Corporate Office Properties Trust 10-K3 Mar 142013 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Feb. 19, 2014	Jun. 28, 2013
Entity Information [Line Items]	'	'	'
Entity Registrant Name	'CORPORATE OFFICE PROPERTIES TRUST	'	'
Entity Central Index Key	'0000860546	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Entity Public Float	'	'	$1,700
Entity Common Stock, Shares Outstanding	'	87,429,122	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Corporate Office Properties, L.P.	'	'	'
Entity Information [Line Items]	'	'	'
Entity Registrant Name	'CORPORATE OFFICE PROPERTIES, L.P.	'	'
Entity Central Index Key	'0001577966	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Non-accelerated Filer	'	'
Entity Public Float	'	'	$16.30
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Properties, net:	'	'
Operating properties, net	$2,702,693	$2,597,666
Projects in development or held for future development	511,608	565,378
Total properties, net	3,214,301	3,163,044
Assets held for sale, net	0	140,229
Cash and cash equivalents	54,373	10,594
Restricted cash and marketable securities	11,448	21,557
Accounts receivable (net of allowance for doubtful accounts of $2,976 and $4,694, respectively)	27,000	16,845
Deferred rent receivable (net of allowance of $2,126 and $913, respectively)	89,456	85,802
Intangible assets on real estate acquisitions, net	59,258	75,879
Deferred leasing and financing costs, net	66,267	59,952
Mortgage and other investing receivables	53,663	35,798
Prepaid expenses and other assets	54,186	44,059
Total assets	3,629,952	3,653,759
Liabilities:	'	'
Debt, net	1,927,703	2,019,168
Accounts payable and accrued expenses	98,785	97,922
Rents received in advance and security deposits	31,492	27,632
Dividends and distributions payable	29,080	28,698
Deferred revenue associated with operating leases	10,369	11,995
Distributions received in excess of investment in unconsolidated real estate joint venture	0	6,420
Interest rate derivatives	3,309	6,185
Other liabilities	14,207	8,942
Total liabilities	2,114,945	2,206,962
Commitments and contingencies (Note 23)	'	'
Redeemable noncontrolling interest	17,758	10,298
Corporate Office Properties Trustâ€™s shareholdersâ€™ equity:	'	'
Preferred Shares of beneficial interest at liquidation preference	249,083	333,833
Common Shares of beneficial interest	874	809
Additional paid-in capital	1,814,015	1,653,672
Cumulative distributions in excess of net income	-641,868	-617,455
Accumulated other comprehensive income (loss)	3,480	-5,435
Total Corporate Office Properties Trustâ€™s shareholdersâ€™ equity	1,425,584	1,365,424
Noncontrolling interests in subsidiaries:	'	'
Common units in COPLP	53,468	52,122
Preferred units in COPLP	8,800	8,800
Other consolidated entities	9,397	10,153
Noncontrolling interests in subsidiaries	71,665	71,075
Total equity	1,497,249	1,436,499
Total liabilities and equity	3,629,952	3,653,759
Corporate Office Properties, L.P.	'	'
Properties, net:	'	'
Operating properties, net	2,702,693	2,597,666
Projects in development or held for future development	511,608	565,378
Total properties, net	3,214,301	3,163,044
Assets held for sale, net	0	140,229
Cash and cash equivalents	54,373	10,594
Restricted cash and marketable securities	3,981	14,781
Accounts receivable (net of allowance for doubtful accounts of $2,976 and $4,694, respectively)	27,000	16,845
Deferred rent receivable (net of allowance of $2,126 and $913, respectively)	89,456	85,802
Intangible assets on real estate acquisitions, net	59,258	75,879
Deferred leasing and financing costs, net	66,267	59,952
Mortgage and other investing receivables	53,663	35,798
Prepaid expenses and other assets	54,186	44,059
Total assets	3,622,485	3,646,983
Liabilities:	'	'
Debt, net	1,927,703	2,019,168
Accounts payable and accrued expenses	98,785	97,922
Rents received in advance and security deposits	31,492	27,632
Dividends and distributions payable	29,080	28,698
Deferred revenue associated with operating leases	10,369	11,995
Distributions received in excess of investment in unconsolidated real estate joint venture	0	6,420
Interest rate derivatives	3,309	6,185
Other liabilities	6,740	2,166
Total liabilities	2,107,478	2,200,186
Commitments and contingencies (Note 23)	'	'
Redeemable noncontrolling interest	17,758	10,298
Corporate Office Properties Trustâ€™s shareholdersâ€™ equity:	'	'
Preferred Shares of beneficial interest at liquidation preference	249,083	'
Common Shares of beneficial interest	1,226,318	1,089,391
Accumulated other comprehensive income (loss)	3,605	-5,708
Total Corporate Office Properties Trustâ€™s shareholdersâ€™ equity	1,487,806	1,426,316
Noncontrolling interests in subsidiaries:	'	'
Noncontrolling interests in subsidiaries	9,443	10,183
Total equity	1,497,249	1,436,499
Total liabilities and equity	3,622,485	3,646,983
Corporate Office Properties, L.P. \| General Partner	'	'
Corporate Office Properties Trustâ€™s shareholdersâ€™ equity:	'	'
Preferred Units, Preferred Partners' Capital Accounts	249,083	333,833
Corporate Office Properties, L.P. \| Limited Partner	'	'
Corporate Office Properties Trustâ€™s shareholdersâ€™ equity:	'	'
Preferred Units, Preferred Partners' Capital Accounts	$8,800	$8,800

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts- AR	$2,976	$4,694
Allowance for deferred rent receivable	2,126	913
Common Shares of beneficial interest, shares outstanding	87,394,512	80,952,986
Corporate Office Properties, L.P.	'	'
Allowance for doubtful accounts- AR	2,976	4,694
Allowance for deferred rent receivable	$2,126	$913
Corporate Office Properties, L.P. \| General Partner	'	'
Preferred Units, Outstanding	9,431,667	12,821,667
Common Shares of beneficial interest, shares outstanding	87,394,512	80,952,986
Corporate Office Properties, L.P. \| Limited Partner	'	'
Preferred Units, Outstanding	352,000	352,000
Common Shares of beneficial interest, shares outstanding	3,977,700	4,067,542

Consolidated_Balance_Sheets_Pa1

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]	'	'
Allowance for doubtful accounts- AR	$2,976	$4,694
Allowance for deferred rent receivable	$2,126	$913
Common Shares of beneficial interest, par value (in dollars per share)	$0.01	$0.01
Common Shares of beneficial interest, shares authorized	125,000,000	125,000,000
Common Shares of beneficial interest, shares issued	87,394,512	80,952,986
Common Shares of beneficial interest, shares outstanding	87,394,512	80,952,986

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Revenues	'		'		'
Rental revenue	$377,611		$353,080		$332,856
Tenant recoveries and other real estate operations revenue	83,386		81,219		75,755
Construction contract and other service revenues	62,363		73,836		84,345
Total revenues	523,360		508,135		492,956
Expenses	'		'		'
Property operating expenses	167,199		159,206		154,375
Depreciation and amortization associated with real estate operations	113,214		107,998		107,003
Construction contract and other service expenses	58,875		70,576		81,639
Impairment losses	5,857		43,678		83,213
General, administrative and leasing expenses	30,869		31,900		30,306
Business development expenses and land carry costs	5,436		5,711		6,122
Total operating expenses	381,450		419,069		462,658
Operating income	141,910		89,066		30,298
Interest expense	-82,010		-86,401		-90,037
Interest and other income	3,834		7,172		5,603
Loss on early extinguishment of debt	-27,030		-943		-1,639
Loss on interest rate derivatives	0		0		-29,805
Income (loss) from continuing operations before equity in income (loss) of unconsolidated entities and income taxes	36,704		8,894		-85,580
Equity in income (loss) of unconsolidated entities	2,110		-546		-331
Income tax (expense) benefit	-1,978		-381		6,710
Income (loss) from continuing operations	36,836		7,967		-79,201
Discontinued operations	55,692		12,353		-51,107
Income (loss) before gain on sales of real estate	92,528		20,320		-130,308
Gain on sales of real estate, net of income taxes	9,016		21		2,732
Net income (loss)	101,544		20,341		-127,576
Net (income) loss attributable to noncontrolling interests:	'		'		'
Common units in COPLP	-3,283		87		8,439
Preferred units in COPLP	-660		-660		-660
Other consolidated entities	-3,894		1,209		369
Net income (loss) attributable to COPT	93,707		20,977		-119,428
Preferred share dividends	-19,971		-20,844		-16,102
Issuance costs associated with redeemed preferred shares	-2,904		-1,827		0
Net income (loss) attributable to COPT common shareholders	70,832		-1,694		-135,530
Net income (loss) attributable to COPT:	'		'		'
Income (loss) from continuing operations	41,366		9,297		-71,341
Discontinued operations, net	52,341		11,680		-48,087
Net income (loss) attributable to COPT	93,707		20,977		-119,428
Basic earnings per common share	'		'		'
Income (loss) from continuing operations (in dollars per share)	$0.21	[1]	($0.19)	[1]	($1.28)	[1]
Discontinued operations (in dollars per share)	$0.62	[1]	$0.16	[1]	($0.69)	[1]
Net income (loss) attributable to COPT common shareholders (in dollars per share)	$0.83	[1]	($0.03)	[1]	($1.97)	[1]
Diluted earnings per common share	'		'		'
Income (loss) from continuing operations (in dollars per share)	$0.21	[1]	($0.19)	[1]	($1.28)	[1]
Discontinued operations (in dollars per share)	$0.62	[1]	$0.16	[1]	($0.69)	[1]
Net income (loss) attributable to COPT common shareholders (in dollars per share)	$0.83	[1]	($0.03)	[1]	($1.97)	[1]
Corporate Office Properties, L.P.	'		'		'
Revenues	'		'		'
Rental revenue	377,611		353,080		332,856
Tenant recoveries and other real estate operations revenue	83,386		81,219		75,755
Construction contract and other service revenues	62,363		73,836		84,345
Total revenues	523,360		508,135		492,956
Expenses	'		'		'
Property operating expenses	167,199		159,206		154,375
Depreciation and amortization associated with real estate operations	113,214		107,998		107,003
Construction contract and other service expenses	58,875		70,576		81,639
Impairment losses	5,857		43,678		83,213
General, administrative and leasing expenses	30,869		31,900		30,300
Business development expenses and land carry costs	5,436		5,711		6,122
Total operating expenses	381,450		419,069		462,652
Operating income	141,910		89,066		30,304
Interest expense	-82,010		-86,401		-90,037
Interest and other income	3,834		7,172		5,603
Loss on early extinguishment of debt	-27,030		-943		-1,639
Loss on interest rate derivatives	0		0		-29,805
Income (loss) from continuing operations before equity in income (loss) of unconsolidated entities and income taxes	36,704		8,894		-85,574
Equity in income (loss) of unconsolidated entities	2,110		-546		-331
Income tax (expense) benefit	-1,978		-381		6,710
Income (loss) from continuing operations	36,836		7,967		-79,195
Discontinued operations	55,692		12,353		-51,107
Income (loss) before gain on sales of real estate	92,528		20,320		-130,302
Gain on sales of real estate, net of income taxes	9,016		21		2,732
Net income (loss)	101,544		20,341		-127,570
Net (income) loss attributable to noncontrolling interests in consolidated entities	-3,907		507		244
Net (income) loss attributable to noncontrolling interests:	'		'		'
Net income (loss) attributable to COPT	97,637		20,848		-127,326
Preferred share dividends	-20,631		-21,504		-16,762
Issuance costs associated with redeemed preferred shares	-2,904		-1,827		0
Net income (loss) attributable to COPT common shareholders	74,102		-2,483		-144,088
Net income (loss) attributable to COPT:	'		'		'
Income (loss) from continuing operations	42,875		9,194		-76,082
Discontinued operations, net	54,762		11,654		-51,244
Net income (loss) attributable to COPT	$97,637		$20,848		($127,326)
Basic earnings per common share	'		'		'
Income (loss) from continuing operations (in dollars per share)	$0.21	[1]	($0.19)	[1]	($1.29)	[1]
Discontinued operations (in dollars per share)	$0.62	[1]	$0.15	[1]	($0.71)	[1]
Net income (loss) attributable to COPT common shareholders (in dollars per share)	$0.83	[1]	($0.04)	[1]	($2)	[1]
Diluted earnings per common share	'		'		'
Income (loss) from continuing operations (in dollars per share)	$0.21	[1]	($0.19)	[1]	($1.29)	[1]
Discontinued operations (in dollars per share)	$0.62	[1]	$0.15	[1]	($0.71)	[1]
Net income (loss) attributable to COPT common shareholders (in dollars per share)	$0.83	[1]	($0.04)	[1]	($2)	[1]

[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income (loss)	$101,544	$20,341	($127,576)
Other comprehensive income (loss)	'	'	'
Unrealized gains (losses) on interest rate derivatives	6,791	-7,676	-31,531
Losses on interest rate derivatives included in interest expense	2,740	3,697	4,601
Unrealized equity in other comprehensive income of equity method investee	1,070	0	0
Realized equity in other comprehensive income of equity method investee	-1,070	0	0
Loss on interest rate derivatives upon discontinuing hedge accounting	0	0	28,430
Other comprehensive income (loss)	9,531	-3,979	1,500
Comprehensive income (loss)	111,075	16,362	-126,076
Comprehensive (income) loss attributable to noncontrolling interests	-8,453	961	8,132
Comprehensive income (loss) attributable to COPT	102,622	17,323	-117,944
Corporate Office Properties, L.P.	'	'	'
Net income (loss)	101,544	20,341	-127,570
Other comprehensive income (loss)	'	'	'
Unrealized gains (losses) on interest rate derivatives	6,791	-7,676	-31,531
Losses on interest rate derivatives included in interest expense	2,740	3,697	4,601
Unrealized equity in other comprehensive income of equity method investee	1,070	0	0
Realized equity in other comprehensive income of equity method investee	-1,070	0	0
Loss on interest rate derivatives upon discontinuing hedge accounting	0	0	28,430
Other comprehensive income (loss)	9,531	-3,979	1,500
Comprehensive income (loss)	111,075	16,362	-126,070
Comprehensive (income) loss attributable to noncontrolling interests	-4,125	615	244
Comprehensive income (loss) attributable to COPT	$106,950	$16,977	($125,826)

Consolidated_Statements_of_Equ

Consolidated Statements of Equity (USD $)

Total

Preferred Shares

Common Shares

Preferred Shares

Common Shares

Additional Paid-in Capital

Cumulative Distributions in Excess of Net Income

Accumulated Other Comprehensive Loss

Noncontrolling Interests

Corporate Office Properties, L.P.

In Thousands, except Share data, unless otherwise specified

USD ($)

Preferred Shares

Common Shares

USD ($)

Preferred Shares

Common Shares

Accumulated Other Comprehensive Loss

Noncontrolling Interests

Limited Partner

General Partner

USD ($)

Preferred Shares

USD ($)

Preferred Shares

USD ($)

Balance at Dec. 31, 2010

$1,314,138

$216,333

$669

$1,295,592

($281,794)

($4,163)

$87,501

$1,314,825

$1,083,963

($4,447)

$10,176

$8,800

$216,333

Balance (in units/ shares) at Dec. 31, 2010

66,931,582

69,668,226

Balance (preferred units) at Dec. 31, 2010

352,000

8,121,667

Increase (Decrease) in Shareholders' Equity

Conversion of common units to common shares (100,939, 234,246 and 311,343 shares in 2011, 2012 and 2013, respectively)

1,520

-1,521

Issuance of common units to COPT to balance units owned with common shares

100,939

1,666,083

Shares issued to the public (in dollars)

145,367

145,321

145,367

Shares issued to the public (in units/shares)

4,600,000

Exercise of share options (in dollars)

2,461

2,459

2,461

Share-based compensation (in units/shares)

302,226

Exercise of share options (in units/shares)

191,264

Share-based compensation

14,265

Share-based compensation

14,267

Restricted common units/shares redemptions

-114,687

Restricted common units/shares redemptions (in dollars)

-3,990

Adjustments to noncontrolling interests resulting from changes in ownership of COPLP

-2,798

2,798

Comprehensive income (loss)

-124,669

-119,428

2,430

-7,671

-124,664

-144,088

2,610

660

16,102

Dividends/Distributions

-132,819

-141,344

-124,582

-660

-16,102

Distributions to owners of common and preferred units in COPLP

-7,833

Contributions from noncontrolling interests

261

-23

284

261

-23

284

Distributions to noncontrolling interests

-16

Adjustment to arrive at fair value of redeemable noncontrolling interest

-1,315

Tax benefit (loss) from share-based compensation

Balance at Dec. 31, 2011

1,205,899

216,333

720

1,451,078

-534,041

-1,733

73,542

1,205,899

972,107

-1,837

10,496

8,800

216,333

Balance (in units/ shares) at Dec. 31, 2011

72,011,324

76,313,112

Balance (preferred units) at Dec. 31, 2011

352,000

8,121,667

Increase (Decrease) in Shareholders' Equity

Conversion of common units to common shares (100,939, 234,246 and 311,343 shares in 2011, 2012 and 2013, respectively)

2,812

-2,814

Issuance of common units to COPT to balance units owned with common shares

234,246

Shares issued to the public (in dollars)

165,652

204,696

172,500

-6,848

204,610

165,652

204,696

-6,848

204,696

172,500

Shares issued to the public (in units/shares)

6,900,000

8,625,000

6,900,000

Stock redeemed or called during period (in units/ shares)

-55,000

1,827

-1,827

-55,000

Stock redeemed or called during period, value

-2,200,000

Exercise of share options (in dollars)

928

Share-based compensation (in units/shares)

160,643

Exercise of share options (in units/shares)

61,624

Share-based compensation

11,183

Share-based compensation

11,184

Restricted common units/shares redemptions

-139,851

Restricted common units/shares redemptions (in dollars)

-3,379

Adjustments to noncontrolling interests resulting from changes in ownership of COPLP

-4,627

4,627

Comprehensive income (loss)

18,927

20,977

-3,702

1,652

18,927

-656

-3,871

1,950

660

20,844

Dividends/Distributions

-102,564

-107,841

-86,337

-660

-20,844

Distributions to owners of common and preferred units in COPLP

-5,277

COPT contribution to COPLP of distribution from subsidiary

1,608

-1,608

Distributions to noncontrolling interests

-655

Adjustment to arrive at fair value of redeemable noncontrolling interest

-3,955

Tax benefit (loss) from share-based compensation

Balance at Dec. 31, 2012

1,436,499

333,833

809

1,653,672

-617,455

-5,435

71,075

1,436,499

1,089,391

-5,708

10,183

8,800

333,833

Balance (in units/ shares) at Dec. 31, 2012

80,952,986

85,020,528

4,067,542

80,952,986

Balance (preferred units) at Dec. 31, 2012

352,000

12,821,667

Increase (Decrease) in Shareholders' Equity

Conversion of common units to common shares (100,939, 234,246 and 311,343 shares in 2011, 2012 and 2013, respectively)

3,994

-3,997

Issuance of common units to COPT to balance units owned with common shares

311,343

Shares issued to the public (in dollars)

117,961

117,916

117,961

Shares issued to the public (in units/shares)

4,485,000

Stock redeemed or called during period (in units/ shares)

-84,750

2,904

-2,904

-84,750

Stock redeemed or called during period, value

-3,390,000

Issuance of common units resulting from common shares issued under at-the-market program (in units)

1,500,000

Issuance of common units resulting from common shares issued under at-the-market program (in dollars)

38,447

38,432

38,447

Acquisition of property and noncontrolling interest in other consolidated entity for COPLP common units

1,369

-1,296

2,665

Acquisition of property and noncontrolling interest in other consolidated entity for COPLP common units (in dollars)

221,501

Acquisition of property and noncontrolling interest in other consolidated entity for COPLP common units (in units)

1,369

3,899

-2,530

Exercise of share options (in dollars)

779

Share-based compensation (in units/shares)

184,292

Exercise of share options (in units/shares)

39,331

Share-based compensation

7,603

Share-based compensation

7,605

Restricted common units/shares redemptions

-78,440

Restricted common units/shares redemptions (in dollars)

-2,002

Adjustments to noncontrolling interests resulting from changes in ownership of COPLP

-744

744

Comprehensive income (loss)

109,699

93,707

8,915

7,077

109,699

77,006

9,313

2,749

660

19,971

Dividends/Distributions

-115,216

-120,156

-99,525

-660

-19,971

Distributions to owners of common and preferred units in COPLP

-4,940

Contributions from noncontrolling interests

Distributions to noncontrolling interests

-1,045

Adjustment to arrive at fair value of redeemable noncontrolling interest

-7,121

Tax benefit (loss) from share-based compensation

-122

Balance 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 (in units/ shares) at Dec. 31, 2013

87,394,512

91,372,212

3,977,700

87,394,512

Balance (preferred units) at Dec. 31, 2013

352,000

9,431,667

Consolidated_Statements_of_Equ1

Consolidated Statements of Equity (Parenthetical)	12 Months Ended
Consolidated Statements of Equity (Parenthetical)	Dec. 31, 2013
Balance (in units/ shares)	87,394,512
Conversion of common units to common shares	311,343
Exercise of share options (in units/shares)	39,331
Restricted common units/shares redemptions	78,440
Preferred Shares	'
Shares issued to the public (in units/shares)	'
Stock redeemed or called during period, value	3,390,000
Common Shares	'
Shares issued to the public (in units/shares)	4,485,000
Common Stock Issued to Public Under At-the-Market Program	'
Shares issued to the public (in units/shares)	1,500,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities	'	'	'
Revenues from real estate operations received	$482,763	$483,421	$476,762
Construction contract and other service revenues received	63,647	77,831	88,433
Property operating expenses paid	-176,243	-174,683	-180,041
Construction contract and other service expenses paid	-63,853	-67,952	-94,140
General, administrative, leasing, business development and land carry costs paid	-28,022	-22,904	-28,027
Interest expense paid	-81,575	-87,394	-93,715
Previously accreted interest expense paid	-11,116	0	-17,314
Settlement of interest rate derivatives	0	-29,738	0
Proceeds from sale of trading marketable securities	298	18,975	0
Exit costs on property dispositions	-979	-4,146	0
Payments in connection with early extinguishment of debt	-27,909	-2,637	-353
Interest and other income received	1,962	1,073	698
Income taxes paid	6	-8	-160
Net cash provided by operating activities	158,979	191,838	152,143
Cash flows from investing activities	'	'	'
Construction, development and redevelopment	-201,808	-165,275	-232,667
Tenant improvements on operating properties	-21,950	-27,103	-37,195
Other capital improvements on operating properties	-23,940	-20,066	-16,906
Acquisitions of operating properties	0	-48,308	-32,856
Proceeds from sales of properties	148,569	290,603	79,638
Mortgage and other loan receivables funded	-14,077	-14,232	-23,377
Mortgage and other loan receivables payments received	144	10,113	16,759
Leasing costs paid	-14,429	-13,278	-15,997
Decrease (increase) in restricted cash associated with investing activities	8,178	-872	-2,232
Other	-477	2,162	4,446
Net cash provided by (used in) investing activities	-119,790	13,744	-260,387
Proceeds from debt	'	'	'
Revolving Credit Facility	504,000	329,000	1,180,000
Unsecured senior notes	592,413	0	0
Other debt proceeds	94,049	403,117	456,206
Repayments of debt	'	'	'
Revolving Credit Facility	-504,000	-991,000	-813,000
Scheduled principal amortization	-9,481	-11,684	-13,755
Other debt repayments	-612,093	-124,386	-698,100
Deferred financing costs paid	-9,361	-3,371	-13,113
Net proceeds from issuance of preferred shares	0	165,652	0
Net proceeds from issuance of common shares	157,444	205,425	147,828
Redemption of preferred shares	-84,750	-55,000	0
Common share dividends paid	-93,474	-89,161	-114,643
Preferred share dividends paid	-21,335	-19,087	-16,102
Distributions paid to noncontrolling interests in the Operating Partnership	-4,958	-5,828	-7,875
Restricted share redemptions	-2,002	-3,379	-3,990
Other	-1,862	-845	245
Net cash (used in) provided by financing activities	4,590	-200,547	103,701
Net increase (decrease) in cash and cash equivalents	43,779	5,035	-4,543
Cash and cash equivalents	'	'	'
Beginning of period	10,594	5,559	10,102
End of period	54,373	10,594	5,559
Reconciliation of net income (loss) to net cash provided by operating activities:	'	'	'
Net income (loss)	101,544	20,341	-127,576
Adjustments to reconcile net income (loss) to net cash provided by operating activities:	'	'	'
Depreciation and other amortization	119,773	124,418	136,594
Impairment losses	31,068	62,702	151,021
Loss on interest rate derivatives	0	0	29,805
Settlement of previously accreted interest expense	-11,116	0	-17,314
Amortization of deferred financing costs	5,451	6,243	6,596
Increase in deferred rent receivable	-5,196	-11,776	-10,102
Amortization of net debt discounts	1,159	3,155	5,540
Gain on sales of real estate	-11,687	-20,961	-7,528
Gain on equity method investment	0	0	-2,452
Share-based compensation	6,530	9,982	11,920
(Gain) loss on early extinguishment of debt	-68,689	-3,430	1,670
Other	-3,093	-4,551	-1,165
Changes in operating assets and liabilities:	'	'	'
(Increase) decrease in accounts receivable	-10,334	8,049	-6,243
Decrease in restricted cash and marketable securities	576	14,934	2,160
(Increase) decrease in prepaid expenses and other assets	-5,128	8,550	-687
Increase (decrease) in accounts payable, accrued expenses and other liabilities	3,960	4,101	-18,041
Increase (decrease) in rents received in advance and security deposits	4,161	-1,916	-2,055
Decrease in interest rate derivatives in connection with cash settlement	0	-28,003	0
Net cash provided by operating activities	158,979	191,838	152,143
Supplemental schedule of non-cash investing and financing activities:	'	'	'
Increase (decrease) in accrued capital improvements, leasing and other investing activity costs	2,947	-1,227	11,719
Increase in property, debt and other liabilities in connection with acquisitions	0	0	3,040
Decrease in property in connection with transfer of property in settlement of debt	73,780	12,042	0
Decrease in debt in connection with transfer of property in settlement of debt	146,500	16,304	0
Increase in fair value of derivatives applied to accumulated other comprehensive income (loss) and noncontrolling interests	9,470	4,040	1,438
Dividends/distribution payable	29,080	28,698	35,038
COPLP common units issued to acquire property and noncontrolling interest in other consolidated entity	5,194	0	0
Decrease in noncontrolling interests and increase in shareholdersâ€™ equity in connection with the conversion of common units into common shares	3,997	2,814	1,521
Adjustments to noncontrolling interests resulting from changes in COPLP ownership	744	4,627	2,798
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	7,121	3,955	1,315
Corporate Office Properties, L.P.	'	'	'
Cash flows from operating activities	'	'	'
Revenues from real estate operations received	482,763	483,421	476,762
Construction contract and other service revenues received	63,647	77,831	88,433
Property operating expenses paid	-176,243	-174,683	-180,041
Construction contract and other service expenses paid	-63,853	-67,952	-94,140
General, administrative, leasing, business development and land carry costs paid	-28,022	-22,904	-28,021
Interest expense paid	-81,575	-87,394	-93,715
Previously accreted interest expense paid	-11,116	0	-17,314
Settlement of interest rate derivatives	0	-29,738	0
Proceeds from sale of trading marketable securities	298	18,975	0
Exit costs on property dispositions	-979	-4,146	0
Payments in connection with early extinguishment of debt	-27,909	-2,637	-353
Interest and other income received	1,962	1,073	698
Income taxes paid	6	-8	-160
Net cash provided by operating activities	158,979	191,838	152,149
Cash flows from investing activities	'	'	'
Construction, development and redevelopment	-201,808	-165,275	-232,667
Tenant improvements on operating properties	-21,950	-27,103	-37,195
Other capital improvements on operating properties	-23,940	-20,066	-16,906
Acquisitions of operating properties	0	-48,308	-32,856
Proceeds from sales of properties	148,569	290,603	79,638
Mortgage and other loan receivables funded	-14,077	-14,232	-23,377
Mortgage and other loan receivables payments received	144	10,113	16,759
Leasing costs paid	-14,429	-13,278	-15,997
Decrease (increase) in restricted cash associated with investing activities	8,178	-872	-2,232
Other	-477	2,162	4,446
Net cash provided by (used in) investing activities	-119,790	13,744	-260,387
Proceeds from debt	'	'	'
Revolving Credit Facility	504,000	329,000	1,180,000
Unsecured senior notes	592,413	0	0
Other debt proceeds	94,049	403,117	456,206
Repayments of debt	'	'	'
Revolving Credit Facility	-504,000	-991,000	-813,000
Scheduled principal amortization	-9,481	-11,684	-13,755
Other debt repayments	-612,093	-124,386	-698,100
Deferred financing costs paid	-9,361	-3,371	-13,113
Net proceeds from issuance of preferred shares	0	165,652	0
Net proceeds from issuance of common shares	157,444	205,425	147,828
Redemption of preferred shares	-84,750	-55,000	0
Common share dividends paid	-97,772	-94,329	-121,864
Preferred share dividends paid	-21,995	-19,747	-16,762
Restricted share redemptions	-2,002	-3,379	-3,990
Other	-1,862	-845	245
Net cash (used in) provided by financing activities	4,590	-200,547	103,695
Net increase (decrease) in cash and cash equivalents	43,779	5,035	-4,543
Cash and cash equivalents	'	'	'
Beginning of period	10,594	5,559	10,102
End of period	54,373	10,594	5,559
Reconciliation of net income (loss) to net cash provided by operating activities:	'	'	'
Net income (loss)	101,544	20,341	-127,570
Adjustments to reconcile net income (loss) to net cash provided by operating activities:	'	'	'
Depreciation and other amortization	119,773	124,418	136,594
Impairment losses	31,068	62,702	151,021
Loss on interest rate derivatives	0	0	29,805
Settlement of previously accreted interest expense	-11,116	0	-17,314
Amortization of deferred financing costs	5,451	6,243	6,596
Increase in deferred rent receivable	-5,196	-11,776	-10,102
Amortization of net debt discounts	1,159	3,155	5,540
Gain on sales of real estate	-11,687	-20,961	-7,528
Gain on equity method investment	0	0	-2,452
Share-based compensation	6,530	9,982	11,920
(Gain) loss on early extinguishment of debt	-68,689	-3,430	1,670
Other	-3,093	-4,551	-1,165
Changes in operating assets and liabilities:	'	'	'
(Increase) decrease in accounts receivable	-10,334	8,049	-6,243
Decrease in restricted cash and marketable securities	1,267	14,122	1,560
(Increase) decrease in prepaid expenses and other assets	-5,128	8,550	-687
Increase (decrease) in accounts payable, accrued expenses and other liabilities	3,269	4,913	-17,441
Increase (decrease) in rents received in advance and security deposits	4,161	-1,916	-2,055
Decrease in interest rate derivatives in connection with cash settlement	0	-28,003	0
Net cash provided by operating activities	158,979	191,838	152,149
Supplemental schedule of non-cash investing and financing activities:	'	'	'
Increase (decrease) in accrued capital improvements, leasing and other investing activity costs	2,947	-1,227	11,719
Increase in property, debt and other liabilities in connection with acquisitions	0	0	3,040
Decrease in property in connection with transfer of property in settlement of debt	73,780	12,042	0
Decrease in debt in connection with transfer of property in settlement of debt	146,500	16,304	0
Increase in fair value of derivatives applied to accumulated other comprehensive income (loss) and noncontrolling interests	9,470	4,040	1,438
Dividends/distribution payable	29,080	28,698	35,038
COPLP common units issued to acquire property and noncontrolling interest in other consolidated entity	5,194	0	0
Increase in redeemable noncontrolling interest and decrease in equity to carry redeemable noncontrolling interest at fair value	$7,121	$3,955	$1,315

Organization

Organization	12 Months Ended
	Dec. 31, 2013
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 defense contractors, most of whom are engaged in defense information technology and national security 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 December 31, 2013, our properties included the following:


	•	183 operating office properties totaling 17.4 million square feet;

	•	10 office properties under, or contractually committed for, construction or approved for redevelopment that
	we estimate will total approximately 1.4 million square feet upon completion, including two partially operational properties included above;

	•	land held or under pre-construction totaling 1,708 acres (including 56 acres controlled but not owned) that we believe are potentially developable into approximately 20.0 million square feet; and

	•	a partially operational, wholesale data center which upon completion and stabilization is expected to have a critical load of 18 megawatts.

	COPLP owns real estate both directly and through subsidiary partnerships and limited liability companies (“LLCs”). In addition to owning real estate, COPLP also owns subsidiaries that provide real estate services such as property management and construction and development services primarily for our properties but also for third parties. Some of these services are performed by a taxable REIT subsidiary (“TRS”).

	Interests in COPLP are in the form of common and preferred units. As of December 31, 2013, COPT owned 95.6% of the outstanding COPLP common units (“common units”) and 96.4% of the outstanding COPLP preferred units (“preferred units”); the remaining common and preferred units in COPLP were owned by third parties. Three of COPT’s trustees controlled, either directly or through ownership by other entities or family members, 3.4% of COPLP’s common units as of December 31, 2013.
	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_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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 they 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 the entity’s operations but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity.

	We use the cost method of accounting when we own an interest in an entity and cannot exert significant influence over its operations.

	Reclassifications

	We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including the following:


	•	amounts associated with our mortgage and other investing receivables were reclassified to a separate line reported on our consolidated balance sheets; and

	•	amounts on our consolidated statements of operations were reclassified in conjunction with the transfer of properties to, and from, discontinued operations during 2013. We provide disclosure regarding our discontinued operations in Note 20.

	Out of Period Adjustment

	During the second quarter of 2013, we identified an error related to the estimated fair value of a redeemable noncontrolling interest in a real estate joint venture. Changes in such fair value are reported as changes in equity with no impact to net income or comprehensive income. The error resulted in an understatement of the line entitled “redeemable noncontrolling interest” in the mezzanine section of our consolidated balance sheet and an overstatement of the line entitled “additional paid-in capital” in the equity section of our consolidation balance sheet of $3.7 million as of December 31, 2012. We have determined that this adjustment was not material to our financial statements for 2012 or 2013. Accordingly, this change is reported as an out-of-period adjustment in the year ended December 31, 2013.
	Use of Estimates in the Preparation of Financial Statements

	We make estimates and assumptions when preparing financial statements under generally accepted accounting principles (“GAAP”). These estimates and assumptions affect various matters, including:

	•	the reported amounts of assets and liabilities in our consolidated balance sheets at the dates of the financial statements;

	•	the disclosure of contingent assets and liabilities at the dates of the financial statements; and

	•	the reported amounts of revenues and expenses in our consolidated statements of operations during the reporting periods.

	Significant estimates are inherent in the presentation of our financial statements in a number of areas, including the evaluation of the collectability of accounts and notes receivable, the allocation of property acquisition costs, the determination of estimated useful lives of assets, the determination of lease terms, the evaluation of impairment of long-lived assets, the amount of revenue recognized relating to tenant improvements and the level of expense recognized in connection with share-based compensation. Actual results could differ from these and other estimates.

	Acquisitions of Properties

	Upon completion of property acquisitions, we allocate the purchase price to tangible and intangible assets and liabilities associated with such acquisitions based on our estimates of their fair values. We determine these fair values by using market data and independent appraisals available to us and making numerous estimates and assumptions. We allocate property acquisitions to the following components:


	•	properties based on a valuation performed under the assumption that the property is vacant upon acquisition (the “if vacant value”). The if-vacant value is allocated between land and buildings or, in the case of properties under development, construction in progress. We also allocate additional amounts to properties for in-place tenant improvements based on our estimate of improvements per square foot provided under market leases that would be attributable to the remaining non-cancellable terms of the respective leases;

	•	above- and below-market lease intangible assets or liabilities based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between: (1) the contractual amounts to be received pursuant to the in-place leases; and (2) our estimate of fair market lease rates for the corresponding space, measured over a period equal to the remaining non-cancelable term of the lease. The capitalized above- and below-market lease values are amortized as adjustments to rental revenue over the remaining non-cancellable terms of the respective leases;

	•	in-place lease value based on our estimates of: (1) the present value of additional income to be realized as a result of leases being in place on the acquired properties; and (2) costs to execute similar leases. Our estimate of additional income to be realized includes carrying costs, such as real estate taxes, insurance and other operating expenses, and revenues during the expected lease-up periods considering current market conditions. Our estimate of costs to execute similar leases includes leasing commissions, legal and other related costs;

	•	tenant relationship value based on our evaluation of the specific characteristics of each tenant's lease and our overall relationship with that respective tenant. Characteristics we consider in determining these values include the nature and extent of our existing business relationships with the tenant, growth prospects for developing new business with the tenant, the tenant's credit quality and expectations of lease renewals, among other factors; and

	•	above- and below- market cost arrangements (such as real estate tax treaties or above- or below- market ground leases) based on the present value of the expected benefit from any such arrangements in place on the property at the time of acquisition.

	Properties

	We report properties to be developed or held and used in operations at our depreciated cost, reduced for impairment losses. The preconstruction stage of the development or redevelopment of an operating property includes efforts and related costs to secure land control and zoning, evaluate feasibility and complete other initial tasks which are essential to development. We capitalize interest expense, real estate taxes and direct and indirect project costs (including related compensation and other indirect costs) associated with properties, or portions thereof, undergoing construction, development and redevelopment activities. We continue to capitalize these costs while construction, development or redevelopment activities are underway until a property becomes “operational,” which occurs upon the earlier of when leases commence or one year after the cessation of major construction activities. When leases commence on portions of a newly-constructed or redeveloped property in the period prior to one year from the cessation of major construction activities, we consider that property to be “partially operational.” When a property is partially operational, we allocate the costs associated with the property between the portion that is operational and the portion under construction. We start depreciating newly-constructed and redeveloped properties as they become operational.
	Most of our leases involve some form of improvements to leased space. When we are required to provide improvements under the terms of a lease, we determine whether the improvements constitute landlord assets or tenant assets. If the improvements are landlord assets, we capitalize the cost of the improvements and recognize depreciation expense associated with such improvements over the shorter of the useful life of the assets or the term of the lease and recognize any payments from the tenant as rental revenue over the term of the lease. If the improvements are tenant assets, we defer the cost of improvements funded by us as a lease incentive asset and amortize it as a reduction of rental revenue over the term of the lease. In determining whether improvements constitute landlord or tenant assets, we consider numerous factors, including: whether the improvements are unique to the tenant or reusable by other tenants; whether the tenant is permitted to alter or remove the improvements without our consent or without compensating us for any lost fair value; whether the ownership of the improvements remains with us or remains with the tenant at the end of the lease term; and whether the economic substance of the lease terms is properly reflected.
	We depreciate our fixed assets using the straight-line method over their estimated useful lives as follows:


			Estimated Useful Lives
	Buildings and building improvements		10-40 years
	Land improvements		10-20 years
	Tenant improvements on operating properties		Related lease term
	Equipment and personal property		3-10 years
	We assess each of our operating properties for impairment quarterly using cash flow projections and estimated fair values that we derive for each of the properties. We update the leasing and other assumptions used in these projections regularly, paying particular attention to properties that have experienced chronic vacancy or face significant market challenges. We review our plans and intentions for our development projects and land parcels quarterly. If our analyses indicate that the carrying values of operating properties, properties in development or land held for future development may be impaired, we perform a recovery analysis for such properties. For long-lived assets to be held and used, we analyze recoverability based on the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over, in most cases, a ten-year holding period. If we believe there is a significant possibility that we might dispose of the assets earlier, we analyze recoverability using a probability weighted analysis of the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over the various possible holding periods. If the recovery analysis indicates that the carrying value of a tested property is not recoverable from estimated future cash flows, it is written down to its estimated fair value and an impairment loss is recognized. If and when our plans change, we revise our recoverability analyses to use the cash flows expected from the operations and eventual disposition of each asset using holding periods that are consistent with our revised plans. Changes in holding periods may require us to recognize significant impairment losses.

Property fair values are determined based on contract prices, indicative bids, discounted cash flow analyses or yield analyses. Estimated cash flows used in such analyses are based on our plans for the property and our views of market and economic conditions. The estimates consider items such as current and future rental rates, occupancies for the tested property and comparable properties, estimated operating and capital expenditures and recent sales data for comparable properties; most of these items are influenced by market data obtained from real estate leasing and brokerage firms and our direct experience with the properties and their markets.

When we determine that a property is held for sale, we discontinue the recording of depreciation expense on the property and estimate the fair value, net of selling costs; if we then determine that the estimated fair value, net of selling costs, is less than the net book value of the property, we recognize an impairment loss equal to the difference and reduce the net book value of the property.
When we dispose of an operating property and determine that we have no significant continuing involvement in such property, or determine that an operating property is held for sale, we classify the results of operations for such property as discontinued operations and classify the assets as held for sale. Interest expense that is specifically identifiable to properties included in discontinued operations is used in the computation of interest expense attributable to discontinued operations.

Sales of Interests in Real Estate

We recognize gains from sales of interests in real estate using the full accrual method, provided that various criteria relating to the terms of sale and any subsequent involvement by us with the real estate sold are met.
Cash and Cash Equivalents

Cash and cash equivalents include all cash and liquid investments that mature three months or less from when they are purchased. Cash equivalents are reported at cost, which approximates fair value. We maintain our cash in bank accounts in amounts that may exceed Federally insured limits at times. We have not experienced any losses in these accounts in the past and believe that we are not exposed to significant credit risk because our accounts are deposited with major financial institutions.
Investments in Marketable Securities

We classify marketable securities as trading securities when we have the intent to sell such securities in the near term, and classify other marketable securities as available-for-sale securities. We determine the appropriate classification of investments in marketable securities at the acquisition date and re-evaluate the classification at each balance sheet date. We report investments in marketable securities classified as trading securities at fair value, with unrealized gains and losses recognized through earnings; on our statements of cash flows, we classify cash flows from these securities as operating activities. We report investments in marketable securities classified as available-for-sale securities at fair value, with net unrealized gains or losses deferred to accumulated other comprehensive income (loss) (“AOCI”) and realized gains and losses resulting from sales of such investments recognized through earnings; on our statements of cash flows, we classify cash flows from interest and dividends earned on these securities as operating activities and cash flows from purchases, sales and maturities of these securities as investing activities.

Accounts and Deferred Rents Receivable and Mortgage and Other Investing Receivables

We maintain allowances for estimated losses resulting from the failure of our customers or borrowers to satisfy their payment obligations. We use judgment in estimating these allowances based primarily upon the payment history and credit status of the entities associated with the individual receivables. We write off these receivables when we believe the facts and circumstances indicate that continued pursuit of collection is no longer warranted. When we earn interest income in connection with receivables for which we have established allowances, we establish allowances in connection with such interest income that is unpaid. When cash is received in connection with receivables for which we have established allowances, we reduce the amount of losses recognized in connection with the receivables’ allowance.

Intangible Assets and Deferred Revenue on Real Estate Acquisitions

We capitalize intangible assets and deferred revenue on real estate acquisitions as described in the section above entitled “Acquisitions of Properties.” We amortize the intangible assets and deferred revenue as follows:


		Amortization Period
Above- and below-market leases		Related lease terms
In-place lease value		Related lease terms
Tenant relationship value		Estimated period of time that tenant will lease space in property
Above- and below-market cost arrangements		Term of arrangements
Market concentration premium		40 years
We recognize the amortization of acquired above-market and below-market leases as adjustments to rental revenue. We recognize the amortization of above- and below- market cost arrangements as adjustments to property operating expenses. We recognize the amortization of other intangible assets on property acquisitions as amortization expense.

Deferred Leasing and Financing Costs, Net

We defer costs incurred to obtain new tenant leases or extend existing tenant leases, including related compensation costs. We amortize these costs evenly over the lease terms. When tenant leases are terminated early, we expense any unamortized deferred leasing costs associated with those leases over the shortened term of the lease.
We defer costs of financing arrangements and recognize these costs as interest expense over the related loan terms on a straight-line basis, which approximates the amortization that would occur under the effective interest method of amortization. We expense any unamortized loan costs when loans are retired early.

Noncontrolling Interests

COPT’s consolidated noncontrolling interests are comprised of interests in COPLP not owned by COPT (discussed further in Note 15) and consolidated real estate joint ventures (discussed further in Note 6). COPLP’s consolidated noncontrolling interests are comprised primarily of interests in our consolidated real estate joint ventures. Also included in COPLP’s consolidated noncontrolling interests are interests in several real estate entities owned directly by COPT, or a wholly owned subsidiary of COPT, that generally do not exceed 1%. We evaluate whether noncontrolling interests are subject to redemption features outside of our control. For noncontrolling interests that are currently redeemable for cash at the option of the holders of such interests or deemed probable to eventually become redeemable, we classify such interests as redeemable noncontrolling interests in the mezzanine section of our consolidated balance sheets; we adjust these interests each period to the greater of their fair value or carrying amount (initial amount as adjusted for allocations of income and losses and future contributions and distributions), with a corresponding offset to additional paid-in capital on COPT’s consolidated balance sheets or common units on COPLP’s balance sheet, and only recognize reductions in such interests to the extent of their carrying amount. Our other noncontrolling interests are reported in the equity section of our consolidated balance sheets. The amounts reported for noncontrolling interests on our consolidated statements of operations represent the portion of these entities’ income or losses not attributable to us.

Revenue Recognition

We recognize minimum rents, net of abatements, on a straight-line basis over the term of tenant leases. The term of a lease generally includes periods when a tenant: (1) may not terminate its lease obligation early; (2) may terminate its lease obligation early in exchange for a fee or penalty that we consider material enough such that termination would not be probable; (3) possesses renewal rights and the tenant’s failure to exercise such rights imposes a penalty on the tenant material enough such that renewal appears reasonably assured; and (4) possesses bargain renewal options for such periods. We report the amount by which our minimum rental revenue recognized on a straight-line basis under leases exceeds the contractual rent billings associated with such leases as deferred rent receivable on our consolidated balance sheets. Amounts by which our minimum rental revenue recognized on a straight-line basis under leases are less than the contractual rent billings associated with such leases are included in deferred revenue associated with operating leases on our consolidated balance sheets.
In connection with a tenant’s entry into, or modification of, a lease, if we make cash payments to, or on behalf of, the tenant for purposes other than funding the construction of landlord assets, we defer the amount of such payments as lease incentives. As discussed above, when we are required to provide improvements under the terms of a lease, we determine whether the improvements constitute landlord assets or tenant assets; if the improvements are tenant assets, we defer the cost of improvements funded by us as a lease incentive asset. We amortize lease incentives as a reduction of rental revenue over the term of the lease.
We recognize tenant recovery revenue in the same periods in which we incur the related expenses. Tenant recovery revenue includes payments from tenants as reimbursement for property taxes, utilities and other property operating expenses.

We recognize fees received for lease terminations as revenue and write off against such revenue any (1) deferred rents receivable, and (2) deferred revenue, lease incentives and intangible assets that are amortizable into rental revenue associated with the leases; the resulting net amount is the net revenue from the early termination of the leases. When a tenant's lease for space in a property is terminated early but the tenant continues to lease such space under a new or modified lease in the property, the net revenue from the early termination of the lease is recognized evenly over the remaining life of the new or modified lease in place on that property.

We recognize fees for services provided by us once services are rendered, fees are determinable and collectability is assured. We recognize revenue under construction contracts using the percentage of completion method when the revenue and costs for such contracts can be estimated with reasonable accuracy; when these criteria do not apply to a contract, we recognize revenue on that contract using the completed contract method. Under the percentage of completion method, we recognize a percentage of the total estimated revenue on a contract based on the cost of services provided on the contract as of a point in time relative to the total estimated costs on the contract.

Interest Rate Derivatives

Our primary objectives in using interest rate derivatives are to add stability to interest expense and to manage exposure to interest rate movements. To accomplish this objective, we primarily use interest rate swaps as part of our interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for our making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Derivatives are used to hedge the cash flows associated with interest rates on existing debt as well as future debt. We recognize all derivatives as assets or liabilities in the balance sheet at fair value. We defer the effective portion of changes in fair value of the designated cash flow hedges to AOCI and reclassify such deferrals to interest expense as interest expense is recognized on the hedged forecasted transactions. We recognize the ineffective portion of the change in fair value of interest rate derivatives directly in interest expense. When an interest rate swap designated as a cash flow hedge no longer qualifies for hedge accounting, we recognize changes in fair value of the hedge previously deferred to AOCI, along with any changes in fair value occurring thereafter, through earnings. We do not use interest rate derivatives for trading or speculative purposes. We manage counter-party risk by only entering into contracts with major financial institutions based upon their credit ratings and other risk factors.

We use standard market conventions and techniques such as discounted cash flow analysis, option pricing models, replacement cost and termination cost in computing the fair value of derivatives at each balance sheet date. We made an accounting policy election to use an exception provided for in the applicable accounting guidance with respect to measuring counterparty credit risk for derivative instruments; this election enables us to measure the fair value of groups of assets and liabilities associated with derivative instruments consistently with how market participants would price the net risk exposure as of the measurement date.

Please refer to Note 12 for additional information pertaining to interest rate derivatives.

Expense Classification
We classify as property operations expense costs incurred for property taxes, ground rents, utilities, property management, insurance, repairs, exterior and interior maintenance and tenant revenue collection losses, as well as associated labor and indirect costs attributable to these costs.

