)	897	(2,911)	(1,804)	(4,339)
Comprehensive income	18,129	6,139	30,163	10,382
Comprehensive income attributable to noncontrolling interests	(872)	(884)	(1,745)	(1,666)
Comprehensive income attributable to COPT	17,257	5,255	28,418	8,716
Corporate Office Properties, L.P. | Interest Expense [Member]
Other comprehensive income (loss)
Losses on interest rate derivatives included in interest expense	$ 769	$ 719	$ 1,542	$ 1,414

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: 87,394,512 shares and 93,255,284 shares as of December 31, 2013 and 2014, respectively) at Dec. 31, 2013	$ 1,497,249	$ 249,083	$ 874	$ 1,814,015	$ (641,868)	$ 3,480	$ 71,665	$ 1,497,249	$ 1,226,318	$ 3,605	$ 9,443		$ 8,800		$ 249,083
Balance (preferred units) at Dec. 31, 2013													352,000		9,431,667
Balance (in units/ shares) at Dec. 31, 2013	87,394,512								91,372,212
Increase (Decrease) in Shareholders' Equity
Redemption of preferred shares (in units/shares)															(2,000,000)
Redemption of preferred shares (in units/shares) (2,000,000 shares)	$ (50,000)	(50,000)		1,769	(1,769)			(50,000)							$ (50,000)
Conversion of common units to common shares (COPT: 78,498 shares and 158,000 shares for the six months ended June 30, 2014 and 2015, respectively)	0		0	1,047			(1,047)
Shares issued to the public (in units/ shares)									0
Costs associated with common shares issued to the public	$ (7)		0	(7)				(7)	$ (7)
Exercise of share options (in units/shares)	51,289								51,289
Exercise of share options (COPT: 51,289 shares and 76,474 shares for the six months ended June 30, 2014 and 2015, respectively)	$ 1,185		0	1,185				1,185	$ 1,185
Share-based compensation issuance, net of redemptions (in units/shares)	144,009								144,009
Share-based compensation issuance, net of redemptions (COPT: 144,009 and 149,619 shares issued, net of redemptions for the six months ended June 30, 2014 and 2015, respectively)	$ 3,545		3	3,542				3,545	$ 3,545
Redemption of vested equity awards (in units/shares)									0
Redemption of vested equity awards	(1,326)			(1,326)				(1,326)	$ (1,326)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0			(72)			72
Comprehensive income	9,366				12,631	(4,241)	976	9,366	3,983	(4,430)	649		$ 330		8,834
Dividends / Distributions to owners of common and preferred units	(57,027)				(57,027)			(59,510)	(50,346)				$ (330)		$ (8,834)
Distributions to owners of common and preferred units in COPLP	(2,483)						(2,483)
Distributions to noncontrolling interests in subsidiaries	(8)						(8)	(8)			(8)
Contributions from noncontrolling interests in subsidiaries	3			0			3	3			3
Adjustment to arrive at fair value of redeemable noncontrolling interest	$ (717)			(717)				(717)	$ (717)
Balance (in units/ shares) at Jun. 30, 2014	87,668,308								91,567,510
Balance (preferred units) at Jun. 30, 2014													352,000		7,431,667
Balance (COPT: 87,668,308 shares and 94,529,618 shares as of June 30, 2014 and 2015, respectively) at Jun. 30, 2014	$ 1,399,780	199,083	877	1,819,436	(688,033)	(761)	69,178	1,399,780	$ 1,182,635	(825)	10,087		$ 8,800		$ 199,083
Balance (COPT: 87,394,512 shares and 93,255,284 shares as of December 31, 2013 and 2014, 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	352,000	7,431,667	7,431,667
Balance (in units/ shares) at Dec. 31, 2014	93,255,284								97,092,835			3,837,551		93,255,284
Increase (Decrease) in Shareholders' Equity
Conversion of common units to common shares (COPT: 78,498 shares and 158,000 shares for the six months ended June 30, 2014 and 2015, respectively)	$ 0		$ 2	2,120			(2,122)
Shares issued to the public (in units/ shares)			890,241						890,241
Issuance of common units resulting from common shares issued under at-the-market program (in units)									890,241
Issuance of common units resulting from common shares issued under at-the-market program (COPT: 890,241 shares for the six months ended June 30, 2015)	$ 26,535		$ 9	26,526				26,535	$ 26,535
Exercise of share options (in units/shares)	76,474								76,474
Exercise of share options (COPT: 51,289 shares and 76,474 shares for the six months ended June 30, 2014 and 2015, respectively)	$ 2,008			2,008				2,008	$ 2,008
Share-based compensation issuance, net of redemptions (in units/shares)	149,619								149,619
Share-based compensation issuance, net of redemptions (COPT: 144,009 and 149,619 shares issued, net of redemptions for the six months ended June 30, 2014 and 2015, respectively)	$ 3,658		2	3,656				3,658	$ 3,658
Redemption of vested equity awards (in units/shares)									0
Redemption of vested equity awards	(2,245)			(2,245)				(2,245)	$ (2,245)
Adjustments to noncontrolling interests resulting from changes in ownership of COPLP	0			(519)			519
Comprehensive income	29,020				29,136	(1,844)	1,728	29,020	22,902	(1,919)	602		$ 330		$ 7,105
Dividends / Distributions to owners of common and preferred units	(59,106)				(59,106)			(61,460)	(54,025)				$ (330)		$ (7,105)
Distributions to owners of common and preferred units in COPLP	(2,354)						(2,354)
Distributions to noncontrolling interests in subsidiaries	(28)						(28)	(28)			(28)
Adjustment to arrive at fair value of redeemable noncontrolling interest	$ (739)			(739)				(739)	$ (739)
Balance (in units/ shares) at Jun. 30, 2015	94,529,618								98,209,169			3,679,551		94,529,618
Balance (preferred units) at Jun. 30, 2015												352,000	352,000	7,431,667	7,431,667
Balance (COPT: 87,668,308 shares and 94,529,618 shares as of June 30, 2014 and 2015, respectively) at Jun. 30, 2015	$ 1,517,633	$ 199,083	$ 946	$ 2,000,775	$ (747,234)	$ (3,141)	$ 67,204	$ 1,517,633	$ 1,303,313	$ (3,300)	$ 9,737		$ 8,800		$ 199,083

Consolidated Statements of Equ7

Consolidated Statements of Equity (Parenthetical) - shares	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Balance (in units/ shares)	94,529,618	87,668,308	93,255,284	87,394,512
Conversion of common units to common shares (in units/ shares)	158,000	78,498
Exercise of share options (in units/shares)	76,474	51,289
Share-based compensation issuance, net of redemptions (in units/shares)	149,619	144,009
Common Shares
Shares issued to the public under at-the-market program (in units/ shares)	890,241
Preferred Shares
Redemption of preferred shares (in units/shares)		2,000,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities
Revenues from real estate operations received	$ 240,538	$ 232,877
Construction contract and other service revenues received	86,790	35,105
Property operating expenses paid	(79,667)	(78,621)
Construction contract and other service expenses paid	(76,355)	(34,588)
General, administrative, leasing, business development and land carry costs paid	(20,121)	(16,904)
Interest expense paid	(32,375)	(35,365)
Payments in connection with early extinguishment of debt	(18)	(104)
Interest and other income received	4,055	346
Income taxes (paid) refunded	(8)	204
Net cash provided by operating activities	122,839	102,950
Cash flows from investing activities
Acquisitions of operating properties and related intangible assets	(137,125)	0
Construction, development and redevelopment	(117,498)	(105,459)
Tenant improvements on operating properties	(10,314)	(10,842)
Other capital improvements on operating properties	(8,372)	(16,482)
Proceeds from dispositions of properties	17,424	1,971
Investing receivables payments received	5,114	151
Leasing costs paid	(6,732)	(7,772)
Increase in prepaid expenses and other assets associated with investing activities	(3,249)	(1,158)
Other	(289)	(450)
Net cash used in investing activities	(261,041)	(140,041)
Proceeds from debt
Revolving Credit Facility	294,000	115,000
Unsecured senior notes	296,580	297,342
Other debt proceeds	50,000	9,931
Repayments of debt
Revolving Credit Facility	(377,000)	(115,000)
Scheduled principal amortization	(3,319)	(3,437)
Other debt repayments	(50,630)	(133,010)
Deferred financing costs paid	(4,693)	(653)
Net proceeds from issuance of common shares/units	28,567	1,178
Redemption of preferred shares/units	0	(50,000)
Common share/unit dividends/distributions paid	(51,642)	(48,118)
Preferred share/unit dividends/distributions paid	(7,105)	(9,626)
Distributions paid to noncontrolling interests in COPLP	(2,461)	(2,641)
Redemption of vested equity awards	(2,245)	(1,326)
Other	(853)	(706)
Net cash provided by financing activities	169,199	58,934
Net increase in cash and cash equivalents	30,997	21,843
Cash and cash equivalents
Beginning of period	6,077	54,373
End of period	37,074	76,216
Reconciliation of net income to net cash provided by operating activities:
Net income	31,967	14,721
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	66,404	75,839
Impairment losses	1,472	1,329
Amortization of deferred financing costs	2,136	2,289
Increase in deferred rent receivable	(5,956)	(1,754)
Amortization of net debt discounts	482	400
(Gain) loss on sales of real estate	(3,985)	4
Share-based compensation	3,210	3,056
(Gain) loss on early extinguishment of debt	(330)	282
Other	2,084	(1,664)
Operating changes in assets and liabilities:
Decrease (increase) in accounts receivable	10,655	(3,916)
Increase in restricted cash and marketable securities	(735)	(113)
Decrease in prepaid expenses and other assets, net	6,518	3,213
Increase in accounts payable, accrued expenses and other liabilities	12,557	13,236
Decrease in rents received in advance and security deposits	(3,640)	(3,972)
Net cash provided by operating activities	122,839	102,950
Supplemental schedule of non-cash investing and financing activities:
Increase (decrease) in accrued capital improvements, leasing and other investing activity costs	15,927	(7,153)
Liabilities assumed on acquisition of operating properties	5,265	0
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(1,540)	(4,369)
Equity in other comprehensive loss of an equity method investee	(264)	0
Dividends/distributions payable	30,178	28,342
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	2,122	1,047
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	519	72
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	739	717
Corporate Office Properties, L.P.
Cash flows from operating activities
Revenues from real estate operations received	240,538	232,877
Construction contract and other service revenues received	86,790	35,105
Property operating expenses paid	(79,667)	(78,621)
Construction contract and other service expenses paid	(76,355)	(34,588)
General, administrative, leasing, business development and land carry costs paid	(20,121)	(16,904)
Interest expense paid	(32,375)	(35,365)
Payments in connection with early extinguishment of debt	(18)	(104)
Interest and other income received	4,055	346
Income taxes (paid) refunded	(8)	204
Net cash provided by operating activities	122,839	102,950
Cash flows from investing activities
Acquisitions of operating properties and related intangible assets	(137,125)	0
Construction, development and redevelopment	(117,498)	(105,459)
Tenant improvements on operating properties	(10,314)	(10,842)
Other capital improvements on operating properties	(8,372)	(16,482)
Proceeds from dispositions of properties	17,424	1,971
Investing receivables payments received	5,114	151
Leasing costs paid	(6,732)	(7,772)
Increase in prepaid expenses and other assets associated with investing activities	(3,249)	(1,158)
Other	(289)	(450)
Net cash used in investing activities	(261,041)	(140,041)
Proceeds from debt
Revolving Credit Facility	294,000	115,000
Unsecured senior notes	296,580	297,342
Other debt proceeds	50,000	9,931
Repayments of debt
Revolving Credit Facility	(377,000)	(115,000)
Scheduled principal amortization	(3,319)	(3,437)
Other debt repayments	(50,630)	(133,010)
Deferred financing costs paid	(4,693)	(653)
Net proceeds from issuance of common shares/units	28,567	1,178
Redemption of preferred shares/units	0	(50,000)
Common share/unit dividends/distributions paid	(53,773)	(50,429)
Preferred share/unit dividends/distributions paid	(7,435)	(9,956)
Redemption of vested equity awards	(2,245)	(1,326)
Other	(853)	(706)
Net cash provided by financing activities	169,199	58,934
Net increase in cash and cash equivalents	30,997	21,843
Cash and cash equivalents
Beginning of period	6,077	54,373
End of period	37,074	76,216
Reconciliation of net income to net cash provided by operating activities:
Net income	31,967	14,721
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	66,404	75,839
Impairment losses	1,472	1,329
Amortization of deferred financing costs	2,136	2,289
Increase in deferred rent receivable	(5,956)	(1,754)
Amortization of net debt discounts	482	400
(Gain) loss on sales of real estate	(3,985)	4
Share-based compensation	3,210	3,056
(Gain) loss on early extinguishment of debt	(330)	282
Other	2,084	(1,664)
Operating changes in assets and liabilities:
Decrease (increase) in accounts receivable	10,655	(3,916)
Increase in restricted cash and marketable securities	(744)	40
Decrease in prepaid expenses and other assets, net	6,518	3,213
Increase in accounts payable, accrued expenses and other liabilities	12,566	13,083
Decrease in rents received in advance and security deposits	(3,640)	(3,972)
Net cash provided by operating activities	122,839	102,950
Supplemental schedule of non-cash investing and financing activities:
Increase (decrease) in accrued capital improvements, leasing and other investing activity costs	15,927	(7,153)
Liabilities assumed on acquisition of operating properties	5,265	0
Decrease in fair value of derivatives applied to accumulated other comprehensive loss and noncontrolling interests	(1,540)	(4,369)
Equity in other comprehensive loss of an equity method investee	(264)	0
Dividends/distributions payable	30,178	28,342
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	$ 739	$ 717

Organization

Organization	6 Months Ended
	Jun. 30, 2015
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 focus primarily on serving the specialized requirements of United States Government agencies and their contractors, most of whom are engaged in national security and information technology related activities. We generally acquire, develop, manage and lease office and data center properties concentrated in large office parks located near knowledge-based government demand drivers and/or in targeted markets or submarkets in the Greater Washington, DC/Baltimore region. As of June 30, 2015 , our properties included the following: • 179 operating office properties totaling 18.0 million square feet (excluding two properties serving as collateral for a nonrecourse mortgage loan in default, as discussed further in the Management’s Discussion and Analysis of Financial Condition and Results of Operations section of this Quarterly Report on Form 10-Q); • 12 office properties under, or contractually committed for, construction or redevelopment that we estimate will total approximately 1.3 million square feet upon completion, including one partially operational property included above; • 1,450 acres of land we control that we believe are potentially developable into approximately 17.7 million square feet; and • a partially operational wholesale data center that is expected to have a critical load of 19.25 megawatts upon completion. COPLP owns real estate both directly and through subsidiary partnerships and limited liability companies (“LLCs”). In addition to owning real estate, COPLP also owns subsidiaries that provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. Some of these services are performed by a taxable REIT subsidiary (“TRS”). Equity interests in COPLP are in the form of common and preferred units. As of June 30, 2015 , COPT owned 96.3% of the outstanding COPLP common units (“common units”) and 95.5% of the outstanding COPLP preferred units (“preferred units”); the remaining common and preferred units in COPLP were owned by third parties. Common units in COPLP not owned by COPT carry certain redemption rights. The number of common units in COPLP owned by COPT is equivalent to the number of outstanding common shares of beneficial interest (“common shares”) of COPT, and the entitlement of all COPLP common units to quarterly distributions and payments in liquidation is substantially the same as those of COPT common shareholders. Similarly, in the case of each series of preferred units in COPLP held by COPT, there is a series of preferred shares of beneficial interest (“preferred shares”) in COPT that is equivalent in number and carries substantially the same terms as such series of COPLP preferred units. COPT’s common shares are publicly traded on the New York Stock Exchange (“NYSE”) under the ticker symbol “OFC”. Because COPLP is managed by COPT, and COPT conducts substantially all of its operations through COPLP, we refer to COPT’s executive officers as COPLP’s executive officers, and although, as a partnership, COPLP does not have a board of trustees, we refer to COPT’s Board of Trustees as COPLP’s Board of Trustees.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2015
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 significant 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. 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, 2014 included in our 2014 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly present our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2014 Annual Report on Form 10-K. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“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 January 2015, the FASB issued guidance 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. This guidance is effective for periods beginning after December 15, 2015. We expect that the application of this guidance will have no effect on our reported consolidated financial statements. In February 2015, the FASB issued guidance regarding amendments to the consolidation analysis. This guidance amends the criteria for determining which entities are considered variable interest entities (“VIE”), amends the criteria for determining if a service provider possesses a variable interest in a VIE and ends the deferral granted to investment companies for application of the VIE consolidation model. This guidance is effective for annual periods, and interim periods therein, beginning after December 15, 2015. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In April 2015, the FASB issued guidance that changes the presentation of debt issuance costs in financial statements. This guidance requires an entity to present such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs will continue to be reported as interest expense. This guidance is effective for annual reporting periods beginning after December 15, 2016. Early adoption is permitted. This guidance will be applied retrospectively to each prior period presented. We expect that the application of this guidance will not materially affect our consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements For a description on how we estimate fair value, see Note 3 to the consolidated financial statements in our 2014 Annual Report on Form 10-K. Recurring Fair Value Measurements Our partner in a real estate joint venture has the right to require us to acquire its interest at fair value beginning in March 2020; accordingly, we classify the fair value of our partner’s interest as a redeemable noncontrolling interest in the mezzanine section of our consolidated balance sheet. In determining the fair value of our partner’s interest as of June 30, 2015 , we used a discount rate of 15.5% which factored in risk appropriate to the level of future property development expected to be undertaken by the joint venture. A significant increase (decrease) in the discount rate used in determining the fair value would result in a significantly (lower) higher fair value. Given our reliance on the unobservable inputs, the valuations are classified in Level 3 of the fair value hierarchy. Please refer to Note 11 for a rollforward of the activity for redeemable noncontrolling interest. 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 7, 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 9, we estimated the fair value of our unsecured senior notes and exchangeable 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 at a specific point in time, are subjective in nature and involve uncertainties and matters of significant judgment. Settlement at such fair value amounts may not be possible and may not be a prudent management decision. For additional fair value information, please refer to Note 7 for investing receivables, Note 9 for debt and Note 10 for interest rate derivatives. COPT and Subsidiaries The table below sets forth financial assets and liabilities of COPT and its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2015 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 $ 5,765 $ — $ — $ 5,765 Other 108 — — 108 Warrants to purchase common stock (2) — 141 — 141 Total assets $ 5,873 $ 141 $ — $ 6,014 Liabilities: Deferred compensation plan liability (3) $ — $ 5,873 $ — $ 5,873 Interest rate derivatives — 3,121 — 3,121 Total liabilities $ — $ 8,994 $ — $ 8,994 Redeemable noncontrolling interest $ — $ — $ 19,414 $ 19,414 (1) Included in the line entitled “restricted cash and marketable securities” on COPT’s consolidated balance sheet. (2) Included in the line entitled “prepaid expenses and other assets” on COPT’s consolidated balance sheet. (3) Included in the line entitled “other liabilities” on COPT’s consolidated balance sheet. COPLP and Subsidiaries The table below sets forth financial assets and liabilities of COPLP and its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2015 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: Warrants to purchase common stock (1) $ — $ 141 $ — $ 141 Liabilities: Interest rate derivatives $ — $ 3,121 $ — $ 3,121 Redeemable noncontrolling interest $ — $ — $ 19,414 $ 19,414 (1) Included in the line entitled “prepaid expenses and other assets” on COPLP’s consolidated balance sheet. Nonrecurring Fair Value Measurements In June 2015, we classified certain operating properties as held for sale, including a property in Northern Virginia on which we received an unsolicited offer. This property’s carrying value exceeded its fair value less costs to sell by approximately $1.2 million . Accordingly, we recognized an impairment loss of this amount during the three months ended June 30, 2015. The table below sets forth the fair value hierarchy of the valuation technique we used to determine the fair value of this property (dollars in thousands): Fair Value as of June 30, 2015 (1) Quoted Prices in Significant Impairment Losses Recognized Active Markets for Significant Other Unobservable Three Months Six Months Identical Assets Observable Inputs Inputs Ended Ended Description (Level 1) (Level 2) (Level 3) Total June 30, 2015 June 30, 2015 Assets: Assets held for sale $ — $ — $ 27,690 $ 27,690 $ 1,238 $ 1,238 (1) Fair value represents contract price less expected costs to sell. In June 2014, we classified certain operating properties in Greater Baltimore, Maryland (“Greater Baltimore”) as held for sale with carrying values exceeding their respective fair values less costs to sell by approximately $1.3 million . Accordingly, we recognized impairment losses totaling this amount during the three months ended June 30, 2014. These properties were subsequently sold. The table below sets forth the fair value hierarchy of the valuation technique used by us in determining the fair values of the properties (dollars in thousands): Fair Value of Properties Held as of June 30, 2014 (1) Quoted Prices in Significant Impairment Losses Recognized Active Markets for Significant Other Unobservable Three Months Six Months Identical Assets Observable Inputs Inputs Ended Ended Description (Level 1) (Level 2) (Level 3) Total June 30, 2014 June 30, 2014 Assets: Assets held for sale $ — $ — $ 9,796 $ 9,796 $ 1,302 $ 1,302 (1) Fair value represents contract price less expected costs to sell.

Properties, net

Properties, net	6 Months Ended
	Jun. 30, 2015
Real Estate [Abstract]
Properties, net	Properties, Net Operating properties, net consisted of the following (in thousands): June 30, December 31, Land $ 460,268 $ 439,355 Buildings and improvements 3,160,011 3,015,216 Less: Accumulated depreciation (723,470 ) (703,083 ) Operating properties, net $ 2,896,809 $ 2,751,488 During the six months ended June 30, 2014, we recognized $12.9 million in additional depreciation expense resulting from our revision of the useful life of a property in Greater Philadelphia, Pennsylvania (“Greater Philadelphia”) that was removed from service for redevelopment. Projects in development or held for future development consisted of the following (in thousands): June 30, December 31, Land $ 221,655 $ 214,977 Construction in progress, excluding land 300,336 330,449 Projects in development or held for future development $ 521,991 $ 545,426 As of June 30, 2015, we had six operating properties in Greater Baltimore and one in Northern Virginia classified as held for sale. The table below sets forth the components of assets held for sale on our consolidated balance sheet for these properties (in thousands): June 30, 2015 Properties, net $ 73,174 Deferred rent receivable 1,683 Intangible assets on real estate acquisitions, net 1,017 Deferred leasing costs, net 977 Lease incentives, net 162 Assets held for sale, net $ 77,013 As of December 31, 2014, we had two land parcels in the Greater Baltimore region classified as held for sale with a cost basis of $14.3 million that were sold during the six months ended June 30, 2015. 2015 Acquisitions In the six months ended June 30, 2015, we acquired the following operating properties: • 250 W. Pratt Street, a 367,000 square foot office property in Baltimore, Maryland that was 96.2% leased, for $61.9 million on March 19, 2015; and • 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. The table below sets forth the allocation of the acquisition costs of these properties (in thousands): Land, operating properties $ 28,361 Building and improvements 69,182 Intangible assets on real estate acquisitions 45,940 Total assets 143,483 Below-market leases (1,093 ) Total acquisition cost $ 142,390 Intangible assets recorded in connection with the these acquisitions included the following (dollars in thousands): Weighted Average Amortization Period (in Years) Tenant relationship value $ 20,024 10 In-place lease value 20,041 5 Above-market leases 5,875 4 $ 45,940 7 These properties contributed revenues of $4.0 million for the three months ended June 30, 2015 and $4.3 million for the six months ended June 30, 2015, and contributed net income from continuing operations of $40,000 for the three months ended June 30, 2015 and $210,000 for the six months ended June 30, 2015. We expensed $1.4 million in operating property acquisition costs during the six months ended June 30, 2015 that are included in business development expenses and land carry costs on our consolidated statements of operations. We accounted for these acquisitions as business combinations. We included the results of operations for the acquisitions in our consolidated statements of operations from their respective purchase dates through June 30, 2015 . 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 the operating property acquisition costs disclosed above from the 2015 periods in which they were incurred to the six months ended June 30, 2014. 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 shares amounts). For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 (Unaudited) (Unaudited) Pro forma total revenues $ 170,719 $ 144,098 $ 335,159 $ 294,769 Pro forma net income attributable to COPT common shareholders $ 12,620 $ 2,126 $ 22,850 $ 835 Pro forma EPS: Basic $ 0.13 $ 0.02 $ 0.24 $ 0.01 Diluted $ 0.13 $ 0.02 $ 0.24 $ 0.01 2015 Dispositions We sold land in the six months ended June 30, 2015 for $18.1 million and recognized gains of $4.0 million on the sales. 2015 Construction Activities During the six months ended June 30, 2015 , we placed into service an aggregate of 509,000 square feet in four newly constructed office properties located in Northern Virginia, San Antonio, Texas (“San Antonio”) and Huntsville, Alabama (“Huntsville”), and 111,000 square feet of a property undergoing redevelopment in Greater Philadelphia. As of June 30, 2015 , we had six office properties under construction, or for which we were contractually committed to construct, that we estimate will total 1.0 million square feet upon completion, including four in Northern Virginia and two in the Baltimore/Washington Corridor. We also had six office properties under redevelopment (including one partially operational property) that we estimate will total 309,000 square feet upon completion, including four in the Baltimore/Washington Corridor, one in Greater Philadelphia and one in St. Mary’s County, Maryland.

Real Estate Joint Ventures

Real Estate Joint Ventures	6 Months Ended
	Jun. 30, 2015
Equity Method Investments and Joint Ventures [Abstract]
Real Estate Joint Ventures	Real Estate Joint Ventures The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of June 30, 2015 (dollars in thousands): Nominal Ownership June 30, 2015 (1) Date % as of Total Encumbered Total Acquired 6/30/2015 Nature of Activity Assets Assets Liabilities LW Redstone Company, LLC 3/23/2010 85% Operates five buildings and developing others (2) $ 142,787 $ 65,200 $ 40,278 M Square Associates, LLC 6/26/2007 50% Operates two buildings and developing others (3) 58,839 48,364 38,249 $ 201,626 $ 113,564 $ 78,527 (1) Excludes amounts eliminated in consolidation. (2) This joint venture’s properties are in Huntsville. (3) This joint venture’s properties are in College Park, Maryland (in the Baltimore/Washington Corridor).

Intangible Assets on Real Estat

Intangible Assets on Real Estate Acquisition, Net	6 Months Ended
	Jun. 30, 2015
Intangible Assets on Real Estate Acquisitions [Abstract]
Intangible Assets on Real Estate Acquisition, Net	Intangible Assets on Real Estate Acquisitions, Net Intangible assets on real estate acquisitions consisted of the following, excluding amounts for properties held for sale (in thousands): June 30, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount In-place lease value $ 134,387 $ 95,910 $ 38,477 $ 123,759 $ 101,040 $ 22,719 Tenant relationship value 58,560 27,666 30,894 42,301 28,492 13,809 Below-market cost arrangements 12,415 6,324 6,091 12,415 5,984 6,431 Above-market leases 14,344 8,467 5,877 8,659 8,159 500 Market concentration premium 1,333 944 389 1,333 938 395 $ 221,039 $ 139,311 $ 81,728 $ 188,467 $ 144,613 $ 43,854 Amortization of the intangible asset categories set forth above totaled $7.0 million in the six months ended June 30, 2015 and $7.4 million in the six months ended June 30, 2014 . The approximate weighted average amortization periods of the categories set forth above follow (excluding amounts for properties held for sale): in-place lease value: five years; tenant relationship value: nine years; below-market cost arrangements: 32 years; above-market leases: four years; and market concentration premium: 27 years. The approximate weighted average amortization period for all of the categories combined is nine years. Estimated amortization expense associated with the intangible asset categories set forth above through 2020 follows (excluding amounts for properties held for sale): $8.6 million for the six months ending December 31, 2015; $16.6 million for 2016; $14.3 million for 2017; $9.5 million for 2018; $6.7 million for 2019; and $5.1 million for 2020.

Investing Receivables

Investing Receivables	6 Months Ended
	Jun. 30, 2015
Receivables [Abstract]
Investing Receivables	Investing Receivables Investing receivables, including accrued interest thereon, consisted of the following (in thousands): June 30, December 31, Notes receivable from the City of Huntsville $ 42,766 $ 49,147 Other investing loans receivable 3,000 3,000 $ 45,766 $ 52,147 Our notes receivable from the City of Huntsville funded infrastructure costs in connection with our LW Redstone Company, LLC joint venture (see Note 5) and carry an interest rate of 9.95% . We did not have an allowance for credit losses in connection with our investing receivables as of June 30, 2015 or December 31, 2014 . The fair value of these receivables approximated their carrying amounts as of June 30, 2015 and December 31, 2014 .

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	6 Months Ended
	Jun. 30, 2015
Prepaid Expense and Other Assets [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets consisted of the following (in thousands): June 30, December 31, Lease incentives, net $ 12,964 $ 13,344 Construction contract costs incurred in excess of billings 12,051 6,656 Prepaid expenses 8,882 20,570 Furniture, fixtures and equipment, net 6,340 6,637 Deferred tax asset, net (1) 4,064 4,002 Operating notes receivable 3,937 3,797 Deposit on acquisitions 2,016 516 Equity method investments 1,616 2,368 Other assets 3,267 2,359 Prepaid expenses and other assets, net $ 55,137 $ 60,249 (1) Includes a valuation allowance of $2.1 million . Operating notes receivable reported above includes amounts due from tenants with remaining terms exceeding one year totaling $3.9 million as of June 30, 2015 and $3.6 million as of December 31, 2014 ; we carried allowances for estimated losses for $312,000 of the June 30, 2015 balance and $252,000 of the December 31, 2014 balance.