We classify as general and administrative and leasing expenses costs incurred for corporate-level management, public company administration, asset management, leasing, investor relations, marketing and corporate-level insurance (including general business, director and officers and key man life) and leasing prospects, as well as associated labor and indirect costs attributable to these costs.

Share-Based Compensation
We issued two forms of share-based compensation: restricted COPT common shares (“restricted shares”) and COPT performance share units (“PSUs”). We also issued options to purchase COPT common shares (“options”) in prior years. We account for share-based compensation in accordance with authoritative guidance provided by the Financial Accounting Standards Board (“FASB”) that establishes standards for the accounting for transactions in which an entity exchanges its equity instruments for goods or services, focusing primarily on accounting for transactions in which an entity obtains employee services in share-based payment transactions. The guidance requires us to measure the cost of employee services received in exchange for an award of equity instruments based generally on the fair value of the award on the grant date; such cost is then recognized over the period during which the employee is required to provide service in exchange for the award. No compensation cost is recognized for equity instruments for which employees do not render the requisite service. The guidance also requires that share-based compensation be computed based on awards that are ultimately expected to vest; as a result, future forfeitures of awards are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. If an award is voluntarily cancelled by an employee, we recognize the previously unrecognized cost associated with the original award on the date of such cancellation. We capitalize costs associated with share-based compensation attributable to employees engaged in construction and development activities.

When we adopted the authoritative guidance on accounting for share-based compensation, we elected to adopt the alternative transition method for calculating the tax effects of share-based compensation. The alternative transition method enabled us to use a simplified method to establishing the beginning balance of the additional paid-in capital pool related to the tax effects of employee share-based compensation, which was available to absorb tax deficiencies recognized subsequent to the adoption of this guidance.

We compute the fair value of options using the Black-Scholes option-pricing model. Under that model, the risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. The expected option life is based on our historical experience of employee exercise behavior. Expected volatility is based on historical volatility of COPT common shares . Expected dividend yield is based on the average historical dividend yield on our common shares over a period of time ending on the grant date of the options.

We compute the fair value of PSUs using a Monte Carlo model. Under that model, the baseline common share value is based on the market value on the grant date. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Expected volatility is based on historical volatility of COPT’s common shares.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements

	Accounting standards define fair value as the exit price, or the amount that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. The standards also establish a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability developed based on market data obtained from sources independent of us. Unobservable inputs are inputs that reflect our assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available in the circumstances. The hierarchy of these inputs is broken down into three levels: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs include (1) quoted prices for similar assets or liabilities in active markets, (2) quoted prices for identical or similar assets or liabilities in markets that are not active and (3) inputs (other than quoted prices) that are observable for the asset or liability, either directly or indirectly; and Level 3 inputs are unobservable inputs for the asset or liability. Categorization within the valuation hierarchy is based upon the lowest level of input that is most significant to the fair value measurement.

	Recurring Fair Value Measurements

	The assets held in connection with a non-qualified elective deferred compensation plan held by COPT (comprised primarily of mutual funds and equity securities) and the corresponding liability to the participants are measured at fair value on a recurring basis on COPT’s consolidated balance sheet using quoted market prices, as are other marketable securities that we hold. The deferred compensation plan assets and other marketable securities are included in the line entitled restricted cash and marketable securities on COPT’s consolidated balance sheets. The offsetting liability associated with the deferred compensation plan is adjusted to fair value at the end of each accounting period based on the fair value of the plan assets and reported in other liabilities on COPT’s consolidated balance sheets. The assets of the non-qualified elective deferred compensation plan and other marketable securities that we hold are classified in Level 1 of the fair value hierarchy. The liability associated with the deferred compensation plan is classified in Level 2 of the fair value hierarchy.

	The fair values of our interest rate derivatives are determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate market data and implied volatilities in such interest rates. While we determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our interest rate derivatives also utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default. However, as of December 31, 2013, we assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivatives and determined that these adjustments are not significant. As a result, we determined that our interest rate derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.

	As of December 31, 2013 and 2012, we owned warrants to purchase 50,000 common shares in The KEYW Holding Corporation (“KEYW”) at an exercise price of $9.25 per share. KEYW is an entity supporting the intelligence community's operations and transformation to Cyber Age mission by providing engineering services and integrated platforms that support the intelligence process. We compute the fair value of these warrants using the Black-Scholes option-pricing model. Under that model, the risk-free interest rate is based on the U.S. Treasury yield curve in effect as of the valuation date. The expected life is based on the period of time until the expiration of the warrants. Expected volatility is based on an average of the historical volatility of companies in KEYW’s industry that we deem to be comparable. Expected dividend yield is based on the dividend yield on KEYW’s common shares as of the date of valuation. The warrants are classified in Level 2 of the fair value hierarchy.

	In addition to the warrants in KEYW described above, we also owned 1.9 million shares, or approximately 7%, of KEYW’s common stock as of December 31, 2011. We sold all of these shares in 2012 for $14.0 million. We recognized revenue from a lease with KEYW in one of our properties of $2.4 million in 2012 and $780,000 in 2011.

	As discussed further in Note 6, 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. We determine the fair value of the interest based on unobservable inputs after considering the assumptions that market participants would make in pricing the interest. We apply a discount rate to the estimated future cash flows allocable to our partner from the properties underlying the joint venture. Estimated cash flows used in such analyses are based on our plans for the properties and our views of market and economic conditions, and consider items such as current and future rental rates, occupancies for the properties and comparable properties and estimated operating and capital expenditures. In determining the fair value of our partner’s interest, we used a discount rate of 15.5% as of December 31, 2013 and 15.6% as of December 31, 2012. The discount rates 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.

	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 9, we estimated the fair values of our mortgage and other 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 11, 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 9 for mortgage loans receivable, Note 11 for debt and Note 12 for interest rate derivatives.

	COPT and Subsidiaries

	The tables below set forth financial assets and liabilities of COPT and its subsidiaries that are accounted for at fair value on a recurring basis as of December 31, 2013 and 2012 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
			Active Markets for			Observable Inputs(Level 2)			Unobservable Inputs(Level 3)
			Identical Assets(Level 1)
	December 31, 2013:
	Assets:

	Marketable securities in deferred compensation plan (1)

	Mutual funds		$	7,090		$	—		$	—		$	7,090

	Common stocks		176			—			—			176

	Other		201			—			—			201

	Common stock (1)		298			—			—			298

	Interest rate derivatives (2)		—			6,594			—			6,594

	Warrants to purchase common stock in KEYW (2)		—			301			—			301

	Total Assets		$	7,765		$	6,895		$	—		$	14,660

	Liabilities:

	Deferred compensation plan liability (3)		$	—		$	7,467		$	—		$	7,467

	Interest rate derivatives		—			3,309			—			3,309

	Total Liabilities		$	—		$	10,776		$	—		$	10,776

	Redeemable noncontrolling interest		$	—		$	—		$	17,758		$	17,758


	December 31, 2012:
	Assets:

	Marketable securities in deferred compensation plan (1)

Mutual funds		$	6,275		$	—		$	—		$	6,275

Common stocks		298			—			—			298

Other		203			—			—			203

Common stock (1)		809			—			—			809

Warrants to purchase common stock in KEYW (2)		—			294			—			294

Total Assets		$	7,585		$	294		$	—		$	7,879

Liabilities:

Deferred compensation plan liability (3)		$	—		$	6,776		$	—		$	6,776

Interest rate derivatives		—			6,185			—			6,185

Total Liabilities		$	—		$	12,961		$	—		$	12,961

Redeemable noncontrolling interest		$	—		$	—		$	10,298		$	10,298


(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 tables below set forth financial assets and liabilities of COPLP and its subsidiaries that are accounted for at fair value on a recurring basis as of December 31, 2013 and 2012 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
		Active Markets for			Observable Inputs(Level 2)			Unobservable Inputs(Level 3)
		Identical Assets(Level 1)
December 31, 2013:
Assets:

Common stock (1)		$	298		$	—		$	—		$	298

Interest rate derivatives (2)		—			6,594			—			6,594

Warrants to purchase common stock in KEYW (2)		—			301			—			301

Total Assets		$	298		$	6,895		$	—		$	7,193

Liabilities:

Interest rate derivatives		$	—		$	3,309		$	—		$	3,309

Redeemable noncontrolling interest		$	—		$	—		$	17,758		$	17,758


December 31, 2012:
Assets:

Common stock (1)		$	809		$	—		$	—		$	809

Warrants to purchase common stock in KEYW (2)		—			294			—			294

Total Assets		$	809		$	294		$	—		$	1,103

Liabilities:

Interest rate derivatives		$	—		$	6,185		$	—		$	6,185

Redeemable noncontrolling interest		$	—		$	—		$	10,298		$	10,298


(1) Included in the line entitled “restricted cash and marketable securities” on COPLP’s consolidated balance sheet.
(2) Included in the line entitled “prepaid expenses and other assets” on COPLP’s consolidated balance sheet.

Nonrecurring Fair Value Measurements

2013 Impairment Losses

We recognized impairment losses in 2013 in connection with the following:


•	for certain of our operating properties that served as collateral for a non recourse loan, we expected that the cash flows to be generated by the properties would be insufficient to fund debt service requirements on the loan. While we sought to negotiate various alternatives with the lender, on December 23, 2013, we conveyed the properties to the lender to extinguish the loan. We recognized non-cash impairment losses of $11.0 million (all classified as discontinued operations and including $560,000 in exit costs) on these properties in 2013 resulting primarily from the carrying amount of certain of these properties located in Colorado Springs, Colorado (“Colorado Springs”) exceeding their fair value;

•	$15.2 million (all classified as discontinued operations and including $419,000 in exit costs) in connection with properties and land no longer aligned with our strategy that we sold, mostly in Colorado Springs; and

•	$5.9 million on two properties in the Greater Baltimore region that Management concluded no longer met our strategic investment criteria. After shortening our expected holding period for these properties during the period, we determined that the carrying amount of the properties would not likely be recovered from the cash flows from the operations and sales of the properties over the shortened period.

The table below sets forth the fair value hierarchy of the valuation techniques used by us in determining the fair values of the properties (dollars in thousands):


		Fair Value of Properties Held as of December 31, 2013
		Quoted Prices in						Significant						Impairment
		Active Markets for			Significant Other			Unobservable						Losses
		Identical Assets			Observable Inputs			Inputs						Recognized in
Description		(Level 1)			(Level 2)			(Level 3)			Total			2013 (1)
Assets

Properties, net		$	—		$	—		$	4,459		$	4,459		$	31,068


(1) Represents aggregate impairment losses on non recurring fair value measurements resulting in impairment losses, excluding exit costs incurred of $979,000.

The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above as of December 31, 2013 (dollars in thousands):


Valuation Technique		Fair Value on			Unobservable Input		Range (Weighted Average)
		Measurement Date
Discounted cash flow		$	4,459		Discount rate		10.0% (1)

					Terminal capitalization rate		9.5% (1)
					Market rent growth rate		3.0% (1)
					Expense growth rate		3.0% (1)

(1) Only one value applied for this unobservable input.

2012 Impairment Losses

We recognized impairment losses in 2012 in connection with the following:


•	our office properties and developable land in Greater Philadelphia, Pennsylvania. Our Board of Trustees approved a plan by Management to shorten the holding period for these properties because they no longer met our strategic investment criteria. We determined that the carrying amounts of these properties would not likely be recovered from the cash flows from the operations and sales of such properties over the likely remaining holding period. Accordingly, we recognized aggregate non-cash impairment losses of $46.1 million in 2012 for the amounts by which the carrying values of the properties exceeded their respective estimated fair values. These losses contemplated our expectation that we would incur future cash expenditures of approximately $25.0 million to complete the redevelopment of certain of these properties;

•	properties sold, or identified for sale, that are no longer aligned with our strategy of $19.0 million ($23.2 million classified as discontinued operations and including $4.2 million in exit costs), including $6.9 million pertaining to certain properties in Colorado Springs classified as held for sale at December 31, 2012, and approximately $5.1 million related to our disposition of an additional property from which the cash flows were not sufficient to recover its carrying value; and

•	construction costs incurred on a property held for future development of $1.9 million.

The table below sets forth the fair value hierarchy of the valuation techniques used by us in determining the fair values of the properties (dollars in thousands):


		Fair Value of Properties Held as of December 31, 2012
		Quoted Prices in						Significant						Impairment
		Active Markets for			Significant Other			Unobservable						Losses
		Identical Assets			Observable Inputs			Inputs						Recognized in
Description		(Level 1)			(Level 2)			(Level 3)			Total			2012 (1)
Assets (2):

Properties, net		$	—		$	—		$	173,949		$	173,949		$	62,702


(1) Represents aggregate impairment losses on non recurring fair value measurements resulting in impairment losses, excluding exit costs incurred of $4.2 million.
(2) Reflects balance sheet classifications of assets at time of fair value measurement, excluding the effect of held for sale classifications.

The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above as of December 31, 2012 (dollars in thousands):


Valuation Technique		Fair Value on			Unobservable Input		Range (Weighted Average)
		Measurement Date
Discounted cash flow		$	166,650		Discount rate		10.0% to 11.0% (10.3%)

					Terminal capitalization rate		8.7% to 10.0% (8.9%)

					Market rent growth rate		3.0% (1)

					Expense growth rate		3.0% (1)

Yield Analysis		$	2,356		Yield		12% (1)

					Market rent rate		$8.50 per square foot (1)

					Leasing costs		$20.00 per square foot (1)

(1) Only one value applied for this unobservable input.

Concentration_of_Rental_Revenu

Concentration of Rental Revenue	12 Months Ended
	Dec. 31, 2013
Risks and Uncertainties [Abstract]	'
Concentration of Rental Revenue	'
	Concentration of Rental Revenue

	We derived large concentrations of our revenue from real estate operations from certain tenants during the periods set forth in our consolidated statements of operations. The following table summarizes the percentage of our rental revenue (which excludes tenant recoveries and other real estate operations revenue) earned from (1) individual tenants that accounted for at least 5% of our rental revenue from continuing and discontinued operations and (2) the aggregate of the five tenants from which we recognized the most rental revenue in the respective years:


		For the Years Ended December 31,
		2013		2012		2011
	United States Government	18	%	18	%	17	%
	Northrop Grumman Corporation (1)	8	%	7	%	8	%
	Booz Allen Hamilton, Inc.	6	%	6	%	6	%
	Computer Sciences Corporation (1)	5	%	5	%	N/A

	Five largest tenants	41	%	39	%	38	%

	(1) Includes affiliated organizations and agencies and predecessor companies.

	Our rental revenue from the United States Government was earned primarily from properties in the Baltimore/Washington Corridor, San Antonio, Texas (“San Antonio”), St. Mary’s & King George Counties and Colorado Springs regions. We also derived in excess of 90% of our construction contract revenue from the United States Government in each of the years set forth on the consolidated statements of operations.

	In addition, we derived large concentrations of our total revenue from real estate operations (defined as the sum of rental revenue and tenant recoveries and other real estate operations revenue) from certain geographic regions. These concentrations are set forth in the segment information provided in Note 18. Several of these regions, including the Baltimore/Washington Corridor, Northern Virginia, Washington, DC - Capitol Riverfront, St. Mary’s & King George Counties and Greater Baltimore, Maryland (“Greater Baltimore”), are within close proximity to each other, and all but three of our regions with real estate operations (San Antonio, Huntsville, Alabama (“Huntsville”) and Colorado Springs) are located in the Mid-Atlantic region of the United States.

Properties_net

Properties, net	12 Months Ended
	Dec. 31, 2013
Real Estate [Abstract]	'
Properties, net	'
	Properties, net

	Operating properties, net consisted of the following (in thousands):


		December 31,
		2013				2012
	Land	$	430,472			$	427,766

	Buildings and improvements	2,869,870				2,725,875

	Less: accumulated depreciation	(597,649		)		(555,975		)
	Operating properties, net	$	2,702,693			$	2,597,666


	Projects we had in development or held for future development consisted of the following (in thousands):


		December 31,
		2013				2012
	Land	$	245,676			$	236,324

	Construction in progress, excluding land	265,932				329,054

	Projects in development or held for future development	$	511,608			$	565,378


	2013 Dispositions

	In April 2011, we completed a review of our portfolio and identified a number of properties that are no longer closely aligned with our strategy, and our Board of Trustees approved a plan by Management to dispose of some of these properties (the “Strategic Reallocation Plan”). In December 2011, we identified additional properties for disposal, and our Board of Trustees approved a plan by management to increase the scope of the Strategic Reallocation Plan to include the disposition of additional properties. We completed dispositions of the following properties in 2013 primarily in connection with the Strategic Reallocation Plan (dollars in thousands):


	Project Name		Location		Date of Sale		Number of Buildings			Total Rentable Square Feet		Transaction Value			Gain on Disposition
	920 Elkridge Landing Road		Linthicum, MD		6/25/13		1			103,000		$	6,900		$	—

	4230 Forbes Boulevard		Lanham, MD		12/11/13		1			56,000		5,600			1,507

	December 2013 Colorado Springs Portfolio Disposition		Colorado Springs, CO		12/12/13		15			1,165,000		133,925			1,164

	December 2013 Portfolio Conveyance		Colorado Springs, CO and Linthicum, MD		12/23/13		14			1,021,000		146,876			—

							31			2,345,000		$	293,301		$	2,671


	Each of the above dispositions represents property sales except for the December 2013 Portfolio Conveyance, the disposition of which was completed in connection with a debt extinguishment, as described further below. We also had a disposition of a non-operating property in 2013 for an aggregate transaction value of $3.5 million. In addition to the gains on dispositions reflected above, we also recognized impairment losses on certain of these sales that are disclosed in Note 3.

	On December 23, 2013, the mortgage lender on a $146.5 million nonrecourse mortgage loan that was secured by the December 2013 Portfolio Conveyance accepted a deed in lieu of foreclosure on the properties. As a result, we transferred title to the properties to the mortgage lender and we were relieved of the debt obligation plus accrued interest. As of the transfer date, the property had an estimated fair value of $74 million. Upon completion of this transfer, we recognized a gain on extinguishment of debt of $67.8 million, representing the difference between the mortgage loan and interest payable extinguished over the carrying value of the property transferred as of the transfer date (which included the effect of previous impairment losses) and related closing costs.

	2013 Construction Activities

	During 2013, we placed into service an aggregate of 812,000 square feet in eight newly constructed office properties located in the Baltimore/Washington Corridor, Northern Virginia and Huntsville. As of December 31, 2013, we had seven 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 three in Northern Virginia, two in the Baltimore/Washington Corridor, one in Huntsville and one in San Antonio. We also had redevelopment underway, or otherwise approved, for three office properties that we estimate will total 376,000 square feet upon completion, including two in Greater Philadelphia and one in the Baltimore/Washington Corridor.

	2012 Dispositions

	We completed dispositions of the following properties in 2012 primarily in connection with the Strategic Reallocation Plan (dollars in thousands):


	Project Name		Location		Date of Sale		Number of Buildings			Total Rentable Square Feet		Transaction Value			Gain on Disposition
	White Marsh Portfolio Disposition		White Marsh, MD		1/30/12		5			163,000		$	19,100		$	2,445

	1101 Sentry Gateway		San Antonio, TX		1/31/12		1			95,000		13,500			1,739

	222 and 224 Schilling Circle		Hunt Valley, MD		2/10/12		2			56,000		4,400			102

15 and 45 West Gude Drive		Rockville, MD		5/2/12		2			231,000		49,107			—

11800 Tech Road		Silver Spring, MD		6/14/12		1			240,000		21,300			—

400 Professional Drive		Gaithersburg, MD		7/2/12		1			130,000		16,198			—

July 2012 Portfolio Disposition		Baltimore/Washington Corridor and Greater Baltimore		7/24/12		23			1,387,000		161,901			16,900

						35			2,302,000		$	285,506		$	21,186


Each of the above dispositions represents property sales except for 400 Professional Drive, the disposition of which was completed in connection with a debt extinguishment, as described further below. We also had dispositions of non-operating properties in 2012 for aggregate transaction values totaling $28.1 million. In addition to the gains on dispositions reflected above, we also recognized impairment losses on certain of these sales that are disclosed in Note 3.

On July 2, 2012, the mortgage lender on a $15 million nonrecourse mortgage loan that was secured by our 400 Professional Drive property accepted a deed in lieu of foreclosure on the property. As a result, we transferred title to the property to the mortgage lender and we were relieved of the debt obligation plus accrued interest. As of the transfer date, the property had an estimated fair value of $11 million. Upon completion of this transfer, we recognized a gain on extinguishment of debt of $3.7 million, representing the difference between the mortgage loan and interest payable extinguished over the carrying value of the property transferred as of the transfer date (which included the effect of previous impairment losses) and related closing costs.

2012 Acquisition

On July 11, 2012, we acquired 13857 McLearen Road, a 202,000 square foot office property in Herndon, Virginia that was 100% leased, for $48.3 million. The table below sets forth the allocation of the acquisition costs of this property (in thousands):



Land, operating properties		$	3,507

Building and improvements		30,177

Intangible assets on real estate acquisitions		14,993

Total assets		48,677

Below-market leases		(369		)
Total acquisition cost		$	48,308


Intangible assets recorded in connection with the above acquisition included the following (dollars in thousands):


					Weighted Average Amortization Period (in Years)
Tenant relationship value	$	7,472			10

In-place lease value	7,109				5

Above-market leases	412				5

	$	14,993			7


We expensed $229,000 in operating property acquisition costs in 2012 that are included in business development expenses and land carry costs on our consolidated statements of operations.

2012 Construction Activities

During 2012, we placed into service an aggregate of 371,000 square feet in four newly constructed office properties, including two properties in the Baltimore/Washington Corridor, one in Greater Baltimore and one in Northern Virginia.

Real_Estate_Joint_Ventures

Real Estate Joint Ventures	12 Months Ended
Real Estate Joint Ventures	Dec. 31, 2013
Equity Method Investments and Joint Ventures [Abstract]	'
Real Estate Joint Ventures	'
	Real Estate Joint Ventures

	Consolidated Real Estate Joint Ventures

	The table below sets forth information pertaining to our investments in consolidated real estate joint ventures as of December 31, 2013 (dollars in thousands):


				Nominal
				Ownership			31-Dec-13						-1
		Date		% as of			Total				Encumbered		Total
		Acquired		12/31/13	Nature of Activity		Assets				Assets		Liabilities
	LW Redstone Company, LLC	3/23/10		85%	Operates three buildings and developing others (2)		$	132,170			$	67,487	$	39,845
	LW Redstone Company, LLC	3/23/10		85%	Operates three buildings and developing others (2)		$	132,170			$	67,487	$	39,845
	M Square Associates, LLC	6/26/07		50%	Operates two buildings and developing others (3)		60,919				48,705		41,009
	M Square Associates, LLC	6/26/07		50%	Operates two buildings and developing others (3)		60,919				48,705		41,009
	COPT-FD Indian Head, LLC	10/23/06		75%	Holding land parcel (4)		6,436				—		—
	COPT-FD Indian Head, LLC	10/23/06		75%	Holding land parcel (4)		6,436				—		—
							$	199,525			$	116,192	$	80,854
							$	199,525			$	116,192	$	80,854
	(1) Excludes amounts eliminated in consolidation.
	(2) This joint venture’s property is in Huntsville, Alabama.
	(3) This joint venture’s properties are in College Park, Maryland (in the Baltimore/Washington Corridor).
	(4) This joint venture’s property is in Charles County, Maryland. In 2012, the joint venture exercised its option under a development agreement to require Charles County to repurchase the land parcel at its original acquisition cost. Under the terms of the agreement with Charles County, the repurchase is expected to occur by August 2014.

	With regard to our consolidated joint ventures:


	•	For LW Redstone, LLC, we anticipate funding certain infrastructure costs (up to a maximum of $76.0 million) that we expect will be reimbursed by the City of Huntsville; as of December 31, 2013, we had advanced $44.1 million to the City to fund such costs (included in mortgage and other investing receivables on our consolidated balance sheets, and including accrued interest thereon). We also expect to fund additional development and construction costs through equity contributions to the extent that third party financing is not obtained. Our partner was credited with a $9.0 million capital account upon formation and is not required to make any future equity contributions. While net cash flow distributions to the partners vary depending on the source of the funds distributed, cash flows are generally distributed as follows:

	•	cumulative preferred returns on capital invested to fund the project’s infrastructure costs on a pro rata basis to us and our partner;

	•	cumulative preferred returns on our capital invested to fund the project’s vertical construction;

	•	return of our invested capital;

	•	return of our partner’s capital;

	•	any remaining residual 85% to us and 15% to our partner.
	Our partner has the right to require us to acquire its interest for fair value beginning in March 2020; accordingly, we classify the fair value of our partner’s interest as redeemable noncontrolling interests in the mezzanine section of our consolidated balance sheet. Disclosure regarding activity for this redeemable noncontrolling interest is included in Note 13. We have the right to purchase our partner’s interest at fair value upon the earlier of five years following the project’s achievement of a construction commencement threshold of 4.4 million square feet or March 2040.

	•	For M Square Associates, LLC, net cash flows of this entity will be distributed to the partners as follows: (1) member loans and accrued interest; (2) our preferred return and capital contributions used to fund infrastructure costs; (3) the partners’ preferred returns and capital contributions used to fund all other costs, including the base land value credit, in proportion to the accrued returns and capital accounts; and (4) residual amounts distributed 50% to each member.

	•	For COPT-FD Indian Head, LLC, net cash flows will be distributed to the partners in proportion to their respective ownership interests.

	The ventures discussed above include only ones in which parties other than COPLP and COPT own interests. During the periods included herein, we also owned investments in the following consolidated real estate joint ventures:


	•	Arundel Preserve #5, LLC, a joint venture owning property in Hanover Maryland (in the Baltimore/Washington Corridor) and in which we had a 50% nominal ownership interest. On September 17, 2013, we acquired our partner’s noncontrolling interest, along with incremental additional land value in the venture, in exchange for 221,501 common units in COPLP valued at $5.2 million; and

	•	MOR Forbes 2 LLC, a joint venture owning property in Lanham, Maryland (in the Baltimore/Washington Corridor) and in which we had a 50% nominal ownership interest. On December 11, 2013, the joint venture sold the property, after which the proceeds were distributed to the partners and there was substantially no remaining business operations or property.

	We consolidate the real estate joint ventures described above because we have: (1) the power to direct the matters that most significantly impact the activities of the joint ventures, including development, leasing and management of the properties constructed by the VIEs; and (2) the right to receive returns on our fundings and, in many cases, the obligation to fund the activities of the ventures to the extent that third-party financing is not obtained, both of which could be potentially significant to the VIEs.

	Our commitments and contingencies pertaining to our real estate joint ventures are disclosed in Note 23.

	Unconsolidated Real Estate Joint Venture

	During the periods included herein, we had a 20% ownership interest in an unconsolidated real estate joint venture that operated 16 operating properties, and in which we had a negative investment balance of $6.4 million as of December 31, 2012. We historically accounted for the investment in the joint venture using the equity method of accounting primarily because: (1) we shared with our partner the power to direct the matters that most significantly impact the activities of the joint venture, including the management and operations of the properties and disposal rights with respect to such properties; and (2) our partner had the right to receive benefits and absorb losses that could be significant to the VIE through its proportionately larger investment. We deferred gain in a prior period on our initial contribution of property to the joint venture due to certain guarantees described in Note 23, and we subsequently recognized losses in excess of our investment due to such guarantees and our intent to support the joint venture. During the fourth quarter of 2012, the holder of the mortgage debt notified us of the debt’s default, initiated foreclosure proceedings and terminated responsibility that we carried for management of the properties; accordingly, we discontinued recognition of losses on this investment under the equity method effective in October 2012 due to our having neither the obligation nor intent to support the joint venture. The carrying amount of our investment in this joint venture was lower than our share of the equity in the joint venture by $4.5 million as of December 31, 2012 due to our deferral of gain on the contribution by us of real estate into the joint venture upon its formation and our discontinuance of loss recognition under the equity method effective October 2012.

	On December 6, 2013, the holder of mortgage debt encumbering all of the joint venture’s properties foreclosed on the properties. As a result, title to the properties was transferred to the mortgage lender and the joint venture was relieved of the debt obligation. The joint venture still had $5.6 million in nonrecourse mezzanine debt as of December 31, 2013; however, the joint venture no longer holds any property or other assets and has ceased all business operations. We continue to be subject to standard nonrecourse loan guarantees relating to this joint venture that are described further in Note 23; however, we assessed the nature of these guarantees and determined that the likelihood of us incurring any liability from these guarantees was remote. Therefore, we recognized a gain on the substantive disposition of our investment in the joint venture in 2013 of $6.3 million, which is included in the line entitled “gain on sales of real estate, net of income taxes” on our consolidated statements of operations.

	Under the terms of the agreements governing the joint venture, net cash flows were to be distributed to the partners in proportion to their respective ownership interests. We did not recognize fees from the joint venture for property management, construction and leasing services we provided in 2012 and 2011.

The following table sets forth condensed balance sheets for this unconsolidated real estate joint venture as of December 31, 2012 (in thousands):


		December 31,
		2012
Properties, net		$	58,460
Properties, net		$	58,460
Other assets		4,376
Other assets		4,376
Total assets		$	62,836
Total assets		$	62,836

Liabilities (primarily debt)		$	72,693
Liabilities (primarily debt)		$	72,693
Owners’ equity		(9,857		)
Total liabilities and owners’ equity		$	62,836
Total liabilities and owners’ equity		$	62,836

The following table sets forth condensed statements of operations for this unconsolidated real estate joint venture (in thousands):


		For the Years Ended December 31,
		2013			2012				2011
Revenues		$	6,519		$	7,316			$	7,577
Revenues		$	6,519		$	7,316			$	7,577
Property operating expenses		(2,818		)	(2,829		)		(3,673		)
Interest expense		(10,463		)	(7,672		)		(3,913		)
Depreciation and amortization expense		(2,067		)	(2,283		)		(2,463		)
Gain on early extinguishment of debt		23,013			—				—
Gain on early extinguishment of debt		23,013			—				—
Net income (loss)		$	14,184		$	(5,468	)		$	(2,472	)
Net income (loss)		$	14,184		$	(5,468	)		$	(2,472	)

Intangible_Assets_on_Real_Esta

Intangible Assets on Real Estate Acquisitions	12 Months Ended
	Dec. 31, 2013
Intangible Assets on Real Estate Acquisitions	'
Intangible Assets on Real Estate Acquisitions	'
	Intangible Assets on Real Estate Acquisitions

	Intangible assets on real estate acquisitions consisted of the following (in thousands):


		December 31, 2013						31-Dec-12
		Gross Carrying Amount		Accumulated Amortization		Net		Gross Carrying Amount		Accumulated Amortization		Net
						Carrying Amount						Carrying Amount
	In-place lease value	$	125,504	$	93,885	$	31,619	$	134,964	$	93,362	$	41,602

	Tenant relationship value	44,414		25,962		18,452		46,828		23,346		23,482

	Below-market cost arrangements	12,416		5,136		7,280		12,416		4,100		8,316

	Above-market leases	8,925		7,970		955		8,925		7,432		1,493

	Market concentration premium	1,333		381		952		1,333		347		986

		$	192,592	$	133,334	$	59,258	$	204,466	$	128,587	$	75,879


	Amortization of the intangible asset categories set forth above totaled: $16.2 million in 2013; $21.4 million in 2012; and $28.3 million in 2011. The approximate weighted average amortization periods of the categories set forth above follow: in-place lease value: six years; tenant relationship value: seven years; below-market cost arrangements: 29 years; above-market leases: three years; and market concentration premium: 29 years. The approximate weighted average amortization period for all of the categories combined is 10 years. Estimated amortization expense associated with the intangible asset categories set forth above for the next five years is: $12.2 million for 2014; $9.9 million for 2015; $8.9 million for 2016; $6.7 million for 2017; and $4.2 million for 2018.

Deferred_Leasing_and_Financing

Deferred Leasing and Financing Costs	12 Months Ended
	Dec. 31, 2013
Deferred Leasing and Financing Costs [Abstract]	'
Deferred Leasing and Financing Costs	'
	Deferred Leasing and Financing Costs
	Deferred leasing and financing costs, net consisted of the following (in thousands):


		December 31,
		2013			2012
	Deferred leasing costs	$	110,711		$	97,852

	Deferred financing costs	36,390			30,520

	Accumulated amortization	(80,834		)	(68,420		)
	Deferred leasing and financing costs, net	$	66,267		$	59,952

Mortgage_and_Other_Investing_R

Mortgage and Other Investing Receivable (Notes)	12 Months Ended
	Dec. 31, 2013
Receivables [Abstract]	'
Mortgage and Other Investing Receivables	'
	Mortgage and Other Investing Receivables

	Mortgage and other investing receivables, including accrued interest thereon, consisted of the following (in thousands):



		December 31,
		2013		2012
	Notes receivable from City of Huntsville	$	44,055	$	35,654

	Mortgage loans receivable	9,608		144

		$	53,663	$	35,798


	Our notes receivable from the City of Huntsville funded infrastructure costs in connection with our LW Redstone Company, LLC joint venture (see Note 6). As of December 31, 2013, our mortgage loans receivable reflected above consisted of one loan secured by a property in Greater Baltimore. We did not have an allowance for credit losses in connection with our mortgage and other investing receivables as of December 31, 2013 or December 31, 2012. The fair value of these receivables approximated their carrying amounts as of December 31, 2013 and December 31, 2012.

Prepaid_Expenses_and_Other_Ass

Prepaid Expenses and Other Assets	12 Months Ended
	Dec. 31, 2013
Prepaid Expense and Other Assets [Abstract]	'
Prepaid Expenses and Other Assets	'
	Prepaid Expenses and Other Assets

	Prepaid expenses and other assets consisted of the following (in thousands):



		December 31,
		2013		2012
	Prepaid expenses	$	19,308	$	19,270

	Lease incentives	8,435		5,578

	Interest rate derivatives	6,594		—

	Furniture, fixtures and equipment, net	6,556		7,991

	Deferred tax asset, net (1)	4,305		6,612

	Construction contract costs incurred in excess of billings	2,462		—

	Other equity method investments	2,258		2,425

	Other assets	4,268		2,183

	Prepaid expenses and other assets	$	54,186	$	44,059



	(1) See Note 19 for further disclosure.

	Other assets, as reported above, include operating notes receivable due from tenants with terms exceeding one year totaling $1.7 million as of December 31, 2013 and $271,000 as of December 31, 2012; we carried allowances for estimated losses for $87,000 of the December 31, 2013 balance and most of the December 31, 2012 balance.

Debt

Debt	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Debt	'
	Debt

	Debt Summary

	Our debt consisted of the following (dollars in thousands):


		Maximum
		Availability at				Carrying Value at							Scheduled Maturity
		December 31,				December 31,			December 31,			Stated Interest Rates at	as of
		2013				2013			2012			December 31, 2013	December 31, 2013
	Mortgage and Other Secured Loans:

	Fixed rate mortgage loans (1)	-2				$	675,060		$	948,414		3.96% - 7.87% (3)	2014-2024

	Variable rate secured loan					37,691			38,475			LIBOR + 2.25% (4)	Nov-15

	Other construction loan facilities					—			29,557			N/A	N/A

	Total mortgage and other secured loans					712,751			1,016,446

	Revolving Credit Facility (5)	$	800,000			—			—			LIBOR + 0.975% to 1.75%	Jul-17

	Term Loan Facilities (5)	-6				620,000			770,000			LIBOR + 1.10% to 2.60% (7)	2015-2019

	Unsecured Senior Notes (5)
	3.600% Senior Notes					347,244			—			3.60%	May-23

	5.250% Senior Notes					245,445			—			5.25%	Feb-24

	Unsecured notes payable					1,700			1,788			0% (8)	2026

	4.25% Exchangeable Senior Notes (5)					563			230,934			4.25%	Apr-30

	Total debt					$	1,927,703		$	2,019,168



	(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 $69,000 at December 31, 2013 and $1.3 million at December 31, 2012.

	-2	Includes $13.9 million balance on construction loans with maximum available borrowings of $26.2 million.

	-3	The weighted average interest rate on these loans was 6.14% at December 31, 2013.

	(4)	The interest rate on the loan outstanding was 2.42% at December 31, 2013.

	-5	Refer to the paragraphs below for further disclosure.

	(6)	As discussed below, we have the ability to borrow an aggregate of an additional $180.0 million under these term loan facilities, provided that there is no default under the facilities and subject to the approval of the lenders.

	(7)	The weighted average interest rate on these loans was 1.79% at December 31, 2013.

	(8)	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 $761,000 at December 31, 2013 and $873,000 at December 31, 2012.

	All debt is owed by the Operating Partnership. While COPT is not directly obligated by any debt, it has guaranteed our Revolving Credit Facility, Term Loan Facilities, Unsecured Senior Notes and 4.25% Exchangeable Senior Notes.

	Certain of our debt instruments require that we comply with a number of restrictive financial covenants, including maximum leverage ratio, unencumbered leverage ratio, minimum net worth, minimum fixed charge coverage, minimum unencumbered interest coverage ratio, minimum debt service and maximum secured indebtedness ratio. In addition, the terms of some of COPLP’s debt may limit its ability to make certain types of payments and other distributions to COPT in the event of default or when such payments or distributions may prompt failure of debt covenants. As of December 31, 2013, we were within the compliance requirements of these financial covenants.

	Our debt matures on the following schedule (in thousands):


	2014	$	89,483

2015	395,969			-1

2016	279,339

2017	405,615			-2

2018	1,374

Thereafter	763,938

Total	$	1,935,718		-3

(1) Includes $250.0 million that may be extended for two one-year periods at our option, subject to certain conditions.
(2) Includes $250.0 million that may be extended for one year at our option, subject to certain conditions.
(3) Represents scheduled principal amortization and maturities only and therefore excludes net discounts of $8.0 million.

We capitalized interest costs of $8.8 million in 2013, $13.9 million in 2012 and $17.4 million in 2011.

The following table sets forth information pertaining to the fair value of our debt (in thousands):


	December 31, 2013							31-Dec-12
	Carrying				Estimated			Carrying			Estimated
	Amount				Fair Value			Amount			Fair Value
Fixed-rate debt

Unsecured Senior Notes	$	592,689			$	575,374		$	—		$	—

4.25% Exchangeable Senior Notes	563				575			230,934			240,282

Other fixed-rate debt	676,760				650,997			950,202			968,180

Variable-rate debt	657,691				657,527			838,032			845,558

	$	1,927,703			$	1,884,473		$	2,019,168		$	2,054,020


Revolving Credit Facility

In 2011, we entered into a credit agreement providing for an unsecured revolving credit facility (the “Revolving Credit Facility”) with a group of lenders for which J.P. Morgan Securities LLC and KeyBanc Capital Markets acted as join lead arrangers and joint book runners, KeyBank National Association acted as administrative agent and JPMorgan Chase Bank, N.A. and Bank of America, N.A. acted as co-syndication agents. We subsequently amended the Revolving Credit Facility on July 16, 2013. The lenders’ aggregate commitment under the facility is $800.0 million, with the ability for us to increase the lenders’ aggregate commitment to $1.3 billion, provided that there is no default under the facility and subject to the approval of the lenders. Amounts available under the facility are computed based on 60% of our unencumbered asset value, as defined in the agreement. The facility matures on July 1, 2017, and may be extended by one year at our option, provided that there is no default under the facility and we pay an extension fee of 0.15% of the total availability under the facility. The interest rate on the facility is based on LIBOR (customarily the 30-day rate) plus 0.975% to 1.750%, as determined by the credit ratings assigned to COPLP by Standard & Poor’s Rating Services, Moody’s Investor Services, Inc. or Fitch Ratings Ltd. (collectively, the “Ratings Agencies”). The facility also carries a quarterly fee that is based on the lenders’ aggregate commitment under the facility multiplied by a per annum rate of 0.125% to 0.350%, as determined by the credit ratings assigned to COPLP by the Ratings Agencies. As of December 31, 2013, the maximum borrowing capacity under this facility totaled $800.0 million, of which $784.6 million was available.

Weighted average borrowings under our Revolving Credit Facilities totaled $55.5 million in 2013 and $276.5 million in 2012. The weighted average interest rate on our Revolving Credit Facilities was 1.74% in 2013 and 2.27% in 2012.

Term Loan Facilities

Effective September 1, 2011, we entered into an unsecured term loan agreement with the same group of lenders as the Revolving Credit Facility under which we borrowed $400.0 million, with a right for us to borrow an additional $100.0 million, provided that there is no default under the agreement and subject to the approval of the lenders. In 2013, we amended this term loan and terminated all but $250.0 million of the loan balance. The term loan matures on September 1, 2015, and may be extended by two one-year periods at our option, provided that there is no default and we pay an extension fee of 0.15% of the total availability of the agreement. The variable interest rate on the term loan is based on LIBOR rate (customarily the 30-day rate) plus 1.10% to 2.00%, as determined by the credit ratings assigned to COPLP by the Ratings Agencies.

Effective February 14, 2012, we entered into an unsecured term loan agreement with a group of lenders for which J.P. Morgan Securities LLC and KeyBank Capital Markets 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. We borrowed $250.0 million under the term loan. In 2013, we amended this term loan. The term loan matures on February 14, 2017, and may be extended by one year at our option, provided that there is no default and we pay an extension fee of 0.15% of the total availability of the agreement. The variable interest rate on the loan is based on the LIBOR rate (customarily the 30-day rate) plus 1.10% to 2.00%, as determined by the credit ratings assigned to COPLP by the Ratings Agencies.

Effective August 3, 2012, we entered into an unsecured term loan agreement with a group of lenders for which Wells Fargo Securities, LLC acted as sole arranger and sole book runner, Wells Fargo Bank, National Association acted as administrative agent and Capital One, N.A. acted as documentation agent. We borrowed $120.0 million under the term loan, with the ability for us to borrow an additional $80.0 million, provided that there is no default under the loan and subject to the approval of the lenders. The term loan matures on August 2, 2019. The variable interest rate on the loan is based on the LIBOR rate (customarily the 30-day rate) plus 2.10% to 2.60%, as determined by our leverage levels.

Unsecured Senior Notes

In 2013, we issued the following senior notes:


•	a $350.0 million aggregate principal amount of 3.600% Senior Notes at an initial offering price of 99.816% of their face value on May 6, 2013, resulting in proceeds, after deducting discounts of the initial purchasers of the notes, but before other offering expenses, of $347.1 million. The notes mature on May 15, 2023. The carrying value of these notes reflects an unamortized discount totaling $2.8 million at December 31, 2013. The effective interest rate under the notes, including amortization of the issuance costs, was 3.70%; and

•	a $250.0 million aggregate principal amount of 5.250% Senior Notes at an initial offering price of 98.783% of their face value on September 16, 2013, resulting in proceeds, after deducting underwriting discounts, but before other offering expenses, of $245.3 million. The notes mature on February 15, 2024. The carrying value of these notes reflects an unamortized discount totaling $4.6 million at December 31, 2013. The effective interest rate under the notes, including amortization of the issuance costs, was 5.49%.

We may redeem these 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 a spread (30 basis points for the 3.600% Senior Notes and 40 basis points for the 5.250% Senior Notes), plus, in each case, accrued and unpaid interest thereon to the date of redemption. However, in each case, 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 applicable redemption date. These notes are unconditionally guaranteed by COPT.

Exchangeable Senior Notes

In 2010, COPLP issued a $240.0 million aggregate principal amount of 4.25% Exchangeable Senior Notes due 2030. In 2013, we repaid $239.4 million principal amount of these notes and recognized a $25.9 million loss on early extinguishment of debt. The carrying value of these notes included a principal amount of $575,000 and an unamortized discount totaling $12,000 as of December 31, 2013 and a principal amount of $240.0 million and an unamortized discount totaling $9.1 million as of December 31, 2012. Interest on the notes is payable on April 15 and October 15 of each year. These notes have an exchange settlement feature that provides that the notes may, under certain circumstances, be exchangeable for cash and, at COPLP’s discretion, COPT common shares at an exchange rate (subject to adjustment) of 20.8513 shares per one thousand dollar principal amount of the notes (exchange rate is as of December 31, 2013 and is equivalent to an exchange price of $47.96 per common share) (the initial exchange rate of the notes was based on a 20% premium over the closing price on the NYSE on the transaction pricing date). On or after April 20, 2015, COPLP may redeem the notes in cash in whole or in part. The holders of the notes have the right to require us to repurchase the notes in cash in whole or in part on each of April 15, 2015, April 15, 2020 and April 15, 2025, or in the event of a “fundamental change,” as defined under the terms of the notes, for a repurchase price equal to 100% of the principal amount of the notes plus accrued and unpaid interest. The notes are general unsecured senior obligations of COPLP and rank equally in right of payment with all other senior unsecured indebtedness of COPLP and are guaranteed by COPT. The effective interest rate under the notes, including amortization of the issuance costs, was 6.05%. Because the closing price of COPT’s common shares at December 31, 2013 and 2012 was less than the exchange price per common share applicable to these notes, the if-converted value of the notes did not exceed the principal amount. The table below sets forth interest expense recognized on these notes (in thousands):


	For the Years Ended December 31,
	2013				2012			2011
Interest expense at stated interest rate	$	4,208			$	10,200		$	10,200

Interest expense associated with amortization of discount	1,615				3,651			3,437

Total	$	5,823			$	13,851		$	13,637


Until September 15, 2011, COPLP had $162.5 million aggregate principal amount of 3.50% Exchangeable Senior Notes due 2026. These notes had an exchange settlement feature that provided that the notes were, under certain circumstances, exchangeable for cash (up to the principal amount of the notes) and, with respect to any excess exchange value, were exchangeable into (at our option) cash, our common shares or a combination of cash and our common shares. On September 15, 2011, we repurchased these notes at 100% of the principal amount of $162.5 million after the holders of such notes surrendered them for repurchase pursuant to the terms of the notes and the related Indenture. The effective interest rate under the notes, including amortization of the issuance costs, was 5.97%. Because the closing price of COPT’s common shares at December 31, 2011 was less than the exchange price per common share applicable to these notes, the if-converted value of the notes did not exceed the principal amount. The table below sets forth interest expense recognized on these notes for 2011:


Interest expense at stated interest rate		$	4,013

Interest expense associated with amortization of discount		2,617

Total		$	6,630

Interest_Rate_Derivatives

Interest Rate Derivatives	12 Months Ended
	Dec. 31, 2013
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									Effective		Expiration		December 31,
	Amount				Fixed Rate			Floating Rate Index		Date		Date		2013			2012
	$	100,000			0.6123	%		One-Month LIBOR		1/3/12		9/1/14		$	(279	)	$	(594	)

	100,000				0.61	%		One-Month LIBOR		1/3/12		9/1/14		(277		)	(591		)

	100,000				0.832	%		One-Month LIBOR		1/3/12		9/1/15		(861		)	(1,313		)

	100,000				0.832	%		One-Month LIBOR		1/3/12		9/1/15		(861		)	(1,313		)

	37,691			-1	3.83	%		One-Month LIBOR + 2.25%		11/2/10		11/2/15		(832		)	(1,268		)

	100,000				0.8055	%		One-Month LIBOR		9/2/14		9/1/16		(94		)	(263		)

	100,000				0.81	%		One-Month LIBOR		9/2/14		9/1/16		(105		)	(272		)

	100,000				1.673	%		One-Month LIBOR		9/1/15		8/1/19		3,377			(154		)

	100,000				1.73	%		One-Month LIBOR		9/1/15		8/1/19		3,217			(417		)

														$	3,285		$	(6,185	)



	-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):


			December 31, 2013						December 31, 2012
	Derivatives		Balance Sheet Location		Fair Value				Balance Sheet Location		Fair Value
	Interest rate swaps designated as cash flow hedges		Prepaid expenses and other assets		$	6,594			Prepaid expenses and other assets		$	—

	Interest rate swaps designated as cash flow hedges		Interest rate derivatives		(3,309		)		Interest rate derivatives		(6,185		)

	The table below presents the effect of our interest rate derivatives on our consolidated statements of operations and comprehensive income (in thousands):


		For the Years Ended December 31,
		2013				2012				2011
	Amount of gains (losses) recognized in accumulated other comprehensive income (loss) (“AOCI”) (effective portion)	$	6,791			$	(7,676	)		$	(31,531	)

	Amount of losses reclassified from AOCI into interest expense (effective portion)	(2,740		)		(3,697		)		(4,601		)
	Amount of loss reclassified from AOCI to loss on interest rate derivatives upon discontinuing hedge accounting	—				—				28,430

	Amount of loss on interest rate derivatives recognized subsequent to such derivatives no longer being designated as hedges	—				—				1,375


	Over the next 12 months, we estimate that approximately $2.7 million will be reclassified from AOCI 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 any 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 December 31, 2013, the fair value of interest rate derivatives in a liability position related to these agreements was $3.3 million, excluding the effects of accrued interest. As of December 31, 2013, 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 $3.6 million.

Redeemable_Noncontrolling_Inte

Redeemable Noncontrolling Interest	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interest [Abstract]	'
Redeemable Noncontrolling Interest	'
	Redeemable Noncontrolling Interest

	The table below sets forth activity in a redeemable noncontrolling interest in a consolidated real estate joint venture described in Note 6 (in thousands):


		For the Years Ended December 31,
		2013			2012			2011
	Beginning balance	$	10,298		$	8,908		$	9,000

	Distribution to noncontrolling interest	(1,037		)	—			—

	Net income (loss) attributable to noncontrolling interest	1,376			(2,565		)	(1,407		)

	Adjustment to arrive at fair value of interest	7,121			3,955			1,315

	Ending balance	$	17,758		$	10,298		$	8,908

Equity_COPT_and_Subsidiaries

Equity - COPT and Subsidiaries

12 Months Ended

Dec. 31, 2013

Stockholders' Equity Note [Abstract]

Equity - COPT and Subsidiaries

Preferred Shares

As of December 31, 2013, COPT had 25.0 million preferred shares authorized at $0.01 par value. The table below sets forth additional information pertaining to COPT’s outstanding preferred shares (dollars in thousands, except per share data):

Series

# of Shares Issued

Aggregate Liquidation Preference

Month of Issuance

Annual Dividend Yield

Annual Dividend Per Share

Earliest Redemption Date

Series H

2,000,000

50,000

Dec-03

7.5

1.875

12/18/08

Series K

531,667

26,583

Jan-07

5.6

2.8

1/9/17

Series L

6,900,000

172,500

Jun-12

7.375

1.84375

6/27/17

9,431,667

249,083

Each series of preferred shares is nonvoting and redeemable for cash in the amount of its liquidation preference at COPT’s option on or after the earliest redemption date. The Series K Cumulative Redeemable Preferred Shares are also convertible, subject to certain conditions, into common shares on the basis of 0.8163 common shares for each preferred share. Holders of all preferred shares are entitled to cumulative dividends, payable quarterly (as and if declared by the Board of Trustees). In the case of each series of preferred shares, there is a series of COPLP preferred units owned by COPT that carries substantially the same terms.

On June 27, 2012, COPT completed the public offering of 6.9 million Series L Cumulative Preferred Shares of beneficial interest (“Series L Preferred Shares”) at a price of $25.00 per share for net proceeds of $165.7 million after underwriting discounts but before offering expenses. COPT contributed the net proceeds from the sale to COPLP in exchange for 6.9 million Series L Preferred Units. The Series L Preferred Units carry terms that are substantially the same as the Series L Preferred Shares.

During 2012 and 2013, COPT redeemed all of the outstanding shares of its following series of preferred shares:

•

the 8% Series G Preferred Shares on August 6, 2012 at a price of $25.00 per share, or $55.0 million in the aggregate, plus accrued and unpaid dividends thereon through the date of redemption, and recognized a $1.8 million decrease to net income available to common shareholders pertaining to the shares’ original issuance costs at the time of the redemption.

•

the 7.625% Series J Preferred Shares on April 22, 2013 at a price of $25.00 per share, or $84.8 million in the aggregate, plus accrued and unpaid dividends thereon through the date of redemption, and recognized a $2.9 million decrease to net income available to common shareholders pertaining to the shares’ original issuance costs incurred at the time of the redemption.

Common Shares

During 2012 and 2013, COPT completed the following public offerings of common shares:

•

8.6 million common shares in October 2012 at a public offering price of $24.75 per share for net proceeds of $204.9 million after underwriter discounts but before offering expenses; and

•

4.485 million common shares in March 2013 at a public offering price of $26.34 per share for net proceeds of $118.1 million after underwriter discounts but before offering expenses.

COPT contributed the net proceeds from these issuances to COPLP in exchange for an equal number of units in COPLP.

In October 2012, COPT established an at-the-market (“ATM”) stock offering program under which it may, from time to time, offer and sell common shares in “at the market” stock offerings having an aggregate gross sales price of up to $150.0 million. On July 15, 2013, COPT issued 1.5 million common shares at a weighted average price of $26.05 per share under the ATM program; net proceeds from the shares issued totaled $38.5 million, after payment of $586,000 in commissions to sales agents. The proceeds from these shares were contributed to COPLP in exchange for an equal number of common units in COPLP. COPT’s remaining capacity under the ATM Plan is an aggregate gross sales price of $110.9 million in stock sales.

Holders of COPLP common units converted their units into COPT common shares on the basis of one common share for each common unit in the amount of 311,343 in 2013 and 234,246 in 2012.

COPT declared dividends per common share of $1.10 in 2013, $1.10 in 2012 and $1.65 in 2011.

See Note 16 for disclosure of common share activity pertaining to our share-based compensation plans.

Equity_COPLP_and_Subsidiaries

Equity - COPLP and Subsidiaries

12 Months Ended

Dec. 31, 2013

Class of Stock [Line Items]

Equity - COPLP and Subsidiaries

Equity - COPT and Subsidiaries

Preferred Shares

Series

# of Shares Issued

Aggregate Liquidation Preference

Month of Issuance

Annual Dividend Yield

Annual Dividend Per Share

Earliest Redemption Date

Series H

2,000,000

50,000

Dec-03

7.5

1.875

12/18/08

Series K

531,667

26,583

Jan-07

5.6

2.8

1/9/17

Series L

6,900,000

172,500

Jun-12

7.375

1.84375

6/27/17

9,431,667

249,083

During 2012 and 2013, COPT redeemed all of the outstanding shares of its following series of preferred shares:

•

Common Shares

During 2012 and 2013, COPT completed the following public offerings of common shares:

•

8.6 million common shares in October 2012 at a public offering price of $24.75 per share for net proceeds of $204.9 million after underwriter discounts but before offering expenses; and

•

4.485 million common shares in March 2013 at a public offering price of $26.34 per share for net proceeds of $118.1 million after underwriter discounts but before offering expenses.

COPT contributed the net proceeds from these issuances to COPLP in exchange for an equal number of units in COPLP.

Holders of COPLP common units converted their units into COPT common shares on the basis of one common share for each common unit in the amount of 311,343 in 2013 and 234,246 in 2012.

COPT declared dividends per common share of $1.10 in 2013, $1.10 in 2012 and $1.65 in 2011.

See Note 16 for disclosure of common share activity pertaining to our share-based compensation plans.

Corporate Office Properties, L.P.

Class of Stock [Line Items]

Equity - COPLP and Subsidiaries

General Partner Preferred Units

The table below sets forth information pertaining to preferred units in COPLP held by COPT at December 31, 2013 (dollars in thousands, except per unit data):

Series

# of Units Issued

Aggregate Liquidation Preference

Month of Issuance

Annual Distribution Yield

Annual Distribution Per Unit

Earliest Redemption Date

Series H

2,000,000

50,000

Dec-03

7.5

1.875

12/18/08

Series K

531,667

26,583

Jan-07

5.6

2.8

1/9/17

Series L

6,900,000

172,500

Jun-12

7.375

1.84375

6/27/17

9,431,667

249,083

In the case of each series of preferred units, COPT had preferred shares that carry substantially the same terms. Each series of preferred units are redeemable for cash in the amount of its liquidation preference at our option on or after the earliest redemption date. The Series K Preferred Units are also convertible, subject to certain conditions, into common units on the basis of 0.8163 common units for each preferred unit. COPT, as holder of these preferred units, is entitled to cumulative distributions, payable quarterly (as and if declared by the Board of Trustees).

On June 27, 2012, in connection with COPT’s public offering of 6.9 million Series L Preferred Shares at a price of $25.00 per share for net proceeds of $165.7 million after underwriting discounts but before offering expenses, COPT contributed the net proceeds from the sale to COPLP in exchange for 6.9 million Series L Preferred Units. The Series L Preferred Units carry terms that are substantially the same as the Series L Preferred Shares.

In 2012 and 2013, COPLP redeemed all of the outstanding units of its following series of preferred units held by COPT:

•

the 8% Series G Preferred Units on August 6, 2012 at a price of $25.00 per unit, or $55.0 million in the aggregate, plus accrued and unpaid distributions thereon through the date of redemption, and recognized a $1.8 million decrease to net income available to common unitholders pertaining to the units’ original issuance costs at the time of the redemption.

•

the 7.625% Series J Preferred Units on April 22, 2013 at a price of $25.00 per unit, or $84.8 million in the aggregate, plus accrued and unpaid distributions thereon through the date of redemption, and recognized a $2.9 million decrease to net income available to common unitholders pertaining to the units’ original issuance costs at the time of the redemption.

Limited Partner Preferred Units

COPLP has 352,000 Series I Preferred Units issued to an unrelated party that have an aggregate liquidation preference of $8.8 million ($25.00 per unit), plus any accrued and unpaid distributions of return thereon (as described below), and may be redeemed for cash by COPLP at COPLP’s option any time after September 22, 2019. The owner of these units is entitled to a priority annual cumulative return equal to 7.5% of their liquidation preference through September 22, 2019; the annual cumulative preferred return increases for each subsequent five-year period, subject to certain maximum limits. These units are convertible into common units on the basis of 0.5 common units for each Series I Preferred Unit; the resulting common units would then be exchangeable for COPT common shares in accordance with the terms of COPLP’s agreement of limited partnership.

Common Units

COPT owned 95.6% of COPLP’s common units as of December 31, 2013 and 95.2% as of December 31, 2012. Three of COPT’s trustees also controlled, either directly or through ownership by other entities or family members, an additional 3.4% of COPLP’s common units as of December 31, 2013.

During 2012 and 2013, COPT acquired additional common units through the following public offerings of common shares:

•

8.6 million common shares in October 2012 at a public offering price of $24.75 per share for net proceeds of $204.9 million (after underwriter discounts but before offering expenses) that were contributed to COPLP in exchange for an equal number of common units in COPLP; and

•

4.485 million common shares in March 2013 at a public offering price of $26.34 per share for net proceeds of $118.1 million (after underwriter discounts but before offering expenses) that were contributed to COPLP in exchange for an equal number of common units in COPLP.

On July 15, 2013, COPT issued 1.5 million common shares at a weighted average price of $26.05 per share, representing its first issuance under the ATM program. Net proceeds from the shares issued totaled $38.5 million, after payment of $586,000 in commissions to sales agents. The common shares were contributed to COPLP in exchange for 1.5 million common units.

Limited partners in COPLP holding common units have the right to require COPLP to redeem all or a portion of their common units. COPLP (or COPT as the general partner) has the right, in its sole discretion, to deliver to such redeeming limited partners for each partnership unit either one COPT common share (subject to anti-dilution adjustment) or a cash payment equal to the then fair market value of such share (so adjusted) (based on the formula for determining such value set forth in the partnership agreement). Limited partners holding common units redeemed their units into common shares on the basis of one common share for each common unit in the amount of 311,343 in 2013 and 234,246 in 2012.

We declared distributions per common unit of $1.10 in 2013, $1.10 in 2012 and $1.65 in 2011.

ShareBased_Compensation_and_Em

Share-Based Compensation and Employee Benefit Plans	12 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-Based Compensation and Employee Benefit Plans	'
	Share-Based Compensation and Employee Benefit Plans

	Share-Based Compensation Plans

	In May 2010, COPT adopted the Amended and Restated 2008 Omnibus Equity and Incentive Plan. COPT may issue equity-based awards under this plan to officers, employees, non-employee trustees and any other key persons of us and our subsidiaries, as defined in the plan. The plan provides for a maximum of 5,900,000 common shares in COPT to be issued in the form of options, share appreciation rights, deferred share awards, restricted share awards, unrestricted share awards, performance shares, dividend equivalent rights and other equity-based awards and for the granting of cash-based awards. The plan expires on May 13, 2020.

	In March 1998, COPT adopted a long-term incentive plan for our Trustees and employees. This plan, which expired in March 2008, provided for the award of options, restricted shares and dividend equivalents.

	Grants of restricted shares and options under these plans to nonemployee Trustees generally vest on the first anniversary of the grant date provided that the Trustee remains in his or her position. Restricted shares and options 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. Options expire ten years after the date of grant. Shares for each of the share-based compensation plans are issued under registration statements on Form S-8 that became effective upon filing with the Securities and Exchange Commission. In connection with awards of common shares granted by COPT under such share-based compensation plans, COPLP issues to COPT an equal number of equity instruments with identical terms.

	The following table summarizes restricted share transactions under the share-based compensation plans for 2011, 2012 and 2013:


			Shares			Weighted Average Grant Date Fair Value
	Unvested at December 31, 2010		669,858			$	32.77

	Granted		320,284			33.68

	Forfeited		(18,058	)		34.23

	Vested		(323,706	)		32.86

	Unvested at December 31, 2011		648,378			33.13

	Granted		177,662			23.64

	Forfeited		(17,019	)		31.43

	Vested		(374,378	)		32.72

	Unvested at December 31, 2012		434,643			29.67

	Granted		193,833			25.91

	Forfeited		(9,541	)		27.59

	Vested		(241,487	)		30.97

	Unvested at December 31, 2013		377,448			$	26.96

	Restricted shares expected to vest		361,064			$	27.02


	The aggregate intrinsic value of restricted shares that vested was $6.3 million in 2013, $9.0 million in 2012 and $11.2 million in 2011.

	Our Board of Trustees made the following grants of PSUs to executives:


	•	100,645 PSUs on March 4, 2010 (the “2010 PSU Grants”) with an aggregate grant date fair value of $5.4 million. Certain executives voluntarily cancelled 58,105 of these PSUs in 2011; we recognized a non-cash compensation charge of $1.2 million in 2011 in connection with these PSU cancellations. The remaining PSUs at December 31, 2011 were held by Mr. Randall M. Griffin, our former Chief Executive Officer, and were terminated upon his retirement on March 31, 2012; based on the COPT’s total shareholder return relative to its peer group of companies, there was no payout value in connection with the termination of the PSUs;

	•	56,883 PSUs on March 3, 2011 (the “2011 PSU Grants”) with an aggregate grant date fair value of $2.8 million which were all outstanding at December 31, 2013;

	•	54,070 PSUs on March 1, 2012 (the “2012 PSU Grants”) with an aggregate grant date fair value of $1.8 million which were all outstanding at December 31, 2013; and

	•	69,579 PSUs on March 1, 2013, (the “2013 PSU Grants”) with an aggregate grant date fair value of $1.9 million which were all outstanding at December 31, 2013.

	The PSUs have a performance period beginning on the respective grant dates and concluding on the earlier of three years from the respective grant dates 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 the COPT’s total shareholder return relative to a peer group of companies, as set forth in the following schedule:


	Percentile Rank		Earned PSUs Payout %
	75th or greater		200% of PSUs granted
	50th or greater		100% of PSUs granted
	25th		50% of PSUs granted
Below 25th		0% of PSUs granted

If the percentile rank exceeds the 25th percentile and is between two of the percentile ranks set forth in the table above, then the percentage of the earned PSUs will be interpolated between the ranges set forth in the table above to reflect any performance between the listed percentiles. At the end of the performance period, we, in settlement of the award, will issue a number of fully-vested COPT common shares equal to the sum of:


•	the number of earned PSUs in settlement of the award plan; plus

•	the aggregate dividends that would have been paid with respect to the common shares issued in settlement of the earned PSUs through the date of settlement had such shares been issued on the grant date, divided by the share price on such settlement date, as defined under the terms of the agreement.

If a performance period ends due to a sale event or qualified termination, the number of earned PSUs is prorated based on the portion of the three-year performance period that has elapsed. If employment is terminated by the employee or by us for cause, all PSUs are forfeited. PSUs do not carry voting rights.

We computed grant date fair values for PSUs using Monte Carlo models and are recognizing these values over three-year periods that commenced on the respective grant dates. The grant date fair value and certain of the assumptions used in the Monte Carlo models for the PSUs granted in 2011, 2012 and 2013 are set forth below:


		For the Years Ended December 31,
		2013				2012			2011
Grant date fair value		$	26.84			$	32.77		$	49.15

Baseline common share value		$	25.85			$	24.39		$	35.17

Expected volatility of common shares		29.5		%		43.2		%	61.1		%
Risk-free interest rate		0.33		%		0.41		%	1.32		%

The following table summarizes option transactions under the share-based compensation plans for 2011, 2012 and 2013 (dollars in thousands, except per share data):


		Shares			Range of Exercise Price per Share		Weighted Average Exercise Price per Share			Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
										(in Years)
Outstanding at December 31, 2010		1,188,284			$9.54 - $57.00		$	33.07		5		$	7,987

Forfeited/Expired – 2011		(51,598	)		$22.49 - $50.59		$	42.82

Exercised – 2011		(191,264	)		$9.54 - $30.25		$	12.82

Outstanding at December 31, 2011		945,422			$13.40 - $57.00		$	36.63		4		$	510

Forfeited/Expired – 2012		(85,588	)		$25.52 - $57.00		$	42.98

Exercised – 2012		(61,624	)		$13.40 - $22.49		$	15.08

Outstanding at December 31, 2012		798,210			$13.60 - $57.00		$	37.62		3		$	325

Forfeited/Expired – 2013		(117,952	)		$18.08 - $51.62		$	40.91

Exercised – 2013		(39,331	)		$13.60 - $26.24		$	19.67

Outstanding at December 31, 2013		640,927			$19.63 - $56.00		$	38.11		2		$	68

Exercisable at December 31, 2011		945,422			-1		$	36.63

Exercisable at December 31, 2012		798,210			-2		$	37.62

Exercisable at December 31, 2013		640,927			-3		$	38.11




-1	53,957 of these options had an exercise price ranging from $13.40 to $16.73; 225,903 had an exercise price ranging from $16.74 to $30.04; 198,762 had an exercise price ranging from $30.05 to $41.28; and 466,800 had an exercise price ranging from $41.29 to $57.00.

-2	9,500 of these options had an exercise price ranging from $13.60 to $16.73; 204,736 had an exercise price ranging from $16.74 to $30.04; 180,962 had an exercise price ranging from $30.05 to $41.28; and 403,012 had an exercise price ranging from $41.29 to $57.00.

-3	171,288 of these options had an exercise price ranging from $19.63 to $30.04; 145,187 had an exercise price ranging from$30.05 to $41.28; 160,402 had an exercise price ranging from $41.29 to $42.74; and 164,050 had an exercise price ranging from $42.75 to $56.00.

The aggregate intrinsic value of options exercised was $258,000 in 2013, $553,000 in 2012 and $4.0 million in 2011.

We own a taxable REIT subsidiary that is subject to Federal and state income taxes. We realized a windfall tax (loss) benefit of $(122,000) in 2013, $43,000 in 2012 and $47,000 in 2011 on options exercised and vesting restricted shares in connection with employees of that subsidiary.

The table below sets forth our reporting for share based compensation expense (in thousands):


		For the Years Ended December 31,
		2013				2012			2011
General, administrative and leasing expenses		$	5,412			$	8,611		$	9,077

Property operating expenses		1,118				1,371			2,843

Capitalized to development activities		1,075				1,202			2,347

Share-based compensation expense		$	7,605			$	11,184		$	14,267


The amounts included in our consolidated statements of operations for share-based compensation reflected an estimate of pre-vesting forfeitures of: 0% for all PSUs; 0% to 5% for restricted shares for 2013 and 2012; and 0% to 4% for restricted shares for 2011.

As of December 31, 2013, all of our options are vested and fully expensed. As of December 31, 2013, there was $6.1 million of unrecognized compensation cost related to unvested restricted shares that is expected to be recognized over a weighted average period of approximately two years. As of December 31, 2013, there was $2.1 million of unrecognized compensation cost related to PSUs that is expected to be recognized over a weighted average performance period of approximately two years.

401(k) Plan

We have a 401(k) defined contribution plan covering substantially all of our employees that permits participants to contribute up to 90% of their compensation, as defined in the Plan, per pay period on a before-tax basis or after-tax basis, or a combination of both, subject to limitations under the Internal Revenue Code of 1986 ( the “IRC”), as amended. Participants who are 50 years of age or older by the end of a particular plan year and have contributed the maximum 401(k) deferral amount allowed under the plan for that year are eligible to contribute an additional portion of their annual compensation on a before-tax basis as catch-up contributions, up to the annual limit under the IRC. We match 100% of the first 1% of pre-tax and/or after-tax contributions that participants contribute to the plan and 50% of the next 5% in participant contributions to the plan (representing an aggregate match by us of 3.5% on the first 6% of participant pre-tax and/or after-tax contributions to the plan). Participants’ contributions are fully vested. Participants are 50% vested in matching contributions after one year of credited service and 100% vested after two years of credited service. We fund all contributions with cash. In 2013, 2012 and 2011, our matching contributions under the plan totaled approximately $1.1 million each year. The 401(k) plan is fully funded as of December 31, 2013.

Deferred Compensation Plan

COPT has a non-qualified elective deferred compensation plan for certain members of our management team that permits participants to defer up to 100% of their compensation on a pre-tax basis and receive a tax-deferred return on such deferrals. The balance of the plan, which was fully funded, totaled $7.5 million as of December 31, 2013 and $6.8 million as of December 31, 2012, and is included in the accompanying COPT consolidated balance sheets.

Operating_Leases

Operating Leases	12 Months Ended
	Dec. 31, 2013
Leases, Operating [Abstract]	'
Operating Leases	'
	Operating Leases

	We lease our properties to tenants under operating leases with various expiration dates extending to the year 2030. Gross minimum future rentals on noncancelable leases in our properties as of December 31, 2013 were as follows (in thousands):


	Year Ending December 31,
	2014	$	344,809

	2015	310,035

	2016	256,228

	2017	213,894

	2018	163,011

	Thereafter	351,111

		$	1,639,088

Information_by_Business_Segmen

Information by Business Segment	12 Months Ended
	Dec. 31, 2013
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). We also have an operating wholesale data center segment. In 2013, we made the following revisions to our reportable segments: (1) commenced the reporting of Huntsville (previously grouped into the Other segment) as a separate segment; (2) reclassified certain properties once included in a segment referred to as Suburban Maryland into the Baltimore/Washington Corridor and Other segments; and (3) reclassified a property once previously included in the Colorado Springs segment into the Other segment. Financial information for prior periods has been presented in conformity with these revisions.

	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/				Northern			San			Huntsville		Washington,		St. Mary’s &		Greater		Greater		Colorado		Other		Operating		Total
		Washington				Virginia			Antonio					DC - Capitol		King George		Baltimore		Philadelphia		Springs				Wholesale
		Corridor												Riverfront		Counties										Data Center
	Year Ended December 31, 2013

	Revenues from real estate operations	$	237,869			$	92,010		$	33,060		$	5,050	$	16,863	$	16,568	$	42,653	$	11,924	$	25,290	$	10,075	$	7,271	$	498,633

	Property operating expenses	80,554				31,973			17,631			1,282		7,844		5,028		16,583		3,431		9,002		1,016		6,360		180,704

	NOI from real estate operations	$	157,315			$	60,037		$	15,429		$	3,768	$	9,019	$	11,540	$	26,070	$	8,493	$	16,288	$	9,059	$	911	$	317,929

	Additions to long-lived assets	$	28,087			$	13,090		$	335		$	3,563	$	2,604	$	2,341	$	2,913	$	406	$	2,940	$	—	$	598	$	56,877

	Transfers from non-operating properties	$	50,105			$	61,434		$	—		$	48,799	$	—	$	14	$	360	$	28,034	$	5,438	$	—	$	70,106	$	264,290

	Segment assets at December 31, 2013	$	1,243,099			$	616,082		$	118,299		$	77,773	$	98,962	$	96,143	$	303,823	$	104,657	$	—	$	80,002	$	166,790	$	2,905,630


	Year Ended December 31, 2012

	Revenues from real estate operations	$	238,488			$	79,574		$	32,018		$	3,867	$	16,697	$	16,392	$	52,616	$	9,698	$	24,987	$	12,116	$	6,647	$	493,100

	Property operating expenses	83,050				29,103			16,499			689		7,555		4,745		19,917		2,562		9,231		2,569		4,815		180,735

	NOI from real estate operations	$	155,438			$	50,471		$	15,519		$	3,178	$	9,142	$	11,647	$	32,699	$	7,136	$	15,756	$	9,547	$	1,832	$	312,365

	Additions to long-lived assets	$	25,921			$	65,157		$	280		$	26	$	317	$	1,844	$	9,690	$	286	$	2,929	$	152	$	199	$	106,801

	Transfers from non-operating properties	$	65,108			$	44,250		$	468		$	—	$	—	$	289	$	37,558	$	10,626	$	4,295	$	394	$	58,009	$	220,997

	Segment assets at December 31, 2012	$	1,267,357			$	569,860		$	119,369		$	28,730	$	104,544	$	98,027	$	320,548	$	78,798	$	175,830	$	82,090	$	100,777	$	2,945,930


	Year Ended December 31, 2011

	Revenues from real estate operations	$	237,162			$	74,214		$	30,066		$	1,368	$	17,878	$	14,366	$	70,668	$	7,458	$	23,675	$	13,923	$	5,054	$	495,832

	Property operating expenses	86,782				28,518			14,371			226		6,762		4,142		29,543		1,402		8,758		3,887		3,429		187,820

	NOI from real estate operations	$	150,380			$	45,696		$	15,695		$	1,142	$	11,116	$	10,224	$	41,125	$	6,056	$	14,917	$	10,036	$	1,625	$	308,012

	Additions to long-lived assets	$	33,142			$	14,770		$	—		$	26,837	$	2,794	$	1,638	$	21,086	$	516	$	4,085	$	182	$	59	$	105,109

	Transfers from non-operating properties	$	67,752			$	4		$	17,638		$	—	$	—	$	16,858	$	16,307	$	5,446	$	214	$	—	$	20,169	$	144,388

	Segment assets at December 31, 2011	$	1,350,678			$	484,392		$	131,412		$	32,341	$	111,318	$	100,818	$	402,067	$	102,572	$	181,384	$	98,808	$	43,650	$	3,039,440

	The following table reconciles our segment revenues to total revenues as reported on our consolidated statements of operations (in thousands):


			For the Years Ended December 31,
			2013				2012			2011
	Segment revenues from real estate operations		$	498,633			$	493,100		$	495,832

	Construction contract and other service revenues		62,363				73,836			84,345

Less: Revenues from discontinued operations (Note 20)		(37,636		)		(58,801		)	(87,221		)
Total revenues		$	523,360			$	508,135		$	492,956


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 Years Ended December 31,
		2013				2012			2011
Segment property operating expenses		$	180,704			$	180,735		$	187,820

Less: Property operating expenses from discontinued operations (Note 20)		(13,505		)		(21,529		)	(33,445		)
Total property operating expenses		$	167,199			$	159,206		$	154,375


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 Years Ended December 31,
		2013				2012			2011
Construction contract and other service revenues		$	62,363			$	73,836		$	84,345

Construction contract and other service expenses		(58,875		)		(70,576		)	(81,639		)
NOI from service operations		$	3,488			$	3,260		$	2,706


The following table reconciles our NOI from real estate operations for reportable segments and NOI from service operations to income (loss) from continuing operations as reported on the consolidated statements of operations of COPT and subsidiaries (in thousands):


		For the Years Ended December 31,
		2013				2012			2011
NOI from real estate operations		$	317,929			$	312,365		$	308,012

NOI from service operations		3,488				3,260			2,706

Interest and other income		3,834				7,172			5,603

Equity in income (loss) of unconsolidated entities		2,110				(546		)	(331		)

Income tax (expense) benefit		(1,978		)		(381		)	6,710

Other adjustments:		—

Depreciation and other amortization associated with real estate operations		(113,214		)		(107,998		)	(107,003		)
Impairment losses		(5,857		)		(43,678		)	(83,213		)
General, administrative and leasing expenses		(30,869		)		(31,900		)	(30,306		)
Business development expenses and land carry costs		(5,436		)		(5,711		)	(6,122		)
Interest expense on continuing operations		(82,010		)		(86,401		)	(90,037		)
NOI from discontinued operations		(24,131		)		(37,272		)	(53,776		)
Loss on interest rate derivatives		—				—			(29,805		)

Loss on early extinguishment of debt		(27,030		)		(943		)	(1,639		)
COPT consolidated income (loss) from continuing operations		$	36,836			$	7,967		$	(79,201	)


The following table reconciles our segment assets to the consolidated total assets of COPT and subsidiaries (in thousands):



	As of December 31,
	2013				2012
Segment assets	$	2,905,630			$	2,945,930

Non-operating property assets	517,564				570,402

Other assets	206,758				137,427

Total COPT consolidated assets	$	3,629,952			$	3,653,759


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 and gain and loss on early extinguishment of debt 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, loss on interest rate derivatives, 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.

Income_Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes

	COPT elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code. To qualify as a REIT, COPT must meet a number of organizational and operational requirements, including a requirement that it distribute at least 90% of the Company’s adjusted taxable income to its shareholders. As a REIT, COPT generally will not be subject to Federal income tax on taxable income that it distributes to its shareholders. If COPT fails to qualify as a REIT in any tax year, it will be subject to Federal income tax on its taxable income at regular corporate rates and may not be able to qualify as a REIT for four subsequent tax years.

	COPLP is a limited partnership and is not subject to federal income tax. Its partners are required to report their respective share of the Operating Partnership’s taxable income on their respective tax returns. COPT’s share of the Operating Partnership’s taxable income is reported on COPT’s income tax return.


	The differences between taxable income reported on our income tax returns (estimated 2013 and actual 2012 and 2011) and net income as reported on our consolidated statements of operations are set forth below (in thousands):


			For the Years Ended December 31,
			2013				2012				2011
			(Estimated)
	COPLP consolidated net income (loss)		$	101,544			$	20,341			$	(127,570	)
	COPLP consolidated net income (loss)		$	101,544			$	20,341			$	(127,570	)
	Adjustments:
	Rental revenue recognition		(973		)		(10,794		)		(10,708		)
	Compensation expense recognition		10,051				(2,669		)		(1,298		)
	Compensation expense recognition		10,051				(2,669		)		(1,298		)
	Operating expense recognition		(1,718		)		1,158				751
	Operating expense recognition		(1,718		)		1,158				751
	Gain on sales of properties		(53,545		)		(74,858		)		1,154
	Gain on sales of properties		(53,545		)		(74,858		)		1,154
	Impairment losses		32,047				66,910				151,021
	Impairment losses		32,047				66,910				151,021
	Loss on interest rate derivatives		—				(29,805		)		29,805
	Loss on interest rate derivatives		—				(29,805		)		29,805
	Gains from non-real estate investments		—				7,854				4,447
	Gains from non-real estate investments		—				7,854				4,447
	Income from service operations		1,224				1,500				(12,078		)
	Income from service operations		1,224				1,500				(12,078		)
	Income tax expense		1,978				381				6,710
	Income tax expense		1,978				381				6,710
	Depreciation and amortization		23,824				24,804				44,070
	Depreciation and amortization		23,824				24,804				44,070
	Interest expense		1,159				3,978				5,548
	Interest expense		1,159				3,978				5,548
	Income from unconsolidated entities		(1,462		)		(725		)		(374		)
	COPLP consolidated noncontrolling interests		(3,907		)		(636		)		(1,919		)
	Other		(624		)		(70		)		80
	Other		(624		)		(70		)		80
	COPLP consolidated taxable income		$	109,598			$	7,369			$	89,639
	COPLP consolidated taxable income		$	109,598			$	7,369			$	89,639
	Noncontrolling interests, other		(4,930		)		(622		)		(5,583		)
	Other		—				741				(6		)
	Other		—				741				(6		)
	COPT consolidated taxable income		$	104,668			$	7,488			$	84,050
	COPT consolidated taxable income		$	104,668			$	7,488			$	84,050

	For Federal income tax purposes, dividends to shareholders may be characterized as ordinary income, capital gains or return of capital. The characterization of dividends declared on COPT’s common and preferred shares during each of the last three years was as follows:


			Common Shares									Preferred Shares
			For the Years Ended December 31,									For the Years Ended December 31,
			2013			2012			2011			2013		2012		2011
	Ordinary income		71.8	%		33.2	%		56.9	%		76.2	%	100	%	85.9	%
	Long-term capital gain		22.4	%		0	%		9.4	%		23.8	%	0	%	14.1	%
	Return of capital		5.8	%		66.8	%		33.7	%		0	%	0	%	0	%

	We distributed all of COPT’s REIT taxable income in 2013, 2012 and 2011 and, as a result, did not incur Federal income tax in those years on such income.

	The net basis of our consolidated assets and liabilities for tax reporting purposes is approximately $324 million lower than the amount reported on our consolidated balance sheet at December 31, 2013, which is primarily related to differences in basis for net properties, intangible assets on property acquisitions and deferred rent receivable.

We own a TRS that is subject to Federal and state income taxes. Our TRS had income (loss) before income taxes under GAAP of $330,000 in 2013, $11.3 million in 2012 and $(27.7) million in 2011. Our TRS’ provision for income tax consisted of the following (in thousands):


		For the Years Ended December 31,
		2013				2012				2011
Deferred
Federal		$	(1,742	)		$	(312	)		$	5,510
Federal		$	(1,742	)		$	(312	)		$	5,510
State		(236		)		(69		)		1,219
State		(236		)		(69		)		1,219
		(1,978		)		(381		)		6,729
		(1,978		)		(381		)		6,729
Current
Federal		—				—				(16		)
Federal		—				—				(16		)
State		—				—				(3		)
State		—				—				(3		)
		—				—				(19		)
		—				—				(19		)
Total income tax (expense) benefit		$	(1,978	)		$	(381	)		$	6,710
Total income tax (expense) benefit		$	(1,978	)		$	(381	)		$	6,710

A reconciliation of our TRS’ Federal statutory rate to the effective tax rate for income tax reported on our statements of operations is set forth below:



		For the Years Ended December 31,
		2013			2012			2011
Income taxes at U.S. statutory rate		34	%		34	%		34	%
State and local, net of U.S. Federal tax benefit		4.5	%		4.6	%		4.6	%
Increase in deferred tax asset valuation allowance		562.9	%		0	%		0	%
Other		(1.1	)%		0	%		0	%
Effective tax rate		600.3	%		38.6	%		38.6	%

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, impairment losses and net operating losses that are not deductible until future periods. As of December 31, 2013, our TRS had a net operating loss carryforward for federal income tax purposes of approximately $14 million expiring in 2033.

The table below sets forth the tax effects of temporary differences and carry forwards included in the net deferred tax asset of our TRS (in thousands):


		December 31,
		2013				2012
Operating loss forward		$	5,382			$	6,014
Operating loss forward		$	5,382			$	6,014
Share-based compensation		869				904
Share-based compensation		869				904
Accrued payroll		221				12
Accrued payroll		221				12
Property		(105		)		(111		)
Valuation allowance		(2,062		)		(207		)
Deferred tax asset, net		$	4,305			$	6,612
Deferred tax asset, net		$	4,305			$	6,612

We recognize a valuation allowance on our deferred tax asset if we believe all or some portion of the deferred tax asset may not be realized. An increase or decrease in the valuation allowance resulting from a change in circumstances that causes a change in our judgment about the realizability of our deferred tax asset is included in income. In 2013, we recognized a $1.9 million increase in our deferred tax asset valuation allowance due to a decrease in future projected operating income in our TRS resulting primarily from our dispositions of certain properties to which the TRS provided amenity services and our planned reduction in amenity services provided by the TRS at certain other properties. We believe it is more likely than not that the results of future operations in our TRS will generate sufficient taxable income to realize our December 31, 2013 net deferred tax asset.

We are subject to certain state and local income and franchise taxes. The expense associated with these state and local taxes is included in general and administrative expense and property operating expenses on our consolidated statements of operations. We did not separately state these amounts on our consolidated statements of operations because they are insignificant.

Discontinued_Operations

Discontinued Operations	12 Months Ended
Discontinued Operations	Dec. 31, 2013
Discontinued Operations and Disposal Groups [Abstract]	'
Discontinued Operations and Assets Held for Sale	'
	Discontinued Operations and Assets Held for Sale

	Income from discontinued operations primarily includes revenues and expenses associated with the following:


	•	1344 and 1348 Ashton Road and 1350 Dorsey Road in the Baltimore/Washington Corridor that were sold on May 24, 2011;

	•	216 Schilling Circle in Greater Baltimore that was sold on August 23, 2011;

	•	four properties comprising the Towson Portfolio in Greater Baltimore that were sold on September 29, 2011;

	•	11011 McCormick Road in Greater Baltimore that was sold on November 1, 2011;

	•	10001 Franklin Square Drive in Greater Baltimore that was sold on December 13, 2011;

	•	13 properties comprising the Rutherford Business Center portfolio in Greater Baltimore that were sold on December 15, 2011;

	•	five properties in White Marsh, Maryland (in the Greater Baltimore region) that were sold on January 30, 2012;

	•	1101 Sentry Gateway in San Antonio that was sold on January 31, 2012;

	•	222 and 224 Schilling Circle in Greater Baltimore that were sold on February 10, 2012;

	•	15 and 45 West Gude Drive in the Baltimore/Washington Corridor that were sold on May 2, 2012;

	•	11800 Tech Road in the Baltimore/Washington Corridor that was sold on June 14, 2012;

	•	400 Professional Drive in the Baltimore/Washington Corridor for which the title to the property was transferred to the mortgage lender on July 2, 2012;

	•	23 operating properties primarily in the Baltimore/Washington Corridor and Greater Baltimore regions that were sold on July 24, 2012;

	•	920 Elkridge Landing Road in the Baltimore/Washington Corridor that was sold on June 25, 2013 (added to discontinued operations in 2013);

	•	4230 Forbes Boulevard in the Baltimore/Washington Corridor that was sold on December 11, 2013;

	•	15 operating properties in Colorado Springs that were sold on December 12, 2013; and

	•	nine operating properties in the Baltimore/Washington Corridor and five operating properties in Colorado Springs for which the title to the properties was transferred to the mortgage lender on December 23, 2013 (added to discontinued operations in 2013).

	The table below sets forth the components of discontinued operations reported on our consolidated statements of operations (in thousands):


			For the Years Ended December 31,
			2013			2012			2011
	Revenue from real estate operations		$	37,636		$	58,801		$	87,221
	Revenue from real estate operations		$	37,636		$	58,801		$	87,221
	Property operating expenses		(13,505		)	(21,529		)	(33,445		)
	Depreciation and amortization		(4,505		)	(13,939		)	(27,128		)
	Impairment losses		(26,190		)	(23,232		)	(67,808		)
	General, administrative and leasing expenses		(4		)	(3		)	(20		)
	Business development and land carry costs		—			(24		)	(75		)
	Business development and land carry costs		—			(24		)	(75		)
	Interest expense		(8,221		)	(10,397		)	(14,264		)
	Gain on sales of real estate		2,671			20,940			4,796
	Gain on sales of real estate		2,671			20,940			4,796
	Gain (loss) on early extinguishment of debt		67,810			1,736			(384		)
	Gain (loss) on early extinguishment of debt		67,810			1,736			(384		)
	Discontinued operations		$	55,692		$	12,353		$	(51,107	)
	Discontinued operations		$	55,692		$	12,353		$	(51,107	)

	The table below sets forth the components of assets held for sale on our consolidated balance sheets (in thousands):



		December 31, 2012
Properties, net		$	128,740
Properties, net		$	128,740
Deferred rent receivable		4,068
Deferred rent receivable		4,068
Intangible assets on real estate acquisitions, net		4,409
Intangible assets on real estate acquisitions, net		4,409
Deferred leasing costs, net		2,923
Deferred leasing costs, net		2,923
Lease incentives		89
Lease incentives		89
Assets held for sale, net		$	140,229
Assets held for sale, net		$	140,229

Earnings_Per_Share_EPS_and_Ear

Earnings Per Share ("EPS") and Earnings Per Unit (â€œEPUâ€)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share (â€œEPSâ€) and Earnings Per Unit (â€œEPUâ€)	'
	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 Years Ended December 31,
			2013				2012				2011
	Numerator:
	Income (loss) from continuing operations		$	36,836			$	7,967			$	(79,201	)

	Gain on sales of real estate, net		9,016				21				2,732

	Preferred share dividends		(19,971		)		(20,844		)		(16,102		)
	Issuance costs associated with redeemed preferred shares		(2,904		)		(1,827		)		—

	(Income) loss from continuing operations attributable to noncontrolling interests		(4,486		)		1,309				5,128

	Income from continuing operations attributable to restricted shares		(414		)		(469		)		(1,037		)
	Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders		$	18,077			$	(13,843	)		$	(88,480	)

	Discontinued operations		55,692				12,353				(51,107		)

	Discontinued operations attributable to noncontrolling interests		(3,351		)		(673		)		3,020

	Numerator for basic and diluted EPS on net income (loss)attributable to COPT common shareholders		$	70,418			$	(2,163	)		$	(136,567	)

	Denominator (all weighted averages):
	Denominator for basic EPS (common shares)		85,167				73,454				69,382

	Dilutive effect of share-based compensation awards		57				—				—

	Denominator for basic and diluted EPS (common shares)		85,224				73,454				69,382

	Basic EPS:
	Income (loss) from continuing operations attributable to COPT common shareholders		$	0.21			$	(0.19	)		$	(1.28	)

	Discontinued operations attributable to COPT common shareholders		0.62				0.16				(0.69		)

	Net income (loss) attributable to COPT common shareholders		$	0.83			$	(0.03	)		$	(1.97	)

	Diluted EPS:
	Income (loss) from continuing operations attributable to COPT common shareholders		$	0.21			$	(0.19	)		$	(1.28	)

	Discontinued operations attributable to COPT common shareholders		0.62				0.16				(0.69		)

	Net income (loss) attributable to COPT common shareholders		$	0.83			$	(0.03	)		$	(1.97	)


	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 Years Ended December 31,
			2013			2012			2011
	Conversion of common units		3,869			4,235			4,355

Conversion of Series I preferred units		176			176			176

Conversion of Series K preferred shares		434			434			434


The following share-based compensation securities were excluded from the computation of diluted EPS because their effect was antidilutive:


•	weighted average restricted shares of 385,000 for 2013, 461,000 for 2012 and 638,000 for 2011; and

•	weighted average options of 636,000 for 2013, 772,000 for 2012 and 712,000 for 2011, respectively.

As discussed in Note 11, we have outstanding senior notes that have an exchange settlement feature but 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 Years Ended December 31,
		2013				2012				2011
Numerator:
Income (loss) from continuing operations		$	36,836			$	7,967			$	(79,195	)

Gain on sales of real estate, net		9,016				21				2,732

Preferred unit distributions		(20,631		)		(21,504		)		(16,762		)
Issuance costs associated with redeemed preferred units		(2,904		)		(1,827		)		—

(Income) loss from continuing operations attributable to noncontrolling interests		(2,977		)		1,206				381

Income from continuing operations attributable to restricted units		(414		)		(469		)		(1,037		)
Numerator for basic and diluted EPU from continuing operations attributable to COPLP common unitholders		$	18,926			$	(14,606	)		$	(93,881	)

Discontinued operations		55,692				12,353				(51,107		)

Discontinued operations attributable to noncontrolling interests		(930		)		(699		)		(137		)
Numerator for basic and diluted EPU on net income (loss) attributable to COPLP common unitholders		$	73,688			$	(2,952	)		$	(145,125	)

Denominator (all weighted averages):
Denominator for basic EPU (common units)		89,036				77,689				72,564

Dilutive effect of share-based compensation awards		57				—				—

Denominator for basic and diluted EPU (common units)		89,093				77,689				72,564

Basic EPU:
Income (loss) from continuing operations attributable to COPLP common unitholders		$	0.21			$	(0.19	)		$	(1.29	)

Discontinued operations attributable to COPLP common unitholders		0.62				0.15				(0.71		)

Net income (loss) attributable to COPLP common unitholders		$	0.83			$	(0.04	)		$	(2.00	)

Diluted EPU:
Income (loss) from continuing operations attributable to COPLP common unitholders		$	0.21			$	(0.19	)		$	(1.29	)

Discontinued operations attributable to COPLP common unitholders		0.62				0.15				(0.71		)

Net income (loss) attributable to COPLP common unitholders		$	0.83			$	(0.04	)		$	(2.00	)


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 Years Ended December 31,
		2013			2012			2011
Conversion of Series I preferred units		176			176			176

Conversion of Series K preferred units		434			434			434


The following share-based compensation securities were excluded from the computation of diluted EPU because their effect was antidilutive:


•	weighted average restricted units of 385,000 for 2013, 461,000 for 2012 and 638,000 for 2011; and

•	weighted average options of 636,000 for 2013, 772,000 for 2012 and 712,000 for 2011.

As discussed in Note 11, we have outstanding senior notes that have an exchange settlement feature but 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.

Quarterly_Data_Unaudited

Quarterly Data (Unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Data (Unaudited)	'
	Quarterly Data (Unaudited)
	COPT and Subsidiaries

	The tables below set forth selected quarterly information for the years ended December 31, 2013 and 2012 (in thousands, except per share data). Certain of the amounts below have been reclassified to conform to the current period presentation of our consolidated financial statements.


		For the Year Ended December 31, 2013
		First Quarter				Second Quarter				Third Quarter				Fourth Quarter
	Revenues	$	126,219			$	136,527			$	131,812			$	128,802

	Operating income	$	36,165			$	40,229			$	30,673			$	34,843

	Income (loss) from continuing operations	$	11,662			$	(232	)		$	10,974			$	14,432

	Discontinued operations	$	1,261			$	(4,502	)		$	(12,974	)		$	71,907

	Net income (loss)	$	15,277			$	(4,405	)		$	(2,000	)		$	92,672

	Net (income) loss attributable to noncontrolling interests	(257		)		(960		)		(964		)		(5,656		)
	Net income (loss) attributable to COPT	15,020				(5,365		)		(2,964		)		87,016

	Preferred share dividends	(6,106		)		(4,885		)		(4,490		)		(4,490		)
	Issuance costs associated with redeemed preferred shares	—				(2,904		)		—				—

	Net income (loss) attributable to COPT common shareholders	$	8,914			$	(13,154	)		$	(7,454	)		$	82,526

	Basic earnings per common share	$	0.11			$	(0.16	)		$	(0.09	)		$	0.94

	Diluted earnings per common share	$	0.11			$	(0.16	)		$	(0.09	)		$	0.94



		For the Year Ended December 31, 2012
		First Quarter				Second Quarter				Third Quarter				Fourth Quarter
	Revenues	$	127,359			$	123,074			$	125,067			$	132,635

	Operating income (loss)	$	34,651			$	32,069			$	(10,844	)		$	33,190

	Income (loss) from continuing operations	$	13,184			$	10,336			$	(32,048	)		$	16,495

	Discontinued operations	$	(2,949	)		$	1,504			$	11,283			$	2,515

	Net income (loss)	$	10,235			$	11,861			$	(20,765	)		$	19,010

	Net loss (income) attributable to noncontrolling interests	60				(556		)		1,603				(471		)

	Net income (loss) attributable to COPT	10,295				11,305				(19,162		)		18,539

	Preferred share dividends	(4,025		)		(4,167		)		(6,546		)		(6,106		)
	Issuance costs associated with redeemed preferred shares	—				—				(1,827		)		—

	Net income (loss) attributable to COPT common shareholders	$	6,270			$	7,138			$	(27,535	)		$	12,433

	Basic earnings per common share	$	0.09			$	0.1			$	(0.39	)		$	0.16

	Diluted earnings per common share	$	0.09			$	0.1			$	(0.39	)		$	0.16


	COPLP and Subsidiaries

	The tables below set forth selected quarterly information for the years ended December 31, 2013 and 2012 (in thousands, except per share data).


	For the Year Ended December 31, 2013
	First Quarter				Second Quarter				Third Quarter				Fourth Quarter
Revenues	$	126,219			$	136,527			$	131,812			$	128,802

Operating income	$	36,165			$	40,229			$	30,673			$	34,843

Income (loss) from continuing operations	$	11,662			$	(232	)		$	10,974			$	14,432

Discontinued operations	$	1,261			$	(4,502	)		$	(12,974	)		$	71,907

Net income (loss)	$	15,277			$	(4,405	)		$	(2,000	)		$	92,672

Net loss (income) attributable to noncontrolling interests	336				(1,473		)		(1,035		)		(1,735		)

Net income (loss) attributable to COPLP	15,613				(5,878		)		(3,035		)		90,937

Preferred unit distributions	(6,271		)		(5,050		)		(4,655		)		(4,655		)
Issuance costs associated with redeemed preferred units	—				(2,904		)		—				—

Net income (loss) attributable to COPLP common unitholders	$	9,342			$	(13,832	)		$	(7,690	)		$	86,282

Basic earnings per common unit	$	0.11			$	(0.16	)		$	(0.09	)		$	0.94

Diluted earnings per common unit	$	0.11			$	(0.16	)		$	(0.09	)		$	0.94



	For the Year Ended December 31, 2012
	First Quarter				Second Quarter				Third Quarter				Fourth Quarter
Revenues	$	127,359			$	123,074			$	125,067			$	132,635

Operating income (loss)	$	34,651			$	32,069			$	(10,844	)		$	33,190

Income (loss) from continuing operations	$	13,184			$	10,336			$	(32,048	)		$	16,495

Discontinued operations	$	(2,949	)		$	1,504			$	11,283			$	2,515

Net income (loss)	$	10,235			$	11,861			$	(20,765	)		$	19,010

Net loss (income) attributable to noncontrolling interests	570				1				(404		)		340

Net income (loss) attributable to COPLP	10,805				11,862				(21,169		)		19,350

Preferred unit distributions	(4,190		)		(4,332		)		(6,711		)		(6,271		)
Issuance costs associated with redeemed preferred units	—				—				(1,827		)		—

Net income (loss) attributable to COPLP common unitholders	$	6,615			$	7,530			$	(29,707	)		$	13,079

Basic earnings per common unit	$	0.09			$	0.1			$	(0.39	)		$	0.16

Diluted earnings per common unit	$	0.09			$	0.1			$	(0.39	)		$	0.16

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
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.