Debt, Net

Debt, Net	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Debt, Net	Debt, Net Our debt consisted of the following (dollars in thousands): Maximum Availability at Carrying Value at Scheduled Maturity June 30, June 30, December 31, Stated Interest Rates as of as of June 30, 2015 June 30, 2015 Mortgage and Other Secured Loans: Fixed rate mortgage loans (1) $ 384,227 $ 387,139 3.96% - 10.65% (2) 2015-2024 Variable rate secured loan 36,457 36,877 LIBOR + 2.25% (3) November 2015 Total mortgage and other secured loans 420,684 424,016 Revolving Credit Facility $ 800,000 — 83,000 LIBOR + 0.875% to 1.60% (4) May 2019 Term Loan Facilities (5) 520,000 520,000 LIBOR + 0.90% to 2.60% (6) 2016-2020 Unsecured Senior Notes 3.600% Senior Notes (7) 347,625 347,496 3.60% May 2023 5.250% Senior Notes (8) 245,980 245,797 5.25% February 2024 3.700% Senior Notes (9) 297,743 297,569 3.70% June 2021 5.000% Senior Note (10) 296,580 — 5.00% July 2025 Unsecured notes payable 1,558 1,607 0% (11) 2026 4.25% Exchangeable Senior Notes (12) — 572 N/A (12) Total debt, net $ 2,130,170 $ 1,920,057 (1) 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 $30,000 as of June 30, 2015 and $42,000 as of December 31, 2014 . (2) Includes a $150.0 million nonrecourse mortgage loan in default secured by two operating properties in Northern Virginia with an aggregate estimated fair value that was less than the loan balance. This loan has an interest rate of 10.65% (including the effect of default interest). The maximum stated interest rate would be 7.87% , excluding the incremental additional interest rate associated with the default rate on the loan in default. The weighted average interest rate on our fixed rate mortgage loans was 8.11% as of June 30, 2015 (or 6.16% excluding the incremental additional interest rate associated with the default rate on the loan in default). (3) The interest rate on the loan outstanding was 2.43% as of June 30, 2015 . (4) The weighted average interest rate on the Revolving Credit Facility was 1.37% as of June 30, 2015 . (5) We have the ability to borrow an additional $380.0 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. (6) The weighted average interest rate on these loans was 1.77% as of June 30, 2015 . (7) The carrying value of these notes included a principal amount of $350.0 million and an unamortized discount totaling $2.4 million as of June 30, 2015 and $2.5 million as of December 31, 2014 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (8) The carrying value of these notes included a principal amount of $250.0 million and an unamortized discount totaling $4.0 million as of June 30, 2015 and $4.2 million as of December 31, 2014 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (9) The carrying value of these notes included a principal amount of $300.0 million and an unamortized discount totaling $2.3 million as of June 30, 2015 and $2.4 million as of December 31, 2014 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (10) Refer to the paragraph below for disclosure pertaining to these notes. (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 $603,000 as of June 30, 2015 and $654,000 as of December 31, 2014 . (12) On April 20, 2015, we redeemed these notes at 100% of their principal amount. 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. On May 6, 2015, we entered into a credit agreement with a group of lenders for which KeyBanc Capital Markets and J.P. Morgan Securities LLC acted as joint lead arrangers and joint book runners, KeyBank National Association acted as administrative agent and JPMorgan Chase Bank, N.A. acted as syndication agent (the “Consolidated Credit Agreement”) to amend, restate and consolidate the terms of our Revolving Credit Facility and one of our term loan facilities. In addition to consolidating the terms of these loan facilities, the Consolidated Credit Agreement included the following provisions: For the Revolving Credit Facility: • an extension of the maturity date from July 14, 2017 to May 6, 2019, with the ability for us to further extend such maturity by two six -month periods at our option, provided that there is no default under the facility and we pay an extension fee based on the total availability of the facility for each extension; • changes to the interest terms of the facility such that the variable interest rate is based on LIBOR (customarily the 30-day rate) plus 0.875% to 1.600% , as determined by the credit ratings assigned to COPLP by Standard & Poor’s Ratings Services, Moody’s Investors Service, Inc. or Fitch Ratings Ltd. (collectively, the “Ratings Agencies”); • changes to the quarterly fee carried by the facility. Such fee is based on the average daily amount of the lenders’ aggregate commitment multiplied by a per annum rate of 0.125% to 0.300% , as determined by the credit ratings assigned to COPLP by the Ratings Agencies; and • certain changes to the financial covenants of the facility. For the term loan facility: • an increase in the loan amount from $250.0 million to $300.0 million , with a right for us to borrow up to an additional $200.0 million during the term for an aggregate maximum loan of $500.0 million , subject to certain conditions. We used the proceeds from the $50.0 million increase in the facility to repay a portion of another existing unsecured term loan; • an extension of the maturity date of the loan from February 14, 2017 to May 6, 2020; • changes to the interest terms of the facility such that the variable interest rate is based on LIBOR (customarily the 30-day rate) plus 0.900% to 1.850% , as determined by the credit ratings assigned to COPLP by the Ratings Agencies; and • certain changes to the financial covenants of the facility. On June 29, 2015 we issued a $300.0 million aggregate principal amount of 5.00% Senior Notes at an initial offering price of 99.510% of their face value. The proceeds from this issuance, after deducting underwriting discounts, but before other offering expenses, were $296.6 million . The notes mature on July 1, 2025. We may redeem the notes, in whole at any time or in part from time to time, at our option, at a redemption price equal to the greater of (1) the aggregate principal amount of the notes being redeemed and (2) the sum of the present values of the remaining scheduled payments of principal and interest thereon (not including any portion of such payments of interest accrued as of the date of redemption) discounted to its present value, on a semi-annual basis at an adjusted treasury rate plus 45 basis points, plus accrued and unpaid interest thereon to the date of redemption. The notes are unconditionally guaranteed by COPT. However, if this redemption occurs on or after three months prior to the maturity date, the redemption price will be equal to 100% of the principal amount of the notes being redeemed, plus accrued and unpaid interest thereon to, but not including, the redemption date. The carrying value of these notes reflects an unamortized discount totaling $3.4 million at June 30, 2015. The effective interest rate under the notes, including amortization of the issuance costs, was 5.15% . We capitalized interest costs of $2.0 million in the three months ended June 30, 2015 , $1.4 million in the three months ended June 30, 2014 , $4.1 million in the six months ended June 30, 2015 and $3.0 million in the six months ended June 30, 2014 . The following table sets forth information pertaining to the fair value of our debt (in thousands): June 30, 2015 December 31, 2014 Carrying Estimated Carrying Estimated Amount Fair Value Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,187,928 $ 1,202,956 $ 890,862 $ 901,599 Other fixed-rate debt 385,785 345,066 389,318 356,377 Variable-rate debt 556,457 557,753 639,877 642,091 $ 2,130,170 $ 2,105,775 $ 1,920,057 $ 1,900,067

Interest Rate Derivatives

Interest Rate Derivatives	6 Months Ended
	Jun. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest Rate Derivatives	Interest Rate Derivatives The following table sets forth the key terms and fair values of our interest rate swap derivatives (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date June 30, December 31, $ 100,000 0.8320% One-Month LIBOR 1/3/2012 9/1/2015 $ (110 ) $ (407 ) 100,000 0.8320% One-Month LIBOR 1/3/2012 9/1/2015 (110 ) (407 ) 36,457 (1) 3.8300% One-Month LIBOR + 2.25% 11/2/2010 11/2/2015 (171 ) (400 ) 100,000 0.8055% One-Month LIBOR 9/2/2014 9/1/2016 (405 ) (317 ) 100,000 0.8100% One-Month LIBOR 9/2/2014 9/1/2016 (410 ) (324 ) 100,000 1.6730% One-Month LIBOR 9/1/2015 8/1/2019 (849 ) 239 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 (1,066 ) 35 $ (3,121 ) $ (1,581 ) (1) The notional amount of this instrument is scheduled to amortize to $36.2 million . Each of the one-month LIBOR 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): June 30, 2015 December 31, 2014 Derivatives Balance Sheet Location Fair Value Balance Sheet Location Fair Value Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets $ — Prepaid expenses and other assets $ 274 Interest rate swaps designated as cash flow hedges Interest rate derivatives (3,121 ) Interest rate derivatives (1,855 ) The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Amount of gain (loss) recognized in accumulated other comprehensive loss (“AOCL”) (effective portion) $ 392 $ (3,630 ) $ (3,082 ) $ (5,753 ) Amount of losses reclassified from AOCL into interest expense (effective portion) 769 719 1,542 1,414 Over the next 12 months, we estimate that approximately $3.3 million of losses will be reclassified from AOCL as an increase to interest expense. We have agreements with each of our interest rate derivative counterparties that contain provisions under which, if we default or are capable of being declared in default on defined levels of our indebtedness, we could also be declared in default on our derivative obligations. These agreements also incorporate the loan covenant provisions of our indebtedness with a lender affiliate of the derivative counterparties. Failure to comply with the loan covenant provisions could result in our being declared in default on any derivative instrument obligations covered by the agreements. As of June 30, 2015 , the fair value of interest rate derivatives in a liability position related to these agreements was $3.1 million , excluding the effects of accrued interest. As of June 30, 2015 , 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 $3.4 million .

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest	6 Months Ended
	Jun. 30, 2015
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest The table below sets forth the activity in a redeemable noncontrolling interest in a consolidated real estate joint venture (in thousands): For the Six Months Ended June 30, 2015 2014 Beginning balance $ 18,417 $ 17,758 Distribution to noncontrolling interest (885 ) (590 ) Net income attributable to noncontrolling interest 1,143 1,016 Adjustment to arrive at fair value of interest 739 717 Ending balance $ 19,414 $ 18,901

Equity

Equity	6 Months Ended
	Jun. 30, 2015
Equity [Abstract]
Equity	Equity During the six months ended June 30, 2015 , COPT issued 890,241 common shares at a weighted average price of $30.29 per share under its at-the-market (“ATM”) stock offering program established in October 2012. Net proceeds from the shares issued totaled $26.6 million , after payment of $0.4 million in commissions to sales agents. These net proceeds were contributed to COPLP in exchange for 890,241 common units. COPT’s remaining capacity under the ATM Plan is an aggregate gross sales price of $84.0 million in common share sales. During the six months ended June 30, 2015 , certain COPLP limited partners redeemed 158,000 common units in COPLP for an equal number of common shares in COPT. See Note 14 for disclosure of COPT common share and COPLP common unit activity pertaining to our share-based compensation plans.

Information by Business Segment

Information by Business Segment	6 Months Ended
	Jun. 30, 2015
Segment Reporting [Abstract]
Information by Business Segment	Information by Business Segment We have ten reportable operating office property segments (comprised of: the Baltimore/Washington Corridor; Northern Virginia; San Antonio; Huntsville; Washington, DC — Capitol Riverfront; St. Mary’s and King George Counties; Greater Baltimore; Greater Philadelphia; Colorado Springs; and Other). In our 2015 quarterly reports on Form 10-Q, our Colorado Springs segment is, and will be, included in our Other segment as it is insignificant in the 2014 and 2015 reporting periods. We also have an operating wholesale data center segment. The table below reports segment financial information for our reportable segments (in thousands). We measure the performance of our segments through the measure we define as NOI from real estate operations, which is derived by subtracting property operating expenses from revenues from real estate operations. Operating Office Property Segments Baltimore/ Washington Corridor Northern Virginia San Antonio Huntsville Washington, DC - Capitol Riverfront St. Mary’s & King George Counties Greater Baltimore Greater Other Operating Wholesale Data Center Total Three Months June 30, 2015 Revenues from real estate operations $ 60,611 $ 24,393 $ 10,204 $ 2,658 $ 3,391 $ 3,795 $ 12,889 $ 3,886 $ 2,548 $ 3,820 $ 128,195 Property operating expenses 19,539 8,687 5,615 888 2,061 1,329 4,909 941 217 2,221 46,407 NOI from real estate operations $ 41,072 $ 15,706 $ 4,589 $ 1,770 $ 1,330 $ 2,466 $ 7,980 $ 2,945 $ 2,331 $ 1,599 $ 81,788 Additions to long-lived assets $ 5,141 $ 84,582 $ — $ 208 $ 806 $ 963 $ 2,476 $ 284 $ 177 $ 78 $ 94,715 Transfers from non-operating properties $ 6,098 $ 8,646 $ 468 $ 8,980 $ — $ — $ 12 $ 5,218 $ — $ 15,202 $ 44,624 Three Months Ended June 30, 2014 — Revenues from real estate operations $ 57,456 $ 20,898 $ 8,758 $ 2,404 $ 3,831 $ 4,202 $ 11,024 $ 2,366 $ 2,533 $ 2,492 $ 115,964 Property operating expenses 19,348 7,651 4,817 859 1,754 1,289 4,500 1,144 613 1,881 43,856 NOI from real estate operations $ 38,108 $ 13,247 $ 3,941 $ 1,545 $ 2,077 $ 2,913 $ 6,524 $ 1,222 $ 1,920 $ 611 $ 72,108 Additions to long-lived assets $ 6,289 $ 4,805 $ — $ 334 $ 478 $ 943 $ 1,242 $ 88 $ (93 ) $ 10 $ 14,096 Transfers from non-operating properties $ 20,712 $ 683 $ — $ 223 $ — $ — $ 2,953 $ 10,198 $ 19 $ 597 $ 35,385 Six Months Ended June 30, 2015 Revenues from real estate operations $ 122,403 $ 46,142 $ 19,375 $ 5,104 $ 6,755 $ 7,696 $ 24,374 $ 7,110 $ 5,091 $ 6,855 $ 250,905 Property operating expenses 43,122 17,808 10,590 1,717 3,875 2,913 9,906 2,316 413 4,433 97,093 NOI from real estate operations $ 79,281 $ 28,334 $ 8,785 $ 3,387 $ 2,880 $ 4,783 $ 14,468 $ 4,794 $ 4,678 $ 2,422 $ 153,812 Additions to long-lived assets $ 8,586 $ 87,403 $ 21 $ 291 $ 1,199 $ 2,163 $ 66,080 $ 578 $ 257 $ 108 $ 166,686 Transfers from non-operating properties $ 19,028 $ 67,217 $ 31,559 $ 11,977 $ — $ — $ 12 $ 16,716 $ 8 $ 15,379 $ 161,896 Segment assets at June 30, 2015 $ 1,279,531 $ 780,250 $ 147,844 $ 107,677 $ 94,099 $ 100,665 $ 332,973 $ 123,112 $ 76,943 $ 175,563 $ 3,218,657 Six Months Ended June 30, 2014 Revenues from real estate operations $ 118,569 $ 45,866 $ 17,237 $ 4,959 $ 7,465 $ 8,518 $ 22,520 $ 5,706 $ 5,127 $ 4,893 $ 240,860 Property operating expenses 42,945 16,624 9,291 1,512 3,519 2,793 9,976 2,444 935 3,569 93,608 NOI from real estate operations $ 75,624 $ 29,242 $ 7,946 $ 3,447 $ 3,946 $ 5,725 $ 12,544 $ 3,262 $ 4,192 $ 1,324 $ 147,252 Additions to long-lived assets $ 12,030 $ 8,300 $ (6 ) $ 2,841 $ 541 $ 1,782 $ 2,254 $ 99 $ (38 ) $ 22 $ 27,825 Transfers from non-operating properties $ 27,623 $ 27,271 $ — $ 20,325 $ — $ — $ 3,027 $ 13,374 $ 30 $ 675 $ 92,325 Segment assets at June 30, 2014 $ 1,259,974 $ 634,834 $ 117,328 $ 97,838 $ 97,136 $ 95,553 $ 300,139 $ 104,436 $ 78,918 $ 165,143 $ 2,951,299 The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Segment revenues from real estate operations $ 128,195 $ 115,964 $ 250,905 $ 240,860 Construction contract and other service revenues 42,172 23,861 80,496 45,651 Less: Revenues from discontinued operations (4 ) (5 ) (4 ) (24 ) Total revenues $ 170,363 $ 139,820 $ 331,397 $ 286,487 The following table reconciles our segment property operating expenses to property operating expenses as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Segment property operating expenses $ 46,407 $ 43,856 $ 97,093 $ 93,608 Less: Property operating expenses from discontinued operations 11 (84 ) 6 (64 ) Total property operating expenses $ 46,418 $ 43,772 $ 97,099 $ 93,544 As previously discussed, we provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. The primary manner in which we evaluate the operating performance of our service activities is through a measure we define as net operating income from service operations (“NOI from service operations”), which is based on the net of revenues and expenses from these activities. Construction contract and other service revenues and expenses consist primarily of subcontracted costs that are reimbursed to us by the customer along with a management fee. The operating margins from these activities are small relative to the revenue. We believe NOI from service operations is a useful measure in assessing both our level of activity and our profitability in conducting such operations. The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Construction contract and other service revenues $ 42,172 $ 23,861 $ 80,496 $ 45,651 Construction contract and other service expenses (41,293 ) (23,136 ) (78,791 ) (41,760 ) NOI from service operations $ 879 $ 725 $ 1,705 $ 3,891 The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to income from continuing operations as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 NOI from real estate operations $ 81,788 $ 72,108 $ 153,812 $ 147,252 NOI from service operations 879 725 1,705 3,891 Interest and other income 1,242 1,299 2,525 2,584 Equity in income (loss) of unconsolidated entities 9 (47 ) 34 13 Income tax expense (50 ) (92 ) (105 ) (156 ) Other adjustments: — — Depreciation and other amortization associated with real estate operations (33,786 ) (30,895 ) (65,385 ) (74,491 ) Impairment losses (1,238 ) (1,302 ) (1,238 ) (1,302 ) General, administrative and leasing expenses (7,534 ) (7,528 ) (15,425 ) (15,671 ) Business development expenses and land carry costs (2,623 ) (1,351 ) (5,413 ) (2,677 ) Interest expense (21,768 ) (23,478 ) (42,606 ) (44,305 ) Less: NOI from discontinued operations (15 ) 79 (10 ) 40 Loss on early extinguishment of debt (65 ) (270 ) (68 ) (270 ) Income from continuing operations $ 16,839 $ 9,248 $ 27,826 $ 14,908 The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): June 30, June 30, Segment assets $ 3,218,657 $ 2,951,299 Non-operating property assets 527,742 535,462 Other assets 164,522 222,739 Total COPT consolidated assets $ 3,910,921 $ 3,709,500 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 on early extinguishment of debt and gain on sales of real estate to our real estate segments since they are not included in the measure of segment profit reviewed by management. We also did not allocate general and administrative expenses, business development expenses and land carry costs, interest and other income, equity in income (loss) of unconsolidated entities, income taxes and noncontrolling interests because these items represent general corporate or non-operating property items not attributable to segments.