	Joint Ventures

	In connection with our 2005 contribution of properties to an unconsolidated partnership in which we hold a partnership interest, we entered into standard nonrecourse loan guarantees (environmental indemnifications and guarantees against fraud and misrepresentation, and springing guarantees of partnership debt in the event of a voluntary bankruptcy of the partnership). On December 6, 2013, the holder of mortgage debt encumbering all of the joint venture’s properties foreclosed on the properties. As a result, title to the properties was transferred to the mortgage lender and the joint venture was relieved of the debt obligation plus accrued interest and penalties. The joint venture still had $5.6 million in nonrecourse mezzanine debt as of December 31, 2013; however, the joint venture no longer holds any property and has ceased all business operations. Management estimates there to be no fair value to the guarantees as of December 31, 2013 because the actions that would trigger performance are all within our control.

	We may be required to make our pro rata share of additional investments in our real estate joint ventures (generally based on our percentage ownership) in the event that additional funds are needed. In the event that the other members of these joint ventures do not pay their share of investments when additional funds are needed, we may then deem it appropriate to make even larger investments in these joint ventures.

	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 $2.5 million liability through December 31, 2013 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.

	Ground Leases

	We are obligated as lessee under ground leases with various lease expiration dates extending to the year 2100. Future minimum rental payments due under the terms of these leases as of December 31, 2013 follow (in thousands):


	Year Ending December 31,
	2014		$	675

	2015		686

	2016		686

	2017		687

	2018		689

	Thereafter		75,501

			$	78,924


	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.

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts (Notes)	12 Months Ended
	Dec. 31, 2013
Valuation and Qualifying Accounts [Abstract]	'
Schedule IIâ€”Valuation and Qualifying Accounts	'
	Corporate Office Properties Trust and Subsidiaries and Corporate Office Properties, L.P. and Subsidiaries
	Schedule II—Valuation and Qualifying Accounts
	Years Ended December 31, 2013, 2012 and 2011
	(Dollars in thousands)


		Balance at		Charged to			Charged to Other Accounts (2)		Deductions (3)			Balance at End of Year
		Beginning		Costs and
		of Year		Expenses (1)
	Accounts Receivables-Allowance for doubtful accounts
	Year ended December 31, 2013	$	4,694	$	(65	)	$	—	$	(1,653	)	$	2,976

	Year ended December 31, 2012	$	3,546	$	1,532		$	232	$	(616	)	$	4,694

	Year ended December 31, 2011	$	2,796	$	1,021		$	125	$	(396	)	$	3,546

	Allowance for Deferred Rent Receivable

	Year ended December 31, 2013	$	913	$	—		$	1,213	$	—		$	2,126

	Year ended December 31, 2012	$	703	$	—		$	416	$	(206	)	$	913

	Year ended December 31, 2011	$	578	$	—		$	162	$	(37	)	$	703

	Allowance for Deferred Tax Asset

	Year ended December 31, 2013	$	207	$	1,855		$	—	$	—		$	2,062

	Year ended December 31, 2012	$	207	$	—		$	—	$	—		$	207

	Year ended December 31, 2011	$	207	$	—		$	—	$	—		$	207


	(1) Amounts charged to costs and expenses are net of recoveries.
	(2) Allowances for certain accounts receivables were charged to service company revenue. Deferred rent receivable allowances were charged to rental revenue.
	(3) Deductions reflect adjustments to reserves due to actual write-offs of accounts.

Schedule_III_Real_Estate_and_A

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2013
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]	'
Schedule III-Real Estate and Accumulated Depreciation	'
	Corporate Office Properties Trust and Subsidiaries and Corporate Office Properties, L.P. and Subsidiaries
	Schedule III—Real Estate and Accumulated Depreciation
	31-Dec-13
	(Dollars in thousands)


						Initial Cost									Gross Amounts Carried At Close of Period
	Property (Type) (1)	Location	Encumbrances (2)			Land			Building and Land Improvements			Costs Capitalized Subsequent to Acquisition			Land			Building and Land Improvements			Total (3)(4)			Accumulated Depreciation (5)			Year Built or Renovated	Date Acquired (6)
	1000 Redstone Gateway (O)	Huntsville, AL	$	11,960		$	—		$	20,435		$	—		$	—		$	20,435		$	20,435		$	(412	)	2013	3/23/10

	1100 Redstone Gateway (O)	Huntsville, AL	5,809			—			20,877			—			—			20,877			20,877			—			-7	3/23/10

	114 National Business Parkway (O)	Annapolis Junction, MD	—			364			3,109			46			364			3,155			3,519			(959		)	2002	6/30/00

	11751 Meadowville Lane (O)	Richmond, VA	—			1,305			52,098			112			1,305			52,210			53,515			(8,583		)	2007	9/15/06

	1200 Redstone Gateway (O)	Huntsville, AL	8,080			—			21,974			—			—			21,974			21,974			(37		)	2013	3/23/10

	1201 M Street (O)	Washington, DC	—			—			49,785			2,508			—			52,293			52,293			(5,656		)	2001	9/28/10

	1201 Winterson Road (O)	Linthicum, MD	—			1,288			5,154			460			1,288			5,614			6,902			(2,228		)	1985	4/30/98

	1220 12th Street, SE (O)	Washington, DC	—			—			42,464			933			—			43,397			43,397			(5,724		)	2003	9/28/10

	1243 Winterson Road (L)	Linthicum, MD	—			630			—			—			630			—			630			—			-8	12/19/01

	1302 Concourse Drive (O)	Linthicum, MD	—			2,078			8,313			4,598			2,078			12,911			14,989			(5,078		)	1996	11/18/99

	1304 Concourse Drive (O)	Linthicum, MD	—			1,999			12,934			1,616			1,999			14,550			16,549			(5,115		)	2002	11/18/99

	1306 Concourse Drive (O)	Linthicum, MD	—			2,796			11,186			4,546			2,796			15,732			18,528			(5,513		)	1990	11/18/99

	131 National Business Parkway (O)	Annapolis Junction, MD	6,785			1,906			7,623			2,946			1,906			10,569			12,475			(4,284		)	1990	9/28/98

	132 National Business Parkway (O)	Annapolis Junction, MD	—			2,917			12,259			2,977			2,917			15,236			18,153			(6,929		)	2000	5/28/99

	13200 Woodland Park Road (O)	Herndon, VA	—			10,428			41,711			13,985			10,428			55,696			66,124			(21,768		)	2002	6/2/03

	133 National Business Parkway (O)	Annapolis Junction, MD	9,079			2,517			10,068			4,950			2,517			15,018			17,535			(6,856		)	1997	9/28/98

	1331 Ashton Road (O)	Hanover, MD	—			587			2,347			697			587			3,044			3,631			(1,047		)	1989	4/28/99

	1334 Ashton Road (O)	Hanover, MD	—			736			1,488			2,459			736			3,947			4,683			(1,744		)	1989	4/28/99

	134 National Business Parkway (O)	Annapolis Junction, MD	19,200			3,684			7,517			2,314			3,684			9,831			13,515			(4,500		)	1999	11/13/98

	1340 Ashton Road (O)	Hanover, MD	—			905			3,620			1,466			905			5,086			5,991			(2,131		)	1989	4/28/99

	1341 Ashton Road (O)	Hanover, MD	—			306			1,223			601			306			1,824			2,130			(794		)	1989	4/28/99

	1343 Ashton Road (O)	Hanover, MD	—			193			774			405			193			1,179			1,372			(516		)	1989	4/28/99

	13450 Sunrise Valley Road (O)	Herndon, VA	—			1,386			5,576			3,345			1,386			8,921			10,307			(3,160		)	1998	7/25/03

	13454 Sunrise Valley Road (O)	Herndon, VA	—			2,899			11,986			4,059			2,899			16,045			18,944			(5,332		)	1998	7/25/03

	135 National Business Parkway (O)	Annapolis Junction, MD	11,692			2,484			9,750			4,472			2,484			14,222			16,706			(5,299		)	1998	12/30/98

	1362 Mellon Road (O)	Hanover, MD	—			1,706			8,670			32			1,706			8,702			10,408			(1,055		)	2006	2/10/06

	13857 McLearen Road (O)	Herndon, VA	—			3,507			30,177			1,906			3,507			32,083			35,590			(3,071		)	2007	7/11/12

	140 National Business Parkway (O)	Annapolis Junction, MD	—			3,407			24,167			643			3,407			24,810			28,217			(6,432		)	2003	12/31/03

141 National Business Parkway (O)	Annapolis Junction, MD	12,155			2,398			9,590			2,995			2,398			12,585			14,983			(4,970		)	1990	9/28/98

14280 Park Meadow Drive (O)	Chantilly, VA	—			3,731			15,953			1,525			3,731			17,478			21,209			(5,080		)	1999	9/29/04

1460 Dorsey Road (L)	Hanover, MD	—			1,800			—			—			1,800			—			1,800			—			-8	2/28/06

14840 Conference Center Drive (O)	Chantilly, VA	—			1,572			8,175			266			1,572			8,441			10,013			(3,579		)	2000	7/25/03

14850 Conference Center Drive (O)	Chantilly, VA	—			1,615			8,358			1,224			1,615			9,582			11,197			(3,702		)	2000	7/25/03

14900 Conference Center Drive (O)	Chantilly, VA	—			3,436			14,402			4,104			3,436			18,506			21,942			(6,558		)	1999	7/25/03



					Initial Cost									Gross Amounts Carried At Close of Period
Property (Type) (1)	Location	Encumbrances (2)			Land			Building and Land Improvements			Costs Capitalized Subsequent to Acquisition			Land			Building and Land Improvements			Total (3)(4)			Accumulated Depreciation (5)			Year Built or Renovated	Date Acquired (6)
15000 Conference Center Drive (O)	Chantilly, VA	54,000			5,193			47,045			19,251			5,193			66,296			71,489			(22,908		)	1989	11/30/01

1501 South Clinton Street (O)	Baltimore, MD	—			27,964			52,145			4,473			27,964			56,618			84,582			(8,191		)	2006	10/27/09

15010 Conference Center Drive (O)	Chantilly, VA	96,000			3,500			41,921			498			3,500			42,419			45,919			(7,571		)	2006	11/30/01

15049 Conference Center Drive (O)	Chantilly, VA	—			4,415			20,365			726			4,415			21,091			25,506			(8,041		)	1997	8/14/02

15059 Conference Center Drive (O)	Chantilly, VA	—			5,753			13,615			1,715			5,753			15,330			21,083			(5,418		)	2000	8/14/02

15395 John Marshall Highway (O)	Haymarket, VA	—			2,479			20,939			—			2,479			20,939			23,418			—			-7	5/7/13

1550 West Nursery Road (O)	Linthicum, MD	—			14,071			16,930			—			14,071			16,930			31,001			(2,450		)	2009	10/28/09

1550 Westbranch Drive (O)	McLean, VA	—			5,595			26,212			116			5,595			26,328			31,923			(3,000		)	2002	6/28/10

1560A Cable Ranch Road (O)	San Antonio, TX	—			1,097			3,770			357			1,097			4,127			5,224			(784		)	1985/2007	6/19/08

1560B Cable Ranch Road (O)	San Antonio, TX	—			2,299			6,545			11			2,299			6,556			8,855			(1,326		)	1985/2006	6/19/08

16442 Commerce Drive (O)	Dahlgren, VA	—			613			2,582			578			613			3,160			3,773			(956		)	2002	12/21/04

16480 Commerce Drive (O)	Dahlgren, VA	—			1,856			7,425			164			1,856			7,589			9,445			(1,835		)	2000	12/28/04

16501 Commerce Drive (O)	Dahlgren, VA	—			522			2,090			201			522			2,291			2,813			(647		)	2002	12/21/04

16539 Commerce Drive (O)	Dahlgren, VA	—			688			2,860			1,469			688			4,329			5,017			(1,460		)	1990	12/21/04

16541 Commerce Drive (O)	Dahlgren, VA	—			773			3,094			1,367			773			4,461			5,234			(1,332		)	1996	12/21/04

16543 Commerce Drive (O)	Dahlgren, VA	—			436			1,742			156			436			1,898			2,334			(414		)	2002	12/21/04

1751 Pinnacle Drive (O)	McLean, VA	—			10,486			42,339			16,116			10,486			58,455			68,941			(18,299		)	1989/1995	9/23/04

1753 Pinnacle Drive (O)	McLean, VA	—			8,275			34,353			9,554			8,275			43,907			52,182			(12,131		)	1976/2004	9/23/04

201 Technology Drive (O)	Lebanon, VA	—			726			31,091			60			726			31,151			31,877			(4,800		)	2007	10/5/07

206 Research Boulevard (O)	Aberdeen, MD	—			1,813			17,484			—			1,813			17,484			19,297			(542		)	2012	9/14/07

209 Research Boulevard (O)	Aberdeen, MD	—			1,045			16,087			32			1,045			16,119			17,164			(1,261		)	2010	9/14/07

210 Research Boulevard (O)	Aberdeen, MD	—			1,065			13,161			—			1,065			13,161			14,226			(848		)	2010	9/14/07

21267 Smith Switch Road (O)	Ashburn, VA	—			4,192			2,849			—			4,192			2,849			7,041			—			-7	12/27/12

21271 Smith Switch Road (O)	Ashburn, VA	—			7,291			15,909			—			7,291			15,909			23,200			(43		)	2013	12/27/12

22289 Exploration Drive (O)	Lexington Park, MD	—			1,422			5,719			1,371			1,422			7,090			8,512			(2,206		)	2000	3/24/04

22299 Exploration Drive (O)	Lexington Park, MD	—			1,362			5,791			853			1,362			6,644			8,006			(2,221		)	1998	3/24/04

22300 Exploration Drive (O)	Lexington Park, MD	—			1,094			5,038			300			1,094			5,338			6,432			(1,748		)	1997	11/9/04

22309 Exploration Drive (O)	Lexington Park, MD	—			2,243			10,419			782			2,243			11,201			13,444			(3,695		)	1984/1997	3/24/04

23535 Cottonwood Parkway (O)	California, MD	—			692			3,051			223			692			3,274			3,966			(928		)	1984	3/24/04

2500 Riva Road (O)	Annapolis, MD	—			2,791			12,145			1			2,791			12,146			14,937			(3,729		)	2000	3/4/03

2691 Technology Drive (O)	Annapolis Junction, MD	24,000			2,098			17,334			5,107			2,098			22,441			24,539			(6,052		)	2005	5/26/00

2701 Technology Drive (O)	Annapolis Junction, MD	23,177			1,737			15,266			2,389			1,737			17,655			19,392			(5,814		)	2001	5/26/00

2711 Technology Drive (O)	Annapolis Junction, MD	18,027			2,251			21,611			1,443			2,251			23,054			25,305			(8,732		)	2002	11/13/00

2720 Technology Drive (O)	Annapolis Junction, MD	23,592			3,863			29,272			105			3,863			29,377			33,240			(6,839		)	2004	1/31/02

2721 Technology Drive (O)	Annapolis Junction, MD	—			4,611			14,597			1,091			4,611			15,688			20,299			(5,316		)	2000	10/21/99

2730 Hercules Road (O)	Annapolis Junction, MD	36,002			8,737			31,612			6,498			8,737			38,110			46,847			(12,973		)	1990	9/28/98

2900 Towerview Road (O)	Herndon, VA	—			3,207			16,379			5,967			3,207			22,346			25,553			(4,830		)	1982/2008	12/20/05

300 Sentinel Drive (O)	Annapolis Junction, MD	—			1,517			44,524			114			1,517			44,638			46,155			(3,785		)	2009	11/14/03

300 Sentinel Drive Garage (O)	Annapolis Junction, MD	12,424			—			14,125			52			—			14,177			14,177			(1,714		)	2009	11/14/03



					Initial Cost									Gross Amounts Carried At Close of Period
Property (Type) (1)	Location	Encumbrances (2)			Land			Building and Land Improvements			Costs Capitalized Subsequent to Acquisition			Land			Building and Land Improvements			Total (3)(4)			Accumulated Depreciation (5)			Year Built or Renovated	Date Acquired (6)
302 Sentinel Drive (O)	Annapolis Junction, MD	22,244			2,648			29,687			409			2,648			30,096			32,744			(4,421		)	2007	11/14/03

304 Sentinel Drive (O)	Annapolis Junction, MD	24,856			3,411			24,917			138			3,411			25,055			28,466			(5,007		)	2005	11/14/03

306 Sentinel Drive (O)	Annapolis Junction, MD	16,688			3,260			22,592			150			3,260			22,742			26,002			(4,112		)	2006	11/14/03

308 Sentinel Drive (O)	Annapolis Junction, MD	—			1,422			26,197			—			1,422			26,197			27,619			(1,740		)	2010	11/14/03

310 The Bridge Street (O)	Huntsville, AL	—			261			26,531			110			261			26,641			26,902			(3,202		)	2009	8/4/11

312 Sentinel Way (O)	Annapolis Junction, MD	—			3,138			18,133			—			3,138			18,133			21,271			—			-7	11/14/03

3120 Fairview Park Drive (O)	Falls Church, VA	—			6,863			35,606			5,863			6,863			41,469			48,332			(3,813		)	2008	11/23/10

314 Sentinel Way (O)	Annapolis Junction, MD	—			1,254			1,325			—			1,254			1,325			2,579			(182		)	2008	11/14/03

316 Sentinel Way (O)	Annapolis Junction, MD	—			2,748			38,228			139			2,748			38,367			41,115			(1,634		)	2011	11/14/03

318 Sentinel Way (O)	Annapolis Junction, MD	21,800			2,185			28,426			—			2,185			28,426			30,611			(5,559		)	2005	11/14/03

320 Sentinel Way (O)	Annapolis Junction, MD	—			2,067			21,623			—			2,067			21,623			23,690			(3,229		)	2007	11/14/03

322 Sentinel Way (O)	Annapolis Junction, MD	22,199			2,605			22,827			—			2,605			22,827			25,432			(4,001		)	2006	11/14/03

324 Sentinel Way (O)	Annapolis Junction, MD	—			1,656			23,018			—			1,656			23,018			24,674			(1,927		)	2010	6/29/06

375 West Padonia Road (O)	Timonium, MD	—			2,483			10,415			4,852			2,483			15,267			17,750			(6,086		)	1986	12/21/99

410 National Business Parkway (O)	Annapolis Junction, MD	—			1,831			23,552			11			1,831			23,563			25,394			(539		)	2012	6/29/06

420 National Business Parkway (O)	Annapolis Junction, MD	—			2,370			23,412			—			2,370			23,412			25,782			(24		)	2013	6/29/06

430 National Business Parkway (O)	Annapolis Junction, MD	—			1,852			20,758			10			1,852			20,768			22,620			(966		)	2011	6/29/06

44408 Pecan Court (O)	California, MD	—			817			1,583			460			817			2,043			2,860			(258		)	1986	3/24/04

44414 Pecan Court (O)	California, MD	—			405			1,619			336			405			1,955			2,360			(558		)	1986	3/24/04

44417 Pecan Court (O)	California, MD	—			434			1,939			88			434			2,027			2,461			(712		)	1989	3/24/04

44420 Pecan Court (O)	California, MD	—			344			890			126			344			1,016			1,360			(145		)	1989	11/9/04

44425 Pecan Court (O)	California, MD	—			1,309			3,506			1,299			1,309			4,805			6,114			(1,202		)	1997	5/5/04

45310 Abell House Lane (O)	California, MD	—			2,272			13,808			—			2,272			13,808			16,080			(712		)	2011	8/30/10

46579 Expedition Drive (O)	Lexington Park, MD	—			1,406			5,796			1,250			1,406			7,046			8,452			(2,409		)	2002	3/24/04

46591 Expedition Drive (O)	Lexington Park, MD	—			1,200			7,199			664			1,200			7,863			9,063			(1,325		)	2005	3/24/04

4851 Stonecroft Boulevard (O)	Chantilly, VA	—			1,878			11,558			21			1,878			11,579			13,457			(2,669		)	2004	8/14/02

4940 Campbell Drive (O)	White Marsh, MD	—			1,379			3,858			1,079			1,379			4,937			6,316			(1,094		)	1990	1/9/07

4969 Mercantile Road (O)	White Marsh, MD	—			1,308			771			62			1,308			833			2,141			(7		)	1983	1/9/07

4979 Mercantile Road (O)	White Marsh, MD	—			1,299			945			111			1,299			1,056			2,355			(25		)	1985	1/9/07

5020 Campbell Boulevard (O)	White Marsh, MD	—			1,014			3,136			784			1,014			3,920			4,934			(840		)	1986-1988	1/9/07

5022 Campbell Boulevard (O)	White Marsh, MD	—			624			1,924			417			624			2,341			2,965			(595		)	1986-1988	1/9/07

5024 Campbell Boulevard (O)	White Marsh, MD	—			767			2,420			643			767			3,063			3,830			(790		)	1986-1988	1/9/07

5026 Campbell Boulevard (O)	White Marsh, MD	—			700			2,138			44			700			2,182			2,882			(448		)	1986-1988	1/9/07

525 Babcock Road (O)	Colorado Springs, CO	—			355			397			79			355			476			831			(124		)	1967	7/12/07

5325 Nottingham Drive (O)	White Marsh, MD	—			816			3,976			485			816			4,461			5,277			(919		)	2002	1/9/07

5355 Nottingham Drive (O)	White Marsh, MD	—			761			3,562			1,758			761			5,320			6,081			(1,614		)	2005	1/9/07

5520 Research Park Drive (O)	Catonsville, MD	—			—			20,072			38			—			20,110			20,110			(2,182		)	2009	4/4/06

5522 Research Park Drive (O)	Catonsville, MD	—			—			4,550			—			—			4,550			4,550			(728		)	2007	3/8/06

5825 University Research Court (O)	College Park, MD	15,960			—			22,522			11			—			22,533			22,533			(2,681		)	2008	1/29/08



					Initial Cost									Gross Amounts Carried At Close of Period
Property (Type) (1)	Location	Encumbrances (2)			Land			Building and Land Improvements			Costs Capitalized Subsequent to Acquisition			Land			Building and Land Improvements			Total (3)(4)			Accumulated Depreciation (5)			Year Built or Renovated	Date Acquired (6)
5850 University Research Court (O)	College Park, MD	21,731			—			30,273			57			—			30,330			30,330			(2,995		)	2008	1/29/08

6700 Alexander Bell Drive (O)	Columbia, MD	4,000			1,755			7,019			5,385			1,755			12,404			14,159			(4,972		)	1988	5/14/01

6708 Alexander Bell Drive (O)	Columbia, MD	6,320			897			3,907			1,591			897			5,498			6,395			(2,596		)	1988	5/14/01

6711 Columbia Gateway Drive (O)	Columbia, MD	—			2,683			23,239			312			2,683			23,551			26,234			(4,135		)	2006-2007	9/28/00

6716 Alexander Bell Drive (O)	Columbia, MD	—			1,242			4,969			3,244			1,242			8,213			9,455			(3,661		)	1990	12/31/98

6721 Columbia Gateway Drive (O)	Columbia, MD	17,512			1,753			34,090			13			1,753			34,103			35,856			(4,085		)	2009	9/28/00

6724 Alexander Bell Drive (O)	Columbia, MD	10,939			449			5,039			368			449			5,407			5,856			(1,946		)	2001	5/14/01

6731 Columbia Gateway Drive (O)	Columbia, MD	—			2,807			19,098			1,946			2,807			21,044			23,851			(7,214		)	2002	3/29/00

6740 Alexander Bell Drive (O)	Columbia, MD	—			1,424			5,696			3,147			1,424			8,843			10,267			(4,275		)	1992	12/31/98

6741 Columbia Gateway Drive (O)	Columbia, MD	—			675			1,711			114			675			1,825			2,500			(249		)	2008	9/28/00

6750 Alexander Bell Drive (O)	Columbia, MD	—			1,263			12,461			3,222			1,263			15,683			16,946			(6,406		)	2001	12/31/98

6760 Alexander Bell Drive (O)	Columbia, MD	—			890			3,561			2,564			890			6,125			7,015			(2,756		)	1991	12/31/98

6940 Columbia Gateway Drive (O)	Columbia, MD	17,300			3,545			9,916			3,894			3,545			13,810			17,355			(5,809		)	1999	11/13/98

6950 Columbia Gateway Drive (O)	Columbia, MD	—			3,596			14,269			2,694			3,596			16,963			20,559			(6,425		)	1998	10/22/98

7000 Columbia Gateway Drive (O)	Columbia, MD	15,800			3,131			12,103			1,137			3,131			13,240			16,371			(3,646		)	1999	5/31/02

7015 Albert Einstein Drive (O)	Columbia, MD	2,204			2,058			6,093			826			2,058			6,919			8,977			(2,424		)	1999	12/1/05

7061 Columbia Gateway Drive (O)	Columbia, MD	—			729			3,094			1,137			729			4,231			4,960			(1,539		)	2000	8/30/01

7063 Columbia Gateway Drive (O)	Columbia, MD	—			902			3,684			1,074			902			4,758			5,660			(2,173		)	2000	8/30/01

7065 Columbia Gateway Drive (O)	Columbia, MD	—			919			3,763			1,245			919			5,008			5,927			(2,137		)	2000	8/30/01

7067 Columbia Gateway Drive (O)	Columbia, MD	—			1,829			11,823			2,468			1,829			14,291			16,120			(4,893		)	2001	8/30/01

7125 Columbia Gateway Drive (L)	Columbia, MD	—			3,361			128			279			3,361			407			3,768			—			1973/1999 (8)	6/29/06

7125 Columbia Gateway Drive (O)	Columbia, MD	—			17,126			46,994			8,586			17,126			55,580			72,706			(12,358		)	1973/1999	6/29/06

7130 Columbia Gateway Drive (O)	Columbia, MD	6,519			1,350			4,359			1,784			1,350			6,143			7,493			(1,949		)	1989	9/19/05

7134 Columbia Gateway Drive (O)	Columbia, MD	2,949			704			1,971			299			704			2,270			2,974			(569		)	1990	9/19/05

7138 Columbia Gateway Drive (O)	Columbia, MD	5,406			1,104			3,518			1,961			1,104			5,479			6,583			(2,495		)	1990	9/19/05

7142 Columbia Gateway Drive (O)	Columbia, MD	6,280			1,342			3,978			2,721			1,342			6,699			8,041			(1,867		)	1994	9/19/05

7150 Columbia Gateway Drive (O)	Columbia, MD	4,850			1,032			3,429			333			1,032			3,762			4,794			(959		)	1991	9/19/05

7150 Riverwood Drive (O)	Columbia, MD	—			1,821			4,388			999			1,821			5,387			7,208			(1,457		)	2000	1/10/07

7160 Riverwood Drive (O)	Columbia, MD	—			2,732			7,006			1,540			2,732			8,546			11,278			(2,857		)	2000	1/10/07

7170 Riverwood Drive (O)	Columbia, MD	—			1,283			3,096			642			1,283			3,738			5,021			(1,007		)	2000	1/10/07

7175 Riverwood Drive (O)	Columbia, MD	—			1,788			7,042			—			1,788			7,042			8,830			(43		)	1996/2013	7/27/05

7200 Redstone Gateway (O)	Huntsville, AL	—			—			4,921			—			—			4,921			4,921			(9		)	2013	3/23/10

7200 Riverwood Road (O)	Columbia, MD	—			4,089			16,356			3,067			4,089			19,423			23,512			(7,341		)	1986	10/13/98

7205 Riverwood Drive (O)	Columbia, MD	—			1,367			16,280			—			1,367			16,280			17,647			(298		)	2013	7/27/05

7272 Park Circle Drive (O)	Hanover, MD	5,081			1,479			6,300			1,988			1,479			8,288			9,767			(2,018		)	1991/1996	1/10/07

7318 Parkway Drive (O)	Hanover, MD	—			972			3,888			871			972			4,759			5,731			(1,725		)	1984	4/16/99

7320 Parkway Drive (O)	Hanover, MD	7,000			905			3,570			3,209			905			6,779			7,684			(1,837		)	1983	4/4/02

7467 Ridge Road (O)	Hanover, MD	—			1,629			6,517			2,065			1,629			8,582			10,211			(3,710		)	1990	4/28/99

7700 Potranco Road (O)	San Antonio, TX	—			14,020			38,804			13			14,020			38,817			52,837			(6,674		)	1982/1985	3/30/05



					Initial Cost									Gross Amounts Carried At Close of Period
Property (Type) (1)	Location	Encumbrances (2)			Land			Building and Land Improvements			Costs Capitalized Subsequent to Acquisition			Land			Building and Land Improvements			Total (3)(4)			Accumulated Depreciation (5)			Year Built or Renovated	Date Acquired (6)
7700-1 Potranco Road (O)	San Antonio, TX	—			—			1,066			—			—			1,066			1,066			(135		)	2007	3/30/05

7700-5 Potranco Road (O)	San Antonio, TX	—			—			1,884			—			—			1,884			1,884			(202		)	2009	3/30/05

7740 Milestone Parkway (O)	Hanover, MD	19,712			3,825			34,365			275			3,825			34,640			38,465			(3,128		)	2009	7/2/07

7770 Backlick Road (O)	Springfield, VA	—			6,387			73,964			8			6,387			73,972			80,359			(1,558		)	2012	3/10/10

8000 Potranco Road (O)	San Antonio, TX	—			1,964			21,178			—			1,964			21,178			23,142			(1,678		)	2010	1/20/06

8003 Corporate Drive (O)	White Marsh, MD	—			611			1,611			191			611			1,802			2,413			(351		)	1999	1/9/07

8007 Corporate Drive (O)	White Marsh, MD	—			1,434			3,336			315			1,434			3,651			5,085			(823		)	1995	1/9/07

8010 Corporate Drive (O)	White Marsh, MD	—			1,349			3,262			1,706			1,349			4,968			6,317			(1,061		)	1998	1/9/07

8013 Corporate Drive (O)	White Marsh, MD	—			642			1,536			1,809			642			3,345			3,987			(600		)	1990	1/9/07

8015 Corporate Drive (O)	White Marsh, MD	—			446			1,116			250			446			1,366			1,812			(366		)	1990	1/9/07

8019 Corporate Drive (O)	White Marsh, MD	—			680			1,898			738			680			2,636			3,316			(652		)	1990	1/9/07

8020 Corporate Drive (O)	White Marsh, MD	—			2,184			3,767			2,199			2,184			5,966			8,150			(1,226		)	1997	1/9/07

8023 Corporate Drive (O)	White Marsh, MD	—			651			1,603			5			651			1,608			2,259			(312		)	1990	1/9/07

8030 Potranco Road (O)	San Antonio, TX	—			1,964			21,298			—			1,964			21,298			23,262			(1,680		)	2010	1/20/06

8094 Sandpiper Circle (O)	White Marsh, MD	—			1,960			3,716			375			1,960			4,091			6,051			(958		)	1998	1/9/07

8098 Sandpiper Circle (O)	White Marsh, MD	—			1,797			3,651			639			1,797			4,290			6,087			(690		)	1998	1/9/07

8100 Potranco Road (O)	San Antonio, TX	—			1,964			5,001			—			1,964			5,001			6,965			—			-7	6/14/05

8110 Corporate Drive (O)	White Marsh, MD	—			2,285			10,117			987			2,285			11,104			13,389			(2,527		)	2001	1/9/07

8140 Corporate Drive (O)	White Marsh, MD	—			2,158			8,457			2,252			2,158			10,709			12,867			(3,381		)	2003	1/9/07

8621 Robert Fulton Drive (O)	Columbia, MD	11,000			2,317			12,642			199			2,317			12,841			15,158			(2,664		)	2005-2006	6/10/05

8661 Robert Fulton Drive (O)	Columbia, MD	6,200			1,510			3,764			1,042			1,510			4,806			6,316			(1,662		)	2002	12/30/03

8671 Robert Fulton Drive (O)	Columbia, MD	7,600			1,718			4,280			1,941			1,718			6,221			7,939			(2,451		)	2002	12/30/03

870 Elkridge Landing Road (O)	Linthicum, MD	18,900			2,003			9,442			6,764			2,003			16,206			18,209			(7,553		)	1981	8/3/01

891 Elkridge Landing Road (O)	Linthicum, MD	—			1,165			4,772			2,000			1,165			6,772			7,937			(2,965		)	1984	7/2/01

900 Elkridge Landing Road (O)	Linthicum, MD	—			1,993			7,972			3,350			1,993			11,322			13,315			(5,230		)	1982	4/30/98

901 Elkridge Landing Road (O)	Linthicum, MD	—			1,156			4,437			1,985			1,156			6,422			7,578			(2,386		)	1984	7/2/01

911 Elkridge Landing Road (O)	Linthicum, MD	—			1,215			4,861			2,024			1,215			6,885			8,100			(3,014		)	1985	4/30/98

921 Elkridge Landing Road (O)	Linthicum, MD	—			1,044			4,176			718			1,044			4,894			5,938			(2,114		)	1983	4/30/98

938 Elkridge Landing Road (O)	Linthicum, MD	—			1,163			4,748			1,131			1,163			5,879			7,042			(1,757		)	1984	7/2/01

939 Elkridge Landing Road (O)	Linthicum, MD	—			939			3,756			2,036			939			5,792			6,731			(2,677		)	1983	4/30/98

940 Elkridge Landing Road (L)	Linthicum, MD	—			1,104			4,725			170			1,104			4,895			5,999			(4,884		)	-8	7/2/01

9651 Hornbaker Road (D)	Manassas, VA	—			6,050			203,609			844			6,050			204,453			210,503			(6,637		)	2010	9/14/10

9690 Deereco Road (O)	Timonium, MD	—			3,415			13,723			6,100			3,415			19,823			23,238			(8,717		)	1988	12/21/99

9900 Franklin Square Drive (O)	White Marsh, MD	—			979			3,466			361			979			3,827			4,806			(854		)	1999	1/9/07

9910 Franklin Square Drive (O)	White Marsh, MD	4,870			1,219			6,590			209			1,219			6,799			8,018			(1,705		)	2005	1/9/07

9920 Franklin Square Drive (O)	White Marsh, MD	—			1,058			5,293			1,429			1,058			6,722			7,780			(1,789		)	2006	1/9/07

9930 Franklin Square Drive (O)	White Marsh, MD	—			1,137			3,921			225			1,137			4,146			5,283			(890		)	2001	1/9/07

9940 Franklin Square Drive (O)	White Marsh, MD	—			1,052			3,382			281			1,052			3,663			4,715			(853		)	2000	1/9/07

Aerotech Commerce (L)	Colorado Springs, CO	—			900			—			—			900			—			900			—			-8	5/19/06



					Initial Cost									Gross Amounts Carried At Close of Period
Property (Type) (1)	Location	Encumbrances (2)			Land			Building and Land Improvements			Costs Capitalized Subsequent to Acquisition			Land			Building and Land Improvements			Total (3)(4)			Accumulated Depreciation (5)			Year Built or Renovated	Date Acquired (6)
Arborcrest (O)	Blue Bell, PA	—			21,968			96,992			1,194			21,968			98,186			120,154			(5,842		)	1991-1996	10/14/97

Arundel Preserve (L)	Hanover, MD	—			5,425			7,125			—			5,425			7,125			12,550			—			-8	7/2/07

Ashburn Crossing (L)	Ashburn, VA	—			4,311			2,646			—			4,311			2,646			6,957			—			-8	12/27/12

Canton Crossing Land (L)	Baltimore, MD	—			16,085			490			—			16,085			490			16,575			—			-8	10/27/09

Canton Crossing Util Distr Ctr (O)	Baltimore, MD	—			7,300			15,556			878			7,300			16,434			23,734			(2,183		)	2006	10/27/09

Columbia Gateway - Southridge (L)	Columbia, MD	—			6,387			2,940			—			6,387			2,940			9,327			—			-8	9/20/04

Dahlgren Technology Center (L)	Dahlgren, VA	—			978			178			—			978			178			1,156			—			-8	3/16/05

Expedition VII (L)	Lexington Park, MD	—			705			726			—			705			726			1,431			—			-8	3/24/04

Indian Head (L)	Bryans Road, MD	—			6,436			—			—			6,436			—			6,436			—			-8	10/23/06

InterQuest (L)	Colorado Springs, CO	—			14,382			8			—			14,382			8			14,390			—			-8	9/28/05

M Square Research Park (L)	College Park, MD	—			—			4,311			—			—			4,311			4,311			—			-8	1/29/08

National Business Park (L)	Annapolis Junction, MD	—			2,372			7,391			—			2,372			7,391			9,763			—			-8	11/14/03

National Business Park North (L)	Jessup, MD	—			27,766			28,000			—			27,766			28,000			55,766			—			-8	6/29/06

North Gate Business Park (L)	Aberdeen, MD	—			6,486			10,910			—			6,486			10,910			17,396			—			-8	9/14/07

Northwest Crossroads (L)	San Antonio, TX	—			7,430			836			—			7,430			836			8,266			—			-8	1/20/06

NOVA Office A (O)	Chantilly, VA	—			2,096			9,963			—			2,096			9,963			12,059			—			-7	7/31/02

Old Annapolis Road (O)	Columbia, MD	—			1,637			5,500			2,103			1,637			7,603			9,240			(2,546		)	1974/1985	12/14/00

Patriot Park (L)	Colorado Springs, CO	—			8,768			248			—			8,768			248			9,016			—			-8	7/8/05

Patriot Ridge (L)	Springfield, VA	—			18,517			14,166			—			18,517			14,166			32,683			—			-8	3/10/10

Redstone Gateway (L)	Huntsville, AL	—			—			13,974			—			—			13,974			13,974			—			-8	3/23/10

Route 15/Biggs Ford Road (L)	Frederick, MD	—			8,703			501			—			8,703			501			9,204			—			-8	8/28/08

Sentry Gateway (L)	San Antonio, TX	—			8,275			3,645			—			8,275			3,645			11,920			—			-8	3/30/05

West Nursery Road (L)	Linthicum, MD	—			1,441			88			—			1,441			88			1,529			—			-8	10/28/09

Westfields - Park Center (L)	Chantilly, VA	—			23,745			3,902			—			23,745			3,902			27,647			—			-8	7/18/02

Westfields Corporate Center (L)	Chantilly, VA	—			7,141			1,379			—			7,141			1,379			8,520			—			-8	7/31/02

White Marsh (L)	White Marsh, MD	—			26,589			12,492			—			26,589			12,492			39,081			—			-8	1/9/07

Woodland Park (L)	Herndon, VA	—			9,614			81			—			9,614			81			9,695			—			-8	4/29/04

Other Developments, including intercompany eliminations (V)	Various	—			8			(155		)	261			8			106			114			(9		)	Various	Various

		$	697,902		$	676,148		$	2,843,246		$	292,556		$	676,148		$	3,135,802		$	3,811,950		$	(597,649	)



-1	A legend for the Property Type follows: (O) =ffice Property; (L) =and held or pre-construction; (D) =ata Center; and (V) =arious.

-2	Excludes our term loan facilities of $620.0 million, unsecured senior notes of $592.7 million, exchangeable senior notes of $563,000, unsecured notes payable of $1.7 million, a letter of credit on a mortgage loan of $14.8 million, and net premiums on the remaining loans of $69,000.

-3	The aggregate cost of these assets for Federal income tax purposes was approximately $3.3 billion at December 31, 2013.

-4	As discussed in Note 3 to our Consolidated Financial Statements, we recognized impairment losses of $5.9 million in connection with two properties in the Greater Baltimore region that we determined no longer met our strategic investment criteria.

-5	The estimated lives over which depreciation is recognized follow: Building and land improvements: 10-40 years; and tenant improvements: related lease terms.

-6	The acquisition date of multi-parcel properties reflects the date of the earliest parcel acquisition.

-7	Under construction or redevelopment at December 31, 2013.

-8	Held or under pre-construction at December 31, 2013.


The following table summarizes our changes in cost of properties for the years ended December 31, 2013, 2012 and 2011 (in thousands):
						2013				2012				2011
	Beginning balance					$	3,859,960			$	4,038,932			$	3,948,487

	Acquisitions of operating properties					—				33,684				26,887

	Improvements and other additions					249,639				214,418				304,079

	Sales					(141,045		)		(291,491		)		(75,315		)
	Impairments					(45,931		)		(121,557		)		(165,206		)
	Other dispositions					(110,673		)		(13,891		)		—

	Other					—				(135		)		—

	Ending balance					$	3,811,950			$	3,859,960			$	4,038,932


The following table summarizes our changes in accumulated depreciation for the same time periods (in thousands):
						2013				2012				2011
	Beginning balance					$	568,176			$	577,601			$	503,032

	Depreciation expense					92,677				93,158				99,173

	Sales					(9,542		)		(40,346		)		(9,640		)
	Impairments					(14,863		)		(58,855		)		(15,039		)
	Other dispositions					(38,799		)		(3,247		)		—

	Other					—				(135		)		75

	Ending balance					$	597,649			$	568,176			$	577,601

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
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 they 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 the entity’s operations but cannot control the entity’s operations. We discontinue equity method accounting if our investment in an entity (and net advances) is reduced to zero unless we have guaranteed obligations of the entity or are otherwise committed to provide further financial support for the entity.

	We use the cost method of accounting when we own an interest in an entity and cannot exert significant influence over its operations.
Reclassifications	'
	Reclassifications

	We reclassified certain amounts from prior periods to conform to the current period presentation of our consolidated financial statements with no effect on previously reported net income or equity, including the following:


	•	amounts associated with our mortgage and other investing receivables were reclassified to a separate line reported on our consolidated balance sheets; and

	•	amounts on our consolidated statements of operations were reclassified in conjunction with the transfer of properties to, and from, discontinued operations during 2013. We provide disclosure regarding our discontinued operations in Note 20.
Use of Estimates in the Preparation of Financial Statements	'
	Use of Estimates in the Preparation of Financial Statements

	We make estimates and assumptions when preparing financial statements under generally accepted accounting principles (“GAAP”). These estimates and assumptions affect various matters, including:

	•	the reported amounts of assets and liabilities in our consolidated balance sheets at the dates of the financial statements;

	•	the disclosure of contingent assets and liabilities at the dates of the financial statements; and

	•	the reported amounts of revenues and expenses in our consolidated statements of operations during the reporting periods.

	Significant estimates are inherent in the presentation of our financial statements in a number of areas, including the evaluation of the collectability of accounts and notes receivable, the allocation of property acquisition costs, the determination of estimated useful lives of assets, the determination of lease terms, the evaluation of impairment of long-lived assets, the amount of revenue recognized relating to tenant improvements and the level of expense recognized in connection with share-based compensation. Actual results could differ from these and other estimates.
Acquisitions of Properties	'
	Acquisitions of Properties

	Upon completion of property acquisitions, we allocate the purchase price to tangible and intangible assets and liabilities associated with such acquisitions based on our estimates of their fair values. We determine these fair values by using market data and independent appraisals available to us and making numerous estimates and assumptions. We allocate property acquisitions to the following components:


	•	properties based on a valuation performed under the assumption that the property is vacant upon acquisition (the “if vacant value”). The if-vacant value is allocated between land and buildings or, in the case of properties under development, construction in progress. We also allocate additional amounts to properties for in-place tenant improvements based on our estimate of improvements per square foot provided under market leases that would be attributable to the remaining non-cancellable terms of the respective leases;

	•	above- and below-market lease intangible assets or liabilities based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between: (1) the contractual amounts to be received pursuant to the in-place leases; and (2) our estimate of fair market lease rates for the corresponding space, measured over a period equal to the remaining non-cancelable term of the lease. The capitalized above- and below-market lease values are amortized as adjustments to rental revenue over the remaining non-cancellable terms of the respective leases;

	•	in-place lease value based on our estimates of: (1) the present value of additional income to be realized as a result of leases being in place on the acquired properties; and (2) costs to execute similar leases. Our estimate of additional income to be realized includes carrying costs, such as real estate taxes, insurance and other operating expenses, and revenues during the expected lease-up periods considering current market conditions. Our estimate of costs to execute similar leases includes leasing commissions, legal and other related costs;

	•	tenant relationship value based on our evaluation of the specific characteristics of each tenant's lease and our overall relationship with that respective tenant. Characteristics we consider in determining these values include the nature and extent of our existing business relationships with the tenant, growth prospects for developing new business with the tenant, the tenant's credit quality and expectations of lease renewals, among other factors; and

	•	above- and below- market cost arrangements (such as real estate tax treaties or above- or below- market ground leases) based on the present value of the expected benefit from any such arrangements in place on the property at the time of acquisition.
Properties	'
	Properties

	We report properties to be developed or held and used in operations at our depreciated cost, reduced for impairment losses. The preconstruction stage of the development or redevelopment of an operating property includes efforts and related costs to secure land control and zoning, evaluate feasibility and complete other initial tasks which are essential to development. We capitalize interest expense, real estate taxes and direct and indirect project costs (including related compensation and other indirect costs) associated with properties, or portions thereof, undergoing construction, development and redevelopment activities. We continue to capitalize these costs while construction, development or redevelopment activities are underway until a property becomes “operational,” which occurs upon the earlier of when leases commence or one year after the cessation of major construction activities. When leases commence on portions of a newly-constructed or redeveloped property in the period prior to one year from the cessation of major construction activities, we consider that property to be “partially operational.” When a property is partially operational, we allocate the costs associated with the property between the portion that is operational and the portion under construction. We start depreciating newly-constructed and redeveloped properties as they become operational.
	Most of our leases involve some form of improvements to leased space. When we are required to provide improvements under the terms of a lease, we determine whether the improvements constitute landlord assets or tenant assets. If the improvements are landlord assets, we capitalize the cost of the improvements and recognize depreciation expense associated with such improvements over the shorter of the useful life of the assets or the term of the lease and recognize any payments from the tenant as rental revenue over the term of the lease. If the improvements are tenant assets, we defer the cost of improvements funded by us as a lease incentive asset and amortize it as a reduction of rental revenue over the term of the lease. In determining whether improvements constitute landlord or tenant assets, we consider numerous factors, including: whether the improvements are unique to the tenant or reusable by other tenants; whether the tenant is permitted to alter or remove the improvements without our consent or without compensating us for any lost fair value; whether the ownership of the improvements remains with us or remains with the tenant at the end of the lease term; and whether the economic substance of the lease terms is properly reflected.
	We depreciate our fixed assets using the straight-line method over their estimated useful lives as follows:


			Estimated Useful Lives
	Buildings and building improvements		10-40 years
	Land improvements		10-20 years
	Tenant improvements on operating properties		Related lease term
	Equipment and personal property		3-10 years
	We assess each of our operating properties for impairment quarterly using cash flow projections and estimated fair values that we derive for each of the properties. We update the leasing and other assumptions used in these projections regularly, paying particular attention to properties that have experienced chronic vacancy or face significant market challenges. We review our plans and intentions for our development projects and land parcels quarterly. If our analyses indicate that the carrying values of operating properties, properties in development or land held for future development may be impaired, we perform a recovery analysis for such properties. For long-lived assets to be held and used, we analyze recoverability based on the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over, in most cases, a ten-year holding period. If we believe there is a significant possibility that we might dispose of the assets earlier, we analyze recoverability using a probability weighted analysis of the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over the various possible holding periods. If the recovery analysis indicates that the carrying value of a tested property is not recoverable from estimated future cash flows, it is written down to its estimated fair value and an impairment loss is recognized. If and when our plans change, we revise our recoverability analyses to use the cash flows expected from the operations and eventual disposition of each asset using holding periods that are consistent with our revised plans. Changes in holding periods may require us to recognize significant impairment losses.

	Property fair values are determined based on contract prices, indicative bids, discounted cash flow analyses or yield analyses. Estimated cash flows used in such analyses are based on our plans for the property and our views of market and economic conditions. The estimates consider items such as current and future rental rates, occupancies for the tested property and comparable properties, estimated operating and capital expenditures and recent sales data for comparable properties; most of these items are influenced by market data obtained from real estate leasing and brokerage firms and our direct experience with the properties and their markets.

	When we determine that a property is held for sale, we discontinue the recording of depreciation expense on the property and estimate the fair value, net of selling costs; if we then determine that the estimated fair value, net of selling costs, is less than the net book value of the property, we recognize an impairment loss equal to the difference and reduce the net book value of the property.
	When we dispose of an operating property and determine that we have no significant continuing involvement in such property, or determine that an operating property is held for sale, we classify the results of operations for such property as discontinued operations and classify the assets as held for sale. Interest expense that is specifically identifiable to properties included in discontinued operations is used in the computation of interest expense attributable to discontinued operations.