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Performance Share Units (“PSUs”) On March 5, 2015, our Board of Trustees granted 45,656 PSUs with an aggregate grant date fair value of $1.7 million to executives. The PSUs have a performance period beginning on January 1, 2015 and concluding on the earlier of December 31, 2017 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 service period ends due to a sale event or qualified termination, the number of earned PSUs is prorated based on the portion of the service 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 $36.76 per PSU using a Monte Carlo model, which included assumptions of, among other things, the following: baseline common share value of $29.28 ; expected volatility for COPT common shares of 19.9% ; and a risk-free interest rate of 0.99% . We are recognizing the grant date fair value in connection with these PSU awards over the period commencing on March 6, 2015 and ending on December 31, 2017. With regard to the PSUs granted to our executives in prior years that were outstanding as of December 31, 2014 as described in our 2014 Annual Report on Form 10-K: • the performance period for the PSUs granted to executives on March 1, 2012 ended on December 31, 2014. Based on COPT’s total shareholder return during the performance period relative to its peer group of companies, we issued 40,309 common shares in settlement of the PSUs on March 5, 2015; and • we issued 15,289 common shares on March 5, 2015 to Mr. Stephen E. Riffee, our former Chief Financial Officer, upon his departure on February 3, 2015, in settlement of PSUs granted on March 1, 2013 and March 6, 2014. Restricted Shares During the six months ended June 30, 2015 , certain employees were granted a total of 184,074 restricted common shares with an aggregate grant date fair value of $5.4 million (weighted average of $29.35 per share). Restricted shares granted to employees vest based on increments and over periods of time set forth under the terms of the respective awards provided that the employees remain employed by us. During the six months ended June 30, 2015 , forfeiture restrictions lapsed on 149,787 previously issued common shares; these shares had a weighted average grant date fair value of $25.96 per share, and the aggregate intrinsic value of the shares on the vesting dates was $4.3 million . Deferred Share Awards During the six months ended June 30, 2015 , nonemployee members of our Board of Trustees were granted a total of 24,056 deferred share awards with an aggregate grant date fair value of $642,000 ( $26.70 per share). Deferred share awards vest on the first anniversary of the grant date, provided that the Trustee remains in his or her position. We settle deferred share awards by issuing an equivalent number of common shares upon vesting of the awards or a later date elected by the Trustee (generally upon cessation of being a Trustee). During the six months ended June 30, 2015 , we issued 15,485 common shares in settlement of deferred share awards granted in 2014; these shares had a grant date fair value of $26.77 per share, and the aggregate intrinsic value of the shares on the settlement date was $413,000 . Options During the six months ended June 30, 2015 , 76,474 options to purchase common shares (“options”) were exercised. The weighted average exercise price of these options was $26.27 per share, and the aggregate intrinsic value of the options exercised was $300,000 .

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We own a TRS that is subject to Federal and state income taxes. Our TRS’s provision for income taxes consisted of the following (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Deferred Federal $ 41 $ 79 $ 86 $ 132 State 9 13 19 24 Total income tax expense $ 50 $ 92 $ 105 $ 156 Items in our TRS contributing to temporary differences that lead to deferred taxes include depreciation and amortization, share-based compensation, certain accrued compensation, compensation paid in the form of contributions to a deferred nonqualified compensation plan and net operating losses that are not deductible until future periods. Our TRS’s combined Federal and state effective tax rate was 37.7% for the three and six months ended June 30, 2015 and 37.4% for the three and six months ended June 30, 2014 .

Earnings Per Share ("EPS") and

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU")	6 Months Ended
	Jun. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”)	Earnings Per Share (“EPS”) and Earnings Per Unit (“EPU”) COPT and Subsidiaries EPS We present both basic and diluted EPS. We compute basic EPS by dividing net income available to common shareholders allocable to unrestricted common shares under the two-class method by the weighted average number of unrestricted common shares outstanding during the period. Our computation of diluted EPS is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common shares that would have been outstanding if securities that are convertible into COPT common shares were converted; and (2) the effect of dilutive potential common shares outstanding during the period attributable to share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common shares that we added to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Numerator: Income from continuing operations $ 16,839 $ 9,248 $ 27,826 $ 14,908 Gain on sales of real estate, net (1 ) — 3,985 — Preferred share dividends (3,553 ) (4,344 ) (7,105 ) (8,834 ) Issuance costs associated with redeemed preferred shares — (1,769 ) — (1,769 ) Income from continuing operations attributable to noncontrolling interests (1,436 ) (1,171 ) (2,828 ) (2,103 ) Income from continuing operations attributable to share-based compensation awards (113 ) (108 ) (235 ) (229 ) Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders $ 11,736 $ 1,856 $ 21,643 $ 1,973 Discontinued operations 394 (198 ) 156 (187 ) Discontinued operations attributable to noncontrolling interests (15 ) 11 (3 ) 13 Numerator for basic and diluted EPS on net income attributable to COPT common shareholders $ 12,115 $ 1,669 $ 21,796 $ 1,799 Denominator (all weighted averages): Denominator for basic EPS (common shares) 94,128 87,214 93,666 87,148 Dilutive effect of share-based compensation awards 35 201 114 156 Denominator for diluted EPS (common shares) 94,163 87,415 93,780 87,304 Basic EPS: Income from continuing operations attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net income attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Diluted EPS: Income from continuing operations attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net income attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Conversion of common units 3,680 3,912 3,706 3,934 Conversion of Series I Preferred Units 176 176 176 176 Conversion of Series K Preferred Shares 434 434 434 434 The following share-based compensation securities were excluded from the computation of diluted EPS because their effects were antidilutive: • weighted average restricted shares and deferred share awards for the three months ended June 30, 2015 and 2014 of 426,000 and 420,000 , respectively, and for the six months ended June 30, 2015 and 2014 of 413,000 and 405,000 , respectively; and • weighted average options for the three months ended June 30, 2015 and 2014 of 473,000 and 496,000 , respectively, and for the six months ended June 30, 2015 and 2014 of 472,000 and 512,000 , respectively. As discussed in Note 9, we had outstanding senior notes, which we redeemed in April 2015, with an exchange settlement feature, but such notes did not affect our diluted EPS reported above since the weighted average closing price of COPT’s common shares during each of the periods was less than the exchange prices per common share applicable for such periods. COPLP and Subsidiaries EPU We present both basic and diluted EPU. We compute basic EPU by dividing net income available to common unitholders allocable to unrestricted common units under the two-class method by the weighted average number of unrestricted common units outstanding during the period. Our computation of diluted EPU is similar except that: • the denominator is increased to include: (1) the weighted average number of potential additional common units that would have been outstanding if securities that are convertible into our common units were converted; and (2) the effect of dilutive potential common units outstanding during the period attributable to share-based compensation using the treasury stock or if-converted methods; and • the numerator is adjusted to add back any changes in income or loss that would result from the assumed conversion into common units that we added to the denominator. Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Numerator: Income from continuing operations $ 16,839 $ 9,248 $ 27,826 $ 14,908 Gain on sales of real estate, net (1 ) — 3,985 — Preferred unit distributions (3,718 ) (4,509 ) (7,435 ) (9,164 ) Issuance costs associated with redeemed preferred units — (1,769 ) — (1,769 ) Income from continuing operations attributable to noncontrolling interests (812 ) (840 ) (1,633 ) (1,579 ) Income from continuing operations attributable to share-based compensation awards (113 ) (108 ) (235 ) (229 ) Numerator for basic and diluted EPU from continuing operations attributable to COPLP common unitholders $ 12,195 $ 2,022 $ 22,508 $ 2,167 Discontinued operations 394 (198 ) 156 (187 ) Discontinued operations attributable to noncontrolling interests — 3 3 5 Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ 12,589 $ 1,827 $ 22,667 $ 1,985 Denominator (all weighted averages): Denominator for basic EPU (common units) 97,808 91,126 97,372 91,082 Dilutive effect of share-based compensation awards 35 201 114 156 Denominator for basic and diluted EPU (common units) 97,843 91,327 97,486 91,238 Basic EPU: Income from continuing operations attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net income attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Diluted EPU: Income from continuing operations attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net income attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Units Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Conversion of Series I preferred units 176 176 176 176 Conversion of Series K preferred units 434 434 434 434 The following share-based compensation securities were excluded from the computation of diluted EPU because their effects were antidilutive: • weighted average restricted units and deferred share awards for the three months ended June 30, 2015 and 2014 of 426,000 and 420,000 , respectively, and for the six months ended June 30, 2015 and 2014 of 413,000 and 405,000 , respectively; and • weighted average options for the three months ended June 30, 2015 and 2014 of 473,000 and 496,000 , respectively, and for the six months ended June 30, 2015 and 2014 of 472,000 and 512,000 , respectively. As discussed in Note 9, we had outstanding senior notes, which we redeemed in April 2015, with an exchange settlement feature, but such notes did not affect our diluted EPU reported above since the weighted average closing price of COPT’s common shares during each of the periods was less than the exchange prices per common share applicable for such periods.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2015
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 $2.4 million liability through June 30, 2015 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. Environmental Indemnity Agreement We agreed to provide certain environmental indemnifications in connection with a lease and subsequent sale of three New Jersey properties. The prior owner of the properties, a Fortune 100 company that is responsible for groundwater contamination at such properties, previously agreed to indemnify us for (1) direct losses incurred in connection with the contamination and (2) its failure to perform remediation activities required by the State of New Jersey, up to the point that the state declares the remediation to be complete. Under the environmental indemnification agreement, we agreed to the following: • to indemnify the tenant against losses covered under the prior owner’s indemnity agreement if the prior owner fails to indemnify the tenant for such losses. This indemnification is capped at $5.0 million in perpetuity after the State of New Jersey declares the remediation to be complete; • to indemnify the tenant for consequential damages (e.g., business interruption) at one of the buildings in perpetuity and another of the buildings through 2025. This indemnification is limited to $12.5 million ; and • to pay 50% of additional costs related to construction and environmental regulatory activities incurred by the tenant as a result of the indemnified environmental condition of the properties. This indemnification is limited to $300,000 annually and $1.5 million in the aggregate.

Subsequent Event

Subsequent Event	6 Months Ended
	Jun. 30, 2015
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event On July 27, 2015 we sold 1550 Westbranch Drive, a 160,000 square foot office property in McLean, Virginia (in the Northern Virginia region), for $27.8 million , which approximated the property’s carrying value.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2015
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 significant 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. 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, 2014 included in our 2014 Annual Report on Form 10-K. The unaudited consolidated financial statements include all adjustments that are necessary, in the opinion of management, to fairly present our financial position and results of operations. All adjustments are of a normal recurring nature. The consolidated financial statements have been prepared using the accounting policies described in our 2014 Annual Report on Form 10-K.
Recent Accounting Pronouncement	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“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 January 2015, the FASB issued guidance 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. This guidance is effective for periods beginning after December 15, 2015. We expect that the application of this guidance will have no effect on our reported consolidated financial statements. In February 2015, the FASB issued guidance regarding amendments to the consolidation analysis. This guidance amends the criteria for determining which entities are considered variable interest entities (“VIE”), amends the criteria for determining if a service provider possesses a variable interest in a VIE and ends the deferral granted to investment companies for application of the VIE consolidation model. This guidance is effective for annual periods, and interim periods therein, beginning after December 15, 2015. We are currently assessing the financial impact of this guidance on our consolidated financial statements. In April 2015, the FASB issued guidance that changes the presentation of debt issuance costs in financial statements. This guidance requires an entity to present such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs will continue to be reported as interest expense. This guidance is effective for annual reporting periods beginning after December 15, 2016. Early adoption is permitted. This guidance will be applied retrospectively to each prior period presented. We expect that the application of this guidance will not materially affect our consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Schedule of fair value assets and liabilities measured on recurring basis	The table below sets forth financial assets and liabilities of COPT and its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2015 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 $ 5,765 $ — $ — $ 5,765 Other 108 — — 108 Warrants to purchase common stock (2) — 141 — 141 Total assets $ 5,873 $ 141 $ — $ 6,014 Liabilities: Deferred compensation plan liability (3) $ — $ 5,873 $ — $ 5,873 Interest rate derivatives — 3,121 — 3,121 Total liabilities $ — $ 8,994 $ — $ 8,994 Redeemable noncontrolling interest $ — $ — $ 19,414 $ 19,414 (1) Included in the line entitled “restricted cash and marketable securities” on COPT’s consolidated balance sheet. (2) Included in the line entitled “prepaid expenses and other assets” on COPT’s consolidated balance sheet. (3) Included in the line entitled “other liabilities” on COPT’s consolidated balance sheet. The table below sets forth financial assets and liabilities of COPLP and its subsidiaries that are accounted for at fair value on a recurring basis as of June 30, 2015 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: Warrants to purchase common stock (1) $ — $ 141 $ — $ 141 Liabilities: Interest rate derivatives $ — $ 3,121 $ — $ 3,121 Redeemable noncontrolling interest $ — $ — $ 19,414 $ 19,414 (1) Included in the line entitled “prepaid expenses and other assets” on COPLP’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 the fair value of this property (dollars in thousands): Fair Value as of June 30, 2015 (1) Quoted Prices in Significant Impairment Losses Recognized Active Markets for Significant Other Unobservable Three Months Six Months Identical Assets Observable Inputs Inputs Ended Ended Description (Level 1) (Level 2) (Level 3) Total June 30, 2015 June 30, 2015 Assets: Assets held for sale $ — $ — $ 27,690 $ 27,690 $ 1,238 $ 1,238 (1) Fair value represents contract price less expected costs to sell. The table below sets forth the fair value hierarchy of the valuation technique used by us in determining the fair values of the properties (dollars in thousands): Fair Value of Properties Held as of June 30, 2014 (1) Quoted Prices in Significant Impairment Losses Recognized Active Markets for Significant Other Unobservable Three Months Six Months Identical Assets Observable Inputs Inputs Ended Ended Description (Level 1) (Level 2) (Level 3) Total June 30, 2014 June 30, 2014 Assets: Assets held for sale $ — $ — $ 9,796 $ 9,796 $ 1,302 $ 1,302 (1) Fair value represents contract price less expected costs to sell.