Sale of Interests in Real Estate	'
	Sales of Interests in Real Estate

	We recognize gains from sales of interests in real estate using the full accrual method, provided that various criteria relating to the terms of sale and any subsequent involvement by us with the real estate sold are met.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents

	Cash and cash equivalents include all cash and liquid investments that mature three months or less from when they are purchased. Cash equivalents are reported at cost, which approximates fair value. We maintain our cash in bank accounts in amounts that may exceed Federally insured limits at times. We have not experienced any losses in these accounts in the past and believe that we are not exposed to significant credit risk because our accounts are deposited with major financial institutions.
Investments in Marketable Securities	'
	Investments in Marketable Securities

	We classify marketable securities as trading securities when we have the intent to sell such securities in the near term, and classify other marketable securities as available-for-sale securities. We determine the appropriate classification of investments in marketable securities at the acquisition date and re-evaluate the classification at each balance sheet date. We report investments in marketable securities classified as trading securities at fair value, with unrealized gains and losses recognized through earnings; on our statements of cash flows, we classify cash flows from these securities as operating activities. We report investments in marketable securities classified as available-for-sale securities at fair value, with net unrealized gains or losses deferred to accumulated other comprehensive income (loss) (“AOCI”) and realized gains and losses resulting from sales of such investments recognized through earnings; on our statements of cash flows, we classify cash flows from interest and dividends earned on these securities as operating activities and cash flows from purchases, sales and maturities of these securities as investing activities.
Accounts and Deferred Rents Receivable and Mortgage and Other Investing Receivables	'
	Accounts and Deferred Rents Receivable and Mortgage and Other Investing Receivables

	We maintain allowances for estimated losses resulting from the failure of our customers or borrowers to satisfy their payment obligations. We use judgment in estimating these allowances based primarily upon the payment history and credit status of the entities associated with the individual receivables. We write off these receivables when we believe the facts and circumstances indicate that continued pursuit of collection is no longer warranted. When we earn interest income in connection with receivables for which we have established allowances, we establish allowances in connection with such interest income that is unpaid. When cash is received in connection with receivables for which we have established allowances, we reduce the amount of losses recognized in connection with the receivables’ allowance.
Intangible Assets and Deferred Revenue on Real Estate Acquisitions	'
	Intangible Assets and Deferred Revenue on Real Estate Acquisitions

	We capitalize intangible assets and deferred revenue on real estate acquisitions as described in the section above entitled “Acquisitions of Properties.” We amortize the intangible assets and deferred revenue as follows:


			Amortization Period
	Above- and below-market leases		Related lease terms
	In-place lease value		Related lease terms
	Tenant relationship value		Estimated period of time that tenant will lease space in property
	Above- and below-market cost arrangements		Term of arrangements
	Market concentration premium		40 years
	We recognize the amortization of acquired above-market and below-market leases as adjustments to rental revenue. We recognize the amortization of above- and below- market cost arrangements as adjustments to property operating expenses. We recognize the amortization of other intangible assets on property acquisitions as amortization expense.
Deferred Leasing and Financing Costs, Net	'
	Deferred Leasing and Financing Costs, Net

	We defer costs incurred to obtain new tenant leases or extend existing tenant leases, including related compensation costs. We amortize these costs evenly over the lease terms. When tenant leases are terminated early, we expense any unamortized deferred leasing costs associated with those leases over the shortened term of the lease.
	We defer costs of financing arrangements and recognize these costs as interest expense over the related loan terms on a straight-line basis, which approximates the amortization that would occur under the effective interest method of amortization. We expense any unamortized loan costs when loans are retired early.
Noncontrolling Interests	'

	Noncontrolling Interests

	COPT’s consolidated noncontrolling interests are comprised of interests in COPLP not owned by COPT (discussed further in Note 15) and consolidated real estate joint ventures (discussed further in Note 6). COPLP’s consolidated noncontrolling interests are comprised primarily of interests in our consolidated real estate joint ventures. Also included in COPLP’s consolidated noncontrolling interests are interests in several real estate entities owned directly by COPT, or a wholly owned subsidiary of COPT, that generally do not exceed 1%. We evaluate whether noncontrolling interests are subject to redemption features outside of our control. For noncontrolling interests that are currently redeemable for cash at the option of the holders of such interests or deemed probable to eventually become redeemable, we classify such interests as redeemable noncontrolling interests in the mezzanine section of our consolidated balance sheets; we adjust these interests each period to the greater of their fair value or carrying amount (initial amount as adjusted for allocations of income and losses and future contributions and distributions), with a corresponding offset to additional paid-in capital on COPT’s consolidated balance sheets or common units on COPLP’s balance sheet, and only recognize reductions in such interests to the extent of their carrying amount. Our other noncontrolling interests are reported in the equity section of our consolidated balance sheets. The amounts reported for noncontrolling interests on our consolidated statements of operations represent the portion of these entities’ income or losses not attributable to us.
Revenue Recognition	'
	Revenue Recognition

	We recognize minimum rents, net of abatements, on a straight-line basis over the term of tenant leases. The term of a lease generally includes periods when a tenant: (1) may not terminate its lease obligation early; (2) may terminate its lease obligation early in exchange for a fee or penalty that we consider material enough such that termination would not be probable; (3) possesses renewal rights and the tenant’s failure to exercise such rights imposes a penalty on the tenant material enough such that renewal appears reasonably assured; and (4) possesses bargain renewal options for such periods. We report the amount by which our minimum rental revenue recognized on a straight-line basis under leases exceeds the contractual rent billings associated with such leases as deferred rent receivable on our consolidated balance sheets. Amounts by which our minimum rental revenue recognized on a straight-line basis under leases are less than the contractual rent billings associated with such leases are included in deferred revenue associated with operating leases on our consolidated balance sheets.
	In connection with a tenant’s entry into, or modification of, a lease, if we make cash payments to, or on behalf of, the tenant for purposes other than funding the construction of landlord assets, we defer the amount of such payments as lease incentives. As discussed above, when we are required to provide improvements under the terms of a lease, we determine whether the improvements constitute landlord assets or tenant assets; if the improvements are tenant assets, we defer the cost of improvements funded by us as a lease incentive asset. We amortize lease incentives as a reduction of rental revenue over the term of the lease.
	We recognize tenant recovery revenue in the same periods in which we incur the related expenses. Tenant recovery revenue includes payments from tenants as reimbursement for property taxes, utilities and other property operating expenses.

	We recognize fees received for lease terminations as revenue and write off against such revenue any (1) deferred rents receivable, and (2) deferred revenue, lease incentives and intangible assets that are amortizable into rental revenue associated with the leases; the resulting net amount is the net revenue from the early termination of the leases. When a tenant's lease for space in a property is terminated early but the tenant continues to lease such space under a new or modified lease in the property, the net revenue from the early termination of the lease is recognized evenly over the remaining life of the new or modified lease in place on that property.

	We recognize fees for services provided by us once services are rendered, fees are determinable and collectability is assured. We recognize revenue under construction contracts using the percentage of completion method when the revenue and costs for such contracts can be estimated with reasonable accuracy; when these criteria do not apply to a contract, we recognize revenue on that contract using the completed contract method. Under the percentage of completion method, we recognize a percentage of the total estimated revenue on a contract based on the cost of services provided on the contract as of a point in time relative to the total estimated costs on the contract.
Interest Rate Derivatives	'
	Interest Rate Derivatives

	Our primary objectives in using interest rate derivatives are to add stability to interest expense and to manage exposure to interest rate movements. To accomplish this objective, we primarily use interest rate swaps as part of our interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for our making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Derivatives are used to hedge the cash flows associated with interest rates on existing debt as well as future debt. We recognize all derivatives as assets or liabilities in the balance sheet at fair value. We defer the effective portion of changes in fair value of the designated cash flow hedges to AOCI and reclassify such deferrals to interest expense as interest expense is recognized on the hedged forecasted transactions. We recognize the ineffective portion of the change in fair value of interest rate derivatives directly in interest expense. When an interest rate swap designated as a cash flow hedge no longer qualifies for hedge accounting, we recognize changes in fair value of the hedge previously deferred to AOCI, along with any changes in fair value occurring thereafter, through earnings. We do not use interest rate derivatives for trading or speculative purposes. We manage counter-party risk by only entering into contracts with major financial institutions based upon their credit ratings and other risk factors.

	We use standard market conventions and techniques such as discounted cash flow analysis, option pricing models, replacement cost and termination cost in computing the fair value of derivatives at each balance sheet date. We made an accounting policy election to use an exception provided for in the applicable accounting guidance with respect to measuring counterparty credit risk for derivative instruments; this election enables us to measure the fair value of groups of assets and liabilities associated with derivative instruments consistently with how market participants would price the net risk exposure as of the measurement date.

	Please refer to Note 12 for additional information pertaining to interest rate derivatives.
Expense Classification	'
	Expense Classification
	We classify as property operations expense costs incurred for property taxes, ground rents, utilities, property management, insurance, repairs, exterior and interior maintenance and tenant revenue collection losses, as well as associated labor and indirect costs attributable to these costs.

	We classify as general and administrative and leasing expenses costs incurred for corporate-level management, public company administration, asset management, leasing, investor relations, marketing and corporate-level insurance (including general business, director and officers and key man life) and leasing prospects, as well as associated labor and indirect costs attributable to these costs.
Share-Based Compensation	'
	Share-Based Compensation
	We issued two forms of share-based compensation: restricted COPT common shares (“restricted shares”) and COPT performance share units (“PSUs”). We also issued options to purchase COPT common shares (“options”) in prior years. We account for share-based compensation in accordance with authoritative guidance provided by the Financial Accounting Standards Board (“FASB”) that establishes standards for the accounting for transactions in which an entity exchanges its equity instruments for goods or services, focusing primarily on accounting for transactions in which an entity obtains employee services in share-based payment transactions. The guidance requires us to measure the cost of employee services received in exchange for an award of equity instruments based generally on the fair value of the award on the grant date; such cost is then recognized over the period during which the employee is required to provide service in exchange for the award. No compensation cost is recognized for equity instruments for which employees do not render the requisite service. The guidance also requires that share-based compensation be computed based on awards that are ultimately expected to vest; as a result, future forfeitures of awards are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. If an award is voluntarily cancelled by an employee, we recognize the previously unrecognized cost associated with the original award on the date of such cancellation. We capitalize costs associated with share-based compensation attributable to employees engaged in construction and development activities.

	When we adopted the authoritative guidance on accounting for share-based compensation, we elected to adopt the alternative transition method for calculating the tax effects of share-based compensation. The alternative transition method enabled us to use a simplified method to establishing the beginning balance of the additional paid-in capital pool related to the tax effects of employee share-based compensation, which was available to absorb tax deficiencies recognized subsequent to the adoption of this guidance.

	We compute the fair value of options using the Black-Scholes option-pricing model. Under that model, the risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. The expected option life is based on our historical experience of employee exercise behavior. Expected volatility is based on historical volatility of COPT common shares . Expected dividend yield is based on the average historical dividend yield on our common shares over a period of time ending on the grant date of the options.

	We compute the fair value of PSUs using a Monte Carlo model. Under that model, the baseline common share value is based on the market value on the grant date. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Expected volatility is based on historical volatility of COPT’s common shares.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2013
Accounting Policies [Abstract]	'
Schedule of the estimated useful lives of fixed assets	'
	We depreciate our fixed assets using the straight-line method over their estimated useful lives as follows:


		Estimated Useful Lives
	Buildings and building improvements	10-40 years
	Land improvements	10-20 years
	Tenant improvements on operating properties	Related lease term
	Equipment and personal property	3-10 years
Schedule of amortization of intangible assets and deferred revenue	'
	We amortize the intangible assets and deferred revenue as follows:


		Amortization Period
	Above- and below-market leases	Related lease terms
	In-place lease value	Related lease terms
	Tenant relationship value	Estimated period of time that tenant will lease space in property
	Above- and below-market cost arrangements	Term of arrangements
	Market concentration premium	40 years

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Schedule of fair value assets and liabilities measured on recurring basis	'
	The tables below set forth financial assets and liabilities of COPT and its subsidiaries that are accounted for at fair value on a recurring basis as of December 31, 2013 and 2012 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
			Active Markets for			Observable Inputs(Level 2)				Unobservable Inputs(Level 3)
			Identical Assets(Level 1)
	December 31, 2013:
	Assets:

	Marketable securities in deferred compensation plan (1)

	Mutual funds		$	7,090		$	—			$	—		$	7,090

	Common stocks		176			—				—			176

	Other		201			—				—			201

	Common stock (1)		298			—				—			298

	Interest rate derivatives (2)		—			6,594				—			6,594

	Warrants to purchase common stock in KEYW (2)		—			301				—			301

	Total Assets		$	7,765		$	6,895			$	—		$	14,660

	Liabilities:

	Deferred compensation plan liability (3)		$	—		$	7,467			$	—		$	7,467

	Interest rate derivatives		—			3,309				—			3,309

	Total Liabilities		$	—		$	10,776			$	—		$	10,776

	Redeemable noncontrolling interest		$	—		$	—			$	17,758		$	17,758


	December 31, 2012:
	Assets:

	Marketable securities in deferred compensation plan (1)

	Mutual funds		$	6,275		$	—			$	—		$	6,275

	Common stocks		298			—				—			298

	Other		203			—				—			203

	Common stock (1)		809			—				—			809

	Warrants to purchase common stock in KEYW (2)		—			294				—			294

	Total Assets		$	7,585		$	294			$	—		$	7,879

	Liabilities:

	Deferred compensation plan liability (3)		$	—		$	6,776			$	—		$	6,776

	Interest rate derivatives		—			6,185				—			6,185

	Total Liabilities		$	—		$	12,961			$	—		$	12,961

	Redeemable noncontrolling interest		$	—		$	—			$	10,298		$	10,298


(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 tables below set forth financial assets and liabilities of COPLP and its subsidiaries that are accounted for at fair value on a recurring basis as of December 31, 2013 and 2012 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
		Active Markets for			Observable Inputs(Level 2)				Unobservable Inputs(Level 3)
		Identical Assets(Level 1)
December 31, 2013:
Assets:

Common stock (1)		$	298		$	—			$	—		$	298

Interest rate derivatives (2)		—			6,594				—			6,594

Warrants to purchase common stock in KEYW (2)		—			301				—			301

Total Assets		$	298		$	6,895			$	—		$	7,193

Liabilities:

Interest rate derivatives		$	—		$	3,309			$	—		$	3,309

Redeemable noncontrolling interest		$	—		$	—			$	17,758		$	17,758


December 31, 2012:
Assets:

Common stock (1)		$	809		$	—			$	—		$	809

Warrants to purchase common stock in KEYW (2)		—			294				—			294

Total Assets		$	809		$	294			$	—		$	1,103

Liabilities:

Interest rate derivatives		$	—		$	6,185			$	—		$	6,185

Redeemable noncontrolling interest		$	—		$	—			$	10,298		$	10,298


(1) Included in the line entitled “restricted cash and marketable securities” on COPLP’s consolidated balance sheet.
(2) 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 techniques used by us in determining the fair values of the properties (dollars in thousands):


			Fair Value of Properties Held as of December 31, 2013
			Quoted Prices in							Significant					Impairment
			Active Markets for			Significant Other				Unobservable					Losses
			Identical Assets			Observable Inputs				Inputs					Recognized in
	Description		(Level 1)			(Level 2)				(Level 3)			Total		2013 (1)
	Assets

	Properties, net		$	—		$	—			$	4,459		$	4,459	$	31,068


	(1) Represents aggregate impairment losses on non recurring fair value measurements resulting in impairment losses, excluding exit costs incurred of $979,000.
	The table below sets forth the fair value hierarchy of the valuation techniques used by us in determining the fair values of the properties (dollars in thousands):


			Fair Value of Properties Held as of December 31, 2012
			Quoted Prices in							Significant					Impairment
			Active Markets for			Significant Other				Unobservable					Losses
			Identical Assets			Observable Inputs				Inputs					Recognized in
	Description		(Level 1)			(Level 2)				(Level 3)			Total		2012 (1)
	Assets (2):

	Properties, net		$	—		$	—			$	173,949		$	173,949	$	62,702


	(1) Represents aggregate impairment losses on non recurring fair value measurements resulting in impairment losses, excluding exit costs incurred of $4.2 million.
	(2) Reflects balance sheet classifications of assets at time of fair value measurement, excluding the effect of held for sale classifications.
Schedule of quantitative information about significant unobservable inputs used for Level 3 fair value measurements	'
	The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above as of December 31, 2012 (dollars in thousands):


	Valuation Technique		Fair Value on			Unobservable Input		Range (Weighted Average)
			Measurement Date
	Discounted cash flow		$	166,650		Discount rate		10.0% to 11.0% (10.3%)

						Terminal capitalization rate		8.7% to 10.0% (8.9%)

						Market rent growth rate		3.0% (1)

						Expense growth rate		3.0% (1)

	Yield Analysis		$	2,356		Yield		12% (1)

						Market rent rate		$8.50 per square foot (1)

						Leasing costs		$20.00 per square foot (1)

	(1) Only one value applied for this unobservable input.
	The table below sets forth quantitative information about significant unobservable inputs used for the Level 3 fair value measurements reported above as of December 31, 2013 (dollars in thousands):


	Valuation Technique		Fair Value on			Unobservable Input		Range (Weighted Average)
			Measurement Date
	Discounted cash flow		$	4,459		Discount rate		10.0% (1)

						Terminal capitalization rate		9.5% (1)
						Market rent growth rate		3.0% (1)
						Expense growth rate		3.0% (1)

	(1) Only one value applied for this unobservable input.

Concentration_of_Rental_Revenu1

Concentration of Rental Revenue (Tables)	12 Months Ended
Concentration of Rental Revenue (Tables)	Dec. 31, 2013
Risks and Uncertainties [Abstract]	'
Schedule of percentage of the entity's rental revenue	'
	The following table summarizes the percentage of our rental revenue (which excludes tenant recoveries and other real estate operations revenue) earned from (1) individual tenants that accounted for at least 5% of our rental revenue from continuing and discontinued operations and (2) the aggregate of the five tenants from which we recognized the most rental revenue in the respective years:


		For the Years Ended December 31,
		2013		2012		2011
	United States Government	18	%	18	%	17	%
	Northrop Grumman Corporation (1)	8	%	7	%	8	%
	Booz Allen Hamilton, Inc.	6	%	6	%	6	%
	Computer Sciences Corporation (1)	5	%	5	%	N/A
	Computer Sciences Corporation (1)	5	%	5	%	N/A
	Five largest tenants	41	%	39	%	38	%

	(1) Includes affiliated organizations and agencies and predecessor companies.

Properties_net_Tables

Properties, net (Tables)	12 Months Ended
	Dec. 31, 2013
Real Estate [Abstract]	'
Schedule of operating properties, net	'
	Operating properties, net consisted of the following (in thousands):


		December 31,
		2013				2012
	Land	$	430,472			$	427,766

	Buildings and improvements	2,869,870				2,725,875

	Less: accumulated depreciation	(597,649		)		(555,975		)
	Operating properties, net	$	2,702,693			$	2,597,666

Schedule of projects in development or held for future development	'
	Projects we had in development or held for future development consisted of the following (in thousands):


		December 31,
		2013				2012
	Land	$	245,676			$	236,324

	Construction in progress, excluding land	265,932				329,054

	Projects in development or held for future development	$	511,608			$	565,378

Schedule of operating property dispositions	'
	We completed dispositions of the following properties in 2013 primarily in connection with the Strategic Reallocation Plan (dollars in thousands):


	Project Name		Location		Date of Sale		Number of Buildings		Total Rentable Square Feet	Transaction Value		Gain on Disposition
	920 Elkridge Landing Road		Linthicum, MD		6/25/13		1		103,000	$	6,900	$	—

	4230 Forbes Boulevard		Lanham, MD		12/11/13		1		56,000	5,600		1,507

	December 2013 Colorado Springs Portfolio Disposition		Colorado Springs, CO		12/12/13		15		1,165,000	133,925		1,164

	December 2013 Portfolio Conveyance		Colorado Springs, CO and Linthicum, MD		12/23/13		14		1,021,000	146,876		—

							31		2,345,000	$	293,301	$	2,671

	We completed dispositions of the following properties in 2012 primarily in connection with the Strategic Reallocation Plan (dollars in thousands):


	Project Name		Location		Date of Sale		Number of Buildings		Total Rentable Square Feet	Transaction Value		Gain on Disposition
	White Marsh Portfolio Disposition		White Marsh, MD		1/30/12		5		163,000	$	19,100	$	2,445

	1101 Sentry Gateway		San Antonio, TX		1/31/12		1		95,000	13,500		1,739

	222 and 224 Schilling Circle		Hunt Valley, MD		2/10/12		2		56,000	4,400		102

	15 and 45 West Gude Drive		Rockville, MD		5/2/12		2		231,000	49,107		—

	11800 Tech Road		Silver Spring, MD		6/14/12		1		240,000	21,300		—

	400 Professional Drive		Gaithersburg, MD		7/2/12		1		130,000	16,198		—

	July 2012 Portfolio Disposition		Baltimore/Washington Corridor and Greater Baltimore		7/24/12		23		1,387,000	161,901		16,900

							35		2,302,000	$	285,506	$	21,186

Schedule of operating property allocation costs	'
	The table below sets forth the allocation of the acquisition costs of this property (in thousands):



	Land, operating properties		$	3,507

	Building and improvements		30,177

	Intangible assets on real estate acquisitions		14,993

	Total assets		48,677

	Below-market leases		(369		)
	Total acquisition cost		$	48,308

Schedule of allocation of intangible assets on acquisition of property	'
	Intangible assets recorded in connection with the above acquisition included the following (dollars in thousands):


						Weighted Average Amortization Period (in Years)
	Tenant relationship value	$	7,472			10

	In-place lease value	7,109				5

	Above-market leases	412				5

		$	14,993			7

Real_Estate_Joint_Ventures_Tab

Real Estate Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2013
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 December 31, 2013 (dollars in thousands):


				Nominal
				Ownership				31-Dec-13					-1
		Date		% as of				Total			Encumbered		Total
		Acquired		12/31/13		Nature of Activity		Assets			Assets		Liabilities
	LW Redstone Company, LLC	3/23/10		85%		Operates three buildings and developing others (2)		$	132,170		$	67,487	$	39,845

	M Square Associates, LLC	6/26/07		50%		Operates two buildings and developing others (3)		60,919			48,705		41,009

	COPT-FD Indian Head, LLC	10/23/06		75%		Holding land parcel (4)		6,436			—		—

								$	199,525		$	116,192	$	80,854

	(1) Excludes amounts eliminated in consolidation.
	(2) This joint venture’s property is in Huntsville, Alabama.
	(3) This joint venture’s properties are in College Park, Maryland (in the Baltimore/Washington Corridor).
	(4) This joint venture’s property is in Charles County, Maryland. In 2012, the joint venture exercised its option under a development agreement to require Charles County to repurchase the land parcel at its original acquisition cost. Under the terms of the agreement with Charles County, the repurchase is expected to occur by August 2014.
Schedule of condensed balance sheets for unconsolidated real estate joint venture	'
	The following table sets forth condensed balance sheets for this unconsolidated real estate joint venture as of December 31, 2012 (in thousands):


			December 31,
			2012
	Properties, net		$	58,460

	Other assets		4,376

	Total assets		$	62,836


	Liabilities (primarily debt)		$	72,693

	Owners’ equity		(9,857		)
	Total liabilities and owners’ equity		$	62,836

Schedule of condensed statements of operations for unconsolidated real estate joint venture	'
	The following table sets forth condensed statements of operations for this unconsolidated real estate joint venture (in thousands):


			For the Years Ended December 31,
			2013				2012			2011
	Revenues		$	6,519			$	7,316		$	7,577

	Property operating expenses		(2,818		)		(2,829		)	(3,673		)
	Interest expense		(10,463		)		(7,672		)	(3,913		)
	Depreciation and amortization expense		(2,067		)		(2,283		)	(2,463		)
	Gain on early extinguishment of debt		23,013				—			—

	Net income (loss)		$	14,184			$	(5,468	)	$	(2,472	)

Intangible_Assets_on_Real_Esta1

Intangible Assets on Real Estate Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2013
Intangible Assets on Real Estate Acquisitions	'
Intangible assets on real estate acquisitions	'
	Intangible assets on real estate acquisitions consisted of the following (in thousands):


		December 31, 2013						31-Dec-12
		Gross Carrying Amount		Accumulated Amortization		Net		Gross Carrying Amount		Accumulated Amortization		Net
						Carrying Amount						Carrying Amount
	In-place lease value	$	125,504	$	93,885	$	31,619	$	134,964	$	93,362	$	41,602

	Tenant relationship value	44,414		25,962		18,452		46,828		23,346		23,482

	Below-market cost arrangements	12,416		5,136		7,280		12,416		4,100		8,316

	Above-market leases	8,925		7,970		955		8,925		7,432		1,493

	Market concentration premium	1,333		381		952		1,333		347		986

		$	192,592	$	133,334	$	59,258	$	204,466	$	128,587	$	75,879

Deferred_Leasing_and_Financing1

Deferred Leasing and Financing Costs (Tables)	12 Months Ended
	Dec. 31, 2013
Deferred Leasing and Financing Costs [Abstract]	'
Schedule of deferred leasing and financing costs, net	'
	Deferred leasing and financing costs, net consisted of the following (in thousands):


		December 31,
		2013			2012
	Deferred leasing costs	$	110,711		$	97,852

	Deferred financing costs	36,390			30,520

	Accumulated amortization	(80,834		)	(68,420		)
	Deferred leasing and financing costs, net	$	66,267		$	59,952

Mortgage_and_Other_Investing_R1

Mortgage and Other Investing Receivable (Tables)	12 Months Ended
	Dec. 31, 2013
Receivables [Abstract]	'
Mortgage and other investing receivables	'
	Mortgage and other investing receivables, including accrued interest thereon, consisted of the following (in thousands):



		December 31,
		2013		2012
	Notes receivable from City of Huntsville	$	44,055	$	35,654

	Mortgage loans receivable	9,608		144

		$	53,663	$	35,798

Prepaid_Expenses_and_Other_Ass1

Prepaid Expenses and Other Assets (Tables)	12 Months Ended
	Dec. 31, 2013
Prepaid Expense and Other Assets [Abstract]	'
Schedule of prepaid expenses and other assets	'
	Prepaid expenses and other assets consisted of the following (in thousands):



		December 31,
		2013		2012
	Prepaid expenses	$	19,308	$	19,270

	Lease incentives	8,435		5,578

	Interest rate derivatives	6,594		—

	Furniture, fixtures and equipment, net	6,556		7,991

	Deferred tax asset, net (1)	4,305		6,612

	Construction contract costs incurred in excess of billings	2,462		—

	Other equity method investments	2,258		2,425

	Other assets	4,268		2,183

	Prepaid expenses and other assets	$	54,186	$	44,059



	(1) See Note 19 for further disclosure.

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Debt Instrument [Line Items]	'
Schedule of debt	'
	Our debt consisted of the following (dollars in thousands):


		Maximum
		Availability at				Carrying Value at						Scheduled Maturity
		December 31,				December 31,		December 31,		Stated Interest Rates at		as of
		2013				2013		2012		December 31, 2013		December 31, 2013
	Mortgage and Other Secured Loans:

	Fixed rate mortgage loans (1)	-2				$	675,060	$	948,414	3.96% - 7.87% (3)		2014-2024

	Variable rate secured loan					37,691		38,475		LIBOR + 2.25% (4)		Nov-15

	Other construction loan facilities					—		29,557		N/A		N/A

	Total mortgage and other secured loans					712,751		1,016,446

	Revolving Credit Facility (5)	$	800,000			—		—		LIBOR + 0.975% to 1.75%		Jul-17

	Term Loan Facilities (5)	-6				620,000		770,000		LIBOR + 1.10% to 2.60% (7)		2015-2019

	Unsecured Senior Notes (5)
	3.600% Senior Notes					347,244		—		3.60%		May-23

	5.250% Senior Notes					245,445		—		5.25%		Feb-24

	Unsecured notes payable					1,700		1,788		0% (8)		2026

	4.25% Exchangeable Senior Notes (5)					563		230,934		4.25%		Apr-30

	Total debt					$	1,927,703	$	2,019,168



	(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 $69,000 at December 31, 2013 and $1.3 million at December 31, 2012.

	-2	Includes $13.9 million balance on construction loans with maximum available borrowings of $26.2 million.

	-3	The weighted average interest rate on these loans was 6.14% at December 31, 2013.

	(4)	The interest rate on the loan outstanding was 2.42% at December 31, 2013.

	-5	Refer to the paragraphs below for further disclosure.

	(6)	As discussed below, we have the ability to borrow an aggregate of an additional $180.0 million under these term loan facilities, provided that there is no default under the facilities and subject to the approval of the lenders.

	(7)	The weighted average interest rate on these loans was 1.79% at December 31, 2013.

	(8)	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 $761,000 at December 31, 2013 and $873,000 at December 31, 2012.
Schedule of debt maturities	'
	Our debt matures on the following schedule (in thousands):


	2014	$	89,483

	2015	395,969			-1

	2016	279,339

	2017	405,615			-2

	2018	1,374

	Thereafter	763,938

	Total	$	1,935,718		-3

	(1) Includes $250.0 million that may be extended for two one-year periods at our option, subject to certain conditions.
	(2) Includes $250.0 million that may be extended for one year at our option, subject to certain conditions.
	(3) Represents scheduled principal amortization and maturities only and therefore excludes net discounts of $8.0 million.
Schedule of the fair value of debt	'
	The following table sets forth information pertaining to the fair value of our debt (in thousands):


		December 31, 2013						31-Dec-12
		Carrying				Estimated		Carrying		Estimated
		Amount				Fair Value		Amount		Fair Value
	Fixed-rate debt

	Unsecured Senior Notes	$	592,689			$	575,374	$	—	$	—

	4.25% Exchangeable Senior Notes	563				575		230,934		240,282

	Other fixed-rate debt	676,760				650,997		950,202		968,180

	Variable-rate debt	657,691				657,527		838,032		845,558

		$	1,927,703			$	1,884,473	$	2,019,168	$	2,054,020

4.25% Exchangeable Senior Notes	'
Debt Instrument [Line Items]	'
Schedule of interest expense recognized on notes before deductions for amounts capitalized	'
	The table below sets forth interest expense recognized on these notes (in thousands):


		For the Years Ended December 31,
		2013				2012		2011
	Interest expense at stated interest rate	$	4,208			$	10,200	$	10,200

	Interest expense associated with amortization of discount	1,615				3,651		3,437

	Total	$	5,823			$	13,851	$	13,637

3.5% Exchangeable Senior Notes	'
Debt Instrument [Line Items]	'
Schedule of interest expense recognized on notes before deductions for amounts capitalized	'
	The table below sets forth interest expense recognized on these notes for 2011:


	Interest expense at stated interest rate		$	4,013

	Interest expense associated with amortization of discount		2,617

	Total		$	6,630

Interest_Rate_Derivatives_Tabl

Interest Rate Derivatives (Tables)	12 Months Ended
	Dec. 31, 2013
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									Effective		Expiration		December 31,
	Amount				Fixed Rate			Floating Rate Index		Date		Date		2013			2012
	$	100,000			0.6123	%		One-Month LIBOR		1/3/12		9/1/14		$	(279	)	$	(594	)

	100,000				0.61	%		One-Month LIBOR		1/3/12		9/1/14		(277		)	(591		)

	100,000				0.832	%		One-Month LIBOR		1/3/12		9/1/15		(861		)	(1,313		)

	100,000				0.832	%		One-Month LIBOR		1/3/12		9/1/15		(861		)	(1,313		)

	37,691			-1	3.83	%		One-Month LIBOR + 2.25%		11/2/10		11/2/15		(832		)	(1,268		)

	100,000				0.8055	%		One-Month LIBOR		9/2/14		9/1/16		(94		)	(263		)

	100,000				0.81	%		One-Month LIBOR		9/2/14		9/1/16		(105		)	(272		)

	100,000				1.673	%		One-Month LIBOR		9/1/15		8/1/19		3,377			(154		)

	100,000				1.73	%		One-Month LIBOR		9/1/15		8/1/19		3,217			(417		)

														$	3,285		$	(6,185	)



	-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):


			December 31, 2013						December 31, 2012
	Derivatives		Balance Sheet Location		Fair Value				Balance Sheet Location		Fair Value
	Interest rate swaps designated as cash flow hedges		Prepaid expenses and other assets		$	6,594			Prepaid expenses and other assets		$	—

	Interest rate swaps designated as cash flow hedges		Interest rate derivatives		(3,309		)		Interest rate derivatives		(6,185		)
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 Years Ended December 31,
		2013				2012				2011
	Amount of gains (losses) recognized in accumulated other comprehensive income (loss) (“AOCI”) (effective portion)	$	6,791			$	(7,676	)		$	(31,531	)

	Amount of losses reclassified from AOCI into interest expense (effective portion)	(2,740		)		(3,697		)		(4,601		)
	Amount of loss reclassified from AOCI to loss on interest rate derivatives upon discontinuing hedge accounting	—				—				28,430

	Amount of loss on interest rate derivatives recognized subsequent to such derivatives no longer being designated as hedges	—				—				1,375

Redeemable_Noncontrolling_Inte1

Redeemable Noncontrolling Interest (Tables)	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interest [Abstract]	'
Redeemable Noncontrolling Interest	'
	The table below sets forth activity in a redeemable noncontrolling interest in a consolidated real estate joint venture described in Note 6 (in thousands):


		For the Years Ended December 31,
		2013			2012			2011
	Beginning balance	$	10,298		$	8,908		$	9,000

	Distribution to noncontrolling interest	(1,037		)	—			—

	Net income (loss) attributable to noncontrolling interest	1,376			(2,565		)	(1,407		)

	Adjustment to arrive at fair value of interest	7,121			3,955			1,315

	Ending balance	$	17,758		$	10,298		$	8,908

Equity_COPT_and_Subsidiaries_T

Equity - COPT and Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity Note [Abstract]	'
Schedule of additional information pertaining to preferred shares	'
	The table below sets forth additional information pertaining to COPT’s outstanding preferred shares (dollars in thousands, except per share data):


	Series	# of Shares Issued	Aggregate Liquidation Preference		Month of Issuance	Annual Dividend Yield		Annual Dividend Per Share		Earliest Redemption Date
	Series H	2,000,000	$	50,000	Dec-03	7.5	%	$	1.875	12/18/08

	Series K	531,667	26,583		Jan-07	5.6	%	$	2.8	1/9/17

	Series L	6,900,000	172,500		Jun-12	7.375	%	$	1.84375	6/27/17

		9,431,667	$	249,083

Equity_COPLP_and_Subsidiaries_

Equity - COPLP and Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2013
Class of Stock [Line Items]	'
Schedule of additional information pertaining to preferred shares	'
	The table below sets forth additional information pertaining to COPT’s outstanding preferred shares (dollars in thousands, except per share data):


	Series	# of Shares Issued	Aggregate Liquidation Preference		Month of Issuance	Annual Dividend Yield		Annual Dividend Per Share		Earliest Redemption Date
	Series H	2,000,000	$	50,000	Dec-03	7.5	%	$	1.875	12/18/08

	Series K	531,667	26,583		Jan-07	5.6	%	$	2.8	1/9/17

	Series L	6,900,000	172,500		Jun-12	7.375	%	$	1.84375	6/27/17

		9,431,667	$	249,083

Corporate Office Properties, L.P.	'
Class of Stock [Line Items]	'
Schedule of additional information pertaining to preferred shares	'
	The table below sets forth information pertaining to preferred units in COPLP held by COPT at December 31, 2013 (dollars in thousands, except per unit data):


	Series	# of Units Issued	Aggregate Liquidation Preference		Month of Issuance	Annual Distribution Yield		Annual Distribution Per Unit		Earliest Redemption Date
	Series H	2,000,000	$	50,000	Dec-03	7.5	%	$	1.875	12/18/08

	Series K	531,667	26,583		Jan-07	5.6	%	$	2.8	1/9/17

	Series L	6,900,000	172,500		Jun-12	7.375	%	$	1.84375	6/27/17

		9,431,667	$	249,083

ShareBased_Compensation_and_Em1

Share-Based Compensation and Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of restricted share transactions under the entity's share-based compensation plans	'
	The following table summarizes restricted share transactions under the share-based compensation plans for 2011, 2012 and 2013:


			Shares			Weighted Average Grant Date Fair Value
	Unvested at December 31, 2010		669,858			$	32.77

	Granted		320,284			33.68

	Forfeited		(18,058	)		34.23

	Vested		(323,706	)		32.86

	Unvested at December 31, 2011		648,378			33.13

	Granted		177,662			23.64

	Forfeited		(17,019	)		31.43

	Vested		(374,378	)		32.72

	Unvested at December 31, 2012		434,643			29.67

	Granted		193,833			25.91

	Forfeited		(9,541	)		27.59

	Vested		(241,487	)		30.97

	Unvested at December 31, 2013		377,448			$	26.96

	Restricted shares expected to vest		361,064			$	27.02

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 the 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
Schedule of assumptions used in Monte Carlo models for PSUs	'
	The grant date fair value and certain of the assumptions used in the Monte Carlo models for the PSUs granted in 2011, 2012 and 2013 are set forth below:


			For the Years Ended December 31,
			2013				2012			2011
	Grant date fair value		$	26.84			$	32.77		$	49.15

	Baseline common share value		$	25.85			$	24.39		$	35.17

	Expected volatility of common shares		29.5		%		43.2		%	61.1		%
	Risk-free interest rate		0.33		%		0.41		%	1.32		%
Summary of stock option transactions under the entity's share-based compensation plans	'
	The following table summarizes option transactions under the share-based compensation plans for 2011, 2012 and 2013 (dollars in thousands, except per share data):


			Shares			Range of Exercise Price per Share		Weighted Average Exercise Price per Share			Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
											(in Years)
	Outstanding at December 31, 2010		1,188,284			$9.54 - $57.00		$	33.07		5		$	7,987

	Forfeited/Expired – 2011		(51,598	)		$22.49 - $50.59		$	42.82

	Exercised – 2011		(191,264	)		$9.54 - $30.25		$	12.82

	Outstanding at December 31, 2011		945,422			$13.40 - $57.00		$	36.63		4		$	510

	Forfeited/Expired – 2012		(85,588	)		$25.52 - $57.00		$	42.98

	Exercised – 2012		(61,624	)		$13.40 - $22.49		$	15.08

	Outstanding at December 31, 2012		798,210			$13.60 - $57.00		$	37.62		3		$	325

	Forfeited/Expired – 2013		(117,952	)		$18.08 - $51.62		$	40.91

	Exercised – 2013		(39,331	)		$13.60 - $26.24		$	19.67

	Outstanding at December 31, 2013		640,927			$19.63 - $56.00		$	38.11		2		$	68

	Exercisable at December 31, 2011		945,422			-1		$	36.63

	Exercisable at December 31, 2012		798,210			-2		$	37.62

	Exercisable at December 31, 2013		640,927			-3		$	38.11




	-1	53,957 of these options had an exercise price ranging from $13.40 to $16.73; 225,903 had an exercise price ranging from $16.74 to $30.04; 198,762 had an exercise price ranging from $30.05 to $41.28; and 466,800 had an exercise price ranging from $41.29 to $57.00.

	-2	9,500 of these options had an exercise price ranging from $13.60 to $16.73; 204,736 had an exercise price ranging from $16.74 to $30.04; 180,962 had an exercise price ranging from $30.05 to $41.28; and 403,012 had an exercise price ranging from $41.29 to $57.00.

	-3	171,288 of these options had an exercise price ranging from $19.63 to $30.04; 145,187 had an exercise price ranging from$30.05 to $41.28; 160,402 had an exercise price ranging from $41.29 to $42.74; and 164,050 had an exercise price ranging from $42.75 to $56.00.
Reporting for share-based compensation expense	'
	The table below sets forth our reporting for share based compensation expense (in thousands):


			For the Years Ended December 31,
			2013				2012			2011
	General, administrative and leasing expenses		$	5,412			$	8,611		$	9,077

	Property operating expenses		1,118				1,371			2,843

	Capitalized to development activities		1,075				1,202			2,347

	Share-based compensation expense		$	7,605			$	11,184		$	14,267

Operating_Leases_Tables

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2013
Leases, Operating [Abstract]	'
Schedule of gross minimum future rentals on noncancelable leases in the entity's properties	'
	Gross minimum future rentals on noncancelable leases in our properties as of December 31, 2013 were as follows (in thousands):


	Year Ending December 31,
	2014	$	344,809

	2015	310,035

	2016	256,228

	2017	213,894

	2018	163,011

	Thereafter	351,111

		$	1,639,088

Information_by_Business_Segmen1

Information by Business Segment (Tables)	12 Months Ended
	Dec. 31, 2013
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/				Northern				San				Huntsville		Washington,		St. Mary’s &		Greater		Greater		Colorado		Other		Operating		Total
		Washington				Virginia				Antonio						DC - Capitol		King George		Baltimore		Philadelphia		Springs				Wholesale
		Corridor														Riverfront		Counties										Data Center
	Year Ended December 31, 2013

	Revenues from real estate operations	$	237,869			$	92,010			$	33,060			$	5,050	$	16,863	$	16,568	$	42,653	$	11,924	$	25,290	$	10,075	$	7,271	$	498,633

	Property operating expenses	80,554				31,973				17,631				1,282		7,844		5,028		16,583		3,431		9,002		1,016		6,360		180,704

	NOI from real estate operations	$	157,315			$	60,037			$	15,429			$	3,768	$	9,019	$	11,540	$	26,070	$	8,493	$	16,288	$	9,059	$	911	$	317,929

	Additions to long-lived assets	$	28,087			$	13,090			$	335			$	3,563	$	2,604	$	2,341	$	2,913	$	406	$	2,940	$	—	$	598	$	56,877

	Transfers from non-operating properties	$	50,105			$	61,434			$	—			$	48,799	$	—	$	14	$	360	$	28,034	$	5,438	$	—	$	70,106	$	264,290

	Segment assets at December 31, 2013	$	1,243,099			$	616,082			$	118,299			$	77,773	$	98,962	$	96,143	$	303,823	$	104,657	$	—	$	80,002	$	166,790	$	2,905,630


	Year Ended December 31, 2012

	Revenues from real estate operations	$	238,488			$	79,574			$	32,018			$	3,867	$	16,697	$	16,392	$	52,616	$	9,698	$	24,987	$	12,116	$	6,647	$	493,100

	Property operating expenses	83,050				29,103				16,499				689		7,555		4,745		19,917		2,562		9,231		2,569		4,815		180,735

	NOI from real estate operations	$	155,438			$	50,471			$	15,519			$	3,178	$	9,142	$	11,647	$	32,699	$	7,136	$	15,756	$	9,547	$	1,832	$	312,365

	Additions to long-lived assets	$	25,921			$	65,157			$	280			$	26	$	317	$	1,844	$	9,690	$	286	$	2,929	$	152	$	199	$	106,801

	Transfers from non-operating properties	$	65,108			$	44,250			$	468			$	—	$	—	$	289	$	37,558	$	10,626	$	4,295	$	394	$	58,009	$	220,997

	Segment assets at December 31, 2012	$	1,267,357			$	569,860			$	119,369			$	28,730	$	104,544	$	98,027	$	320,548	$	78,798	$	175,830	$	82,090	$	100,777	$	2,945,930


	Year Ended December 31, 2011

	Revenues from real estate operations	$	237,162			$	74,214			$	30,066			$	1,368	$	17,878	$	14,366	$	70,668	$	7,458	$	23,675	$	13,923	$	5,054	$	495,832

	Property operating expenses	86,782				28,518				14,371				226		6,762		4,142		29,543		1,402		8,758		3,887		3,429		187,820

	NOI from real estate operations	$	150,380			$	45,696			$	15,695			$	1,142	$	11,116	$	10,224	$	41,125	$	6,056	$	14,917	$	10,036	$	1,625	$	308,012

	Additions to long-lived assets	$	33,142			$	14,770			$	—			$	26,837	$	2,794	$	1,638	$	21,086	$	516	$	4,085	$	182	$	59	$	105,109

	Transfers from non-operating properties	$	67,752			$	4			$	17,638			$	—	$	—	$	16,858	$	16,307	$	5,446	$	214	$	—	$	20,169	$	144,388

	Segment assets at December 31, 2011	$	1,350,678			$	484,392			$	131,412			$	32,341	$	111,318	$	100,818	$	402,067	$	102,572	$	181,384	$	98,808	$	43,650	$	3,039,440

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 Years Ended December 31,
			2013				2012				2011
	Segment revenues from real estate operations		$	498,633			$	493,100			$	495,832

	Construction contract and other service revenues		62,363				73,836				84,345

	Less: Revenues from discontinued operations (Note 20)		(37,636		)		(58,801		)		(87,221		)
	Total revenues		$	523,360			$	508,135			$	492,956

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 Years Ended December 31,
			2013				2012				2011
	Segment property operating expenses		$	180,704			$	180,735			$	187,820

	Less: Property operating expenses from discontinued operations (Note 20)		(13,505		)		(21,529		)		(33,445		)
	Total property operating expenses		$	167,199			$	159,206			$	154,375

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 Years Ended December 31,
			2013				2012				2011
	Construction contract and other service revenues		$	62,363			$	73,836			$	84,345

	Construction contract and other service expenses		(58,875		)		(70,576		)		(81,639		)
	NOI from service operations		$	3,488			$	3,260			$	2,706

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 (loss) from continuing operations as reported on the consolidated statements of operations of COPT and subsidiaries (in thousands):


			For the Years Ended December 31,
			2013				2012				2011
	NOI from real estate operations		$	317,929			$	312,365			$	308,012

	NOI from service operations		3,488				3,260				2,706

	Interest and other income		3,834				7,172				5,603

	Equity in income (loss) of unconsolidated entities		2,110				(546		)		(331		)

	Income tax (expense) benefit		(1,978		)		(381		)		6,710

	Other adjustments:		—

	Depreciation and other amortization associated with real estate operations		(113,214		)		(107,998		)		(107,003		)
	Impairment losses		(5,857		)		(43,678		)		(83,213		)
	General, administrative and leasing expenses		(30,869		)		(31,900		)		(30,306		)
	Business development expenses and land carry costs		(5,436		)		(5,711		)		(6,122		)
	Interest expense on continuing operations		(82,010		)		(86,401		)		(90,037		)
	NOI from discontinued operations		(24,131		)		(37,272		)		(53,776		)
	Loss on interest rate derivatives		—				—				(29,805		)

	Loss on early extinguishment of debt		(27,030		)		(943		)		(1,639		)
	COPT consolidated income (loss) from continuing operations		$	36,836			$	7,967			$	(79,201	)

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):



		As of December 31,
		2013				2012
	Segment assets	$	2,905,630			$	2,945,930

	Non-operating property assets	517,564				570,402

	Other assets	206,758				137,427

	Total COPT consolidated assets	$	3,629,952			$	3,653,759

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Schedule of differences between taxable income reported on income tax returns and net income as reported on consolidated statements of operations	'
	The differences between taxable income reported on our income tax returns (estimated 2013 and actual 2012 and 2011) and net income as reported on our consolidated statements of operations are set forth below (in thousands):


		For the Years Ended December 31,
		2013				2012				2011
		(Estimated)
	COPLP consolidated net income (loss)	$	101,544			$	20,341			$	(127,570	)
	COPLP consolidated net income (loss)	$	101,544			$	20,341			$	(127,570	)
	Adjustments:
	Rental revenue recognition	(973		)		(10,794		)		(10,708		)
	Compensation expense recognition	10,051				(2,669		)		(1,298		)
	Compensation expense recognition	10,051				(2,669		)		(1,298		)
	Operating expense recognition	(1,718		)		1,158				751
	Operating expense recognition	(1,718		)		1,158				751
	Gain on sales of properties	(53,545		)		(74,858		)		1,154
	Gain on sales of properties	(53,545		)		(74,858		)		1,154
	Impairment losses	32,047				66,910				151,021
	Impairment losses	32,047				66,910				151,021
	Loss on interest rate derivatives	—				(29,805		)		29,805
	Loss on interest rate derivatives	—				(29,805		)		29,805
	Gains from non-real estate investments	—				7,854				4,447
	Gains from non-real estate investments	—				7,854				4,447
	Income from service operations	1,224				1,500				(12,078		)
	Income from service operations	1,224				1,500				(12,078		)
	Income tax expense	1,978				381				6,710
	Income tax expense	1,978				381				6,710
	Depreciation and amortization	23,824				24,804				44,070
	Depreciation and amortization	23,824				24,804				44,070
	Interest expense	1,159				3,978				5,548
	Interest expense	1,159				3,978				5,548
	Income from unconsolidated entities	(1,462		)		(725		)		(374		)
	COPLP consolidated noncontrolling interests	(3,907		)		(636		)		(1,919		)
	Other	(624		)		(70		)		80
	Other	(624		)		(70		)		80
	COPLP consolidated taxable income	$	109,598			$	7,369			$	89,639
	COPLP consolidated taxable income	$	109,598			$	7,369			$	89,639
	Noncontrolling interests, other	(4,930		)		(622		)		(5,583		)
	Other	—				741				(6		)
	Other	—				741				(6		)
	COPT consolidated taxable income	$	104,668			$	7,488			$	84,050
	COPT consolidated taxable income	$	104,668			$	7,488			$	84,050
Schedule of characterization of dividends declared on common and preferred shares	'
	The characterization of dividends declared on COPT’s common and preferred shares during each of the last three years was as follows:


		Common Shares									Preferred Shares
		For the Years Ended December 31,									For the Years Ended December 31,
		2013			2012			2011			2013		2012		2011
	Ordinary income	71.8	%		33.2	%		56.9	%		76.2	%	100	%	85.9	%
	Long-term capital gain	22.4	%		0	%		9.4	%		23.8	%	0	%	14.1	%
	Return of capital	5.8	%		66.8	%		33.7	%		0	%	0	%	0	%
Components of provision for income tax	'
	Our TRS’ provision for income tax consisted of the following (in thousands):


		For the Years Ended December 31,
		2013				2012				2011
	Deferred
	Federal	$	(1,742	)		$	(312	)		$	5,510
	Federal	$	(1,742	)		$	(312	)		$	5,510
	State	(236		)		(69		)		1,219
	State	(236		)		(69		)		1,219
		(1,978		)		(381		)		6,729
		(1,978		)		(381		)		6,729
	Current
	Federal	—				—				(16		)
	Federal	—				—				(16		)
	State	—				—				(3		)
	State	—				—				(3		)
		—				—				(19		)
		—				—				(19		)
	Total income tax (expense) benefit	$	(1,978	)		$	(381	)		$	6,710
	Total income tax (expense) benefit	$	(1,978	)		$	(381	)		$	6,710
Schedule of reconciliation of Federal statutory rate to effective tax rate	'
	A reconciliation of our TRS’ Federal statutory rate to the effective tax rate for income tax reported on our statements of operations is set forth below:



		For the Years Ended December 31,
		2013			2012			2011
	Income taxes at U.S. statutory rate	34	%		34	%		34	%
	State and local, net of U.S. Federal tax benefit	4.5	%		4.6	%		4.6	%
	Increase in deferred tax asset valuation allowance	562.9	%		0	%		0	%
	Other	(1.1	)%		0	%		0	%
	Effective tax rate	600.3	%		38.6	%		38.6	%
Schedule of tax effects of temporary differences and carry forwards in net deferred tax assets	'
	The table below sets forth the tax effects of temporary differences and carry forwards included in the net deferred tax asset of our TRS (in thousands):


		December 31,
		2013				2012
	Operating loss forward	$	5,382			$	6,014
	Operating loss forward	$	5,382			$	6,014
	Share-based compensation	869				904
	Share-based compensation	869				904
	Accrued payroll	221				12
	Accrued payroll	221				12
	Property	(105		)		(111		)
	Valuation allowance	(2,062		)		(207		)
	Deferred tax asset, net	$	4,305			$	6,612
	Deferred tax asset, net	$	4,305			$	6,612

Discontinued_Operations_Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2013
Discontinued Operations and Disposal Groups [Abstract]	'
Components of discontinued operations	'
	The table below sets forth the components of discontinued operations reported on our consolidated statements of operations (in thousands):


		For the Years Ended December 31,
		2013			2012			2011
	Revenue from real estate operations	$	37,636		$	58,801		$	87,221

	Property operating expenses	(13,505		)	(21,529		)	(33,445		)
	Depreciation and amortization	(4,505		)	(13,939		)	(27,128		)
	Impairment losses	(26,190		)	(23,232		)	(67,808		)
	General, administrative and leasing expenses	(4		)	(3		)	(20		)
	Business development and land carry costs	—			(24		)	(75		)

	Interest expense	(8,221		)	(10,397		)	(14,264		)
	Gain on sales of real estate	2,671			20,940			4,796

	Gain (loss) on early extinguishment of debt	67,810			1,736			(384		)

	Discontinued operations	$	55,692		$	12,353		$	(51,107	)

Components of assets held for sale	'
	The table below sets forth the components of assets held for sale on our consolidated balance sheets (in thousands):



		December 31, 2012
	Properties, net	$	128,740

	Deferred rent receivable	4,068

	Intangible assets on real estate acquisitions, net	4,409

	Deferred leasing costs, net	2,923

	Lease incentives	89

	Assets held for sale, net	$	140,229

Earnings_Per_Share_EPS_and_Ear1

Earnings Per Share ("EPS") and Earnings Per Unit (â€œEPUâ€) (Tables)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Line Items]	'
Summary of calculation of numerator and denominator in basic and diluted earning 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 Years Ended December 31,
		2013				2012			2011
	Numerator:
	Income (loss) from continuing operations	$	36,836			$	7,967		$	(79,201	)

	Gain on sales of real estate, net	9,016				21			2,732

	Preferred share dividends	(19,971		)		(20,844		)	(16,102		)
	Issuance costs associated with redeemed preferred shares	(2,904		)		(1,827		)	—

	(Income) loss from continuing operations attributable to noncontrolling interests	(4,486		)		1,309			5,128

	Income from continuing operations attributable to restricted shares	(414		)		(469		)	(1,037		)
	Numerator for basic and diluted EPS from continuing operations attributable to COPT common shareholders	$	18,077			$	(13,843	)	$	(88,480	)

	Discontinued operations	55,692				12,353			(51,107		)

	Discontinued operations attributable to noncontrolling interests	(3,351		)		(673		)	3,020

	Numerator for basic and diluted EPS on net income (loss)attributable to COPT common shareholders	$	70,418			$	(2,163	)	$	(136,567	)

	Denominator (all weighted averages):
	Denominator for basic EPS (common shares)	85,167				73,454			69,382

	Dilutive effect of share-based compensation awards	57				—			—

	Denominator for basic and diluted EPS (common shares)	85,224				73,454			69,382

	Basic EPS:
	Income (loss) from continuing operations attributable to COPT common shareholders	$	0.21			$	(0.19	)	$	(1.28	)

	Discontinued operations attributable to COPT common shareholders	0.62				0.16			(0.69		)

	Net income (loss) attributable to COPT common shareholders	$	0.83			$	(0.03	)	$	(1.97	)

	Diluted EPS:
	Income (loss) from continuing operations attributable to COPT common shareholders	$	0.21			$	(0.19	)	$	(1.28	)

	Discontinued operations attributable to COPT common shareholders	0.62				0.16			(0.69		)

	Net income (loss) attributable to COPT common shareholders	$	0.83			$	(0.03	)	$	(1.97	)

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 Years Ended December 31,
		2013			2012			2011
	Conversion of common units	3,869			4,235			4,355

	Conversion of Series I preferred units	176			176			176

	Conversion of Series K preferred shares	434			434			434

Corporate Office Properties, L.P.	'
Earnings Per Share [Line Items]	'
Summary of calculation of numerator and denominator in basic and diluted earning 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 Years Ended December 31,
		2013				2012			2011
	Numerator:
	Income (loss) from continuing operations	$	36,836			$	7,967		$	(79,195	)

	Gain on sales of real estate, net	9,016				21			2,732

	Preferred unit distributions	(20,631		)		(21,504		)	(16,762		)
	Issuance costs associated with redeemed preferred units	(2,904		)		(1,827		)	—

	(Income) loss from continuing operations attributable to noncontrolling interests	(2,977		)		1,206			381

	Income from continuing operations attributable to restricted units	(414		)		(469		)	(1,037		)
	Numerator for basic and diluted EPU from continuing operations attributable to COPLP common unitholders	$	18,926			$	(14,606	)	$	(93,881	)

	Discontinued operations	55,692				12,353			(51,107		)

	Discontinued operations attributable to noncontrolling interests	(930		)		(699		)	(137		)
	Numerator for basic and diluted EPU on net income (loss) attributable to COPLP common unitholders	$	73,688			$	(2,952	)	$	(145,125	)

	Denominator (all weighted averages):
	Denominator for basic EPU (common units)	89,036				77,689			72,564

	Dilutive effect of share-based compensation awards	57				—			—

	Denominator for basic and diluted EPU (common units)	89,093				77,689			72,564

	Basic EPU:
	Income (loss) from continuing operations attributable to COPLP common unitholders	$	0.21			$	(0.19	)	$	(1.29	)

	Discontinued operations attributable to COPLP common unitholders	0.62				0.15			(0.71		)

	Net income (loss) attributable to COPLP common unitholders	$	0.83			$	(0.04	)	$	(2.00	)

	Diluted EPU:
	Income (loss) from continuing operations attributable to COPLP common unitholders	$	0.21			$	(0.19	)	$	(1.29	)

	Discontinued operations attributable to COPLP common unitholders	0.62				0.15			(0.71		)

	Net income (loss) attributable to COPLP common unitholders	$	0.83			$	(0.04	)	$	(2.00	)

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 Years Ended December 31,
		2013			2012			2011
	Conversion of Series I preferred units	176			176			176

	Conversion of Series K preferred units	434			434			434

Quarterly_Data_Unaudited_Table

Quarterly Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Data [Line Items]	'
Schedule of selected quarterly information	'
	Certain of the amounts below have been reclassified to conform to the current period presentation of our consolidated financial statements.


		For the Year Ended December 31, 2013
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Revenues	$	126,219		$	136,527		$	131,812		$	128,802

	Operating income	$	36,165		$	40,229		$	30,673		$	34,843

	Income (loss) from continuing operations	$	11,662		$	(232	)	$	10,974		$	14,432

	Discontinued operations	$	1,261		$	(4,502	)	$	(12,974	)	$	71,907

	Net income (loss)	$	15,277		$	(4,405	)	$	(2,000	)	$	92,672

	Net (income) loss attributable to noncontrolling interests	(257		)	(960		)	(964		)	(5,656		)
	Net income (loss) attributable to COPT	15,020			(5,365		)	(2,964		)	87,016

	Preferred share dividends	(6,106		)	(4,885		)	(4,490		)	(4,490		)
	Issuance costs associated with redeemed preferred shares	—			(2,904		)	—			—

	Net income (loss) attributable to COPT common shareholders	$	8,914		$	(13,154	)	$	(7,454	)	$	82,526

	Basic earnings per common share	$	0.11		$	(0.16	)	$	(0.09	)	$	0.94

	Diluted earnings per common share	$	0.11		$	(0.16	)	$	(0.09	)	$	0.94



		For the Year Ended December 31, 2012
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Revenues	$	127,359		$	123,074		$	125,067		$	132,635

	Operating income (loss)	$	34,651		$	32,069		$	(10,844	)	$	33,190

	Income (loss) from continuing operations	$	13,184		$	10,336		$	(32,048	)	$	16,495

	Discontinued operations	$	(2,949	)	$	1,504		$	11,283		$	2,515

	Net income (loss)	$	10,235		$	11,861		$	(20,765	)	$	19,010

	Net loss (income) attributable to noncontrolling interests	60			(556		)	1,603			(471		)

	Net income (loss) attributable to COPT	10,295			11,305			(19,162		)	18,539

	Preferred share dividends	(4,025		)	(4,167		)	(6,546		)	(6,106		)
	Issuance costs associated with redeemed preferred shares	—			—			(1,827		)	—

	Net income (loss) attributable to COPT common shareholders	$	6,270		$	7,138		$	(27,535	)	$	12,433

	Basic earnings per common share	$	0.09		$	0.1		$	(0.39	)	$	0.16

	Diluted earnings per common share	$	0.09		$	0.1		$	(0.39	)	$	0.16

Corporate Office Properties, L.P.	'
Quarterly Data [Line Items]	'
Schedule of selected quarterly information	'
	The tables below set forth selected quarterly information for the years ended December 31, 2013 and 2012 (in thousands, except per share data).


		For the Year Ended December 31, 2013
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Revenues	$	126,219		$	136,527		$	131,812		$	128,802

	Operating income	$	36,165		$	40,229		$	30,673		$	34,843

	Income (loss) from continuing operations	$	11,662		$	(232	)	$	10,974		$	14,432

	Discontinued operations	$	1,261		$	(4,502	)	$	(12,974	)	$	71,907

	Net income (loss)	$	15,277		$	(4,405	)	$	(2,000	)	$	92,672

	Net loss (income) attributable to noncontrolling interests	336			(1,473		)	(1,035		)	(1,735		)

	Net income (loss) attributable to COPLP	15,613			(5,878		)	(3,035		)	90,937

	Preferred unit distributions	(6,271		)	(5,050		)	(4,655		)	(4,655		)
	Issuance costs associated with redeemed preferred units	—			(2,904		)	—			—

	Net income (loss) attributable to COPLP common unitholders	$	9,342		$	(13,832	)	$	(7,690	)	$	86,282

	Basic earnings per common unit	$	0.11		$	(0.16	)	$	(0.09	)	$	0.94

	Diluted earnings per common unit	$	0.11		$	(0.16	)	$	(0.09	)	$	0.94



		For the Year Ended December 31, 2012
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Revenues	$	127,359		$	123,074		$	125,067		$	132,635

	Operating income (loss)	$	34,651		$	32,069		$	(10,844	)	$	33,190

	Income (loss) from continuing operations	$	13,184		$	10,336		$	(32,048	)	$	16,495

	Discontinued operations	$	(2,949	)	$	1,504		$	11,283		$	2,515

	Net income (loss)	$	10,235		$	11,861		$	(20,765	)	$	19,010

	Net loss (income) attributable to noncontrolling interests	570			1			(404		)	340

	Net income (loss) attributable to COPLP	10,805			11,862			(21,169		)	19,350

	Preferred unit distributions	(4,190		)	(4,332		)	(6,711		)	(6,271		)
	Issuance costs associated with redeemed preferred units	—			—			(1,827		)	—

	Net income (loss) attributable to COPLP common unitholders	$	6,615		$	7,530		$	(29,707	)	$	13,079

	Basic earnings per common unit	$	0.09		$	0.1		$	(0.39	)	$	0.16

	Diluted earnings per common unit	$	0.09		$	0.1		$	(0.39	)	$	0.16

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Schedule of future minimum rental payments	'
	Future minimum rental payments due under the terms of these leases as of December 31, 2013 follow (in thousands):


	Year Ending December 31,
	2014	$	675

	2015	686

	2016	686

	2017	687

	2018	689

	Thereafter	75,501

		$	78,924

Organization_Details

Organization (Details)	12 Months Ended
	Dec. 31, 2013
	sqft
	acre
Operating office properties	'
Investments in real estate	'
Number of real estate properties	183
Square footage of real estate properties (in square feet)	17,400,000
Office properties under, or contractually committed for, construction or approved for redevelopment	'
Investments in real estate	'
Number of real estate properties	10
Square footage of real estate properties (in square feet)	1,400,000
Office properties under construction or redevelopment which are partially operational	'
Investments in real estate	'
Number of real estate properties	2
Land held or under pre-construction	'
Investments in real estate	'
Area of land held or under pre-construction (in acres)	1,708
Area of land parcels controlled but not owned (in acres)	56
Developable square footage of real estate properties (in square feet)	20,000,000
Partially operational, wholesale data center	'
Investments in real estate	'
The expected stabilization critical load after completion of development (in megawatts)	18

Organization_Details_2

Organization (Details 2) (Corporate Office Properties, L.P.)	12 Months Ended
	Dec. 31, 2013
	Trustee
Common Units	'
Forms of ownership in Operating Partnership and ownership percentage by the entity	'
Percentage ownership in operating partnership	95.60%
Number of trustees controlling additional common units	3
Additional percentage of common units controlled by trustees (as a percent)	3.40%
Preferred Units	'
Forms of ownership in Operating Partnership and ownership percentage by the entity	'
Percentage ownership in operating partnership	96.40%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details)	12 Months Ended
Summary of Significant Accounting Policies (Details)	Dec. 31, 2013
Properties	'
Period after the cessation of major construction activities for considering property as operational if leases have not commenced earlier (in years)	'1 year
Period after the cessation of major construction activities for considering property as partially operational if leases have commenced earlier (in years)	'1 year
Property, Plant and Equipment [Line Items]	'
Period used for recovery analysis of long-lived assets to be held and used that may be impaired (in years)	'10 years
Minimum \| Buildings and building improvements	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life	'10 years
Minimum \| Land improvements	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life	'10 years
Minimum \| Equipment and personal property	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life	'3 years
Maximum \| Buildings and building improvements	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life	'40 years
Maximum \| Land improvements	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life	'20 years
Maximum \| Equipment and personal property	'
Property, Plant and Equipment [Line Items]	'
Estimated useful life	'10 years

Summary_of_Significant_Account4

Summary of Significant Accounting Policies 1 (Details)	12 Months Ended
	Dec. 31, 2013
	Form
Cash and Cash Equivalents	'
Maximum term until original maturity to classify cash and liquid investments as cash and cash equivalent (in months)	'3 months
Share-Based Compensation	'
Number of forms of share based compensation plans	2
Market concentration premium	'
Useful Lifes Related To Intangible Assets and Property [Abstract]	'
Finite-Lived Intangible Asset, Useful Life	'40 years
Corporate Office Properties, L.P.	'
Noncontrolling Interest [Abstract]	'
Interests in several real estate entities owned directly by COPT	1.00%

Summary_of_Significant_Account5

Summary of Significant Accounting Policies 2 (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Additional Paid in Capital	($1,814,015)	($1,653,672)	'	'
Redeemable noncontrolling interest	17,758	10,298	8,908	9,000
Restatement Adjustment [Member] \| Misapplication of Fair Value Assumptions [Member]	'	'	'	'
Additional Paid in Capital	3,700	'	'	'
Redeemable noncontrolling interest	$3,700	'	'	'

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
	KEYW Holding Corporation	KEYW Holding Corporation	KEYW Holding Corporation	Redeemable non-controlling interest	Redeemable non-controlling interest
				Fair value measurement on a recurring basis	Fair value measurement on a recurring basis
				Significant Unobservable Inputs (Level 3)	Significant Unobservable Inputs (Level 3)
Warrants	'	'	'	'	'
Number of warrants owned (in shares)	50,000	'	50,000	'	'
Exercise price of warrants (in dollars per share)	$9.25	'	$9.25	'	'
Number of shares owned in investee (in shares)	'	1,900,000	'	'	'
Percentage of common stock owned	'	7.00%	'	'	'
Amount of sale of owned shares	$14,000,000	'	'	'	'
Revenue earned from investee	$2,400,000	$780,000	'	'	'
Discount rate	'	'	'	15.50%	15.60%

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (USD $)	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Liabilities:	'		'		'	'
Interest rate derivatives	$3,309		$6,185		'	'
Redeemable noncontrolling interest	17,758		10,298		8,908	9,000
Corporate Office Properties, L.P.	'		'		'	'
Liabilities:	'		'		'	'
Interest rate derivatives	3,309		6,185		'	'
Fair value measurement on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1)	'		'		'	'
Assets:	'		'		'	'
Common stocks	298	[1]	809	[1]	'	'
Assets	7,765		7,585		'	'
Liabilities:	'		'		'	'
Liabilities	0		0		'	'
Fair value measurement on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Mutual funds	'		'		'	'
Assets:	'		'		'	'
Marketable securities in deferred compensation plan	7,090	[1]	6,275	[1]	'	'
Fair value measurement on a recurring basis \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Common Shares	'		'		'	'
Assets:	'		'		'	'
Marketable securities in deferred compensation plan	176	[1]	298	[1]	'	'
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	201	[1]	203	[1]	'	'
Fair value measurement on a recurring basis \| Significant Other Observable Inputs (Level 2)	'		'		'	'
Assets:	'		'		'	'
Interest rate derivative	6,594	[2]	'		'	'
Warrants to purchase common shares in KEYW	301	[2]	294	[2]	'	'
Assets	6,895	[2]	294		'	'
Liabilities:	'		'		'	'
Deferred compensation plan liability	7,467	[3]	6,776	[3]	'	'
Interest rate derivatives	3,309		6,185		'	'
Liabilities	10,776		12,961		'	'
Fair value measurement on a recurring basis \| Significant Unobservable Inputs (Level 3)	'		'		'	'
Liabilities:	'		'		'	'
Redeemable noncontrolling interest	17,758		10,298		'	'
Fair value measurement on a recurring basis \| Total Estimated Fair Value	'		'		'	'
Assets:	'		'		'	'
Common stocks	298	[1]	809	[1]	'	'
Interest rate derivative	6,594	[2]	'		'	'
Warrants to purchase common shares in KEYW	301	[2]	294	[2]	'	'
Assets	14,660		7,879		'	'
Liabilities:	'		'		'	'
Deferred compensation plan liability	7,467	[3]	6,776	[3]	'	'
Interest rate derivatives	3,309		6,185		'	'
Liabilities	10,776		12,961		'	'
Redeemable noncontrolling interest	17,758		10,298		'	'
Fair value measurement on a recurring basis \| Total Estimated Fair Value \| Mutual funds	'		'		'	'
Assets:	'		'		'	'
Marketable securities in deferred compensation plan	7,090	[1]	6,275	[1]	'	'
Fair value measurement on a recurring basis \| Total Estimated Fair Value \| Common Shares	'		'		'	'
Assets:	'		'		'	'
Marketable securities in deferred compensation plan	176	[1]	298	[1]	'	'
Fair value measurement on a recurring basis \| Total Estimated Fair Value \| Other	'		'		'	'
Assets:	'		'		'	'
Marketable securities in deferred compensation plan	201	[1]	203	[1]	'	'
Fair value measurement on a recurring basis \| Corporate Office Properties, L.P. \| Quoted Prices in Active Markets for Identical Assets (Level 1)	'		'		'	'
Assets:	'		'		'	'
Common stocks	298	[4]	809	[4]	'	'
Assets	298		809		'	'
Fair value measurement on a recurring basis \| Corporate Office Properties, L.P. \| Significant Other Observable Inputs (Level 2)	'		'		'	'
Assets:	'		'		'	'
Interest rate derivative	6,594	[5]	'		'	'
Warrants to purchase common shares in KEYW	301	[5]	294	[5]	'	'
Assets	6,895		294		'	'
Liabilities:	'		'		'	'
Interest rate derivatives	3,309		6,185		'	'
Fair value measurement on a recurring basis \| Corporate Office Properties, L.P. \| Significant Unobservable Inputs (Level 3)	'		'		'	'
Assets:	'		'		'	'
Assets	'		0		'	'
Liabilities:	'		'		'	'
Redeemable noncontrolling interest	'		10,298		'	'
Fair value measurement on a recurring basis \| Corporate Office Properties, L.P. \| Total Estimated Fair Value	'		'		'	'
Assets:	'		'		'	'
Common stocks	298	[4]	809	[4]	'	'
Interest rate derivative	6,594	[5]	'		'	'
Warrants to purchase common shares in KEYW	301	[5]	294	[5]	'	'
Assets	7,193		1,103		'	'
Liabilities:	'		'		'	'
Interest rate derivatives	'		6,185		'	'
Redeemable noncontrolling interest	'		$10,298		'	'

[1]	Included in the line entitled â€œrestricted cash and marketable securitiesâ€ on COPTâ€™s consolidated balance sheet.
[2]	Included in the line entitled â€œprepaid expenses and other assetsâ€ on COPTâ€™s consolidated balance sheet.
[3]	Included in the line entitled â€œother liabilitiesâ€ on COPTâ€™s consolidated balance sheet.
[4]	Included in the line entitled â€œrestricted cash and marketable securitiesâ€ on COPLPâ€™s consolidated balance sheet.
[5]	Included in the line entitled â€œprepaid expenses and other assetsâ€ on COPLPâ€™s consolidated balance sheet.

Fair_Value_Measurements_Detail2

Fair Value Measurements (Details 3) (USD $)	12 Months Ended
Fair Value Measurements (Details 3) (USD $)	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Fair value of impaired properties and other assets	'		'		'
Impairment losses	$5,857,000		$43,678,000		$83,213,000
Exit costs included in impairment losses in connection with dispositions	979,000		4,146,000		0
Fair value measurement on a nonrecurring basis \| Projects in development or held for future development	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	'		1,900,000		'
Fair value measurement on a nonrecurring basis \| Property Conveyances	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	11,000,000		'		'
Exit costs included in impairment losses in connection with dispositions	560,000		'		'
Fair value measurement on a nonrecurring basis \| Other Properties with Shortened Holding Periods	'		'		'
Fair value of impaired properties and other assets	'		'		'
Number of properties, shortened holding period	2		'		'
Fair value measurement on a nonrecurring basis \| Strategic Reallocation Plan	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	'		19,000,000		'
Exit costs included in impairment losses in connection with dispositions	419,000		'		'
Fair value measurement on a nonrecurring basis \| Additional Property Disposed	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	'		5,100,000		'
Fair value measurement on a nonrecurring basis \| Properties, Net	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	31,068,000	[1]	62,702,000	[2],[3]	'
Fair value measurement on a nonrecurring basis \| Significant Unobservable Inputs (Level 3)	'		'		'
Fair value of impaired properties and other assets	'		'		'
Exit costs included in impairment losses in connection with dispositions	979,000		'		'
Fair value measurement on a nonrecurring basis \| Significant Unobservable Inputs (Level 3) \| Strategic Reallocation Plan	'		'		'
Fair value of impaired properties and other assets	'		'		'
Exit costs included in impairment losses in connection with dispositions	'		4,200,000		'
Fair value measurement on a nonrecurring basis \| Significant Unobservable Inputs (Level 3) \| Properties, Net	'		'		'
Fair value of impaired properties and other assets	'		'		'
Exit costs included in impairment losses in connection with dispositions	'		4,200,000		'
Assets	4,459,000		173,949,000	[2]	'
Fair value measurement on a nonrecurring basis \| Total Estimated Fair Value \| Properties, Net	'		'		'
Fair value of impaired properties and other assets	'		'		'
Assets	4,459,000		173,949,000	[2]	'
Fair value measurement on a nonrecurring basis \| Discounted Cash Flow	'		'		'
Fair value of impaired properties and other assets	'		'		'
Discount rate	10.00%	[4]	'		'
Terminal capitalization rate	9.50%	[4]	'		'
Market rent growth rate	3.00%	[4]	3.00%	[4]	'
Expense growth rate	3.00%	[4]	3.00%	[4]	'
Fair value measurement on a nonrecurring basis \| Discounted Cash Flow \| Significant Unobservable Inputs (Level 3) \| Properties, Net	'		'		'
Fair value of impaired properties and other assets	'		'		'
Assets	4,459,000		166,650,000		'
Fair value measurement on a nonrecurring basis \| Discounted Cash Flow \| Minimum	'		'		'
Fair value of impaired properties and other assets	'		'		'
Discount rate	'		10.00%		'
Terminal capitalization rate	'		8.70%		'
Fair value measurement on a nonrecurring basis \| Discounted Cash Flow \| Maximum	'		'		'
Fair value of impaired properties and other assets	'		'		'
Discount rate	'		11.00%		'
Terminal capitalization rate	'		10.00%		'
Fair value measurement on a nonrecurring basis \| Discounted Cash Flow \| Weighted Average	'		'		'
Fair value of impaired properties and other assets	'		'		'
Discount rate	'		10.30%		'
Terminal capitalization rate	'		8.90%		'
Fair value measurement on a nonrecurring basis \| Yield Analysis Valuation Technique	'		'		'
Fair value of impaired properties and other assets	'		'		'
Fair value inputs yield	'		12.00%	[4]	'
Fair value inputs market rent rate per square foot	'		8.5	[4]	'
Fair value inputs leasing costs per square foot	'		20	[4]	'
Fair value measurement on a nonrecurring basis \| Yield Analysis Valuation Technique \| Significant Unobservable Inputs (Level 3) \| Properties, Net	'		'		'
Fair value of impaired properties and other assets	'		'		'
Assets	'		2,356,000		'
Fair value measurement on a nonrecurring basis \| Discontinued Operations \| Strategic Reallocation Plan	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	15,200,000		23,200,000		'
Fair value measurement on a nonrecurring basis \| Greater Baltimore \| Other Properties with Shortened Holding Periods	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	5,900,000		'		'
Fair value measurement on a nonrecurring basis \| Greater Philadelphia	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	'		46,100,000		'
Future expenditure redevelopment	'		25,000,000		'
Fair value measurement on a nonrecurring basis \| Colorado Springs \| Strategic Reallocation Plan	'		'		'
Fair value of impaired properties and other assets	'		'		'
Impairment losses	'		$6,900,000		'

[1]	Represents aggregate impairment losses on non recurring fair value measurements resulting in impairment losses, excluding exit costs incurred of $979,000.
[2]	Reflects balance sheet classifications of assets at time of fair value measurement, excluding the effect of held for sale classifications.
[3]	Represents aggregate impairment losses on non recurring fair value measurements resulting in impairment losses, excluding exit costs incurred of $4.2 million.
[4]	Only one value applied for this unobservable input.

Concentration_of_Rental_Revenu2

Concentration of Rental Revenue (Details)	12 Months Ended
Concentration of Rental Revenue (Details)	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Concentration Risk	'		'		'
Number of regions with real estate operations which are not located in the Mid-Atlantic region of the United States	3		'		'
Rental revenue \| Tenants	'		'		'
Concentration Risk	'		'		'
Percentage required for qualification as major customer	5.00%		'		'
Number of tenants from which the entity has recognized the most rental revenue aggregated for revenue concentration disclosure	5		'		'
Rental revenue \| Tenants \| United States Government	'		'		'
Concentration Risk	'		'		'
Percentage of revenue	18.00%		18.00%		17.00%
Rental revenue \| Tenants \| Northrop Grumman Corporation	'		'		'
Concentration Risk	'		'		'
Percentage of revenue	8.00%	[1]	7.00%	[1]	8.00%	[1]
Rental revenue \| Tenants \| Booz Allen Hamilton, Inc.	'		'		'
Concentration Risk	'		'		'
Percentage of revenue	6.00%		6.00%		6.00%
Rental revenue \| Tenants \| Computer Sciences Corporation	'		'		'
Concentration Risk	'		'		'
Percentage of revenue	5.00%	[1]	5.00%	[1]	'
Rental revenue \| Tenants \| Five largest tenants	'		'		'
Concentration Risk	'		'		'
Percentage of revenue	41.00%		39.00%		38.00%
Construction contract revenue \| United States Government	'		'		'
Concentration Risk	'		'		'
Percentage of revenue	90.00%		90.00%		90.00%

[1]	Includes affiliated organizations and agencies and predecessor companies.

Properties_net_Details

Properties, net (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Properties	'		'	'	'
Gross	$3,811,950	[1],[2]	$3,859,960	$4,038,932	$3,948,487
Operating properties, net	2,702,693		2,597,666	2,597,666	'
Operating properties, net	'		'	'	'
Properties	'		'	'	'
Less: accumulated depreciation	-597,649		-555,975	'	'
Operating properties, net \| Land	'		'	'	'
Properties	'		'	'	'
Gross	430,472		427,766	'	'
Operating properties, net \| Buildings and improvements	'		'	'	'
Properties	'		'	'	'
Gross	$2,869,870		$2,725,875	'	'

[1]	The aggregate cost of these assets for Federal income tax purposes was approximately $3.3 billion at DecemberÂ 31, 2013.
[2]	As discussed in Note 3 to our Consolidated Financial Statements, we recognized impairment losses of $5.9 million in connection with two properties in the Greater Baltimore region that we determined no longer met our strategic investment criteria.

Properties_net_Details_2

Properties, net (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Properties	'	'
Projects in development or held for future development	$511,608	$565,378
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	245,676	236,324
Projects in development or held for future development \| Construction in progress, excluding land	'	'
Properties	'	'
Projects in development or held for future development	$265,932	$329,054

Properties_net_Details_3

Properties, net (Details 3) (USD $)

12 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 23, 2013

Jul. 02, 2012

Dec. 23, 2013

Jul. 02, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Non-operating Properties

Secured Debt

Operating properties

December 2013 Portfolio Conveyance

400 Professional Drive

Fair value measurement on a nonrecurring basis

buillding

920 Elkridge Landing Road

4230 Forbes Boulevard

December 2013 Colorado Springs Portfolio Disposition

December 2013 Portfolio Conveyance

White Marsh Portfolio

1101 Sentry Gateway

222 and 224 Schilling Circle

15 and 45 West Gude Drive

11800 Tech Road

400 Professional Drive

July 2012 Portfolio Disposition

December 2013 Portfolio Conveyance

400 Professional Drive

sqft

buillding

sqft

Dispositions

Number of Buildings Disposed

Total Rentable Square Feet

2,345,000

2,302,000

103,000

56,000

1,165,000

1,021,000

163,000

95,000

56,000

231,000

240,000

130,000

1,387,000

Transaction Value of Operating Property Dispositions

$293,301,000

$285,506,000

$6,900,000

$5,600,000

$133,925,000

$146,876,000

$19,100,000

$13,500,000

$4,400,000

$49,107,000

$21,300,000

$16,198,000

$161,901,000

Gain on Sale

2,671,000

21,186,000

1,507,000

1,164,000

2,445,000

1,739,000

102,000

16,900,000

Sale Price of Non-operating Properties

3,500,000

28,100,000

Debt settled through the surrender of real estate assets

146,500,000

15,000,000

Fair value of real estate disposed in settlement of debt

74,000,000

11,000,000

Gain on early extinguishment of debt

($27,030,000)

($943,000)

($1,639,000)

$67,800,000

$3,700,000

Properties_net_Details_4

Properties, net (Details 4) (USD $)

12 Months Ended

0 Months Ended

12 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jul. 11, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Tenant relationship value

In-place lease value

Above-market leases

13857 McLearen Road

Newly-constructed properties placed in service

Properties under construction or contractually committed for construction

Properties under redevelopment

sqft

Tenant relationship value

In-place lease value

Above-market leases

sqft

Northern Virginia

Baltimore and Washington Corridor

Greater Baltimore

sqft

Northern Virginia

Huntsville

Baltimore and Washington Corridor

San Antonio

sqft

Baltimore and Washington Corridor

Greater Philadelphia

Property

Acquisitions

Square Feet of Properties Placed in Service

812,000

371,000

Number of Real Estate Properties Placed In Service

Number of real estate properties

Square footage of real estate properties (in square feet)

202,000

1,000,000

376,000

Acquisitions

Acquired property, percentage leased (as a percent)

100.00%

Land, operating properties

$3,507

Building and improvements

30,177

Intangible assets on real estate acquisitions

14,993

Total assets

48,677

Below market leases

-369

Total acquisition costs

48,308

Intangible assets on real estate acquisitions

Gross carrying amount

14,993

7,472

7,109

412

Weighted average amortization period of intangible assets

'10 years

'7 years

'6 years

'3 years

'7 years

'10 years

'5 years

Costs expensed in connection with acquisition of operating properties

$229

Real_Estate_Joint_Ventures_Det

Real Estate Joint Ventures (Details) (USD $)	12 Months Ended
Real Estate Joint Ventures (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Investments in consolidated real estate joint ventures	'		'	'
Amounts advanced to fund Huntsville infrastructure costs	$53,663,000		$35,798,000	'
Investment Balance	0		-6,420,000	'
Gain on disposal	0		0	2,452,000
LW Redstone Company, LLC	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Ownership (as a percent)	85.00%		'	'
Number of buildings operated by the joint venture	3		'	'
Total Assets	132,170,000	[1],[2]	'	'
Encumbered Assets	67,487,000	[1],[2]	'	'
Total Liabilities	39,845,000	[1],[2]	'	'
Amounts advanced to fund Huntsville infrastructure costs	44,100,000		'	'
Partner's capital account upon formation	9,000,000		'	'
Percentage of residual distributable cash flows in excess of unpaid cumulative preferred returns and return of invested capital entitled to the company	85.00%		'	'
Percentage of residual distributable cash flows in excess of unpaid cumulative preferred returns and return of invested capital entitled to the entity's partners	15.00%		'	'
Number of years following construction commencement threshold achievement before partner's interest can be purchased at fair value	'5 years		'	'
Construction commencement threshold (in square feet)	4,400,000		'	'
LW Redstone Company, LLC \| Maximum	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Infrastructure costs anticipated to be funded by entity for reimbursement by the City of Huntsville (in dollars)	76,000,000		'	'
M Square Associates, LLC	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Ownership (as a percent)	50.00%		'	'
Number of buildings operated by the joint venture	2		'	'
Total Assets	60,919,000	[1],[3]	'	'
Encumbered Assets	48,705,000	[1],[3]	'	'
Total Liabilities	41,009,000	[1],[3]	'	'
Percentage of residual amounts distributed to each member	50.00%		'	'
COPT-FD Indian Head, LLC	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Ownership (as a percent)	75.00%		'	'
Total Assets	6,436,000	[1],[4]	'	'
Total Liabilities	0	[1],[4]	'	'
Consolidated real estate joint ventures	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Total Assets	199,525,000	[1]	'	'
Encumbered Assets	116,192,000	[1]	'	'
Total Liabilities	80,854,000	[1]	'	'
Arundel Preserve 5, LLC	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Ownership (as a percent)	'		50.00%	'
Arundel Preserve 5, LLC \| Common Shares	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Stock Issued During Period, Shares, Acquisitions	221,501		'	'
Stock Issued During Period, Value, Acquisitions	5,200,000		'	'
MOR Forbes 2 LLC	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Ownership (as a percent)	50.00%		'	'
Unconsolidated real estate joint ventures	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Ownership (as a percent)	'		20.00%	'
Number of buildings operated by the joint venture	'		16	'
Investment Balance	'		-6,400,000	'
Gain on disposal	6,300,000		'	'
Difference between carrying amount of investment and share of the equity in the joint venture	'		4,500,000	'
Condensed balance sheets for unconsolidated real estate joint venture	'		'	'
Properties, net	'		58,460,000	'
Other assets	'		4,376,000	'
Total assets	'		62,836,000	'
Liabilities (primarily debt)	'		72,693,000	'
Owners' equity	'		-9,857,000	'
Total liabilities and owners' equity	'		62,836,000	'
Condensed statements of operations for unconsolidated real estate joint venture	'		'	'
Revenues	6,519,000		7,316,000	7,577,000
Property operating expenses	-2,818,000		-2,829,000	-3,673,000
Interest expense	-10,463,000		-7,672,000	-3,913,000
Depreciation and amortization expense	-2,067,000		-2,283,000	-2,463,000
Gain on early extinguishment of debt	23,013,000		0	0
Net income (loss)	14,184,000		-5,468,000	-2,472,000
Unconsolidated real estate joint ventures \| Nonrecourse loan guarantees of unconsolidated partnership \| Nonrecourse mezzanine loan	'		'	'
Investments in consolidated real estate joint ventures	'		'	'
Nonrecourse Mezzanine Debt Balance, equity method joint venture	$5,600,000		'	'

[1]	Excludes amounts eliminated in consolidation.
[2]	This joint ventureâ€™s property is in Huntsville, Alabama.
[3]	This joint ventureâ€™s properties are in College Park, Maryland (in the Baltimore/Washington Corridor).
[4]	This joint ventureâ€™s property is in Charles County, Maryland. In 2012, the joint venture exercised its option under a development agreement to require Charles County to repurchase the land parcel at its original acquisition cost. Under the terms of the agreement with Charles County, the repurchase is expected to occur by August 2014.

Intangible_Assets_on_Real_Esta2

Intangible Assets on Real Estate Acquisitions (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Intangible assets on real estate acquisitions	'	'	'
Gross Carrying Amount	$192,592,000	$204,466,000	'
Accumulated Amortization	133,334,000	128,587,000	'
Net Carrying Amount	59,258,000	75,879,000	'
Amortization of the intangible assets	16,200,000	21,400,000	28,300,000
Weighted average amortization period of intangible assets	'10 years	'	'
Estimated future amortization expense associated with the intangible asset categories for the next five years	'	'	'
2014	12,200,000	'	'
2015	9,900,000	'	'
2016	8,900,000	'	'
2017	6,700,000	'	'
2018	4,200,000	'	'
In-place lease value	'	'	'
Intangible assets on real estate acquisitions	'	'	'
Gross Carrying Amount	125,504,000	134,964,000	'
Accumulated Amortization	93,885,000	93,362,000	'
Net Carrying Amount	31,619,000	41,602,000	'
Weighted average amortization period of intangible assets	'6 years	'	'
Tenant relationship value	'	'	'
Intangible assets on real estate acquisitions	'	'	'
Gross Carrying Amount	44,414,000	46,828,000	'
Accumulated Amortization	25,962,000	23,346,000	'
Net Carrying Amount	18,452,000	23,482,000	'
Weighted average amortization period of intangible assets	'7 years	'	'
Below-market cost arrangements	'	'	'
Intangible assets on real estate acquisitions	'	'	'
Gross Carrying Amount	12,416,000	12,416,000	'
Accumulated Amortization	5,136,000	4,100,000	'
Net Carrying Amount	7,280,000	8,316,000	'
Weighted average amortization period of intangible assets	'29 years	'	'
Above-market leases	'	'	'
Intangible assets on real estate acquisitions	'	'	'
Gross Carrying Amount	8,925,000	8,925,000	'
Accumulated Amortization	7,970,000	7,432,000	'
Net Carrying Amount	955,000	1,493,000	'
Weighted average amortization period of intangible assets	'3 years	'	'
Market concentration premium	'	'	'
Intangible assets on real estate acquisitions	'	'	'
Gross Carrying Amount	1,333,000	1,333,000	'
Accumulated Amortization	381,000	347,000	'
Net Carrying Amount	$952,000	$986,000	'
Weighted average amortization period of intangible assets	'29 years	'	'

Deferred_Leasing_and_Financing2

Deferred Leasing and Financing Costs (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred Leasing and Financing Costs [Abstract]	'	'
Deferred leasing costs	$110,711	$97,852
Deferred financing costs	36,390	30,520
Accumulated amortization	-80,834	-68,420
Deferred leasing and financing costs, net	$66,267	$59,952

Mortgage_and_Other_Investing_R2

Mortgage and Other Investing Receivable (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Mortgage and other investing receivables	$53,663	$35,798
Notes receivable from City of Huntsville	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Mortgage and other investing receivables	44,055	35,654
Mortgage loans receivable	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Mortgage and other investing receivables	$9,608	$144
Number of mortgage loans receivable	1	'

Prepaid_Expenses_and_Other_Ass2

Prepaid Expenses and Other Assets (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Prepaid Expense and Other Assets [Abstract]	'		'
Prepaid expenses	$19,308		$19,270
Lease incentives	8,435		5,578
Interest rate derivatives	6,594		0
Furniture, fixtures and equipment, net	6,556		7,991
Deferred tax asset, net	4,305	[1]	6,612	[1]
Construction contract costs incurred in excess of billings	2,462		0
Other equity method investments	2,258		2,425
Other assets	4,268		2,183
Prepaid expenses and other assets	54,186		44,059
Mortgage and Other Investing Receivables [Line Items]	'		'
Operating Notes Receivable Long-Term, Allowance for Estimated Losses	87		'
Operating notes receivable	'		'
Mortgage and Other Investing Receivables [Line Items]	'		'
Operating notes receivables due from tenants with terms exceeding one year	$1,700		$271

[1]	See Note 19 for further disclosure.

Debt_Details

Debt (Details) (USD $)

12 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Sep. 30, 2011

Dec. 31, 2013

Feb. 14, 2012

Dec. 31, 2013

Aug. 03, 2012

Dec. 31, 2013

Dec. 31, 2012

Apr. 30, 2010

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Sep. 30, 2011

Dec. 31, 2011

Sep. 15, 2011

Dec. 31, 2013

6-May-13

Dec. 31, 2013

Sep. 15, 2013

Dec. 31, 2013

Sep. 16, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Mortgage and Other Secured Loans:

Fixed rate mortgage loans

Variable rate secured loans

Other construction loan facilities

Revolving Credit Facility

Term Credit Facility Effective September 2011

Term Credit Facility Effective February 2012

Term Credit Facility Effective August 2012

Term Loan Facilities

4.25% Exchangeable Senior Notes

Unsecured notes payable

3.5% Exchangeable Senior Notes

Construction loans

Senior Notes

London Interbank Offered Rate (LIBOR)

Adjusted Treasury [Member]

Revolving Credit Facility

Minimum

Maximum

Fixed rate mortgage loans

3.60% Senior Notes

5.250% Senior Notes

Term Credit Facility Effective September 2011

Term Credit Facility Effective February 2012

Term Credit Facility Effective August 2012

Senior Notes

Revolving Credit Facility

Term Loan Facilities

London Interbank Offered Rate (LIBOR)

Revolving Credit Facility

Term Loan Facilities

London Interbank Offered Rate (LIBOR)

Revolving Credit Facility

3.60% Senior Notes

5.250% Senior Notes

Term Credit Facility Effective September 2011

Term Credit Facility Effective February 2012

Term Credit Facility Effective August 2012

London Interbank Offered Rate (LIBOR)

Term Credit Facility Effective September 2011

Term Credit Facility Effective February 2012

Term Credit Facility Effective August 2012

London Interbank Offered Rate (LIBOR)

Debt

Maximum Availability

$800,000,000

[1]

Debt, net

1,927,703,000

2,019,168,000

712,751,000

1,016,446,000

675,060,000

[2],[3]

948,414,000

[2],[3]

37,691,000

38,475,000

29,557,000

[1]

620,000,000

[1],[4]

770,000,000

[1],[4]

563,000

[1]

230,934,000

[1]

1,700,000

1,788,000

13,900,000

347,244,000

245,445,000

Debt instrument, maximum borrowing capacity

26,200,000

Stated interest rate (as a percent)

4.25%

0.00%

[5]

3.50%

3.60%

5.25%

Stated Interest Rates, low end of range (as a percent)

3.96%

[6]

Stated Interest Rates, high end of range (as a percent)

7.87%

[6]

Description of variable rate basis

'LIBOR

[7]

'LIBOR

[8]

'LIBOR

Variable rate, spread (as a percent)

2.25%

[7]

0.98%

1.10%

[8]

1.10%

2.10%

0.98%

1.75%

2.60%

[8]

2.00%

2.60%

1.75%

Line of Credit Facility, Commitment Fee Percentage

0.13%

0.35%

Unamortized premium included in carrying value

69,000

1,300,000

Weighted average interest rate (as a percent)

6.14%

1.79%

Interest rate on debt (as a percent)

2.42%

Additional borrowing capacity available provided there is no default under the agreement

100,000,000

80,000,000

180,000,000

Unamortized discount included in carrying value

12,000

9,100,000

761,000

873,000

2,800,000

4,600,000

Expansion right, maximum borrowing capacity

1,300,000,000

Amount available as a percentage of unencumbered Asset value

60.00%

Extension option period (in years)

'1 year

Line of credit facility, extension fee percentage

0.15%

Remaining borrowing capacity

784,600,000

Initial amount borrowed

400,000,000

250,000,000

120,000,000

240,000,000

347,100,000

245,300,000

Term Facility, Amount Remaining After Partial Early Termination

250,000,000

Extension fee as a percentage of total availability of the facility

0.15%

Exchange rate per $1000 principal amount (in common shares)

20.8513

Convertible debt principal amount, basis for exchange

1,000

Exchange price per common share based on exchange rate (in dollars per share)

$47.96

Percentage over the entity's common stock price at the time of issuance which was used to determine the initial exchange rate

20.00%

Repurchase of notes, percentage of principal paid

100.00%

Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement

239,400,000

Loss on early extinguishment of debt

27,030,000

943,000

1,639,000

25,900,000

Principal amount of debt

1,935,718,000

[9]

575,000

240,000,000

162,500,000

Effective interest rate, including amortization of issuance costs (as a percent)

6.05%

5.97%

3.70%

5.49%

Interest expense at stated interest rate

4,208,000

10,200,000

4,013,000

Interest expense associated with amortization of discount

1,159,000

3,155,000

5,540,000

1,615,000

3,651,000

3,437,000

2,617,000

Total interest expenses

5,823,000

13,851,000

13,637,000

6,630,000

Debt Instrument, Decrease, Repayments

162,500,000

Loan amount

350,000,000

250,000,000

Debt issuance as a percentage of principal amount

99.82%

98.78%

Basis points used in determining redemption price prior to maturity

30.00%

40.00%

Redemption percentage within three months of maturity

100.00%

Weighted average borrowings

$55,500,000

$276,500,000

Weighted average interest rate (as a percent)

1.74%

2.27%

[1]

Refer to the paragraphs below for further disclosure.

[2]

Several of the fixed rate mortgages carry interest rates that were above or below market rates upon assumption and therefore were recorded at their fair value based on applicable effective interest rates. The carrying values of these loans reflect net unamortized premiums totaling $69,000 at DecemberÂ 31, 2013 and $1.3 million at DecemberÂ 31, 2012.

[3]

Includes $13.9 million balance on construction loans with maximum available borrowings of $26.2 million.

[4]

As discussed below, we have the ability to borrow an aggregate of an additional $180.0 million under these term loan facilities, provided that there is no default under the facilities and subject to the approval of the lenders.

[5]

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 $761,000 at DecemberÂ 31, 2013 and $873,000 at DecemberÂ 31, 2012.

[6]

The weighted average interest rate on these loans was 6.14% at DecemberÂ 31, 2013.

[7]

The interest rate on the loan outstanding was 2.42% at DecemberÂ 31, 2013.

[8]

The weighted average interest rate on these loans was 1.79% at DecemberÂ 31, 2013.

[9]

Represents scheduled principal amortization and maturities only and therefore excludes net discounts of $8.0 million.

Debt_Details_2

Debt (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
	period		Dec. 31, 2012	Dec. 31, 2011
Schedule on basis of which debt matures	'		'	'
2014	$89,483,000		'	'
2015	395,969,000	[1]	'	'
2016	279,339,000		'	'
2017	405,615,000	[2]	'	'
2018	1,374,000		'	'
Thereafter	763,938,000		'	'
Total	1,935,718,000	[3]	'	'
Debt maturing in 2015 that may be extended for two one year periods	250,000,000		'	'
Number Of Extension Option Periods For Year Two Long-term Debt Maturities Repayments of Principal	2		'	'
Extension option period for portion of debt maturing in 2015 (in years)	'1 year		'	'
Debt maturing in 2017 that may be extended for a one year period	250,000,000		'	'
Extension option period for portion of debt maturing in 2017 (in years)	'1 year		'	'
Net discounts	8,000,000		'	'
Capitalized interest costs	$8,800,000		$13,900,000	$17,400,000

[1]	Includes $250.0 million that may be extended for two one-year periods at our option, subject to certain conditions.
[2]	ncludes $250.0 million that may be extended for one year at our option, subject to certain conditions.
[3]	Represents scheduled principal amortization and maturities only and therefore excludes net discounts of $8.0 million.