Properties, net (Tables)

Properties, net (Tables)	6 Months Ended
	Jun. 30, 2015
Real Estate [Abstract]
Schedule of operating properties, net	Operating properties, net consisted of the following (in thousands): June 30, December 31, Land $ 460,268 $ 439,355 Buildings and improvements 3,160,011 3,015,216 Less: Accumulated depreciation (723,470 ) (703,083 ) Operating properties, net $ 2,896,809 $ 2,751,488
Schedule of projects in development or held for future development	Projects in development or held for future development consisted of the following (in thousands): June 30, December 31, Land $ 221,655 $ 214,977 Construction in progress, excluding land 300,336 330,449 Projects in development or held for future development $ 521,991 $ 545,426
Components of assets held for sale	The table below sets forth the components of assets held for sale on our consolidated balance sheet for these properties (in thousands): June 30, 2015 Properties, net $ 73,174 Deferred rent receivable 1,683 Intangible assets on real estate acquisitions, net 1,017 Deferred leasing costs, net 977 Lease incentives, net 162 Assets held for sale, net $ 77,013
Schedule of allocation of acquisition costs	The table below sets forth the allocation of the acquisition costs of these properties (in thousands): Land, operating properties $ 28,361 Building and improvements 69,182 Intangible assets on real estate acquisitions 45,940 Total assets 143,483 Below-market leases (1,093 ) Total acquisition cost $ 142,390
Schedule of intangible assets recorded in connection with acquisition	Intangible assets recorded in connection with the these acquisitions included the following (dollars in thousands): Weighted Average Amortization Period (in Years) Tenant relationship value $ 20,024 10 In-place lease value 20,041 5 Above-market leases 5,875 4 $ 45,940 7
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 shares amounts). For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 (Unaudited) (Unaudited) Pro forma total revenues $ 170,719 $ 144,098 $ 335,159 $ 294,769 Pro forma net income attributable to COPT common shareholders $ 12,620 $ 2,126 $ 22,850 $ 835 Pro forma EPS: Basic $ 0.13 $ 0.02 $ 0.24 $ 0.01 Diluted $ 0.13 $ 0.02 $ 0.24 $ 0.01

Real Estate Joint Ventures (Tab

Real Estate Joint Ventures (Tables)	6 Months Ended
	Jun. 30, 2015
Equity Method Investments and Joint Ventures [Abstract]
Schedule of information related to investments in consolidated real estate joint ventures	The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of June 30, 2015 (dollars in thousands): Nominal Ownership June 30, 2015 (1) Date % as of Total Encumbered Total Acquired 6/30/2015 Nature of Activity Assets Assets Liabilities LW Redstone Company, LLC 3/23/2010 85% Operates five buildings and developing others (2) $ 142,787 $ 65,200 $ 40,278 M Square Associates, LLC 6/26/2007 50% Operates two buildings and developing others (3) 58,839 48,364 38,249 $ 201,626 $ 113,564 $ 78,527 (1) Excludes amounts eliminated in consolidation. (2) This joint venture’s properties are in Huntsville. (3) This joint venture’s properties are in College Park, Maryland (in the Baltimore/Washington Corridor).

Intangible Assets on Real Est31

Intangible Assets on Real Estate Acquisition, Net (Tables)	6 Months Ended
	Jun. 30, 2015
Intangible Assets on Real Estate Acquisitions [Abstract]
Schedule of intangible assets on real estate acquisitions	Intangible assets on real estate acquisitions consisted of the following, excluding amounts for properties held for sale (in thousands): June 30, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount In-place lease value $ 134,387 $ 95,910 $ 38,477 $ 123,759 $ 101,040 $ 22,719 Tenant relationship value 58,560 27,666 30,894 42,301 28,492 13,809 Below-market cost arrangements 12,415 6,324 6,091 12,415 5,984 6,431 Above-market leases 14,344 8,467 5,877 8,659 8,159 500 Market concentration premium 1,333 944 389 1,333 938 395 $ 221,039 $ 139,311 $ 81,728 $ 188,467 $ 144,613 $ 43,854

Investing Receivables (Tables)

Investing Receivables (Tables)	6 Months Ended
	Jun. 30, 2015
Receivables [Abstract]
Schedule of investing receivables	Investing receivables, including accrued interest thereon, consisted of the following (in thousands): June 30, December 31, Notes receivable from the City of Huntsville $ 42,766 $ 49,147 Other investing loans receivable 3,000 3,000 $ 45,766 $ 52,147

Prepaid Expenses and Other As33

Prepaid Expenses and Other Assets, Net (Tables)	6 Months Ended
	Jun. 30, 2015
Prepaid Expense and Other Assets [Abstract]
Schedule of prepaid expenses and other assets	Prepaid expenses and other assets consisted of the following (in thousands): June 30, December 31, Lease incentives, net $ 12,964 $ 13,344 Construction contract costs incurred in excess of billings 12,051 6,656 Prepaid expenses 8,882 20,570 Furniture, fixtures and equipment, net 6,340 6,637 Deferred tax asset, net (1) 4,064 4,002 Operating notes receivable 3,937 3,797 Deposit on acquisitions 2,016 516 Equity method investments 1,616 2,368 Other assets 3,267 2,359 Prepaid expenses and other assets, net $ 55,137 $ 60,249 (1) Includes a valuation allowance of $2.1 million .

Debt, Net (Tables)

Debt, Net (Tables)	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Schedule of debt	Our debt consisted of the following (dollars in thousands): Maximum Availability at Carrying Value at Scheduled Maturity June 30, June 30, December 31, Stated Interest Rates as of as of June 30, 2015 June 30, 2015 Mortgage and Other Secured Loans: Fixed rate mortgage loans (1) $ 384,227 $ 387,139 3.96% - 10.65% (2) 2015-2024 Variable rate secured loan 36,457 36,877 LIBOR + 2.25% (3) November 2015 Total mortgage and other secured loans 420,684 424,016 Revolving Credit Facility $ 800,000 — 83,000 LIBOR + 0.875% to 1.60% (4) May 2019 Term Loan Facilities (5) 520,000 520,000 LIBOR + 0.90% to 2.60% (6) 2016-2020 Unsecured Senior Notes 3.600% Senior Notes (7) 347,625 347,496 3.60% May 2023 5.250% Senior Notes (8) 245,980 245,797 5.25% February 2024 3.700% Senior Notes (9) 297,743 297,569 3.70% June 2021 5.000% Senior Note (10) 296,580 — 5.00% July 2025 Unsecured notes payable 1,558 1,607 0% (11) 2026 4.25% Exchangeable Senior Notes (12) — 572 N/A (12) Total debt, net $ 2,130,170 $ 1,920,057 (1) 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 $30,000 as of June 30, 2015 and $42,000 as of December 31, 2014 . (2) Includes a $150.0 million nonrecourse mortgage loan in default secured by two operating properties in Northern Virginia with an aggregate estimated fair value that was less than the loan balance. This loan has an interest rate of 10.65% (including the effect of default interest). The maximum stated interest rate would be 7.87% , excluding the incremental additional interest rate associated with the default rate on the loan in default. The weighted average interest rate on our fixed rate mortgage loans was 8.11% as of June 30, 2015 (or 6.16% excluding the incremental additional interest rate associated with the default rate on the loan in default). (3) The interest rate on the loan outstanding was 2.43% as of June 30, 2015 . (4) The weighted average interest rate on the Revolving Credit Facility was 1.37% as of June 30, 2015 . (5) We have the ability to borrow an additional $380.0 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. (6) The weighted average interest rate on these loans was 1.77% as of June 30, 2015 . (7) The carrying value of these notes included a principal amount of $350.0 million and an unamortized discount totaling $2.4 million as of June 30, 2015 and $2.5 million as of December 31, 2014 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.70% . (8) The carrying value of these notes included a principal amount of $250.0 million and an unamortized discount totaling $4.0 million as of June 30, 2015 and $4.2 million as of December 31, 2014 . The effective interest rate under the notes, including amortization of the issuance costs, was 5.49% . (9) The carrying value of these notes included a principal amount of $300.0 million and an unamortized discount totaling $2.3 million as of June 30, 2015 and $2.4 million as of December 31, 2014 . The effective interest rate under the notes, including amortization of the issuance costs, was 3.85% . (10) Refer to the paragraph below for disclosure pertaining to these notes. (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 $603,000 as of June 30, 2015 and $654,000 as of December 31, 2014 . (12) On April 20, 2015, we redeemed these notes at 100% of their principal amount.
Schedule of the fair value of debt	The following table sets forth information pertaining to the fair value of our debt (in thousands): June 30, 2015 December 31, 2014 Carrying Estimated Carrying Estimated Amount Fair Value Amount Fair Value Fixed-rate debt Unsecured Senior Notes $ 1,187,928 $ 1,202,956 $ 890,862 $ 901,599 Other fixed-rate debt 385,785 345,066 389,318 356,377 Variable-rate debt 556,457 557,753 639,877 642,091 $ 2,130,170 $ 2,105,775 $ 1,920,057 $ 1,900,067

Interest Rate Derivatives (Tabl

Interest Rate Derivatives (Tables)	6 Months Ended
	Jun. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of key terms and fair values of interest rate swap derivatives	The following table sets forth the key terms and fair values of our interest rate swap derivatives (dollars in thousands): Fair Value at Notional Amount Fixed Rate Floating Rate Index Effective Date Expiration Date June 30, December 31, $ 100,000 0.8320% One-Month LIBOR 1/3/2012 9/1/2015 $ (110 ) $ (407 ) 100,000 0.8320% One-Month LIBOR 1/3/2012 9/1/2015 (110 ) (407 ) 36,457 (1) 3.8300% One-Month LIBOR + 2.25% 11/2/2010 11/2/2015 (171 ) (400 ) 100,000 0.8055% One-Month LIBOR 9/2/2014 9/1/2016 (405 ) (317 ) 100,000 0.8100% One-Month LIBOR 9/2/2014 9/1/2016 (410 ) (324 ) 100,000 1.6730% One-Month LIBOR 9/1/2015 8/1/2019 (849 ) 239 100,000 1.7300% One-Month LIBOR 9/1/2015 8/1/2019 (1,066 ) 35 $ (3,121 ) $ (1,581 ) (1) The notional amount of this instrument is scheduled to amortize to $36.2 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): June 30, 2015 December 31, 2014 Derivatives Balance Sheet Location Fair Value Balance Sheet Location Fair Value Interest rate swaps designated as cash flow hedges Prepaid expenses and other assets $ — Prepaid expenses and other assets $ 274 Interest rate swaps designated as cash flow hedges Interest rate derivatives (3,121 ) Interest rate derivatives (1,855 )
Schedule of effect of interest rate derivatives on consolidated statements of operations and comprehensive income	The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Amount of gain (loss) recognized in accumulated other comprehensive loss (“AOCL”) (effective portion) $ 392 $ (3,630 ) $ (3,082 ) $ (5,753 ) Amount of losses reclassified from AOCL into interest expense (effective portion) 769 719 1,542 1,414

Redeemable Noncontrolling Int36

Redeemable Noncontrolling Interest (Tables)	6 Months Ended
	Jun. 30, 2015
Noncontrolling Interest [Abstract]
Schedule of activity for redeemable noncontrolling interest	The table below sets forth the activity in a redeemable noncontrolling interest in a consolidated real estate joint venture (in thousands): For the Six Months Ended June 30, 2015 2014 Beginning balance $ 18,417 $ 17,758 Distribution to noncontrolling interest (885 ) (590 ) Net income attributable to noncontrolling interest 1,143 1,016 Adjustment to arrive at fair value of interest 739 717 Ending balance $ 19,414 $ 18,901