Debt_Details_3

Debt (Details 3) (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Carrying amount and estimated fair value of debt	'		'
Debt, net	$1,927,703		$2,019,168
Senior Notes	'		'
Carrying amount and estimated fair value of debt	'		'
Debt, net	592,700		'
4.25% Exchangeable Senior Notes	'		'
Carrying amount and estimated fair value of debt	'		'
Debt, net	563	[1]	230,934	[1]
Carrying Amount	'		'
Carrying amount and estimated fair value of debt	'		'
Variable-rate debt	657,691		838,032
Debt, net	1,927,703		2,019,168
Carrying Amount \| Senior Notes	'		'
Carrying amount and estimated fair value of debt	'		'
Fixed-rate debt	592,689		0
Carrying Amount \| 4.25% Exchangeable Senior Notes	'		'
Carrying amount and estimated fair value of debt	'		'
Fixed-rate debt	563		230,934
Carrying Amount \| Fixed-rate debt excluding other fixed rate debt not separately disclosed	'		'
Carrying amount and estimated fair value of debt	'		'
Fixed-rate debt	676,760		950,202
Total Estimated Fair Value	'		'
Carrying amount and estimated fair value of debt	'		'
Variable-rate debt	657,527		845,558
Debt, net	1,884,473		2,054,020
Total Estimated Fair Value \| Senior Notes	'		'
Carrying amount and estimated fair value of debt	'		'
Fixed-rate debt	575,374		0
Total Estimated Fair Value \| 4.25% Exchangeable Senior Notes	'		'
Carrying amount and estimated fair value of debt	'		'
Fixed-rate debt	575		240,282
Total Estimated Fair Value \| Fixed-rate debt excluding other fixed rate debt not separately disclosed	'		'
Carrying amount and estimated fair value of debt	'		'
Fixed-rate debt	$650,997		$968,180

[1]	Refer to the paragraphs below for further disclosure.

Interest_Rate_Derivatives_Deta

Interest Rate Derivatives (Details) (USD $)	12 Months Ended
Interest Rate Derivatives (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Fair values of interest rate swap derivatives	'		'	'
Fair value of interest rate swaps	$3,285,000		($6,185,000)	'
Fair value of interest rate derivatives and balance sheet classification	'		'	'
Interest rate derivatives	6,594,000		0	'
Interest rate swaps	'		'	'
Fair value of interest rate derivatives and balance sheet classification	'		'	'
Interest rate derivatives	6,594,000		0	'
Fair value of Interest rate swaps classified as interest rate derivatives	-3,309,000		-6,185,000	'
Effect of interest rate derivatives on consolidated statements of operations and comprehensive income	'		'	'
Amount of gains (losses) recognized in accumulated other comprehensive income (loss) (â€œAOCIâ€) (effective portion)	6,791,000		-7,676,000	-31,531,000
Amount of losses reclassified from AOCI into interest expense (effective portion)	-2,740,000		-3,697,000	-4,601,000
Amount of loss reclassified from AOCI to loss on interest rate derivatives upon discontinuing hedge accounting	0		0	28,430,000
Amount of loss on interest rate derivatives recognized subsequent to such derivatives no longer being designated as hedges	0		0	1,375,000
Approximate amount to be reclassified from AOCL to interest expense over the next 12 months	2,700,000		'	'
Interest rate derivatives in liability position, fair value	3,300,000		'	'
Termination value to settle obligations under interest rate derivative agreements	3,600,000		'	'
Designated \| Interest rate swap, effective date January 3, 2012, swap one	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	0.61%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	-279,000		-594,000	'
Designated \| Interest rate swap, effective date January 3, 2012, swap two	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	0.61%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	-277,000		-591,000	'
Designated \| Interest rate swap, effective date January 3, 2012, swap three	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	0.83%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	-861,000		-1,313,000	'
Designated \| Interest rate swap, effective date January 3, 2012, swap four	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	0.83%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	-861,000		-1,313,000	'
Designated \| Interest rate swap, effective date November 2, 2010	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	37,691,000	[1]	'	'
Fixed rate (as a percent)	3.83%		'	'
Floating rate index	'One-Month LIBOR + 2.25%		'	'
Derivative, Basis Spread on Variable Rate	2.25%		'	'
Fair value of interest rate swaps	-832,000		-1,268,000	'
Notional amount of interest rate derivatives after scheduled amortization	36,200,000		'	'
Designated \| Interest rate swap, effective date September 2, 2014, swap one	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	0.81%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	-94,000		-263,000	'
Designated \| Interest rate swap, effective date September 2, 2014, swap two	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	0.81%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	-105,000		-272,000	'
Designated \| Interest rate swap, effective date September 1, 2015, swap one	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	1.67%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	3,377,000		-154,000	'
Designated \| Interest rate swap, effective date September 1, 2015, swap two	'		'	'
Fair values of interest rate swap derivatives	'		'	'
Notional Amount	100,000,000		'	'
Fixed rate (as a percent)	1.73%		'	'
Floating rate index	'One-Month LIBOR		'	'
Fair value of interest rate swaps	$3,217,000		($417,000)	'

[1]	The notional amount of this instrument is scheduled to amortize to $36.2 million

Redeemable_Noncontrolling_Inte2

Redeemable Noncontrolling Interest (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]	'	'	'
Beginning balance	$10,298	$8,908	$9,000
Distribution to noncontrolling interest	-1,037	0	0
Net income (loss) attributable to noncontrolling interest	1,376	-2,565	-1,407
Adjustment to arrive at fair value of interest	7,121	3,955	1,315
Ending balance	$17,758	$10,298	$8,908

Equity_COPT_and_Subsidiaries_D

Equity - COPT and Subsidiaries (Details) (USD $)

0 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

Mar. 19, 2013

Oct. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 16, 2013

Dec. 31, 2013

Jun. 27, 2012

Aug. 06, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jun. 27, 2012

Apr. 22, 2013

Common Stock Issued to Public Under At-the-Market Program

Series L Preferred Units

Series G Preferred Shares

Preferred Shares

Series H

Series K

Series L Cumulative Preferred Stock

Series J

Public Offering

Preferred Stock

Number of shares issued

9,431,667

2,000,000

531,667

6,900,000

Preferred Stock, Shares Authorized

25,000,000

Number of preferred shares of beneficial interest authorized (in dollars per share)

$0.01

Aggregate Liquidation Preference

$249,083,000

$333,833,000

$50,000,000

$26,583,000

$172,500,000

Annual dividend yield

8.00%

7.50%

5.60%

7.38%

7.63%

Annual dividend per share (in dollars per share)

$1.88

$2.80

$1.84

Number of common shares to be issued on conversion of each preferred share

0.8163

Net proceeds from issuance of Series L preferred shares

165,652,000

165,700,000

Number of Series L preferred units of operating partnerships received in exchange for offering proceeds (in units)

6,900,000

Preferred stock, redemption price per share

$25

Stock redeemed or called during period (in units/ shares)

84,750,000

55,000,000

84,800,000

Issuance costs associated with redeemed preferred shares

1,800,000

2,900,000

Common Shares

Shares issued to the public

4,485,000

8,600,000

4,600,000

1,500,000

6,900,000

Per share value of common and preferred shares issued to the public (in dollars per share)

$26.34

$24.75

$25

Net proceeds from issue of shares after underwriter discounts but before offering expenses

118,100,000

204,900,000

117,961,000

145,367,000

38,500,000

165,652,000

At-market-stock, offering program established, aggregate value

150,000,000

Issuance of stock, weighted average price per share

$26.05

Payments of stock issuance costs

586,000

At-market stock, offering program established, remaining capacity

$110,900,000

Number of common shares for each converted common unit (in shares)

Number of operating partnerships units converted into common shares (in units)

311,343

234,246

100,939

Dividends declared per common share

$1.10

$1.65

Equity_COPLP_and_Subsidiaries_1

Equity - COPLP and Subsidiaries (Details) (USD $)

0 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

Mar. 19, 2013

Oct. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 16, 2013

Jun. 27, 2012

Aug. 06, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jun. 27, 2012

Apr. 22, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 16, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jun. 27, 2012

Aug. 06, 2012

Dec. 31, 2012

Dec. 31, 2013

Jun. 27, 2012

Apr. 22, 2013

Mar. 31, 2013

Oct. 31, 2012

Dec. 31, 2012

Common Stock Issued to Public Under At-the-Market Program

Series L Preferred Units

Series G Preferred Shares

Preferred Shares

Series H

Series K

Series L Cumulative Preferred Stock

Series J

Common Shares

Corporate Office Properties, L.P.

Public Offering

Common Stock Issued to Public Under At-the-Market Program

Common Units

Conversion of Series I preferred units

Series L Preferred Units

Series G Preferred Shares

Preferred Shares

Series H

Series K

Series L Cumulative Preferred Stock

Series J

Common Shares

Trustee

Public Offering

Preferred Stock

Number of shares issued

9,431,667

2,000,000

531,667

6,900,000

9,431,667

2,000,000

531,667

6,900,000

Aggregate Liquidation Preference

$249,083,000

$333,833,000

$50,000,000

$26,583,000

$172,500,000

$249,083,000

$50,000,000

$26,583,000

$172,500,000

Annual dividend yield

8.00%

7.50%

5.60%

7.38%

7.63%

7.50%

8.00%

7.50%

5.60%

7.38%

7.63%

Annual dividend per share (in dollars per share)

$1.88

$2.80

$1.84

$1.88

$2.80

$1.84

Number of common shares to be issued on conversion of each preferred share

0.8163

Net proceeds from issuance of Series L preferred shares

165,652,000

165,700,000

165,652,000

165,700,000

Number of Series L preferred units of operating partnerships received in exchange for offering proceeds (in units)

6,900,000

Preferred stock, redemption price per share

$25

Stock redeemed or called during period (in units/ shares)

84,750,000

55,000,000

84,800,000

84,750,000

55,000,000

84,800,000

Issuance costs associated with redeemed preferred shares

1,800,000

2,900,000

1,800,000

2,900,000

Annual Cumulative Preferred Return Increment Frequency

'5 years

Common Shares

Shares issued to the public

4,485,000

8,600,000

4,600,000

1,500,000

6,900,000

4,485,000

8,625,000

4,600,000

1,500,000

6,900,000

4,485,000

8,600,000

Per share value of common and preferred shares issued to the public (in dollars per share)

$26.34

$24.75

$25

$26.34

$24.75

Net proceeds from issue of shares after underwriter discounts but before offering expenses

118,100,000

204,900,000

117,961,000

145,367,000

38,500,000

165,652,000

204,696,000

117,961,000

145,367,000

38,500,000

165,652,000

118,100,000

204,900,000

204,696,000

Issuance of stock, weighted average price per share

$26.05

Payments of stock issuance costs

586,000

Number of common shares for each converted common unit (in shares)

Number of operating partnerships units converted into common shares (in units)

311,343

234,246

100,939

311,343

234,246

Dividends declared per common share

$1.10

$1.65

$1.10

$1.65

Limited Partners' Capital Account, Units Issued

352,000

Preferred units in COPLP

$8,800,000

Preferred Stock, Liquidation Preference Per Share

$25

Common Units Conversion Basis Units Issuable

0.5

Percentage ownership in operating partnership

95.60%

95.20%

Number of trustees controlling additional common units

Additional percentage of common units controlled by trustees (as a percent)

3.40%

ShareBased_Compensation_and_Em2

Share-Based Compensation and Employee Benefit Plans (Details) (USD $)

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

In Millions, except Share data, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Mar. 04, 2010

Dec. 31, 2011

Mar. 03, 2011

Mar. 02, 2012

Mar. 01, 2013

31-May-10

Stock Options

Restricted shares

Performance share units

Maximum

Percentile_Rank

2010 PSU Grants

2011 PSU Grants

2012 PSU Grants

2013 PSU Grants

Amended and Restated 2008 Omnibus Equity and Incentive Plan

Share-Based Compensation

Number of common shares of beneficial interest authorized to be issued

5,900,000

Expiration period

'10 years

Unvested at the beginning of the period (in shares)

434,643

648,378

669,858

Stock awards granted (in shares or units)

193,833

177,662

320,284

100,645

56,883

54,070

69,579

Forfeited (in shares)

-9,541

-17,019

-18,058

-58,105

Vested (in shares)

-241,487

-374,378

-323,706

Unvested at the end of the period (in shares)

377,448

434,643

648,378

Restricted shares expected to vest (in shares)

361,064

Weighted Average Grant Date Fair Value

Unvested at the beginning of the period (in dollars per share)

$29.67

$33.13

$32.77

Grant date fair value (in dollars per share)

$25.91

$23.64

$33.68

$26.84

$32.77

$49.15

Forfeited (in dollars per share)

$27.59

$31.43

$34.23

Vested (in dollars per share)

$30.97

$32.72

$32.86

Unvested at the end of the period (in dollars per share)

$26.96

$29.67

$33.13

Restricted shares expected to vest (in dollars per share)

$27.02

Other Share-based Compensation Additional Disclosures

Aggregate intrinsic value of restricted common shares, forfeiture restrictions lapsed

$6.30

$11.20

Aggregate grant date fair value

5.4

2.8

1.8

1.9

Non-cash compensation charge recognized in connection with cancellations

$1.20

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%

Performance period of the award

'3 years

Assumptions used to value stock awards

Baseline value per common share (in dollars per share)

$25.85

$24.39

$35.17

Expected volatility of common shares (as a percent)

29.50%

43.20%

61.10%

Risk-free interest rate (as a percent)

0.33%

0.41%

1.32%

ShareBased_Compensation_and_Em3

Share-Based Compensation and Employee Benefit Plans (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Stock Options	'		'		'		'
Exercised (in shares)	-39,331		-61,624		-191,264		'
Aggregate Intrinsic Value	'		'		'		'
Increase (decrease) in tax benefit from share-based compensation	($122,000)		$43,000		$47,000		'
Options	'		'		'		'
Stock Options	'		'		'		'
Outstanding at the beginning of the period (in shares)	798,210		945,422		1,188,284		'
Forfeited/Expired (in shares)	-117,952		-85,588		-51,598		'
Exercised (in shares)	-39,331		-61,624		-191,264		'
Outstanding at the end of the period (in shares)	640,927		798,210		945,422		1,188,284
Exercisable at the end of the period (in shares)	640,927	[1]	798,210	[2]	945,422	[3]	'
Exercise price range, options outstanding, low end of range (in dollars per share)	$19.63		$13.60		$13.40		$9.54
Exercise price range, options outstanding, high end of range (in dollars per share)	$56		$57		$57		$57
Weighted Average Exercise Price per Share	'		'		'		'
Outstanding at the beginning of the period (in dollars per share)	$37.62		$36.63		$33.07		'
Forfeited/Expired (in dollars per share)	$40.91		$42.98		$42.82		'
Exercised (in dollars per share)	$19.67		$15.08		$12.82		'
Outstanding at the end of the period (in dollars per share)	$38.11		$37.62		$36.63		$33.07
Exercisable at the end of the period (in dollars per share)	$38.11	[1]	$37.62	[2]	$36.63	[3]	'
Weighted Average Remaining Contractual Term	'		'		'		'
Weighted average remaining contractual term	'2 years		'3 years		'4 years		'5 years
Aggregate Intrinsic Value	'		'		'		'
Balance outstanding	68,000		325,000		510,000		7,987,000
Aggregate intrinsic value of options exercised	258,000		553,000		4,000,000		'
Options \| Range of Exercise Price One \| Vested	'		'		'		'
Stock Options	'		'		'		'
Exercisable at the end of the period (in shares)	171,288		9,500		53,957		'
Exercise price range, options outstanding, low end of range (in dollars per share)	$19.63		$13.60		$13.40		'
Exercise price range, options outstanding, high end of range (in dollars per share)	$30.04		$16.73		$16.73		'
Options \| Range of Exercise Price Two \| Vested	'		'		'		'
Stock Options	'		'		'		'
Exercisable at the end of the period (in shares)	145,187		204,736		225,903		'
Exercise price range, options outstanding, low end of range (in dollars per share)	$30.05		$16.74		$16.74		'
Exercise price range, options outstanding, high end of range (in dollars per share)	$41.28		$30.04		$30.04		'
Options \| Range of Exercise Price Three \| Vested	'		'		'		'
Stock Options	'		'		'		'
Exercisable at the end of the period (in shares)	160,402		180,962		198,762		'
Exercise price range, options outstanding, low end of range (in dollars per share)	$41.29		$30.05		$30.05		'
Exercise price range, options outstanding, high end of range (in dollars per share)	$42.74		$41.28		$41.28		'
Options \| Range of Exercise Price Four \| Vested	'		'		'		'
Stock Options	'		'		'		'
Exercisable at the end of the period (in shares)	164,050		403,012		466,800		'
Exercise price range, options outstanding, low end of range (in dollars per share)	$42.75		$41.29		$41.29		'
Exercise price range, options outstanding, high end of range (in dollars per share)	$56		$57		$57		'
Performance share units	'		'		'		'
Aggregate Intrinsic Value	'		'		'		'
Estimated pre-vesting forfeitures (as a percent)	0.00%		0.00%		0.00%		'
Unrecognized compensation cost	2,100,000		'		'		'
Expected weighted average period during which unrecognized compensation cost will be recognized	'2 years		'		'		'
Restricted shares	'		'		'		'
Aggregate Intrinsic Value	'		'		'		'
Unrecognized compensation cost	$6,100,000		'		'		'
Expected weighted average period during which unrecognized compensation cost will be recognized	'2 years		'		'		'
Minimum \| Options	'		'		'		'
Stock Options	'		'		'		'
Exercise price range, options forfeited (in dollars per share)	$18.08		$25.52		$22.49		'
Exercise price range, options exercised (in dollars per share)	$13.60		$13.40		$9.54		'
Minimum \| Restricted shares	'		'		'		'
Aggregate Intrinsic Value	'		'		'		'
Estimated pre-vesting forfeitures (as a percent)	0.00%		0.00%		0.00%		'
Maximum \| Options	'		'		'		'
Stock Options	'		'		'		'
Exercise price range, options forfeited (in dollars per share)	$51.62		$57		$50.59		'
Exercise price range, options exercised (in dollars per share)	$26.24		$22.49		$30.25		'
Maximum \| Restricted shares	'		'		'		'
Aggregate Intrinsic Value	'		'		'		'
Estimated pre-vesting forfeitures (as a percent)	5.00%		5.00%		4.00%		'

[1]	171,288 of these options had an exercise price ranging from $19.63 to $30.04; 145,187 had an exercise price ranging from$30.05 to $41.28; 160,402 had an exercise price ranging from $41.29 to $42.74; and 164,050 had an exercise price ranging from $42.75 to $56.00.
[2]	9,500 of these options had an exercise price ranging from $13.60 to $16.73; 204,736 had an exercise price ranging from $16.74 to $30.04; 180,962 had an exercise price ranging from $30.05 to $41.28; and 403,012 had an exercise price ranging from $41.29 to $57.00.
[3]	53,957 of these options had an exercise price ranging from $13.40 to $16.73; 225,903 had an exercise price ranging from $16.74 to $30.04; 198,762 had an exercise price ranging from $30.05 to $41.28; and 466,800 had an exercise price ranging from $41.29 to $57.00.

ShareBased_Compensation_and_Em4

Share-Based Compensation and Employee Benefit Plans (Details 3) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-Based Compensation	'	'	'
Share-based compensation expense	$7,605	$11,184	$14,267
General, adminstrative and leasing expenses	'	'	'
Share-Based Compensation	'	'	'
Share-based compensation expense	5,412	8,611	9,077
Property operating expenses	'	'	'
Share-Based Compensation	'	'	'
Share-based compensation expense	1,118	1,371	2,843
Capitalized to development activities	'	'	'
Share-Based Compensation	'	'	'
Share-based compensation expense	$1,075	$1,202	$2,347

ShareBased_Compensation_and_Em5

Share-Based Compensation and Employee Benefit Plans Share-Based Compensation and Employee Benefit Plans (Details 4) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'
Maximum percentage of compensation employees can contribute to the 401K plan	90.00%	'	'
Minimum age of participants who are eligible to contribute an additional portion of their annual compensation	'50 years	'	'
Employer matching contribution for the first 1% of the participants' eligible compensation (as a percent)	100.00%	'	'
Maximum percentage of participants' compensation eligible for 100% employer matching contribution (as a percent)	1.00%	'	'
Employer matching contribution for the next 5% after first 1% of the participants' eligible compensation (as a percent)	50.00%	'	'
Maximum percentage of participants' compensation eligible for 50% employer matching contribution (as a percent)	5.00%	'	'
Employer's aggregate matching contribution for the first 6% of the participants' eligible compensation (as a percent)	3.50%	'	'
Maximum percentage of participants' compensation eligible for 3.5% aggregate employer matching contribution	6.00%	'	'
Participants' vesting portion in employer matching contribution after one year of credited service (as a percent)	50.00%	'	'
Period of credited service after which participants are 50% vested in employer matching contribution	'1 year	'	'
Participants' vesting portion in employer matching contribution after two years of credited service (as a percent)	100.00%	'	'
Period of credited service after which participants are 100% vested in employer matching contribution	'2 years	'	'
Matching contribution under the plan	$1.10	$1.10	$1.10

ShareBased_Compensation_and_Em6

Share-Based Compensation and Employee Benefit Plans (Details 5) (Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member], Management, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member] \| Management	'	'
Deferred Compensation Plan	'	'
Maximum percentage of participants' compensation which is deferrable (as a percent)	100.00%	'
Balance of the plan which was fully funded	$7.50	$6.80

Operating_Leases_Details

Operating Leases (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2013
Gross minimum future rentals	'
2014	$344,809
2015	310,035
2016	256,228
2017	213,894
2018	163,011
Thereafter	351,111
Total	$1,639,088

Information_by_Business_Segmen2

Information by Business Segment (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	segment	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting [Abstract]	'	'	'
Number of primary office property segments (in number of segments)	10	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	$498,633	$493,100	$495,832
Property operating expenses	180,704	180,735	187,820
NOI from real estate operations	317,929	312,365	308,012
Segment assets	3,629,952	3,653,759	'
Operating Segment Total	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	498,633	493,100	495,832
Property operating expenses	180,704	180,735	187,820
NOI from real estate operations	317,929	312,365	308,012
Additions to long-lived assets	56,877	106,801	105,109
Transfers from non-operating properties	264,290	220,997	144,388
Segment assets	2,905,630	2,945,930	3,039,440
Baltimore and Washington Corridor	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	237,869	238,488	237,162
Property operating expenses	80,554	83,050	86,782
NOI from real estate operations	157,315	155,438	150,380
Additions to long-lived assets	28,087	25,921	33,142
Transfers from non-operating properties	50,105	65,108	67,752
Segment assets	1,243,099	1,267,357	1,350,678
Northern Virginia	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	92,010	79,574	74,214
Property operating expenses	31,973	29,103	28,518
NOI from real estate operations	60,037	50,471	45,696
Additions to long-lived assets	13,090	65,157	14,770
Transfers from non-operating properties	61,434	44,250	4
Segment assets	616,082	569,860	484,392
San Antonio	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	33,060	32,018	30,066
Property operating expenses	17,631	16,499	14,371
NOI from real estate operations	15,429	15,519	15,695
Additions to long-lived assets	335	280	0
Transfers from non-operating properties	0	468	17,638
Segment assets	118,299	119,369	131,412
Huntsville	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	5,050	3,867	1,368
Property operating expenses	1,282	689	226
NOI from real estate operations	3,768	3,178	1,142
Additions to long-lived assets	3,563	26	26,837
Transfers from non-operating properties	48,799	0	0
Segment assets	77,773	28,730	32,341
Washington, DC - Capitol Riverfront	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	16,863	16,697	17,878
Property operating expenses	7,844	7,555	6,762
NOI from real estate operations	9,019	9,142	11,116
Additions to long-lived assets	2,604	317	2,794
Transfers from non-operating properties	0	0	0
Segment assets	98,962	104,544	111,318
St. Mary's and King George Counties	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	16,568	16,392	14,366
Property operating expenses	5,028	4,745	4,142
NOI from real estate operations	11,540	11,647	10,224
Additions to long-lived assets	2,341	1,844	1,638
Transfers from non-operating properties	14	289	16,858
Segment assets	96,143	98,027	100,818
Greater Baltimore	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	42,653	52,616	70,668
Property operating expenses	16,583	19,917	29,543
NOI from real estate operations	26,070	32,699	41,125
Additions to long-lived assets	2,913	9,690	21,086
Transfers from non-operating properties	360	37,558	16,307
Segment assets	303,823	320,548	402,067
Greater Philadelphia	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	11,924	9,698	7,458
Property operating expenses	3,431	2,562	1,402
NOI from real estate operations	8,493	7,136	6,056
Additions to long-lived assets	406	286	516
Transfers from non-operating properties	28,034	10,626	5,446
Segment assets	104,657	78,798	102,572
Colorado Springs	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	25,290	24,987	23,675
Property operating expenses	9,002	9,231	8,758
NOI from real estate operations	16,288	15,756	14,917
Additions to long-lived assets	2,940	2,929	4,085
Transfers from non-operating properties	5,438	4,295	214
Segment assets	0	175,830	181,384
Other	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	10,075	12,116	13,923
Property operating expenses	1,016	2,569	3,887
NOI from real estate operations	9,059	9,547	10,036
Additions to long-lived assets	0	152	182
Transfers from non-operating properties	0	394	0
Segment assets	80,002	82,090	98,808
Operating Wholesale Data Center	'	'	'
Segment financial information for real estate operations	'	'	'
Revenues from real estate operations	7,271	6,647	5,054
Property operating expenses	6,360	4,815	3,429
NOI from real estate operations	911	1,832	1,625
Additions to long-lived assets	598	199	59
Transfers from non-operating properties	70,106	58,009	20,169
Segment assets	$166,790	$100,777	$43,650

Information_by_Business_Segmen3

Information by Business Segment (Details 2) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of segment revenues to total revenues	'	'	'	'	'	'	'	'	'	'	'
Segment revenues from real estate operations	'	'	'	'	'	'	'	'	$498,633	$493,100	$495,832
Construction contract and other service revenues	'	'	'	'	'	'	'	'	62,363	73,836	84,345
Less: Revenues from discontinued operations (Note 20)	'	'	'	'	'	'	'	'	-37,636	-58,801	-87,221
Total revenues	128,802	131,812	136,527	126,219	132,635	125,067	123,074	127,359	523,360	508,135	492,956
Reconciliation of segment property operating expenses to property operating expenses	'	'	'	'	'	'	'	'	'	'	'
Segment property operating expenses	'	'	'	'	'	'	'	'	180,704	180,735	187,820
Less: Property operating expenses from discontinued operations	'	'	'	'	'	'	'	'	-13,505	-21,529	-33,445
Total property operating expenses	'	'	'	'	'	'	'	'	167,199	159,206	154,375
Computation of net operating income from service operations	'	'	'	'	'	'	'	'	'	'	'
Construction contract and other service revenues	'	'	'	'	'	'	'	'	62,363	73,836	84,345
Construction contract and other service expenses	'	'	'	'	'	'	'	'	-58,875	-70,576	-81,639
NOI from service operations	'	'	'	'	'	'	'	'	3,488	3,260	2,706
Reconciliation of NOI from real estate operations and NOI from service operations to (loss) income from continuing operations	'	'	'	'	'	'	'	'	'	'	'
NOI from real estate operations	'	'	'	'	'	'	'	'	317,929	312,365	308,012
NOI from service operations	'	'	'	'	'	'	'	'	3,488	3,260	2,706
Interest and other income	'	'	'	'	'	'	'	'	3,834	7,172	5,603
Equity in income (loss) of unconsolidated entities	'	'	'	'	'	'	'	'	2,110	-546	-331
Income tax (expense) benefit	'	'	'	'	'	'	'	'	-1,978	-381	6,710
Other adjustments:	'	'	'	'	'	'	'	'	'	'	'
Depreciation and amortization associated with real estate operations	'	'	'	'	'	'	'	'	-113,214	-107,998	-107,003
Impairment losses	'	'	'	'	'	'	'	'	-5,857	-43,678	-83,213
General, administrative and leasing expenses	'	'	'	'	'	'	'	'	-30,869	-31,900	-30,306
Business development expenses and land carry costs	'	'	'	'	'	'	'	'	-5,436	-5,711	-6,122
Interest expense on continuing operations	'	'	'	'	'	'	'	'	-82,010	-86,401	-90,037
NOI from discontinued operations	'	'	'	'	'	'	'	'	-24,131	-37,272	-53,776
Loss on interest rate derivatives	'	'	'	'	'	'	'	'	0	0	-29,805
Loss on early extinguishment of debt	'	'	'	'	'	'	'	'	-27,030	-943	-1,639
Income (loss) from continuing operations	$14,432	$10,974	($232)	$11,662	$16,495	($32,048)	$10,336	$13,184	$36,836	$7,967	($79,201)

Information_by_Business_Segmen4

Information by Business Segment (Details 3) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of segment assets to total assets	'	'	'
Assets	$3,629,952	$3,653,759	'
Segment assets	'	'	'
Reconciliation of segment assets to total assets	'	'	'
Assets	2,905,630	2,945,930	3,039,440
Non-operating property assets	'	'	'
Reconciliation of segment assets to total assets	'	'	'
Assets	517,564	570,402	'
Other	'	'	'
Reconciliation of segment assets to total assets	'	'	'
Assets	$206,758	$137,427	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Minimum adjusted taxable income to be distributed to shareholders to qualify as a REIT (as a percent)	'	'	'	'	'	'	'	'	90.00%	'	'
Subsequent period during which entity would be disqualified as a REIT if during any tax year entity fails to qualify as a REIT (in years)	'	'	'	'	'	'	'	'	'4 years	'	'
Net income (loss)	$92,672	($2,000)	($4,405)	$15,277	$19,010	($20,765)	$11,861	$10,235	$101,544	$20,341	($127,576)
Adjustments:	'	'	'	'	'	'	'	'	'	'	'
Noncontrolling interests, gross	'	'	'	'	'	'	'	'	-4,930	-622	-5,583
Other	'	'	'	'	'	'	'	'	0	741	-6
Taxable income	'	'	'	'	'	'	'	'	104,668	7,488	84,050
Corporate Office Properties, L.P.	'	'	'	'	'	'	'	'	'	'	'
Income Tax [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net income (loss)	92,672	-2,000	-4,405	15,277	19,010	-20,765	11,861	10,235	101,544	20,341	-127,570
Adjustments:	'	'	'	'	'	'	'	'	'	'	'
Rental revenue recognition	'	'	'	'	'	'	'	'	-973	-10,794	-10,708
Compensation expense recognition	'	'	'	'	'	'	'	'	10,051	-2,669	-1,298
Operating expense recognition	'	'	'	'	'	'	'	'	-1,718	1,158	751
Gain on sales of properties	'	'	'	'	'	'	'	'	-53,545	-74,858	1,154
Asset Impairment Charges, Continuing and Noncontinuing Operations Including Exit Costs	'	'	'	'	'	'	'	'	32,047	66,910	151,021
Loss on interest rate derivatives	'	'	'	'	'	'	'	'	0	-29,805	29,805
Gains from non-real estate investments	'	'	'	'	'	'	'	'	0	7,854	4,447
Income from service operations	'	'	'	'	'	'	'	'	1,224	1,500	-12,078
Income tax expense	'	'	'	'	'	'	'	'	1,978	381	6,710
Depreciation and amortization	'	'	'	'	'	'	'	'	23,824	24,804	44,070
Interest expense	'	'	'	'	'	'	'	'	1,159	3,978	5,548
Income from unconsolidated entities	'	'	'	'	'	'	'	'	-1,462	-725	-374
Noncontrolling interests, gross	'	'	'	'	'	'	'	'	-3,907	-636	-1,919
Other	'	'	'	'	'	'	'	'	-624	-70	80
Taxable income	'	'	'	'	'	'	'	'	$109,598	$7,369	$89,639

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
Income Taxes (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other income tax information	'	'	'
Approximate amount by which basis of assets and liabilities for tax reporting purposes is lower than amount reported on consolidated balance sheet	$324,000,000	'	'
TRS	'	'	'
Other income tax information	'	'	'
(Loss) income before income taxes	330,000	11,300,000	-27,700,000
Deferred income tax (benefit) expense	'	'	'
Federal	-1,742,000	-312,000	5,510,000
State	-236,000	-69,000	1,219,000
Total deferred income tax (benefit) expense	-1,978,000	-381,000	6,729,000
Current income tax (benefit) expense	'	'	'
Federal	0	0	-16,000
State	0	0	-3,000
Total current income tax (benefit) expense	0	0	-19,000
Total income tax (expense) benefit	-1,978,000	-381,000	6,710,000
Reconciliation of Federal statutory rate to the effective tax rate	'	'	'
Income taxes at U.S. statutory rate (as a percent)	34.00%	34.00%	34.00%
State and local, net of U.S. Federal tax benefit (as a percent)	4.50%	4.60%	4.60%
Increase in deferred tax asset valuation allowance (as a percent)	562.90%	0.00%	0.00%
Other (as a percent)	-1.10%	0.00%	0.00%
Effective tax rate (as a percent)	600.30%	38.60%	38.60%
Operating Loss Carryforwards	14,000,000	'	'
Deferred Tax Assets, Net [Abstract]	'	'	'
Operating loss forward	5,382,000	6,014,000	'
Share-based compensation	869,000	904,000	'
Accrued payroll	221,000	12,000	'
Property	-105,000	-111,000	'
Valuation allowance	-2,062,000	-207,000	'
Deferred tax asset, net	4,305,000	6,612,000	'
Increase in deferred tax asset valuation	$1,900,000	'	'
Common Shares	'	'	'
Income Tax [Line Items]	'	'	'
Ordinary income (as a percent)	71.80%	33.20%	56.90%
Long-term capital gain (as a percent)	22.40%	0.00%	9.40%
Return of capital (as a percent)	5.80%	66.80%	33.70%
Preferred Shares	'	'	'
Income Tax [Line Items]	'	'	'
Ordinary income (as a percent)	76.20%	100.00%	85.90%
Long-term capital gain (as a percent)	23.80%	0.00%	14.10%
Return of capital (as a percent)	0.00%	0.00%	0.00%

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)

3 Months Ended

12 Months Ended

0 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2012

Sep. 29, 2011

Dec. 15, 2011

Jan. 30, 2012

Jul. 24, 2012

Dec. 12, 2013

Dec. 23, 2013

Assets Held-for-sale

Towson Portfolio

Rutherford Business Center Portfolio

White Marsh Portfolio Disposition Property

July 2012 Portfolio Disposition

December 2013 Colorado Springs Portfolio Disposition

Baltimore and Washington Corridor

Colorado Springs

Property

Properties

Number of properties sold

Number of properties transferred

Revenue from real estate operations

$37,636

$58,801

$87,221

Property operating expenses

-13,505

-21,529

-33,445

Depreciation and amortization

-4,505

-13,939

-27,128

Impairment losses

-26,190

-23,232

-67,808

General, administrative and leasing expenses

-4

-3

-20

Business development and land carry costs

-24

-75

Interest expense

-8,221

-10,397

-14,264

Gain on sales of real estate

2,671

20,940

4,796

Gain (loss) on early extinguishment of debt

67,810

1,736

-384

Discontinued operations

71,907

-12,974

-4,502

1,261

2,515

11,283

1,504

-2,949

55,692

12,353

-51,107

Properties, net

3,214,301

3,163,044

3,214,301

3,163,044

128,740

Deferred rent receivable (net of allowance of $2,126 and $913, respectively)

89,456

85,802

89,456

85,802

4,068

Intangible assets on real estate acquisitions, net

59,258

75,879

59,258

75,879

4,409

Deferred leasing costs, net

2,923

Lease incentives

8,435

5,578

8,435

5,578

Assets held for sale, net

$140,229

Earnings_Per_Share_EPS_and_Ear2

Earnings Per Share ("EPS") and Earnings Per Unit (â€œEPUâ€) (Details) (USD $)

3 Months Ended

12 Months Ended

In Thousands, except Per Share data, unless otherwise specified

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Numerator:

Income (loss) from continuing operations

$14,432

$10,974

($232)

$11,662

$16,495

($32,048)

$10,336

$13,184

$36,836

$7,967

($79,201)

Gain on sales of real estate, net

9,016

2,732

Preferred share dividends

-4,490

-4,885

-6,106

-6,546

-4,167

-4,025

-19,971

-20,844

-16,102

Issuance costs associated with redeemed preferred shares

-2,904

-1,827

-2,904

-1,827

(Income) loss from continuing operations attributable to noncontrolling interests

-4,486

1,309

5,128

Income from continuing operations attributable to restricted shares

-414

-469

-1,037

Numerator for basic and diluted EPS on net income (loss)attributable to COPT common shareholders

18,077

-13,843

-88,480

Discontinued operations

71,907

-12,974

-4,502

1,261

2,515

11,283

1,504

-2,949

55,692

12,353

-51,107

Discontinued operations attributable to noncontrolling interests

-3,351

-673

3,020

Numerator for basic and diluted EPS on net income (loss)attributable to COPT common shareholders

70,418

-2,163

-136,567

Denominator (all weighted averages):

Denominator for basic EPS (common shares)

85,167

73,454

69,382

Dilutive effect of share-based compensation awards

Denominator for basic and diluted EPS (common shares)

85,224

73,454

69,382

Basic EPS:

Income (loss) from continuing operations (in dollars per share)

$0.21

[1]

($0.19)

[1]

($1.28)

[1]

Discontinued operations (in dollars per share)

$0.62

[1]

$0.16

[1]

($0.69)

[1]

Net income (loss) attributable to COPT common shareholders (in dollars per share)

$0.94

($0.09)

($0.16)

$0.11

$0.16

($0.39)

$0.10

$0.09

$0.83

[1]

($0.03)

[1]

($1.97)

[1]

Diluted EPS:

Income (loss) from continuing operations (in dollars per share)

$0.21

[1]

($0.19)

[1]

($1.28)

[1]

Discontinued operations (in dollars per share)

$0.62

[1]

$0.16

[1]

($0.69)

[1]

Net income (loss) attributable to COPT common shareholders (in dollars per share)

$0.94

($0.09)

($0.16)

$0.11

$0.16

($0.39)

$0.10

$0.09

$0.83

[1]

($0.03)

[1]

($1.97)

[1]

Corporate Office Properties, L.P.

Numerator:

Income (loss) from continuing operations

14,432

10,974

-232

11,662

16,495

-32,048

10,336

13,184

36,836

7,967

-79,195

Gain on sales of real estate, net

9,016

2,732

Preferred share dividends

-4,655

-5,050

-6,271

-6,711

-4,332

-4,190

-20,631

-21,504

-16,762

Issuance costs associated with redeemed preferred shares

-2,904

-1,827

-2,904

-1,827

(Income) loss from continuing operations attributable to noncontrolling interests

-2,977

1,206

381

Income from continuing operations attributable to restricted shares

-414

-469

-1,037

Numerator for basic and diluted EPS on net income (loss)attributable to COPT common shareholders

18,926

-14,606

-93,881

Discontinued operations

71,907

-12,974

-4,502

1,261

2,515

11,283

1,504

-2,949

55,692

12,353

-51,107

Discontinued operations attributable to noncontrolling interests

-930

-699

-137

Numerator for basic and diluted EPS on net income (loss)attributable to COPT common shareholders

$73,688

($2,952)

($145,125)

Denominator (all weighted averages):

Denominator for basic EPS (common shares)

89,036

77,689

72,564

Dilutive effect of share-based compensation awards

Denominator for basic and diluted EPS (common shares)

89,093

77,689

72,564

Basic EPS:

Income (loss) from continuing operations (in dollars per share)

$0.21

[1]

($0.19)

[1]

($1.29)

[1]

Discontinued operations (in dollars per share)

$0.62

[1]

$0.15

[1]

($0.71)

[1]

Net income (loss) attributable to COPT common shareholders (in dollars per share)

$0.94

($0.09)

($0.16)

$0.11

$0.16

($0.39)

$0.10

$0.09

$0.83

[1]

($0.04)

[1]

($2)

[1]

Diluted EPS:

Income (loss) from continuing operations (in dollars per share)

$0.21

[1]

($0.19)

[1]

($1.29)

[1]

Discontinued operations (in dollars per share)

$0.62

[1]

$0.15

[1]

($0.71)

[1]

Net income (loss) attributable to COPT common shareholders (in dollars per share)

$0.94

($0.09)

($0.16)

$0.11

$0.16

($0.39)

$0.10

$0.09

$0.83

[1]

($0.04)

[1]

($2)

[1]

Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.

Earnings_Per_Share_EPS_and_Ear3

Earnings Per Share ("EPS") and Earnings Per Unit (â€œEPUâ€) (Details 2)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Conversion of common units	'	'	'
Antidilutive securities	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	3,869	4,235	4,355
Conversion of Series I preferred units	'	'	'
Antidilutive securities	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	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
Restricted Stock	'	'	'
Antidilutive securities	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	385	461	638
Stock Options	'	'	'
Antidilutive securities	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	636	772	712
Corporate Office Properties, L.P. \| Restricted Stock	'	'	'
Antidilutive securities	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	385	461	638
Corporate Office Properties, L.P. \| Stock Options	'	'	'
Antidilutive securities	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	636	772	712
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
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

Quarterly_Data_Unaudited_Detai

Quarterly Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Revenues	$128,802	$131,812	$136,527	$126,219	$132,635	$125,067	$123,074	$127,359	$523,360		$508,135		$492,956
Operating income (loss)	34,843	30,673	40,229	36,165	33,190	-10,844	32,069	34,651	141,910		89,066		30,298
Income (loss) from continuing operations	14,432	10,974	-232	11,662	16,495	-32,048	10,336	13,184	36,836		7,967		-79,201
Discontinued operations	71,907	-12,974	-4,502	1,261	2,515	11,283	1,504	-2,949	55,692		12,353		-51,107
Net income (loss)	92,672	-2,000	-4,405	15,277	19,010	-20,765	11,861	10,235	101,544		20,341		-127,576
Net (income) loss attributable to noncontrolling interests in consolidated entities	-5,656	-964	-960	-257	-471	1,603	-556	60	'		'		'
Net income (loss) attributable to COPT	87,016	-2,964	-5,365	15,020	18,539	-19,162	11,305	10,295	93,707		20,977		-119,428
Preferred share dividends	-4,490	-4,490	-4,885	-6,106	-6,106	-6,546	-4,167	-4,025	-19,971		-20,844		-16,102
Issuance costs associated with redeemed preferred shares	0	0	-2,904	0	0	-1,827	0	0	-2,904		-1,827		0
Net income (loss) attributable to COPT common shareholders	82,526	-7,454	-13,154	8,914	12,433	-27,535	7,138	6,270	70,832		-1,694		-135,530
Basic earnings per common share/unit (in dollars per share/unit)	$0.94	($0.09)	($0.16)	$0.11	$0.16	($0.39)	$0.10	$0.09	$0.83	[1]	($0.03)	[1]	($1.97)	[1]
Diluted earnings per common share/unit (in dollars per share/unit)	$0.94	($0.09)	($0.16)	$0.11	$0.16	($0.39)	$0.10	$0.09	$0.83	[1]	($0.03)	[1]	($1.97)	[1]
Corporate Office Properties, L.P.	'	'	'	'	'	'	'	'	'		'		'
Revenues	128,802	131,812	136,527	126,219	132,635	125,067	123,074	127,359	523,360		508,135		492,956
Operating income (loss)	34,843	30,673	40,229	36,165	33,190	-10,844	32,069	34,651	141,910		89,066		30,304
Income (loss) from continuing operations	14,432	10,974	-232	11,662	16,495	-32,048	10,336	13,184	36,836		7,967		-79,195
Discontinued operations	71,907	-12,974	-4,502	1,261	2,515	11,283	1,504	-2,949	55,692		12,353		-51,107
Net income (loss)	92,672	-2,000	-4,405	15,277	19,010	-20,765	11,861	10,235	101,544		20,341		-127,570
Net (income) loss attributable to noncontrolling interests in consolidated entities	-1,735	-1,035	-1,473	336	340	-404	1	570	-3,907		507		244
Net income (loss) attributable to COPT	90,937	-3,035	-5,878	15,613	19,350	-21,169	11,862	10,805	97,637		20,848		-127,326
Preferred share dividends	-4,655	-4,655	-5,050	-6,271	-6,271	-6,711	-4,332	-4,190	-20,631		-21,504		-16,762
Issuance costs associated with redeemed preferred shares	0	0	-2,904	0	0	-1,827	0	0	-2,904		-1,827		0
Net income (loss) attributable to COPT common shareholders	$86,282	($7,690)	($13,832)	$9,342	$13,079	($29,707)	$7,530	$6,615	$74,102		($2,483)		($144,088)
Basic earnings per common share/unit (in dollars per share/unit)	$0.94	($0.09)	($0.16)	$0.11	$0.16	($0.39)	$0.10	$0.09	$0.83	[1]	($0.04)	[1]	($2)	[1]
Diluted earnings per common share/unit (in dollars per share/unit)	$0.94	($0.09)	($0.16)	$0.11	$0.16	($0.39)	$0.10	$0.09	$0.83	[1]	($0.04)	[1]	($2)	[1]

[1]	Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	1 Months Ended
	Aug. 31, 2010	Dec. 31, 2013
	Aug. 31, 2010	Property
Tax incremental financing obligation	'	'
The amount of tax incremental financing bonds issued by Anne Arundel County, Maryland	$30,000,000	'
Liability recognized with regard to tax incremental financing obligation at end of current period	'	2,500,000
Future minimum rental payments due:	'	'
2014	'	675,000
2015	'	686,000
2016	'	686,000
2017	'	687,000
2018	'	689,000
Thereafter	'	75,501,000
Total	'	78,924,000
Environmental Indemnity Agreement	'	'
Number of lease properties which were provided environmental indemnifications	'	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

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Accounts Receivables-Allowance for doubtful accounts	'		'		'
Movement in Valuation Allowances and Reserves [Roll Forward]	'		'		'
Balance at Beginning of Year	$4,694		$3,546		$2,796
Charged to Costs and Expenses (1)	-65	[1]	1,532	[1]	1,021	[1]
Charged to Other Accounts	0	[2]	232	[2]	125	[2]
Deductions	-1,653	[3]	-616	[3]	-396	[3]
Balance at End of Year	2,976		4,694		3,546
Allowance for Deferred Rent Receivable	'		'		'
Movement in Valuation Allowances and Reserves [Roll Forward]	'		'		'
Balance at Beginning of Year	913		703		578
Charged to Costs and Expenses (1)	0	[1]	0	[1]	0	[1]
Charged to Other Accounts	1,213	[2]	416	[2]	162	[2]
Deductions	0	[3]	-206	[3]	-37	[3]
Balance at End of Year	2,126		913		703
Allowance for Deferred Tax Asset	'		'		'
Movement in Valuation Allowances and Reserves [Roll Forward]	'		'		'
Balance at Beginning of Year	207		207		207
Charged to Costs and Expenses (1)	1,855	[1]	0	[1]	0	[1]
Charged to Other Accounts	0	[2]	0	[2]	0	[2]
Deductions	0	[3]	0	[3]	0	[3]
Balance at End of Year	$2,062		$207		$207

[1]	Amounts charged to costs and expenses are net of recoveries.
[2]	Allowances for certain accounts receivables were charged to service company revenue. Deferred rent receivable allowances were charged to rental revenue.
[3]	Deductions reflect adjustments to reserves due to actual write-offs of accounts.