Information by Business Segme37

Information by Business Segment (Tables)	6 Months Ended
	Jun. 30, 2015
Segment Reporting [Abstract]
Schedule of segment financial information for real estate operations	The table below reports segment financial information for our reportable segments (in thousands). We measure the performance of our segments through the measure we define as NOI from real estate operations, which is derived by subtracting property operating expenses from revenues from real estate operations. Operating Office Property Segments Baltimore/ Washington Corridor Northern Virginia San Antonio Huntsville Washington, DC - Capitol Riverfront St. Mary’s & King George Counties Greater Baltimore Greater Other Operating Wholesale Data Center Total Three Months June 30, 2015 Revenues from real estate operations $ 60,611 $ 24,393 $ 10,204 $ 2,658 $ 3,391 $ 3,795 $ 12,889 $ 3,886 $ 2,548 $ 3,820 $ 128,195 Property operating expenses 19,539 8,687 5,615 888 2,061 1,329 4,909 941 217 2,221 46,407 NOI from real estate operations $ 41,072 $ 15,706 $ 4,589 $ 1,770 $ 1,330 $ 2,466 $ 7,980 $ 2,945 $ 2,331 $ 1,599 $ 81,788 Additions to long-lived assets $ 5,141 $ 84,582 $ — $ 208 $ 806 $ 963 $ 2,476 $ 284 $ 177 $ 78 $ 94,715 Transfers from non-operating properties $ 6,098 $ 8,646 $ 468 $ 8,980 $ — $ — $ 12 $ 5,218 $ — $ 15,202 $ 44,624 Three Months Ended June 30, 2014 — Revenues from real estate operations $ 57,456 $ 20,898 $ 8,758 $ 2,404 $ 3,831 $ 4,202 $ 11,024 $ 2,366 $ 2,533 $ 2,492 $ 115,964 Property operating expenses 19,348 7,651 4,817 859 1,754 1,289 4,500 1,144 613 1,881 43,856 NOI from real estate operations $ 38,108 $ 13,247 $ 3,941 $ 1,545 $ 2,077 $ 2,913 $ 6,524 $ 1,222 $ 1,920 $ 611 $ 72,108 Additions to long-lived assets $ 6,289 $ 4,805 $ — $ 334 $ 478 $ 943 $ 1,242 $ 88 $ (93 ) $ 10 $ 14,096 Transfers from non-operating properties $ 20,712 $ 683 $ — $ 223 $ — $ — $ 2,953 $ 10,198 $ 19 $ 597 $ 35,385 Six Months Ended June 30, 2015 Revenues from real estate operations $ 122,403 $ 46,142 $ 19,375 $ 5,104 $ 6,755 $ 7,696 $ 24,374 $ 7,110 $ 5,091 $ 6,855 $ 250,905 Property operating expenses 43,122 17,808 10,590 1,717 3,875 2,913 9,906 2,316 413 4,433 97,093 NOI from real estate operations $ 79,281 $ 28,334 $ 8,785 $ 3,387 $ 2,880 $ 4,783 $ 14,468 $ 4,794 $ 4,678 $ 2,422 $ 153,812 Additions to long-lived assets $ 8,586 $ 87,403 $ 21 $ 291 $ 1,199 $ 2,163 $ 66,080 $ 578 $ 257 $ 108 $ 166,686 Transfers from non-operating properties $ 19,028 $ 67,217 $ 31,559 $ 11,977 $ — $ — $ 12 $ 16,716 $ 8 $ 15,379 $ 161,896 Segment assets at June 30, 2015 $ 1,279,531 $ 780,250 $ 147,844 $ 107,677 $ 94,099 $ 100,665 $ 332,973 $ 123,112 $ 76,943 $ 175,563 $ 3,218,657 Six Months Ended June 30, 2014 Revenues from real estate operations $ 118,569 $ 45,866 $ 17,237 $ 4,959 $ 7,465 $ 8,518 $ 22,520 $ 5,706 $ 5,127 $ 4,893 $ 240,860 Property operating expenses 42,945 16,624 9,291 1,512 3,519 2,793 9,976 2,444 935 3,569 93,608 NOI from real estate operations $ 75,624 $ 29,242 $ 7,946 $ 3,447 $ 3,946 $ 5,725 $ 12,544 $ 3,262 $ 4,192 $ 1,324 $ 147,252 Additions to long-lived assets $ 12,030 $ 8,300 $ (6 ) $ 2,841 $ 541 $ 1,782 $ 2,254 $ 99 $ (38 ) $ 22 $ 27,825 Transfers from non-operating properties $ 27,623 $ 27,271 $ — $ 20,325 $ — $ — $ 3,027 $ 13,374 $ 30 $ 675 $ 92,325 Segment assets at June 30, 2014 $ 1,259,974 $ 634,834 $ 117,328 $ 97,838 $ 97,136 $ 95,553 $ 300,139 $ 104,436 $ 78,918 $ 165,143 $ 2,951,299
Schedule of reconciliation of segment revenues to total revenues	The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Segment revenues from real estate operations $ 128,195 $ 115,964 $ 250,905 $ 240,860 Construction contract and other service revenues 42,172 23,861 80,496 45,651 Less: Revenues from discontinued operations (4 ) (5 ) (4 ) (24 ) Total revenues $ 170,363 $ 139,820 $ 331,397 $ 286,487
Schedule of reconciliation of segment property operating expenses to total property operating expenses	The following table reconciles our segment property operating expenses to property operating expenses as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Segment property operating expenses $ 46,407 $ 43,856 $ 97,093 $ 93,608 Less: Property operating expenses from discontinued operations 11 (84 ) 6 (64 ) Total property operating expenses $ 46,418 $ 43,772 $ 97,099 $ 93,544
Schedule of computation of net operating income from service operations	The table below sets forth the computation of our NOI from service operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Construction contract and other service revenues $ 42,172 $ 23,861 $ 80,496 $ 45,651 Construction contract and other service expenses (41,293 ) (23,136 ) (78,791 ) (41,760 ) NOI from service operations $ 879 $ 725 $ 1,705 $ 3,891
Schedule of reconciliation of net operating income from real estate operations and service operations to (loss) income from continuing operations	The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to income from continuing operations as reported on our consolidated statements of operations (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 NOI from real estate operations $ 81,788 $ 72,108 $ 153,812 $ 147,252 NOI from service operations 879 725 1,705 3,891 Interest and other income 1,242 1,299 2,525 2,584 Equity in income (loss) of unconsolidated entities 9 (47 ) 34 13 Income tax expense (50 ) (92 ) (105 ) (156 ) Other adjustments: — — Depreciation and other amortization associated with real estate operations (33,786 ) (30,895 ) (65,385 ) (74,491 ) Impairment losses (1,238 ) (1,302 ) (1,238 ) (1,302 ) General, administrative and leasing expenses (7,534 ) (7,528 ) (15,425 ) (15,671 ) Business development expenses and land carry costs (2,623 ) (1,351 ) (5,413 ) (2,677 ) Interest expense (21,768 ) (23,478 ) (42,606 ) (44,305 ) Less: NOI from discontinued operations (15 ) 79 (10 ) 40 Loss on early extinguishment of debt (65 ) (270 ) (68 ) (270 ) Income from continuing operations $ 16,839 $ 9,248 $ 27,826 $ 14,908
Schedule of reconciliation of segment assets to total assets	The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands): June 30, June 30, Segment assets $ 3,218,657 $ 2,951,299 Non-operating property assets 527,742 535,462 Other assets 164,522 222,739 Total COPT consolidated assets $ 3,910,921 $ 3,709,500

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2015
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

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Components of provision for income tax	Our TRS’s provision for income taxes consisted of the following (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Deferred Federal $ 41 $ 79 $ 86 $ 132 State 9 13 19 24 Total income tax expense $ 50 $ 92 $ 105 $ 156

Earnings Per Share ("EPS") an40

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Tables)	6 Months Ended
	Jun. 30, 2015
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPS calculations are set forth below (in thousands, except per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Numerator: Income from continuing operations $ 16,839 $ 9,248 $ 27,826 $ 14,908 Gain on sales of real estate, net (1 ) — 3,985 — Preferred share dividends (3,553 ) (4,344 ) (7,105 ) (8,834 ) Issuance costs associated with redeemed preferred shares — (1,769 ) — (1,769 ) Income from continuing operations attributable to noncontrolling interests (1,436 ) (1,171 ) (2,828 ) (2,103 ) Income from continuing operations attributable to share-based compensation awards (113 ) (108 ) (235 ) (229 ) Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders $ 11,736 $ 1,856 $ 21,643 $ 1,973 Discontinued operations 394 (198 ) 156 (187 ) Discontinued operations attributable to noncontrolling interests (15 ) 11 (3 ) 13 Numerator for basic and diluted EPS on net income attributable to COPT common shareholders $ 12,115 $ 1,669 $ 21,796 $ 1,799 Denominator (all weighted averages): Denominator for basic EPS (common shares) 94,128 87,214 93,666 87,148 Dilutive effect of share-based compensation awards 35 201 114 156 Denominator for diluted EPS (common shares) 94,163 87,415 93,780 87,304 Basic EPS: Income from continuing operations attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net income attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Diluted EPS: Income from continuing operations attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPT common shareholders 0.00 0.00 0.00 0.00 Net income attributable to COPT common shareholders $ 0.13 $ 0.02 $ 0.23 $ 0.02
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPS computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPS for the respective periods (in thousands): Weighted Average Shares Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Conversion of common units 3,680 3,912 3,706 3,934 Conversion of Series I Preferred Units 176 176 176 176 Conversion of Series K Preferred Shares 434 434 434 434
Corporate Office Properties, L.P.
Earnings Per Share [Line Items]
Summary of calculation of numerator and denominator in basic and diluted earnings per share	Summaries of the numerator and denominator for purposes of basic and diluted EPU calculations are set forth below (in thousands, except per unit data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Numerator: Income from continuing operations $ 16,839 $ 9,248 $ 27,826 $ 14,908 Gain on sales of real estate, net (1 ) — 3,985 — Preferred unit distributions (3,718 ) (4,509 ) (7,435 ) (9,164 ) Issuance costs associated with redeemed preferred units — (1,769 ) — (1,769 ) Income from continuing operations attributable to noncontrolling interests (812 ) (840 ) (1,633 ) (1,579 ) Income from continuing operations attributable to share-based compensation awards (113 ) (108 ) (235 ) (229 ) Numerator for basic and diluted EPU from continuing operations attributable to COPLP common unitholders $ 12,195 $ 2,022 $ 22,508 $ 2,167 Discontinued operations 394 (198 ) 156 (187 ) Discontinued operations attributable to noncontrolling interests — 3 3 5 Numerator for basic and diluted EPU on net income attributable to COPLP common unitholders $ 12,589 $ 1,827 $ 22,667 $ 1,985 Denominator (all weighted averages): Denominator for basic EPU (common units) 97,808 91,126 97,372 91,082 Dilutive effect of share-based compensation awards 35 201 114 156 Denominator for basic and diluted EPU (common units) 97,843 91,327 97,486 91,238 Basic EPU: Income from continuing operations attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net income attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Diluted EPU: Income from continuing operations attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02 Discontinued operations attributable to COPLP common unitholders 0.00 0.00 0.00 0.00 Net income attributable to COPLP common unitholders $ 0.13 $ 0.02 $ 0.23 $ 0.02
Schedule of securities excluded from computation of diluted earnings per share	Our diluted EPU computations do not include the effects of the following securities since the conversions of such securities would increase diluted EPU for the respective periods (in thousands): Weighted Average Units Excluded from Denominator For the Three Months Ended June 30, For the Six Months Ended June 30, 2015 2014 2015 2014 Conversion of Series I preferred units 176 176 176 176 Conversion of Series K preferred units 434 434 434 434

Organization (Details)

Organization (Details) - Jun. 30, 2015 ft² in Millions	aft²PropertyMW
Debt in default of payment terms | Northern Virginia | Wholly owned subsidiary
Investments in real estate
Number of real estate properties | Property	2
Operating office properties
Investments in real estate
Number of real estate properties | Property	179
Square footage of real estate properties (in square feet)	18
Office properties under, or contractually committed for, construction or approved for redevelopment
Investments in real estate
Number of real estate properties | Property	12
Square footage of real estate properties (in square feet)	1.3
Land controlled for future development
Investments in real estate
Square footage of real estate properties (in square feet) | a	1,450
Developable square feet	17.7
Partially operational, wholesale data center
Investments in real estate
The expected stabilization critical load after completion of development (in megawatts) | MW	19.25

Organization (Details 2)

Organization (Details 2) - Corporate Office Properties, L.P.	6 Months Ended
	Jun. 30, 2015
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) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Liabilities:
Interest rate derivatives	$ 3,121	$ 1,855
Redeemable noncontrolling interest	19,414	18,417	$ 18,901	$ 17,758
Corporate Office Properties, L.P.
Liabilities:
Interest rate derivatives	3,121	$ 1,855
Fair value measurement on a recurring basis
Assets:
Warrants to purchase common stock	141
Assets	6,014
Liabilities:
Deferred compensation plan liability	5,873
Interest rate derivatives	3,121
Liabilities	8,994
Redeemable noncontrolling interest	19,414
Fair value measurement on a recurring basis | Mutual funds
Assets:
Marketable securities in deferred compensation plan	5,765
Fair value measurement on a recurring basis | Other
Assets:
Marketable securities in deferred compensation plan	108
Fair value measurement on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Assets	5,873
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	5,765
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	108
Fair value measurement on a recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Warrants to purchase common stock	141
Assets	141
Liabilities:
Deferred compensation plan liability	5,873
Interest rate derivatives	3,121
Liabilities	8,994
Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3)
Liabilities:
Redeemable noncontrolling interest	19,414
Fair value measurement on a recurring basis | Corporate Office Properties, L.P.
Assets:
Warrants to purchase common stock	141
Liabilities:
Interest rate derivatives	3,121
Redeemable noncontrolling interest	19,414
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Other Observable Inputs (Level 2)
Assets:
Warrants to purchase common stock	141
Liabilities:
Interest rate derivatives	3,121
Fair value measurement on a recurring basis | Corporate Office Properties, L.P. | Significant Unobservable Inputs (Level 3)
Liabilities:
Redeemable noncontrolling interest	$ 19,414

Fair Value Measurements (Deta44

Fair Value Measurements (Details 2) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses			$ 1,238	$ 1,302	$ 1,238	$ 1,302
Redeemable Non-Controlling Interest | Fair value measurement on a recurring basis | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value on a non-recurring basis
Fair value inputs, discount rate					15.50%
Real Estate Investment Properties, Net [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses			$ 1,238	$ 1,302	$ 1,238	$ 1,302
Northern Virginia | Real Estate Investment Properties, Net [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	$ 1,200
Greater Baltimore | Real Estate Investment Properties, Net [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses		$ 1,300

Fair Value Measurements (Deta45

Fair Value Measurements (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Assets and liabilities measured at fair value on a non-recurring basis
Impairment losses	$ 1,238	$ 1,302	$ 1,238	$ 1,302
Real Estate Investment Properties, Net [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets and liabilities measured at fair value on a non-recurring basis
Assets	27,690	9,796	27,690	9,796
Impairment losses	1,238	1,302	1,238	1,302
Real Estate Investment Properties, Net [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value on a non-recurring basis
Assets	$ 27,690	$ 9,796	$ 27,690	$ 9,796

Properties, net (Details)

Properties, net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2015	Dec. 31, 2014
Investments in real estate
Operating properties, net		$ 2,896,809	$ 2,751,488
Greater Philadelphia
Investments in real estate
Depreciation expense on reclassified assets	$ 12,900
Operating properties, net
Investments in real estate
Less: accumulated depreciation		(723,470)	(703,083)
Operating properties, net | Land
Investments in real estate
Gross		460,268	439,355
Operating properties, net | Buildings and improvements
Investments in real estate
Gross		$ 3,160,011	$ 3,015,216

Properties, net (Details 2)

Properties, net (Details 2) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Properties
Projects in development or held for future development	$ 521,991	$ 545,426
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	221,655	214,977
Projects in development or held for future development | Construction in progress, excluding land
Properties
Projects in development or held for future development	$ 300,336	$ 330,449

Properties, net (Details 3)

Properties, net (Details 3) $ in Thousands	Jun. 30, 2015USD ($)Property	Dec. 31, 2014USD ($)Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, net	$ 77,013	$ 14,339
Greater Baltimore | Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties held-for-sale | Property		2
Assets held for sale, net		$ 14,300
2015 Assets Held For Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties, net	73,174
Deferred rent receivable	1,683
Intangible assets on real estate acquisitions, net	1,017
Deferred leasing costs, net	977
Lease incentives, net	162
Assets held for sale, net	$ 77,013
2015 Assets Held For Sale | Greater Baltimore
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties held-for-sale | Property	6
2015 Assets Held For Sale | Northern Virginia
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties held-for-sale | Property	1

Properties, net (Details 4)

Properties, net (Details 4) ft² in Thousands, $ in Thousands	Apr. 15, 2015USD ($)ft²	Mar. 19, 2015USD ($)ft²	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)
Business Acquisition [Line Items]
Weighted average useful life					9 years
Revenues			$ 170,363	$ 139,820	$ 331,397	$ 286,487
Income from continuing operations			15,402	$ 8,077	$ 28,983	$ 12,805
Tenant relationship value
Business Acquisition [Line Items]
Weighted average useful life					9 years
2015 Acquisitions
Business Acquisition [Line Items]
Land			28,361		$ 28,361
Building and improvements			69,182		69,182
Intangible assets on real estate acquisitions			45,940		45,940
Total assets			143,483		143,483
Below-market leases			(1,093)		(1,093)
Total acquisition cost			142,390		142,390
Finite-lived intangible assets acquired					$ 45,940
Weighted average useful life					7 years
Revenues			4,000		$ 4,300
Income from continuing operations			$ 40		210
Operating property acquisition costs					1,400
2015 Acquisitions | Tenant relationship value
Business Acquisition [Line Items]
Finite-lived intangible assets acquired					$ 20,024
Weighted average useful life					10 years
2015 Acquisitions | In-place lease value
Business Acquisition [Line Items]
Finite-lived intangible assets acquired					$ 20,041
Weighted average useful life					5 years
2015 Acquisitions | Above market leases
Business Acquisition [Line Items]
Finite-lived intangible assets acquired					$ 5,875
Weighted average useful life					4 years
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		$ 61,900
2600 Park Tower Drive | Vienna, 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

Properties, net Properties, net

Properties, net Properties, net (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Real Estate [Abstract]
Pro forma total revenues	$ 170,719	$ 144,098	$ 335,159	$ 294,769
Pro forma net income attributable to COPT common shareholders	$ 12,620	$ 2,126	$ 22,850	$ 835
Pro Forma EPS, Basic (in dollars per share)	$ 0.13	$ 0.02	$ 0.24	$ 0.01
Pro Forma EPS, Diluted (in dollars per share)	$ 0.13	$ 0.02	$ 0.24	$ 0.01

Properties, net (Details 6)

Properties, net (Details 6) - Jun. 30, 2015 ft² in Thousands, $ in Millions	USD ($)ft²Property
Newly constructed properties placed in service
Construction and Redevelopment Activities
Square feet of properties placed in service | ft²	509
Number of real estate properties placed in service	4
Properties redeveloped | Greater Philadelphia
Construction and Redevelopment Activities
Square feet of properties placed in service | ft²	111
Properties under construction or contractually committed for construction
Construction and Redevelopment Activities
Number of real estate properties	6
Square footage of real estate properties (in square feet) | ft²	1,000
Properties under construction or contractually committed for construction | Northern Virginia
Construction and Redevelopment Activities
Number of real estate properties	4
Properties under construction or contractually committed for construction | Baltimore and Washington Corridor
Construction and Redevelopment Activities
Number of real estate properties	2
Properties under or approved for redevelopment
Construction and Redevelopment Activities
Number of real estate properties	6
Square footage of real estate properties (in square feet) | ft²	309
Properties under or approved for redevelopment | Baltimore and Washington Corridor
Construction and Redevelopment Activities
Number of real estate properties	4
Properties under or approved for redevelopment | Greater Philadelphia
Construction and Redevelopment Activities
Number of real estate properties	1
Properties under or approved for redevelopment | St Marys County
Construction and Redevelopment Activities
Number of real estate properties	1
Non-operating properties
Construction and Redevelopment Activities
Sale price of land | $	$ 18.1
Gain on sale | $	$ 4
Partially operational properties | Properties under or approved for redevelopment
Construction and Redevelopment Activities
Number of real estate properties	1

Real Estate Joint Ventures (Det

Real Estate Joint Ventures (Details) - Jun. 30, 2015 $ in Thousands	USD ($)buillding
Consolidated real estate joint ventures
Investments in consolidated real estate joint ventures
Total Assets	$ 201,626
Encumbered Assets	113,564
Total Liabilities	$ 78,527
LW Redstone Company, LLC
Investments in consolidated real estate joint ventures
Buildings Operated by Joint Ventures Number | buillding	5
LW Redstone Company, LLC | Variable Interest Entity, Primary Beneficiary [Member]
Investments in consolidated real estate joint ventures
Ownership (as a percent)	85.00%
Total Assets	$ 142,787
Encumbered Assets	65,200
Total Liabilities	$ 40,278
M Square Associates, LLC
Investments in consolidated real estate joint ventures
Buildings Operated by Joint Ventures Number | buillding	2
M Square Associates, LLC | Variable Interest Entity, Primary Beneficiary [Member]
Investments in consolidated real estate joint ventures
Ownership (as a percent)	50.00%
Total Assets	$ 58,839
Encumbered Assets	48,364
Total Liabilities	$ 38,249

Intangible Assets on Real Est53

Intangible Assets on Real Estate Acquisition, Net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Intangible assets on real estate acquisitions
Gross Carrying Amount	$ 221,039		$ 188,467
Accumulated Amortization	139,311		144,613
Net Carrying Amount	81,728		43,854
Amortization of intangible assets	$ 7,000	$ 7,400
Weighted average useful life	9 years
Estimated future amortization expense associated with the intangible asset categories for the next five years
Remainder of fiscal year	$ 8,600
2,016	16,600
2,017	14,300
2,018	9,500
2,019	6,700
2,020	5,100
In-place lease value
Intangible assets on real estate acquisitions
Gross Carrying Amount	134,387		123,759
Accumulated Amortization	95,910		101,040
Net Carrying Amount	$ 38,477		22,719
Weighted average useful life	5 years
Tenant relationship value
Intangible assets on real estate acquisitions
Gross Carrying Amount	$ 58,560		42,301
Accumulated Amortization	27,666		28,492
Net Carrying Amount	$ 30,894		13,809
Weighted average useful life	9 years
Below-market cost arrangements
Intangible assets on real estate acquisitions
Gross Carrying Amount	$ 12,415		12,415
Accumulated Amortization	6,324		5,984
Net Carrying Amount	$ 6,091		6,431
Weighted average useful life	32 years
Above-market leases
Intangible assets on real estate acquisitions
Gross Carrying Amount	$ 14,344		8,659
Accumulated Amortization	8,467		8,159
Net Carrying Amount	$ 5,877		500
Weighted average useful life	4 years
Market concentration premium
Intangible assets on real estate acquisitions
Gross Carrying Amount	$ 1,333		1,333
Accumulated Amortization	944		938
Net Carrying Amount	$ 389		$ 395
Weighted average useful life	27 years

Investing Receivables (Details)

Investing Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 45,766	$ 52,147
Notes Receivable from City of Huntsville
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investing receivables	$ 42,766	49,147
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	$ 3,000	$ 3,000

Prepaid Expenses and Other As55

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Prepaid Expense and Other Assets [Abstract]
Lease incentives, net	$ 12,964	$ 13,344
Construction contract costs incurred in excess of billings	12,051	6,656
Prepaid expenses	8,882	20,570
Furniture, fixtures and equipment, net	6,340	6,637
Deferred tax asset, net	4,064	4,002
Operating notes receivable	3,937	3,797
Deposit on acquisitions	2,016	516
Equity method investments	1,616	2,368
Other assets	3,267	2,359
Prepaid expenses and other assets, net	55,137	60,249
Long-term Operating Notes Receivable
Mortgage and Other Investing Receivables [Line Items]
Operating notes receivable	3,900	3,600
Allowances for estimated losses	312	252
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)	Jun. 29, 2015USD ($)	May. 06, 2015USD ($)extensions	Apr. 20, 2015	Jun. 30, 2015USD ($)Property	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)Property	Jun. 30, 2014USD ($)	May. 05, 2015USD ($)	Dec. 31, 2014USD ($)
Debt
Carrying Value				$ 2,130,170,000		$ 2,130,170,000			$ 1,920,057,000
Interest costs capitalized				2,000,000	$ 1,400,000	4,100,000	$ 3,000,000
Wholly owned subsidiary
Debt
Debt default amount				150,000,000		150,000,000
Line of Credit | Revolving Credit Facility
Debt
Number of extensions | extensions		2
Term of extension option		6 months
Line of Credit | Revolving Credit Facility | Minimum
Debt
Commitment fee (as a percent)		0.125%
Line of Credit | Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		0.875%
Line of Credit | Revolving Credit Facility | Maximum
Debt
Commitment fee (as a percent)		0.30%
Line of Credit | Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		1.60%
Line of Credit | Term Loan Facilities
Debt
Maximum availability		$ 300,000,000						$ 250,000,000
Increase to maximum borrowing capacity		200,000,000
Aggregate maximum borrowing capacity		500,000,000
Proceeds from issuance of debt		$ 50,000,000
Line of Credit | Term Loan Facilities | Minimum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		0.90%
Line of Credit | Term Loan Facilities | Maximum | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)		1.85%
Mortgage and Other Secured Loans:
Debt
Carrying Value				420,684,000		420,684,000			424,016,000
Fixed rate mortgage loans
Debt
Carrying Value				384,227,000		$ 384,227,000			387,139,000
Stated interest rates, low end of range (as a percent)						3.96%
Stated interest rates, high end of range (as a percent)						10.65%
Unamortized premium included in carrying value				$ 30,000		$ 30,000			42,000
Weighted average interest rate (as a percent)				8.11%		8.11%
Weighted-average interest rate excluding incremental rate on default rate				6.16%		6.16%
Fixed rate mortgage loans | Maximum
Debt
Interest rate excluding incremental rate on default rate (percent)				7.87%		7.87%
Variable rate secured loans
Debt
Carrying Value				$ 36,457,000		$ 36,457,000			36,877,000
Description of variable rate basis						LIBOR
Stated interest rate (as a percent)				2.43%		2.43%
Variable rate secured loans | London Interbank Offered Rate (LIBOR)
Debt
Variable rate, spread (as a percent)						2.25%
Variable rate secured loans | Revolving Credit Facility
Debt
Weighted average interest rate (as a percent)				1.37%		1.37%
Revolving Credit Facility
Debt
Carrying Value				$ 0		$ 0			83,000,000
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%
Revolving Credit Facility | Revolving Credit Facility
Debt
Maximum availability				800,000,000		$ 800,000,000
Term Loan Facilities
Debt
Carrying Value				$ 520,000,000		$ 520,000,000			520,000,000
Description of variable rate basis						LIBOR
Weighted average interest rate (as a percent)				1.77%		1.77%
Additional borrowing capacity available provided there is no default under the agreement				$ 380,000,000		$ 380,000,000
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%
3.60% Senior Notes | Unsecured senior notes
Debt
Carrying Value				$ 347,625,000		$ 347,625,000			347,496,000
Stated interest rate (as a percent)				3.60%		3.60%
Debt instrument, face amount				$ 350,000,000		$ 350,000,000
Unamortized discount included in carrying value				$ 2,400,000		$ 2,400,000			2,500,000
Interest rate on debt (as a percent)				3.70%		3.70%
5.250% Senior Notes | Unsecured senior notes
Debt
Carrying Value				$ 245,980,000		$ 245,980,000			245,797,000
Stated interest rate (as a percent)				5.25%		5.25%
Debt instrument, face amount				$ 250,000,000		$ 250,000,000
Unamortized discount included in carrying value				$ 4,000,000		$ 4,000,000			4,200,000
Interest rate on debt (as a percent)				5.49%		5.49%
3.70% Senior Notes | Unsecured senior notes
Debt
Carrying Value				$ 297,743,000		$ 297,743,000			297,569,000
Stated interest rate (as a percent)				3.70%		3.70%
Debt instrument, face amount				$ 300,000,000		$ 300,000,000
Unamortized discount included in carrying value				$ 2,300,000		$ 2,300,000			2,400,000
Interest rate on debt (as a percent)				3.85%		3.85%
5.000% Senior Notes | Unsecured senior notes
Debt
Carrying Value				$ 296,580,000		$ 296,580,000			0
Stated interest rate (as a percent)	5.00%			5.00%		5.00%
Debt instrument, face amount	$ 300,000,000
Unamortized discount included in carrying value				$ 3,400,000		$ 3,400,000
Interest rate on debt (as a percent)				5.15%		5.15%
Debt issuance as a percentage of principal amount	99.51%
Proceeds from debt, net	$ 296,600,000
Redemption price ( as a percent)	100.00%
5.000% Senior Notes | Unsecured senior notes | Adjusted Treasury
Debt
Basis points used in determining redemption price prior to maturity	0.45%
Unsecured notes payable
Debt
Carrying Value				$ 1,558,000		$ 1,558,000			1,607,000
Stated interest rate (as a percent)				0.00%		0.00%
Unamortized discount included in carrying value				$ 603,000		$ 603,000			654,000
4.25% Exchangeable Senior Notes
Debt
Carrying Value				$ 0		$ 0			$ 572,000
Stated interest rate (as a percent)				4.25%		4.25%
Percentage of principal amount redeemed			100.00%
Debt in default of payment terms | Wholly owned subsidiary
Debt
Stated interest rate (as a percent)				10.65%		10.65%
Debt in default of payment terms | Wholly owned subsidiary | Northern Virginia
Debt
Number of real estate properties | Property				2		2

Debt, Net (Details 2)

Debt, Net (Details 2) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Carrying amount and estimated fair value of debt
Carrying Value	$ 2,130,170	$ 1,920,057
4.25% Exchangeable Senior Notes
Carrying amount and estimated fair value of debt
Carrying Value	0	572
Carrying Amount
Carrying amount and estimated fair value of debt
Variable-rate debt	556,457	639,877
Carrying Value	2,130,170	1,920,057
Carrying Amount | Unsecured senior notes
Carrying amount and estimated fair value of debt
Fixed-rate debt	1,187,928	890,862
Carrying Amount | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Fixed-rate debt	385,785	389,318
Total Estimated Fair Value
Carrying amount and estimated fair value of debt
Variable-rate debt	557,753	642,091
Carrying Value	2,105,775	1,900,067
Total Estimated Fair Value | Unsecured senior notes
Carrying amount and estimated fair value of debt
Fixed-rate debt	1,202,956	901,599
Total Estimated Fair Value | Other fixed-rate debt
Carrying amount and estimated fair value of debt
Fixed-rate debt	$ 345,066	$ 356,377

Interest Rate Derivatives (Deta

Interest Rate Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
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)	$ 392	$ (3,630)	$ (3,082)	$ (5,753)
Interest Expense [Member]
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income
Amount of losses reclassified from AOCL into interest expense (effective portion)	769	$ 719	1,542	$ 1,414
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	3,300		3,300
Interest rate derivatives in liability position, fair value	3,100		3,100
Termination value to settle obligations under interest rate derivative agreements	3,400		3,400
Interest rate swaps | Prepaid expenses and other current assets
Fair value of interest rate derivatives and balance sheet classification
Interest rate derivatives	0		0		$ 274
Interest rate swaps | Interest rate derivatives
Fair value of interest rate derivatives and balance sheet classification
Fair value of Interest rate swaps classified as interest rate derivatives	(3,121)		(3,121)		(1,855)
Designated
Fair values of interest rate swap derivatives
Fair value of interest rate swaps	(3,121)		(3,121)		(1,581)
Designated | Interest rate swap, effective date January 3, 2012, swap three
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	0.832%		0.832%
Fair value of interest rate swaps	$ (110)		$ (110)		(407)
Designated | Interest rate swap, effective date January 3, 2012, swap four
Fair values of interest rate swap derivatives
Notional Amount	$ 100,000		$ 100,000
Fixed rate (as a percent)	0.832%		0.832%
Fair value of interest rate swaps	$ (110)		$ (110)		(407)
Designated | Interest rate swap, effective date November 2, 2010
Fair values of interest rate swap derivatives
Notional Amount	$ 36,457		$ 36,457
Fixed rate (as a percent)	3.83%		3.83%
Fair value of interest rate swaps	$ (171)		$ (171)		(400)
Notional amount of interest rate derivatives after scheduled amortization	$ 36,200		$ 36,200
Designated | Interest rate swap, effective date November 2, 2010 | London Interbank Offered Rate (LIBOR)
Fair values of interest rate swap derivatives
Derivative, basis spread on variable rate	2.25%		2.25%
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	$ (405)		$ (405)		(317)
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	$ (410)		$ (410)		(324)
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	$ (849)		$ (849)		239
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	$ (1,066)		$ (1,066)		$ 35

Redeemable Noncontrolling Int59

Redeemable Noncontrolling Interests (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Redeemable Noncontrolling Interest [Roll Forward]
Beginning balance	$ 18,417	$ 17,758
Distribution to noncontrolling interest	(885)	(590)
Net income attributable to noncontrolling interest	1,143	1,016
Adjustment to arrive at fair value of interest	739	717
Ending balance	$ 19,414	$ 18,901

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Class of Stock [Line Items]
Number of operating partnerships units converted into common shares (in units)	158,000	78,498
Common Shares
Class of Stock [Line Items]
Shares issued to the public (in units/ shares)	890,241
Weighted average price per share of stock issued	$ 30.29
Net proceeds of stock issuance	$ 26.6
Commission costs	0.4
Remaining capacity under ATM Plan	$ 84
Corporate Office Properties, L.P. | Common Shares
Class of Stock [Line Items]
Shares issued to the public (in units/ shares)	890,241	0

Information by Business Segme61

Information by Business Segment (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015USD ($)segment	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)segment	Jun. 30, 2014USD ($)	Dec. 31, 2014USD ($)
Segment Reporting [Abstract]
Number of primary office property segments | segment	10		10
Segment financial information for real estate operations
Revenues from real estate operations	$ 128,195	$ 115,964	$ 250,905	$ 240,860
Property operating expenses	46,407	43,856	97,093	93,608
NOI from real estate operations	81,788	72,108	153,812	147,252
Segment assets	3,910,921	3,709,500	3,910,921	3,709,500	$ 3,670,257
Operating Segment Total
Segment financial information for real estate operations
Revenues from real estate operations	128,195	115,964	250,905	240,860
Property operating expenses	46,407	43,856	97,093	93,608
NOI from real estate operations	81,788	72,108	153,812	147,252
Additions to long-lived assets	94,715	14,096	166,686	27,825
Transfers from non-operating properties	44,624	35,385	161,896	92,325
Segment assets	3,218,657	2,951,299	3,218,657	2,951,299
Baltimore and Washington Corridor
Segment financial information for real estate operations
Revenues from real estate operations	60,611	57,456	122,403	118,569
Property operating expenses	19,539	19,348	43,122	42,945
NOI from real estate operations	41,072	38,108	79,281	75,624
Additions to long-lived assets	5,141	6,289	8,586	12,030
Transfers from non-operating properties	6,098	20,712	19,028	27,623
Segment assets	1,279,531	1,259,974	1,279,531	1,259,974
Northern Virginia
Segment financial information for real estate operations
Revenues from real estate operations	24,393	20,898	46,142	45,866
Property operating expenses	8,687	7,651	17,808	16,624
NOI from real estate operations	15,706	13,247	28,334	29,242
Additions to long-lived assets	84,582	4,805	87,403	8,300
Transfers from non-operating properties	8,646	683	67,217	27,271
Segment assets	780,250	634,834	780,250	634,834
San Antonio
Segment financial information for real estate operations
Revenues from real estate operations	10,204	8,758	19,375	17,237
Property operating expenses	5,615	4,817	10,590	9,291
NOI from real estate operations	4,589	3,941	8,785	7,946
Additions to long-lived assets	0	0	21	(6)
Transfers from non-operating properties	468	0	31,559	0
Segment assets	147,844	117,328	147,844	117,328
Huntsville
Segment financial information for real estate operations
Revenues from real estate operations	2,658	2,404	5,104	4,959
Property operating expenses	888	859	1,717	1,512
NOI from real estate operations	1,770	1,545	3,387	3,447
Additions to long-lived assets	208	334	291	2,841
Transfers from non-operating properties	8,980	223	11,977	20,325
Segment assets	107,677	97,838	107,677	97,838
Washington, DC - Capitol Riverfront
Segment financial information for real estate operations
Revenues from real estate operations	3,391	3,831	6,755	7,465
Property operating expenses	2,061	1,754	3,875	3,519
NOI from real estate operations	1,330	2,077	2,880	3,946
Additions to long-lived assets	806	478	1,199	541
Transfers from non-operating properties	0	0	0	0
Segment assets	94,099	97,136	94,099	97,136
St. Mary's and King George Counties
Segment financial information for real estate operations
Revenues from real estate operations	3,795	4,202	7,696	8,518
Property operating expenses	1,329	1,289	2,913	2,793
NOI from real estate operations	2,466	2,913	4,783	5,725
Additions to long-lived assets	963	943	2,163	1,782
Transfers from non-operating properties	0	0	0	0
Segment assets	100,665	95,553	100,665	95,553
Greater Baltimore
Segment financial information for real estate operations
Revenues from real estate operations	12,889	11,024	24,374	22,520
Property operating expenses	4,909	4,500	9,906	9,976
NOI from real estate operations	7,980	6,524	14,468	12,544
Additions to long-lived assets	2,476	1,242	66,080	2,254
Transfers from non-operating properties	12	2,953	12	3,027
Segment assets	332,973	300,139	332,973	300,139
Greater Philadelphia
Segment financial information for real estate operations
Revenues from real estate operations	3,886	2,366	7,110	5,706
Property operating expenses	941	1,144	2,316	2,444
NOI from real estate operations	2,945	1,222	4,794	3,262
Additions to long-lived assets	284	88	578	99
Transfers from non-operating properties	5,218	10,198	16,716	13,374
Segment assets	123,112	104,436	123,112	104,436
Other
Segment financial information for real estate operations
Revenues from real estate operations	2,548	2,533	5,091	5,127
Property operating expenses	217	613	413	935
NOI from real estate operations	2,331	1,920	4,678	4,192
Additions to long-lived assets	177	(93)	257	(38)
Transfers from non-operating properties	0	19	8	30
Segment assets	76,943	78,918	76,943	78,918
Wholesale Data Center
Segment financial information for real estate operations
Revenues from real estate operations	3,820	2,492	6,855	4,893
Property operating expenses	2,221	1,881	4,433	3,569
NOI from real estate operations	1,599	611	2,422	1,324
Additions to long-lived assets	78	10	108	22
Transfers from non-operating properties	15,202	597	15,379	675
Segment assets	$ 175,563	$ 165,143	$ 175,563	$ 165,143

Information by Business Segme62

Information by Business Segment (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reconciliation of segment revenues to total revenues
Segment revenues from real estate operations	$ 128,195	$ 115,964	$ 250,905	$ 240,860
Construction contract and other service revenues	42,172	23,861	80,496	45,651
Less: Revenues from discontinued operations	(4)	(5)	(4)	(24)
Total revenues	170,363	139,820	331,397	286,487
Reconciliation of segment property operating expenses to property operating expenses
Segment property operating expenses	46,407	43,856	97,093	93,608
Less: Property operating expenses from discontinued operations	11	(84)	6	(64)
Total property operating expenses	46,418	43,772	97,099	93,544
Computation of net operating income from service operations
Construction contract and other service revenues	42,172	23,861	80,496	45,651
Construction contract and other service expenses	(41,293)	(23,136)	(78,791)	(41,760)
NOI from service operations	879	725	1,705	3,891
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations
NOI from real estate operations	81,788	72,108	153,812	147,252
NOI from service operations	879	725	1,705	3,891
Interest and other income	1,242	1,299	2,525	2,584
Equity in income (loss) of unconsolidated entities	9	(47)	34	13
Income tax expense	(50)	(92)	(105)	(156)
Other adjustments:
Depreciation and other amortization associated with real estate operations	(33,786)	(30,895)	(65,385)	(74,491)
Impairment losses	(1,238)	(1,302)	(1,238)	(1,302)
General, administrative and leasing expenses	(7,534)	(7,528)	(15,425)	(15,671)
Business development expenses and land carry costs	(2,623)	(1,351)	(5,413)	(2,677)
Interest expense	(21,768)	(23,478)	(42,606)	(44,305)
Less: NOI from discontinued operations	(15)	79	(10)	40
Loss on early extinguishment of debt	(65)	(270)	(68)	(270)
Income from continuing operations	$ 16,839	$ 9,248	$ 27,826	$ 14,908

Information by Business Segme63

Information by Business Segment (Details 3) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Reconciliation of segment assets to total assets
Assets	$ 3,910,921	$ 3,670,257	$ 3,709,500
Segment assets
Reconciliation of segment assets to total assets
Assets	3,218,657		2,951,299
Non-operating property assets
Reconciliation of segment assets to total assets
Assets	527,742		535,462
Other assets
Reconciliation of segment assets to total assets
Assets	$ 164,522		$ 222,739

Share-Based Compensation (Detai

Share-Based Compensation (Details) $ / shares in Units, $ in Thousands	Mar. 05, 2015USD ($)shares	Jun. 30, 2015USD ($)Percentile_Rank$ / sharesshares	Jun. 30, 2014shares
Options
Exercised (in shares)		76,474	51,289
Performance share units
Assumptions used to value stock awards
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 36.76
Baseline value per common share (in dollars per share) | $ / shares		$ 29.28
Expected volatility of common shares (as a percent)		19.90%
Risk-free interest rate (as a percent)		0.99%
Restricted shares
Share-Based Compensation
Stock awards granted (in shares or units)		184,074
Aggregate grant date fair value | $		$ 5,400
Assumptions used to value stock awards
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 29.35
Other Share-based Compensation Additional Disclosures
Shares vested (in shares)		149,787
Weighted average fair value of shares vested (in dollars per share) | $ / shares		$ 25.96
Aggregate intrinsic value of awards upon vesting | $		$ 4,300
Deferred shares
Share-Based Compensation
Stock awards granted (in shares or units)		24,056
Aggregate grant date fair value | $		$ 642
Assumptions used to value stock awards
Weighted average grant date fair value (in dollars per share) | $ / shares		$ 26.70
Other Share-based Compensation Additional Disclosures
Shares vested (in shares)		15,485
Weighted average fair value of shares vested (in dollars per share) | $ / shares		$ 26.77
Aggregate intrinsic value of awards upon vesting | $		$ 413
Options
Options
Exercised (in shares)		76,474
Weighted average exercise price (in dollars per share) | $ / shares		$ 26.27
Aggregate intrinsic value of options exercised (in dollars) | $		$ 300
2014 PSU Grants | Performance share units
Share-Based Compensation
Stock awards granted (in shares or units)	45,656
Aggregate grant date fair value | $	$ 1,700
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
2012 PSU Grants | Performance share units
Assumptions used to value stock awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Shares issued for Awards Vested in Period	40,309
2013 PSU Grants | Performance share units | Former Chief Financial Officer
Assumptions used to value stock awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Shares issued for Awards Vested in Period	15,289

Income Taxes (Details)

Income Taxes (Details) - Taxable REIT Subsidiary - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Deferred income tax (expense) benefit
Federal	$ 41	$ 79	$ 86	$ 132
State	9	13	19	24
Total income tax expense	$ 50	$ 92	$ 105	$ 156
Effective tax rate (as a percent)			37.70%	37.40%

Earnings Per Share ("EPS") an66

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Income from continuing operations		$ 16,839	$ 9,248	$ 27,826	$ 14,908
Gain on sales of real estate, net		(1)	0	3,985	0
Preferred share/unit dividends/distributions		(3,553)	(4,344)	(7,105)	(8,834)
Issuance costs associated with redeemed preferred shares/unit		0	(1,769)	0	(1,769)
Income from continuing operations attributable to noncontrolling interests		(1,436)	(1,171)	(2,828)	(2,103)
Income from continuing operations attributable to share-based compensation awards		(113)	(108)	(235)	(229)
Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders		11,736	1,856	21,643	1,973
Discontinued operations		394	(198)	156	(187)
Discontinued operations attributable to noncontrolling interests		(15)	11	(3)	13
Numerator for basic and diluted EPS on net income attributable to COPT common shareholders		$ 12,115	$ 1,669	$ 21,796	$ 1,799
Denominator (all weighted averages):
Denominator for basic EPS (common shares)		94,128	87,214	93,666	87,148
Dilutive effect of share-based compensation awards		35	201	114	156
Denominator for diluted EPS (common shares)		94,163	87,415	93,780	87,304
Basic EPS:
Income from continuing operations (in dollars per share/unit)	[1]	$ 0.13	$ 0.02	$ 0.23	$ 0.02
Discontinued operations (in dollars per share/unit)	[1]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[1]	0.13	0.02	0.23	0.02
Diluted EPS:
Income from continuing operations (in dollars per share/unit)	[1]	0.13	0.02	0.23	0.02
Discontinued operations (in dollars per share/unit)	[1]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[1]	$ 0.13	$ 0.02	$ 0.23	$ 0.02
Corporate Office Properties, L.P.
Numerator:
Income from continuing operations		$ 16,839	$ 9,248	$ 27,826	$ 14,908
Gain on sales of real estate, net		(1)	0	3,985	0
Preferred share/unit dividends/distributions		(3,718)	(4,509)	(7,435)	(9,164)
Issuance costs associated with redeemed preferred shares/unit		0	(1,769)	0	(1,769)
Income from continuing operations attributable to noncontrolling interests		(812)	(840)	(1,633)	(1,579)
Income from continuing operations attributable to share-based compensation awards		(113)	(108)	(235)	(229)
Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders		12,195	2,022	22,508	2,167
Discontinued operations		394	(198)	156	(187)
Discontinued operations attributable to noncontrolling interests		0	3	3	5
Numerator for basic and diluted EPS on net income attributable to COPT common shareholders		$ 12,589	$ 1,827	$ 22,667	$ 1,985
Denominator (all weighted averages):
Denominator for basic EPS (common shares)		97,808	91,126	97,372	91,082
Dilutive effect of share-based compensation awards		35	201	114	156
Denominator for diluted EPS (common shares)		97,843	91,327	97,486	91,238
Basic EPS:
Income from continuing operations (in dollars per share/unit)	[2]	$ 0.13	$ 0.02	$ 0.23	$ 0.02
Discontinued operations (in dollars per share/unit)	[2]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[2]	0.13	0.02	0.23	0.02
Diluted EPS:
Income from continuing operations (in dollars per share/unit)	[2]	0.13	0.02	0.23	0.02
Discontinued operations (in dollars per share/unit)	[2]	0	0	0	0
Net income attributable to COPT common shareholders (in dollars per share/unit)	[2]	$ 0.13	$ 0.02	$ 0.23	$ 0.02
[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") an67

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details 2) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Conversion of common units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	3,680	3,912	3,706	3,934
Conversion of Series I Preferred Units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	176	176	176	176
Conversion of Series K Preferred Shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	434	434	434	434
Weighted average restricted stock and deferred shares
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	426	420	413	405
Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	473	496	472	512
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)	426	420	413	405
Corporate Office Properties, L.P. | Weighted average options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	473	496	472	512
Corporate Office Properties, L.P. | Conversion of Series I preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	176	176	176	176
Corporate Office Properties, L.P. | Conversion of Series K preferred units
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	434	434	434	434

Commitments and Contingencies (

Commitments and Contingencies (Details)	Jun. 30, 2015USD ($)Property	Aug. 31, 2010USD ($)
Tax incremental financing obligation
Liability recognized with regard to tax incremental financing obligation at end of current period	$ 2,400,000
Environmental Indemnity Agreement
Number of lease properties which were provided environmental indemnifications | Property	3
Environmental indemnification to the tenant against losses covered under prior owner's indemnity agreement	$ 5,000,000
Maximum environmental indemnification to the tenant against consequential damages after acquisition of property	$ 12,500,000
Additional costs agreed to be paid by the entity related to construction and environmental regulatory activities (as a percent)	50.00%
Maximum annual additional costs agreed to be paid by the entity related to construction and environmental regulatory activities	$ 300,000
Maximum additional costs agreed to be paid by the entity related to construction and environmental regulatory activities	$ 1,500,000
Anne Arundel County, Maryland [Member] | Tax Incremental Financing Bond [Member]
Tax incremental financing obligation
Debt instrument, face amount		$ 30,000,000

Subsequent Event (Details)

Subsequent Event (Details) - Jul. 27, 2015 - 1550 Westbranch Drive - Subsequent Event - Northern Virginia ft² in Thousands, $ in Millions	USD ($)ft²
Subsequent Event [Line Items]
Square footage of real estate properties (in square feet)	160
Transaction value of operating property disposition | $	$ 27.8