Schedule_III_Real_Estate_and_A1

Schedule III - Real Estate and Accumulated Depreciation (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	$697,902,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	676,148,000		'		'	'
Building and Land Improvements	2,843,246,000		'		'	'
Costs Capitalized Subsequent to Acquisition	292,556,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	676,148,000	[2],[3]	'		'	'
Building and Land Improvements	3,135,802,000	[2],[3]	'		'	'
Total	3,811,950,000	[2],[3]	3,859,960,000		4,038,932,000	3,948,487,000
Accumulated Depreciation	-597,649,000	[4]	-568,176,000		-577,601,000	-503,032,000
Additional information	'		'		'	'
Debt excluded from encumbrances	1,927,703,000		2,019,168,000		'	'
Aggregate cost of assets for federal income tax purposes	3,300,000,000		'		'	'
Impairment losses	5,857,000		43,678,000		83,213,000	'
Buildings improvements \| Minimum	'		'		'	'
Additional information	'		'		'	'
Estimated lives over which depreciation is recognized	'10 years		'		'	'
Buildings improvements \| Maximum	'		'		'	'
Additional information	'		'		'	'
Estimated lives over which depreciation is recognized	'40 years		'		'	'
Term Loan Facilities	'		'		'	'
Additional information	'		'		'	'
Debt excluded from encumbrances	620,000,000	[5],[6]	770,000,000	[5],[6]	'	'
Senior Unsecured Notes	'		'		'	'
Additional information	'		'		'	'
Debt excluded from encumbrances	592,700,000		'		'	'
4.25% Exchangeable Senior Notes	'		'		'	'
Additional information	'		'		'	'
Debt excluded from encumbrances	563,000	[5]	230,934,000	[5]	'	'
Unsecured notes payable	'		'		'	'
Additional information	'		'		'	'
Debt excluded from encumbrances	1,700,000		1,788,000		'	'
Letter of Credit	'		'		'	'
Additional information	'		'		'	'
Debt excluded from encumbrances	14,800,000		'		'	'
Fixed rate mortgage loans	'		'		'	'
Additional information	'		'		'	'
Debt excluded from encumbrances	675,060,000	[7],[8]	948,414,000	[7],[8]	'	'
Unamortized premium included in carrying value	69,000		1,300,000		'	'
1000 Redstone Gateway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	11,960,000	[1]	'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	20,435,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	20,435,000		'		'	'
Total	20,435,000	[2],[3]	'		'	'
Accumulated Depreciation	-412,000	[4]	'		'	'
1100 Redstone Gateway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	5,809,000	[1],[9]	'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	20,877,000	[9]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	20,877,000	[9]	'		'	'
Total	20,877,000	[2],[3],[9]	'		'	'
114 National Business Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	364,000		'		'	'
Building and Land Improvements	3,109,000		'		'	'
Costs Capitalized Subsequent to Acquisition	46,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	364,000		'		'	'
Building and Land Improvements	3,155,000		'		'	'
Total	3,519,000	[2],[3]	'		'	'
Accumulated Depreciation	-959,000	[4]	'		'	'
11751 Meadowville Lane	'		'		'	'
Initial Cost	'		'		'	'
Land	1,305,000		'		'	'
Building and Land Improvements	52,098,000		'		'	'
Costs Capitalized Subsequent to Acquisition	112,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,305,000		'		'	'
Building and Land Improvements	52,210,000		'		'	'
Total	53,515,000	[2],[3]	'		'	'
Accumulated Depreciation	-8,583,000	[4]	'		'	'
1200 Redstone Gateway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	8,080,000	[1]	'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	21,974,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	21,974,000		'		'	'
Total	21,974,000	[2],[3]	'		'	'
Accumulated Depreciation	-37,000	[4]	'		'	'
1201 M Street	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	49,785,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,508,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	52,293,000		'		'	'
Total	52,293,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,656,000	[4]	'		'	'
1201 Winterson Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,288,000		'		'	'
Building and Land Improvements	5,154,000		'		'	'
Costs Capitalized Subsequent to Acquisition	460,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,288,000		'		'	'
Building and Land Improvements	5,614,000		'		'	'
Total	6,902,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,228,000	[4]	'		'	'
1220 12th Street, SE	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	42,464,000		'		'	'
Costs Capitalized Subsequent to Acquisition	933,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	43,397,000		'		'	'
Total	43,397,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,724,000	[4]	'		'	'
1243 Winterson Road	'		'		'	'
Initial Cost	'		'		'	'
Land	630,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	630,000	[10]	'		'	'
Total	630,000	[10],[2],[3]	'		'	'
1302 Concourse Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,078,000		'		'	'
Building and Land Improvements	8,313,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,598,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,078,000		'		'	'
Building and Land Improvements	12,911,000		'		'	'
Total	14,989,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,078,000	[4]	'		'	'
1304 Concourse Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,999,000		'		'	'
Building and Land Improvements	12,934,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,616,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,999,000		'		'	'
Building and Land Improvements	14,550,000		'		'	'
Total	16,549,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,115,000	[4]	'		'	'
1306 Concourse Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,796,000		'		'	'
Building and Land Improvements	11,186,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,546,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,796,000		'		'	'
Building and Land Improvements	15,732,000		'		'	'
Total	18,528,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,513,000	[4]	'		'	'
131 National Business Parkway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	6,785,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,906,000		'		'	'
Building and Land Improvements	7,623,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,946,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,906,000		'		'	'
Building and Land Improvements	10,569,000		'		'	'
Total	12,475,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,284,000	[4]	'		'	'
132 National Business Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	2,917,000		'		'	'
Building and Land Improvements	12,259,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,977,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,917,000		'		'	'
Building and Land Improvements	15,236,000		'		'	'
Total	18,153,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,929,000	[4]	'		'	'
13200 Woodland Park Road	'		'		'	'
Initial Cost	'		'		'	'
Land	10,428,000		'		'	'
Building and Land Improvements	41,711,000		'		'	'
Costs Capitalized Subsequent to Acquisition	13,985,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	10,428,000		'		'	'
Building and Land Improvements	55,696,000		'		'	'
Total	66,124,000	[2],[3]	'		'	'
Accumulated Depreciation	-21,768,000	[4]	'		'	'
133 National Business Parkway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	9,079,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,517,000		'		'	'
Building and Land Improvements	10,068,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,950,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,517,000		'		'	'
Building and Land Improvements	15,018,000		'		'	'
Total	17,535,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,856,000	[4]	'		'	'
1331 Ashton Road	'		'		'	'
Initial Cost	'		'		'	'
Land	587,000		'		'	'
Building and Land Improvements	2,347,000		'		'	'
Costs Capitalized Subsequent to Acquisition	697,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	587,000		'		'	'
Building and Land Improvements	3,044,000		'		'	'
Total	3,631,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,047,000	[4]	'		'	'
1334 Ashton Road	'		'		'	'
Initial Cost	'		'		'	'
Land	736,000		'		'	'
Building and Land Improvements	1,488,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,459,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	736,000		'		'	'
Building and Land Improvements	3,947,000		'		'	'
Total	4,683,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,744,000	[4]	'		'	'
134 National Business Parkway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	19,200,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,684,000		'		'	'
Building and Land Improvements	7,517,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,314,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,684,000		'		'	'
Building and Land Improvements	9,831,000		'		'	'
Total	13,515,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,500,000	[4]	'		'	'
1340 Ashton Road	'		'		'	'
Initial Cost	'		'		'	'
Land	905,000		'		'	'
Building and Land Improvements	3,620,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,466,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	905,000		'		'	'
Building and Land Improvements	5,086,000		'		'	'
Total	5,991,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,131,000	[4]	'		'	'
1341 Ashton Road	'		'		'	'
Initial Cost	'		'		'	'
Land	306,000		'		'	'
Building and Land Improvements	1,223,000		'		'	'
Costs Capitalized Subsequent to Acquisition	601,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	306,000		'		'	'
Building and Land Improvements	1,824,000		'		'	'
Total	2,130,000	[2],[3]	'		'	'
Accumulated Depreciation	-794,000	[4]	'		'	'
1343 Ashton Road	'		'		'	'
Initial Cost	'		'		'	'
Land	193,000		'		'	'
Building and Land Improvements	774,000		'		'	'
Costs Capitalized Subsequent to Acquisition	405,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	193,000		'		'	'
Building and Land Improvements	1,179,000		'		'	'
Total	1,372,000	[2],[3]	'		'	'
Accumulated Depreciation	-516,000	[4]	'		'	'
13450 Sunrise Valley Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,386,000		'		'	'
Building and Land Improvements	5,576,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,345,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,386,000		'		'	'
Building and Land Improvements	8,921,000		'		'	'
Total	10,307,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,160,000	[4]	'		'	'
13454 Sunrise Valley Road	'		'		'	'
Initial Cost	'		'		'	'
Land	2,899,000		'		'	'
Building and Land Improvements	11,986,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,059,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,899,000		'		'	'
Building and Land Improvements	16,045,000		'		'	'
Total	18,944,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,332,000	[4]	'		'	'
135 National Business Parkway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	11,692,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,484,000		'		'	'
Building and Land Improvements	9,750,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,472,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,484,000		'		'	'
Building and Land Improvements	14,222,000		'		'	'
Total	16,706,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,299,000	[4]	'		'	'
1362 Mellon Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,706,000		'		'	'
Building and Land Improvements	8,670,000		'		'	'
Costs Capitalized Subsequent to Acquisition	32,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,706,000		'		'	'
Building and Land Improvements	8,702,000		'		'	'
Total	10,408,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,055,000	[4]	'		'	'
13857 McLearen Road	'		'		'	'
Initial Cost	'		'		'	'
Land	3,507,000		'		'	'
Building and Land Improvements	30,177,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,906,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,507,000		'		'	'
Building and Land Improvements	32,083,000		'		'	'
Total	35,590,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,071,000	[4]	'		'	'
140 National Business Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	3,407,000		'		'	'
Building and Land Improvements	24,167,000		'		'	'
Costs Capitalized Subsequent to Acquisition	643,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,407,000		'		'	'
Building and Land Improvements	24,810,000		'		'	'
Total	28,217,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,432,000	[4]	'		'	'
141 National Business Parkway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	12,155,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,398,000		'		'	'
Building and Land Improvements	9,590,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,995,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,398,000		'		'	'
Building and Land Improvements	12,585,000		'		'	'
Total	14,983,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,970,000	[4]	'		'	'
14280 Park Meadow Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	3,731,000		'		'	'
Building and Land Improvements	15,953,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,525,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,731,000		'		'	'
Building and Land Improvements	17,478,000		'		'	'
Total	21,209,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,080,000	[4]	'		'	'
1460 Dorsey Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,800,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,800,000	[10]	'		'	'
Total	1,800,000	[10],[2],[3]	'		'	'
14840 Conference Center Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,572,000		'		'	'
Building and Land Improvements	8,175,000		'		'	'
Costs Capitalized Subsequent to Acquisition	266,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,572,000		'		'	'
Building and Land Improvements	8,441,000		'		'	'
Total	10,013,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,579,000	[4]	'		'	'
14850 Conference Center Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,615,000		'		'	'
Building and Land Improvements	8,358,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,224,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,615,000		'		'	'
Building and Land Improvements	9,582,000		'		'	'
Total	11,197,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,702,000	[4]	'		'	'
14900 Conference Center Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	3,436,000		'		'	'
Building and Land Improvements	14,402,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,104,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,436,000		'		'	'
Building and Land Improvements	18,506,000		'		'	'
Total	21,942,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,558,000	[4]	'		'	'
15000 Conference Center Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	54,000,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	5,193,000		'		'	'
Building and Land Improvements	47,045,000		'		'	'
Costs Capitalized Subsequent to Acquisition	19,251,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	5,193,000		'		'	'
Building and Land Improvements	66,296,000		'		'	'
Total	71,489,000	[2],[3]	'		'	'
Accumulated Depreciation	-22,908,000	[4]	'		'	'
1501 South Clinton Street	'		'		'	'
Initial Cost	'		'		'	'
Land	27,964,000		'		'	'
Building and Land Improvements	52,145,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,473,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	27,964,000		'		'	'
Building and Land Improvements	56,618,000		'		'	'
Total	84,582,000	[2],[3]	'		'	'
Accumulated Depreciation	-8,191,000	[4]	'		'	'
15010 Conference Center Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	96,000,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,500,000		'		'	'
Building and Land Improvements	41,921,000		'		'	'
Costs Capitalized Subsequent to Acquisition	498,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,500,000		'		'	'
Building and Land Improvements	42,419,000		'		'	'
Total	45,919,000	[2],[3]	'		'	'
Accumulated Depreciation	-7,571,000	[4]	'		'	'
15049 Conference Center Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	4,415,000		'		'	'
Building and Land Improvements	20,365,000		'		'	'
Costs Capitalized Subsequent to Acquisition	726,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	4,415,000		'		'	'
Building and Land Improvements	21,091,000		'		'	'
Total	25,506,000	[2],[3]	'		'	'
Accumulated Depreciation	-8,041,000	[4]	'		'	'
15059 Conference Center Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	5,753,000		'		'	'
Building and Land Improvements	13,615,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,715,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	5,753,000		'		'	'
Building and Land Improvements	15,330,000		'		'	'
Total	21,083,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,418,000	[4]	'		'	'
15395 John Marshall Highway	'		'		'	'
Initial Cost	'		'		'	'
Land	2,479,000	[9]	'		'	'
Building and Land Improvements	20,939,000	[9]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,479,000	[9]	'		'	'
Building and Land Improvements	20,939,000	[9]	'		'	'
Total	23,418,000	[2],[3],[9]	'		'	'
1550 West Nursery Road	'		'		'	'
Initial Cost	'		'		'	'
Land	14,071,000		'		'	'
Building and Land Improvements	16,930,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	14,071,000		'		'	'
Building and Land Improvements	16,930,000		'		'	'
Total	31,001,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,450,000	[4]	'		'	'
1550 Westbranch Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	5,595,000		'		'	'
Building and Land Improvements	26,212,000		'		'	'
Costs Capitalized Subsequent to Acquisition	116,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	5,595,000		'		'	'
Building and Land Improvements	26,328,000		'		'	'
Total	31,923,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,000,000	[4]	'		'	'
1560A Cable Ranch Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,097,000		'		'	'
Building and Land Improvements	3,770,000		'		'	'
Costs Capitalized Subsequent to Acquisition	357,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,097,000		'		'	'
Building and Land Improvements	4,127,000		'		'	'
Total	5,224,000	[2],[3]	'		'	'
Accumulated Depreciation	-784,000	[4]	'		'	'
1560B Cable Ranch Road	'		'		'	'
Initial Cost	'		'		'	'
Land	2,299,000		'		'	'
Building and Land Improvements	6,545,000		'		'	'
Costs Capitalized Subsequent to Acquisition	11,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,299,000		'		'	'
Building and Land Improvements	6,556,000		'		'	'
Total	8,855,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,326,000	[4]	'		'	'
16442 Commerce Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	613,000		'		'	'
Building and Land Improvements	2,582,000		'		'	'
Costs Capitalized Subsequent to Acquisition	578,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	613,000		'		'	'
Building and Land Improvements	3,160,000		'		'	'
Total	3,773,000	[2],[3]	'		'	'
Accumulated Depreciation	-956,000	[4]	'		'	'
16480 Commerce Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,856,000		'		'	'
Building and Land Improvements	7,425,000		'		'	'
Costs Capitalized Subsequent to Acquisition	164,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,856,000		'		'	'
Building and Land Improvements	7,589,000		'		'	'
Total	9,445,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,835,000	[4]	'		'	'
16501 Commerce Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	522,000		'		'	'
Building and Land Improvements	2,090,000		'		'	'
Costs Capitalized Subsequent to Acquisition	201,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	522,000		'		'	'
Building and Land Improvements	2,291,000		'		'	'
Total	2,813,000	[2],[3]	'		'	'
Accumulated Depreciation	-647,000	[4]	'		'	'
16539 Commerce Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	688,000		'		'	'
Building and Land Improvements	2,860,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,469,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	688,000		'		'	'
Building and Land Improvements	4,329,000		'		'	'
Total	5,017,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,460,000	[4]	'		'	'
16541 Commerce Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	773,000		'		'	'
Building and Land Improvements	3,094,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,367,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	773,000		'		'	'
Building and Land Improvements	4,461,000		'		'	'
Total	5,234,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,332,000	[4]	'		'	'
16543 Commerce Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	436,000		'		'	'
Building and Land Improvements	1,742,000		'		'	'
Costs Capitalized Subsequent to Acquisition	156,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	436,000		'		'	'
Building and Land Improvements	1,898,000		'		'	'
Total	2,334,000	[2],[3]	'		'	'
Accumulated Depreciation	-414,000	[4]	'		'	'
1751 Pinnacle Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	10,486,000		'		'	'
Building and Land Improvements	42,339,000		'		'	'
Costs Capitalized Subsequent to Acquisition	16,116,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	10,486,000		'		'	'
Building and Land Improvements	58,455,000		'		'	'
Total	68,941,000	[2],[3]	'		'	'
Accumulated Depreciation	-18,299,000	[4]	'		'	'
1753 Pinnacle Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	8,275,000		'		'	'
Building and Land Improvements	34,353,000		'		'	'
Costs Capitalized Subsequent to Acquisition	9,554,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	8,275,000		'		'	'
Building and Land Improvements	43,907,000		'		'	'
Total	52,182,000	[2],[3]	'		'	'
Accumulated Depreciation	-12,131,000	[4]	'		'	'
201 Technology Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	726,000		'		'	'
Building and Land Improvements	31,091,000		'		'	'
Costs Capitalized Subsequent to Acquisition	60,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	726,000		'		'	'
Building and Land Improvements	31,151,000		'		'	'
Total	31,877,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,800,000	[4]	'		'	'
206 Research Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	1,813,000		'		'	'
Building and Land Improvements	17,484,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,813,000		'		'	'
Building and Land Improvements	17,484,000		'		'	'
Total	19,297,000	[2],[3]	'		'	'
Accumulated Depreciation	-542,000	[4]	'		'	'
209 Research Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	1,045,000		'		'	'
Building and Land Improvements	16,087,000		'		'	'
Costs Capitalized Subsequent to Acquisition	32,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,045,000		'		'	'
Building and Land Improvements	16,119,000		'		'	'
Total	17,164,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,261,000	[4]	'		'	'
210 Research Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	1,065,000		'		'	'
Building and Land Improvements	13,161,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,065,000		'		'	'
Building and Land Improvements	13,161,000		'		'	'
Total	14,226,000	[2],[3]	'		'	'
Accumulated Depreciation	-848,000	[4]	'		'	'
21267 Smith Switch Road	'		'		'	'
Initial Cost	'		'		'	'
Land	4,192,000	[9]	'		'	'
Building and Land Improvements	2,849,000	[9]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	4,192,000	[9]	'		'	'
Building and Land Improvements	2,849,000	[9]	'		'	'
Total	7,041,000	[2],[3],[9]	'		'	'
21271 Smith Switch Road	'		'		'	'
Initial Cost	'		'		'	'
Land	7,291,000		'		'	'
Building and Land Improvements	15,909,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	7,291,000		'		'	'
Building and Land Improvements	15,909,000		'		'	'
Total	23,200,000	[2],[3]	'		'	'
Accumulated Depreciation	-43,000	[4]	'		'	'
22289 Exploration Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,422,000		'		'	'
Building and Land Improvements	5,719,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,371,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,422,000		'		'	'
Building and Land Improvements	7,090,000		'		'	'
Total	8,512,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,206,000	[4]	'		'	'
22299 Exploration Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,362,000		'		'	'
Building and Land Improvements	5,791,000		'		'	'
Costs Capitalized Subsequent to Acquisition	853,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,362,000		'		'	'
Building and Land Improvements	6,644,000		'		'	'
Total	8,006,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,221,000	[4]	'		'	'
22300 Exploration Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,094,000		'		'	'
Building and Land Improvements	5,038,000		'		'	'
Costs Capitalized Subsequent to Acquisition	300,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,094,000		'		'	'
Building and Land Improvements	5,338,000		'		'	'
Total	6,432,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,748,000	[4]	'		'	'
22309 Exploration Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,243,000		'		'	'
Building and Land Improvements	10,419,000		'		'	'
Costs Capitalized Subsequent to Acquisition	782,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,243,000		'		'	'
Building and Land Improvements	11,201,000		'		'	'
Total	13,444,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,695,000	[4]	'		'	'
23535 Cottonwood Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	692,000		'		'	'
Building and Land Improvements	3,051,000		'		'	'
Costs Capitalized Subsequent to Acquisition	223,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	692,000		'		'	'
Building and Land Improvements	3,274,000		'		'	'
Total	3,966,000	[2],[3]	'		'	'
Accumulated Depreciation	-928,000	[4]	'		'	'
2500 Riva Road	'		'		'	'
Initial Cost	'		'		'	'
Land	2,791,000		'		'	'
Building and Land Improvements	12,145,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,791,000		'		'	'
Building and Land Improvements	12,146,000		'		'	'
Total	14,937,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,729,000	[4]	'		'	'
2691 Technology Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	24,000,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,098,000		'		'	'
Building and Land Improvements	17,334,000		'		'	'
Costs Capitalized Subsequent to Acquisition	5,107,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,098,000		'		'	'
Building and Land Improvements	22,441,000		'		'	'
Total	24,539,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,052,000	[4]	'		'	'
2701 Technology Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	23,177,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,737,000		'		'	'
Building and Land Improvements	15,266,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,389,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,737,000		'		'	'
Building and Land Improvements	17,655,000		'		'	'
Total	19,392,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,814,000	[4]	'		'	'
2711 Technology Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	18,027,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,251,000		'		'	'
Building and Land Improvements	21,611,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,443,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,251,000		'		'	'
Building and Land Improvements	23,054,000		'		'	'
Total	25,305,000	[2],[3]	'		'	'
Accumulated Depreciation	-8,732,000	[4]	'		'	'
2720 Technology Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	23,592,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,863,000		'		'	'
Building and Land Improvements	29,272,000		'		'	'
Costs Capitalized Subsequent to Acquisition	105,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,863,000		'		'	'
Building and Land Improvements	29,377,000		'		'	'
Total	33,240,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,839,000	[4]	'		'	'
2721 Technology Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	4,611,000		'		'	'
Building and Land Improvements	14,597,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,091,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	4,611,000		'		'	'
Building and Land Improvements	15,688,000		'		'	'
Total	20,299,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,316,000	[4]	'		'	'
2730 Hercules Road	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	36,002,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	8,737,000		'		'	'
Building and Land Improvements	31,612,000		'		'	'
Costs Capitalized Subsequent to Acquisition	6,498,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	8,737,000		'		'	'
Building and Land Improvements	38,110,000		'		'	'
Total	46,847,000	[2],[3]	'		'	'
Accumulated Depreciation	-12,973,000	[4]	'		'	'
2900 Towerview Road	'		'		'	'
Initial Cost	'		'		'	'
Land	3,207,000		'		'	'
Building and Land Improvements	16,379,000		'		'	'
Costs Capitalized Subsequent to Acquisition	5,967,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,207,000		'		'	'
Building and Land Improvements	22,346,000		'		'	'
Total	25,553,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,830,000	[4]	'		'	'
300 Sentinel Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,517,000		'		'	'
Building and Land Improvements	44,524,000		'		'	'
Costs Capitalized Subsequent to Acquisition	114,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,517,000		'		'	'
Building and Land Improvements	44,638,000		'		'	'
Total	46,155,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,785,000	[4]	'		'	'
300 Sentinel Drive Garage	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	12,424,000	[1]	'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	14,125,000		'		'	'
Costs Capitalized Subsequent to Acquisition	52,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	14,177,000		'		'	'
Total	14,177,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,714,000	[4]	'		'	'
302 Sentinel Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	22,244,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,648,000		'		'	'
Building and Land Improvements	29,687,000		'		'	'
Costs Capitalized Subsequent to Acquisition	409,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,648,000		'		'	'
Building and Land Improvements	30,096,000		'		'	'
Total	32,744,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,421,000	[4]	'		'	'
304 Sentinel Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	24,856,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,411,000		'		'	'
Building and Land Improvements	24,917,000		'		'	'
Costs Capitalized Subsequent to Acquisition	138,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,411,000		'		'	'
Building and Land Improvements	25,055,000		'		'	'
Total	28,466,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,007,000	[4]	'		'	'
306 Sentinel Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	16,688,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,260,000		'		'	'
Building and Land Improvements	22,592,000		'		'	'
Costs Capitalized Subsequent to Acquisition	150,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,260,000		'		'	'
Building and Land Improvements	22,742,000		'		'	'
Total	26,002,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,112,000	[4]	'		'	'
308 Sentinel Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,422,000		'		'	'
Building and Land Improvements	26,197,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,422,000		'		'	'
Building and Land Improvements	26,197,000		'		'	'
Total	27,619,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,740,000	[4]	'		'	'
310 The Bridge Street	'		'		'	'
Initial Cost	'		'		'	'
Land	261,000		'		'	'
Building and Land Improvements	26,531,000		'		'	'
Costs Capitalized Subsequent to Acquisition	110,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	261,000		'		'	'
Building and Land Improvements	26,641,000		'		'	'
Total	26,902,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,202,000	[4]	'		'	'
312 Sentinel Way	'		'		'	'
Initial Cost	'		'		'	'
Land	3,138,000	[9]	'		'	'
Building and Land Improvements	18,133,000	[9]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,138,000	[9]	'		'	'
Building and Land Improvements	18,133,000	[9]	'		'	'
Total	21,271,000	[2],[3],[9]	'		'	'
3120 Fairview Park Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	6,863,000		'		'	'
Building and Land Improvements	35,606,000		'		'	'
Costs Capitalized Subsequent to Acquisition	5,863,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	6,863,000		'		'	'
Building and Land Improvements	41,469,000		'		'	'
Total	48,332,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,813,000	[4]	'		'	'
314 Sentinel Way	'		'		'	'
Initial Cost	'		'		'	'
Land	1,254,000		'		'	'
Building and Land Improvements	1,325,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,254,000		'		'	'
Building and Land Improvements	1,325,000		'		'	'
Total	2,579,000	[2],[3]	'		'	'
Accumulated Depreciation	-182,000	[4]	'		'	'
316 Sentinel Way	'		'		'	'
Initial Cost	'		'		'	'
Land	2,748,000		'		'	'
Building and Land Improvements	38,228,000		'		'	'
Costs Capitalized Subsequent to Acquisition	139,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,748,000		'		'	'
Building and Land Improvements	38,367,000		'		'	'
Total	41,115,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,634,000	[4]	'		'	'
318 Sentinel Way	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	21,800,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,185,000		'		'	'
Building and Land Improvements	28,426,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,185,000		'		'	'
Building and Land Improvements	28,426,000		'		'	'
Total	30,611,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,559,000	[4]	'		'	'
320 Sentinel Way	'		'		'	'
Initial Cost	'		'		'	'
Land	2,067,000		'		'	'
Building and Land Improvements	21,623,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,067,000		'		'	'
Building and Land Improvements	21,623,000		'		'	'
Total	23,690,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,229,000	[4]	'		'	'
322 Sentinel Way	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	22,199,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,605,000		'		'	'
Building and Land Improvements	22,827,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,605,000		'		'	'
Building and Land Improvements	22,827,000		'		'	'
Total	25,432,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,001,000	[4]	'		'	'
324 Sentinel Way	'		'		'	'
Initial Cost	'		'		'	'
Land	1,656,000		'		'	'
Building and Land Improvements	23,018,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,656,000		'		'	'
Building and Land Improvements	23,018,000		'		'	'
Total	24,674,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,927,000	[4]	'		'	'
375 West Padonia Road	'		'		'	'
Initial Cost	'		'		'	'
Land	2,483,000		'		'	'
Building and Land Improvements	10,415,000		'		'	'
Costs Capitalized Subsequent to Acquisition	4,852,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,483,000		'		'	'
Building and Land Improvements	15,267,000		'		'	'
Total	17,750,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,086,000	[4]	'		'	'
410 National Business Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	1,831,000		'		'	'
Building and Land Improvements	23,552,000		'		'	'
Costs Capitalized Subsequent to Acquisition	11,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,831,000		'		'	'
Building and Land Improvements	23,563,000		'		'	'
Total	25,394,000	[2],[3]	'		'	'
Accumulated Depreciation	-539,000	[4]	'		'	'
420 National Business Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	2,370,000		'		'	'
Building and Land Improvements	23,412,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,370,000		'		'	'
Building and Land Improvements	23,412,000		'		'	'
Total	25,782,000	[2],[3]	'		'	'
Accumulated Depreciation	-24,000	[4]	'		'	'
430 National Business Parkway	'		'		'	'
Initial Cost	'		'		'	'
Land	1,852,000		'		'	'
Building and Land Improvements	20,758,000		'		'	'
Costs Capitalized Subsequent to Acquisition	10,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,852,000		'		'	'
Building and Land Improvements	20,768,000		'		'	'
Total	22,620,000	[2],[3]	'		'	'
Accumulated Depreciation	-966,000	[4]	'		'	'
44408 Pecan Court	'		'		'	'
Initial Cost	'		'		'	'
Land	817,000		'		'	'
Building and Land Improvements	1,583,000		'		'	'
Costs Capitalized Subsequent to Acquisition	460,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	817,000		'		'	'
Building and Land Improvements	2,043,000		'		'	'
Total	2,860,000	[2],[3]	'		'	'
Accumulated Depreciation	-258,000	[4]	'		'	'
44414 Pecan Court	'		'		'	'
Initial Cost	'		'		'	'
Land	405,000		'		'	'
Building and Land Improvements	1,619,000		'		'	'
Costs Capitalized Subsequent to Acquisition	336,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	405,000		'		'	'
Building and Land Improvements	1,955,000		'		'	'
Total	2,360,000	[2],[3]	'		'	'
Accumulated Depreciation	-558,000	[4]	'		'	'
44417 Pecan Court	'		'		'	'
Initial Cost	'		'		'	'
Land	434,000		'		'	'
Building and Land Improvements	1,939,000		'		'	'
Costs Capitalized Subsequent to Acquisition	88,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	434,000		'		'	'
Building and Land Improvements	2,027,000		'		'	'
Total	2,461,000	[2],[3]	'		'	'
Accumulated Depreciation	-712,000	[4]	'		'	'
44420 Pecan Court	'		'		'	'
Initial Cost	'		'		'	'
Land	344,000		'		'	'
Building and Land Improvements	890,000		'		'	'
Costs Capitalized Subsequent to Acquisition	126,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	344,000		'		'	'
Building and Land Improvements	1,016,000		'		'	'
Total	1,360,000	[2],[3]	'		'	'
Accumulated Depreciation	-145,000	[4]	'		'	'
44425 Pecan Court	'		'		'	'
Initial Cost	'		'		'	'
Land	1,309,000		'		'	'
Building and Land Improvements	3,506,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,299,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,309,000		'		'	'
Building and Land Improvements	4,805,000		'		'	'
Total	6,114,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,202,000	[4]	'		'	'
45310 Abell House Lane	'		'		'	'
Initial Cost	'		'		'	'
Land	2,272,000		'		'	'
Building and Land Improvements	13,808,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,272,000		'		'	'
Building and Land Improvements	13,808,000		'		'	'
Total	16,080,000	[2],[3]	'		'	'
Accumulated Depreciation	-712,000	[4]	'		'	'
46579 Expedition Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,406,000		'		'	'
Building and Land Improvements	5,796,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,250,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,406,000		'		'	'
Building and Land Improvements	7,046,000		'		'	'
Total	8,452,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,409,000	[4]	'		'	'
46591 Expedition Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,200,000		'		'	'
Building and Land Improvements	7,199,000		'		'	'
Costs Capitalized Subsequent to Acquisition	664,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,200,000		'		'	'
Building and Land Improvements	7,863,000		'		'	'
Total	9,063,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,325,000	[4]	'		'	'
4851 Stonecroft Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	1,878,000		'		'	'
Building and Land Improvements	11,558,000		'		'	'
Costs Capitalized Subsequent to Acquisition	21,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,878,000		'		'	'
Building and Land Improvements	11,579,000		'		'	'
Total	13,457,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,669,000	[4]	'		'	'
4940 Campbell Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,379,000		'		'	'
Building and Land Improvements	3,858,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,079,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,379,000		'		'	'
Building and Land Improvements	4,937,000		'		'	'
Total	6,316,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,094,000	[4]	'		'	'
4969 Mercantile Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,308,000		'		'	'
Building and Land Improvements	771,000		'		'	'
Costs Capitalized Subsequent to Acquisition	62,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,308,000		'		'	'
Building and Land Improvements	833,000		'		'	'
Total	2,141,000	[2],[3]	'		'	'
Accumulated Depreciation	-7,000	[4]	'		'	'
4979 Mercantile Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,299,000		'		'	'
Building and Land Improvements	945,000		'		'	'
Costs Capitalized Subsequent to Acquisition	111,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,299,000		'		'	'
Building and Land Improvements	1,056,000		'		'	'
Total	2,355,000	[2],[3]	'		'	'
Accumulated Depreciation	-25,000	[4]	'		'	'
5020 Campbell Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	1,014,000		'		'	'
Building and Land Improvements	3,136,000		'		'	'
Costs Capitalized Subsequent to Acquisition	784,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,014,000		'		'	'
Building and Land Improvements	3,920,000		'		'	'
Total	4,934,000	[2],[3]	'		'	'
Accumulated Depreciation	-840,000	[4]	'		'	'
5022 Campbell Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	624,000		'		'	'
Building and Land Improvements	1,924,000		'		'	'
Costs Capitalized Subsequent to Acquisition	417,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	624,000		'		'	'
Building and Land Improvements	2,341,000		'		'	'
Total	2,965,000	[2],[3]	'		'	'
Accumulated Depreciation	-595,000	[4]	'		'	'
5024 Campbell Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	767,000		'		'	'
Building and Land Improvements	2,420,000		'		'	'
Costs Capitalized Subsequent to Acquisition	643,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	767,000		'		'	'
Building and Land Improvements	3,063,000		'		'	'
Total	3,830,000	[2],[3]	'		'	'
Accumulated Depreciation	-790,000	[4]	'		'	'
5026 Campbell Boulevard	'		'		'	'
Initial Cost	'		'		'	'
Land	700,000		'		'	'
Building and Land Improvements	2,138,000		'		'	'
Costs Capitalized Subsequent to Acquisition	44,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	700,000		'		'	'
Building and Land Improvements	2,182,000		'		'	'
Total	2,882,000	[2],[3]	'		'	'
Accumulated Depreciation	-448,000	[4]	'		'	'
525 Babcock Road	'		'		'	'
Initial Cost	'		'		'	'
Land	355,000		'		'	'
Building and Land Improvements	397,000		'		'	'
Costs Capitalized Subsequent to Acquisition	79,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	355,000		'		'	'
Building and Land Improvements	476,000		'		'	'
Total	831,000	[2],[3]	'		'	'
Accumulated Depreciation	-124,000	[4]	'		'	'
5325 Nottingham Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	816,000		'		'	'
Building and Land Improvements	3,976,000		'		'	'
Costs Capitalized Subsequent to Acquisition	485,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	816,000		'		'	'
Building and Land Improvements	4,461,000		'		'	'
Total	5,277,000	[2],[3]	'		'	'
Accumulated Depreciation	-919,000	[4]	'		'	'
5355 Nottingham Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	761,000		'		'	'
Building and Land Improvements	3,562,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,758,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	761,000		'		'	'
Building and Land Improvements	5,320,000		'		'	'
Total	6,081,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,614,000	[4]	'		'	'
5520 Research Park Drive	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	20,072,000		'		'	'
Costs Capitalized Subsequent to Acquisition	38,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	20,110,000		'		'	'
Total	20,110,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,182,000	[4]	'		'	'
5522 Research Park Drive	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	4,550,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	4,550,000		'		'	'
Total	4,550,000	[2],[3]	'		'	'
Accumulated Depreciation	-728,000	[4]	'		'	'
5825 University Research Court	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	15,960,000	[1]	'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	22,522,000		'		'	'
Costs Capitalized Subsequent to Acquisition	11,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	22,533,000		'		'	'
Total	22,533,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,681,000	[4]	'		'	'
5850 University Research Court	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	21,731,000	[1]	'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	30,273,000		'		'	'
Costs Capitalized Subsequent to Acquisition	57,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	30,330,000		'		'	'
Total	30,330,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,995,000	[4]	'		'	'
6700 Alexander Bell Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	4,000,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,755,000		'		'	'
Building and Land Improvements	7,019,000		'		'	'
Costs Capitalized Subsequent to Acquisition	5,385,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,755,000		'		'	'
Building and Land Improvements	12,404,000		'		'	'
Total	14,159,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,972,000	[4]	'		'	'
6708 Alexander Bell Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	6,320,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	897,000		'		'	'
Building and Land Improvements	3,907,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,591,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	897,000		'		'	'
Building and Land Improvements	5,498,000		'		'	'
Total	6,395,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,596,000	[4]	'		'	'
6711 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,683,000		'		'	'
Building and Land Improvements	23,239,000		'		'	'
Costs Capitalized Subsequent to Acquisition	312,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,683,000		'		'	'
Building and Land Improvements	23,551,000		'		'	'
Total	26,234,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,135,000	[4]	'		'	'
6716 Alexander Bell Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,242,000		'		'	'
Building and Land Improvements	4,969,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,244,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,242,000		'		'	'
Building and Land Improvements	8,213,000		'		'	'
Total	9,455,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,661,000	[4]	'		'	'
6721 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	17,512,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,753,000		'		'	'
Building and Land Improvements	34,090,000		'		'	'
Costs Capitalized Subsequent to Acquisition	13,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,753,000		'		'	'
Building and Land Improvements	34,103,000		'		'	'
Total	35,856,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,085,000	[4]	'		'	'
6724 Alexander Bell Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	10,939,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	449,000		'		'	'
Building and Land Improvements	5,039,000		'		'	'
Costs Capitalized Subsequent to Acquisition	368,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	449,000		'		'	'
Building and Land Improvements	5,407,000		'		'	'
Total	5,856,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,946,000	[4]	'		'	'
6731 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,807,000		'		'	'
Building and Land Improvements	19,098,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,946,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,807,000		'		'	'
Building and Land Improvements	21,044,000		'		'	'
Total	23,851,000	[2],[3]	'		'	'
Accumulated Depreciation	-7,214,000	[4]	'		'	'
6740 Alexander Bell Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,424,000		'		'	'
Building and Land Improvements	5,696,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,147,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,424,000		'		'	'
Building and Land Improvements	8,843,000		'		'	'
Total	10,267,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,275,000	[4]	'		'	'
6741 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	675,000		'		'	'
Building and Land Improvements	1,711,000		'		'	'
Costs Capitalized Subsequent to Acquisition	114,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	675,000		'		'	'
Building and Land Improvements	1,825,000		'		'	'
Total	2,500,000	[2],[3]	'		'	'
Accumulated Depreciation	-249,000	[4]	'		'	'
6750 Alexander Bell Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,263,000		'		'	'
Building and Land Improvements	12,461,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,222,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,263,000		'		'	'
Building and Land Improvements	15,683,000		'		'	'
Total	16,946,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,406,000	[4]	'		'	'
6760 Alexander Bell Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	890,000		'		'	'
Building and Land Improvements	3,561,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,564,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	890,000		'		'	'
Building and Land Improvements	6,125,000		'		'	'
Total	7,015,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,756,000	[4]	'		'	'
6940 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	17,300,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,545,000		'		'	'
Building and Land Improvements	9,916,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,894,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,545,000		'		'	'
Building and Land Improvements	13,810,000		'		'	'
Total	17,355,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,809,000	[4]	'		'	'
6950 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	3,596,000		'		'	'
Building and Land Improvements	14,269,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,694,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,596,000		'		'	'
Building and Land Improvements	16,963,000		'		'	'
Total	20,559,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,425,000	[4]	'		'	'
7000 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	15,800,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,131,000		'		'	'
Building and Land Improvements	12,103,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,137,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,131,000		'		'	'
Building and Land Improvements	13,240,000		'		'	'
Total	16,371,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,646,000	[4]	'		'	'
7015 Albert Einstein Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	2,204,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,058,000		'		'	'
Building and Land Improvements	6,093,000		'		'	'
Costs Capitalized Subsequent to Acquisition	826,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,058,000		'		'	'
Building and Land Improvements	6,919,000		'		'	'
Total	8,977,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,424,000	[4]	'		'	'
7061 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	729,000		'		'	'
Building and Land Improvements	3,094,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,137,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	729,000		'		'	'
Building and Land Improvements	4,231,000		'		'	'
Total	4,960,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,539,000	[4]	'		'	'
7063 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	902,000		'		'	'
Building and Land Improvements	3,684,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,074,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	902,000		'		'	'
Building and Land Improvements	4,758,000		'		'	'
Total	5,660,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,173,000	[4]	'		'	'
7065 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	919,000		'		'	'
Building and Land Improvements	3,763,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,245,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	919,000		'		'	'
Building and Land Improvements	5,008,000		'		'	'
Total	5,927,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,137,000	[4]	'		'	'
7067 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,829,000		'		'	'
Building and Land Improvements	11,823,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,468,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,829,000		'		'	'
Building and Land Improvements	14,291,000		'		'	'
Total	16,120,000	[2],[3]	'		'	'
Accumulated Depreciation	-4,893,000	[4]	'		'	'
7125 Columbia Gateway Drive Land	'		'		'	'
Initial Cost	'		'		'	'
Land	3,361,000	[10]	'		'	'
Building and Land Improvements	128,000	[10]	'		'	'
Costs Capitalized Subsequent to Acquisition	279,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,361,000	[10]	'		'	'
Building and Land Improvements	407,000	[10]	'		'	'
Total	3,768,000	[10],[2],[3]	'		'	'
7125 Columbia Gateway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	17,126,000		'		'	'
Building and Land Improvements	46,994,000		'		'	'
Costs Capitalized Subsequent to Acquisition	8,586,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	17,126,000		'		'	'
Building and Land Improvements	55,580,000		'		'	'
Total	72,706,000	[2],[3]	'		'	'
Accumulated Depreciation	-12,358,000	[4]	'		'	'
7130 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	6,519,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,350,000		'		'	'
Building and Land Improvements	4,359,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,784,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,350,000		'		'	'
Building and Land Improvements	6,143,000		'		'	'
Total	7,493,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,949,000	[4]	'		'	'
7134 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	2,949,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	704,000		'		'	'
Building and Land Improvements	1,971,000		'		'	'
Costs Capitalized Subsequent to Acquisition	299,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	704,000		'		'	'
Building and Land Improvements	2,270,000		'		'	'
Total	2,974,000	[2],[3]	'		'	'
Accumulated Depreciation	-569,000	[4]	'		'	'
7138 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	5,406,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,104,000		'		'	'
Building and Land Improvements	3,518,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,961,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,104,000		'		'	'
Building and Land Improvements	5,479,000		'		'	'
Total	6,583,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,495,000	[4]	'		'	'
7142 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	6,280,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,342,000		'		'	'
Building and Land Improvements	3,978,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,721,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,342,000		'		'	'
Building and Land Improvements	6,699,000		'		'	'
Total	8,041,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,867,000	[4]	'		'	'
7150 Columbia Gateway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	4,850,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,032,000		'		'	'
Building and Land Improvements	3,429,000		'		'	'
Costs Capitalized Subsequent to Acquisition	333,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,032,000		'		'	'
Building and Land Improvements	3,762,000		'		'	'
Total	4,794,000	[2],[3]	'		'	'
Accumulated Depreciation	-959,000	[4]	'		'	'
7150 Riverwood Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,821,000		'		'	'
Building and Land Improvements	4,388,000		'		'	'
Costs Capitalized Subsequent to Acquisition	999,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,821,000		'		'	'
Building and Land Improvements	5,387,000		'		'	'
Total	7,208,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,457,000	[4]	'		'	'
7160 Riverwood Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,732,000		'		'	'
Building and Land Improvements	7,006,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,540,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,732,000		'		'	'
Building and Land Improvements	8,546,000		'		'	'
Total	11,278,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,857,000	[4]	'		'	'
7170 Riverwood Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,283,000		'		'	'
Building and Land Improvements	3,096,000		'		'	'
Costs Capitalized Subsequent to Acquisition	642,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,283,000		'		'	'
Building and Land Improvements	3,738,000		'		'	'
Total	5,021,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,007,000	[4]	'		'	'
7175 Riverwood Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,788,000		'		'	'
Building and Land Improvements	7,042,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,788,000		'		'	'
Building and Land Improvements	7,042,000		'		'	'
Total	8,830,000	[2],[3]	'		'	'
Accumulated Depreciation	-43,000	[4]	'		'	'
7200 Redstone Gateway	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	4,921,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	4,921,000		'		'	'
Total	4,921,000	[2],[3]	'		'	'
Accumulated Depreciation	-9,000	[4]	'		'	'
7200 Riverwood Road	'		'		'	'
Initial Cost	'		'		'	'
Land	4,089,000		'		'	'
Building and Land Improvements	16,356,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,067,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	4,089,000		'		'	'
Building and Land Improvements	19,423,000		'		'	'
Total	23,512,000	[2],[3]	'		'	'
Accumulated Depreciation	-7,341,000	[4]	'		'	'
7205 Riverwood Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,367,000		'		'	'
Building and Land Improvements	16,280,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,367,000		'		'	'
Building and Land Improvements	16,280,000		'		'	'
Total	17,647,000	[2],[3]	'		'	'
Accumulated Depreciation	-298,000	[4]	'		'	'
7272 Park Circle Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	5,081,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,479,000		'		'	'
Building and Land Improvements	6,300,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,988,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,479,000		'		'	'
Building and Land Improvements	8,288,000		'		'	'
Total	9,767,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,018,000	[4]	'		'	'
7318 Parkway Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	972,000		'		'	'
Building and Land Improvements	3,888,000		'		'	'
Costs Capitalized Subsequent to Acquisition	871,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	972,000		'		'	'
Building and Land Improvements	4,759,000		'		'	'
Total	5,731,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,725,000	[4]	'		'	'
7320 Parkway Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	7,000,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	905,000		'		'	'
Building and Land Improvements	3,570,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,209,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	905,000		'		'	'
Building and Land Improvements	6,779,000		'		'	'
Total	7,684,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,837,000	[4]	'		'	'
7467 Ridge Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,629,000		'		'	'
Building and Land Improvements	6,517,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,065,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,629,000		'		'	'
Building and Land Improvements	8,582,000		'		'	'
Total	10,211,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,710,000	[4]	'		'	'
7700 Potranco Road	'		'		'	'
Initial Cost	'		'		'	'
Land	14,020,000		'		'	'
Building and Land Improvements	38,804,000		'		'	'
Costs Capitalized Subsequent to Acquisition	13,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	14,020,000		'		'	'
Building and Land Improvements	38,817,000		'		'	'
Total	52,837,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,674,000	[4]	'		'	'
7700-1 Potranco Road	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	1,066,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	1,066,000		'		'	'
Total	1,066,000	[2],[3]	'		'	'
Accumulated Depreciation	-135,000	[4]	'		'	'
7700-5 Potranco Road	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	1,884,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	1,884,000		'		'	'
Total	1,884,000	[2],[3]	'		'	'
Accumulated Depreciation	-202,000	[4]	'		'	'
7740 Milestone Parkway	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	19,712,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	3,825,000		'		'	'
Building and Land Improvements	34,365,000		'		'	'
Costs Capitalized Subsequent to Acquisition	275,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,825,000		'		'	'
Building and Land Improvements	34,640,000		'		'	'
Total	38,465,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,128,000	[4]	'		'	'
7770 Backlick Road	'		'		'	'
Initial Cost	'		'		'	'
Land	6,387,000		'		'	'
Building and Land Improvements	73,964,000		'		'	'
Costs Capitalized Subsequent to Acquisition	8,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	6,387,000		'		'	'
Building and Land Improvements	73,972,000		'		'	'
Total	80,359,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,558,000	[4]	'		'	'
8000 Potranco Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,964,000		'		'	'
Building and Land Improvements	21,178,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,964,000		'		'	'
Building and Land Improvements	21,178,000		'		'	'
Total	23,142,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,678,000	[4]	'		'	'
8003 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	611,000		'		'	'
Building and Land Improvements	1,611,000		'		'	'
Costs Capitalized Subsequent to Acquisition	191,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	611,000		'		'	'
Building and Land Improvements	1,802,000		'		'	'
Total	2,413,000	[2],[3]	'		'	'
Accumulated Depreciation	-351,000	[4]	'		'	'
8007 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,434,000		'		'	'
Building and Land Improvements	3,336,000		'		'	'
Costs Capitalized Subsequent to Acquisition	315,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,434,000		'		'	'
Building and Land Improvements	3,651,000		'		'	'
Total	5,085,000	[2],[3]	'		'	'
Accumulated Depreciation	-823,000	[4]	'		'	'
8010 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,349,000		'		'	'
Building and Land Improvements	3,262,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,706,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,349,000		'		'	'
Building and Land Improvements	4,968,000		'		'	'
Total	6,317,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,061,000	[4]	'		'	'
8013 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	642,000		'		'	'
Building and Land Improvements	1,536,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,809,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	642,000		'		'	'
Building and Land Improvements	3,345,000		'		'	'
Total	3,987,000	[2],[3]	'		'	'
Accumulated Depreciation	-600,000	[4]	'		'	'
8015 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	446,000		'		'	'
Building and Land Improvements	1,116,000		'		'	'
Costs Capitalized Subsequent to Acquisition	250,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	446,000		'		'	'
Building and Land Improvements	1,366,000		'		'	'
Total	1,812,000	[2],[3]	'		'	'
Accumulated Depreciation	-366,000	[4]	'		'	'
8019 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	680,000		'		'	'
Building and Land Improvements	1,898,000		'		'	'
Costs Capitalized Subsequent to Acquisition	738,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	680,000		'		'	'
Building and Land Improvements	2,636,000		'		'	'
Total	3,316,000	[2],[3]	'		'	'
Accumulated Depreciation	-652,000	[4]	'		'	'
8020 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,184,000		'		'	'
Building and Land Improvements	3,767,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,199,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,184,000		'		'	'
Building and Land Improvements	5,966,000		'		'	'
Total	8,150,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,226,000	[4]	'		'	'
8023 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	651,000		'		'	'
Building and Land Improvements	1,603,000		'		'	'
Costs Capitalized Subsequent to Acquisition	5,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	651,000		'		'	'
Building and Land Improvements	1,608,000		'		'	'
Total	2,259,000	[2],[3]	'		'	'
Accumulated Depreciation	-312,000	[4]	'		'	'
8030 Potranco Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,964,000		'		'	'
Building and Land Improvements	21,298,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,964,000		'		'	'
Building and Land Improvements	21,298,000		'		'	'
Total	23,262,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,680,000	[4]	'		'	'
8094 Sandpiper Circle	'		'		'	'
Initial Cost	'		'		'	'
Land	1,960,000		'		'	'
Building and Land Improvements	3,716,000		'		'	'
Costs Capitalized Subsequent to Acquisition	375,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,960,000		'		'	'
Building and Land Improvements	4,091,000		'		'	'
Total	6,051,000	[2],[3]	'		'	'
Accumulated Depreciation	-958,000	[4]	'		'	'
8098 Sandpiper Circle	'		'		'	'
Initial Cost	'		'		'	'
Land	1,797,000		'		'	'
Building and Land Improvements	3,651,000		'		'	'
Costs Capitalized Subsequent to Acquisition	639,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,797,000		'		'	'
Building and Land Improvements	4,290,000		'		'	'
Total	6,087,000	[2],[3]	'		'	'
Accumulated Depreciation	-690,000	[4]	'		'	'
8100 Potranco Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,964,000	[9]	'		'	'
Building and Land Improvements	5,001,000	[9]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,964,000	[9]	'		'	'
Building and Land Improvements	5,001,000	[9]	'		'	'
Total	6,965,000	[2],[3],[9]	'		'	'
8110 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,285,000		'		'	'
Building and Land Improvements	10,117,000		'		'	'
Costs Capitalized Subsequent to Acquisition	987,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,285,000		'		'	'
Building and Land Improvements	11,104,000		'		'	'
Total	13,389,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,527,000	[4]	'		'	'
8140 Corporate Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	2,158,000		'		'	'
Building and Land Improvements	8,457,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,252,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,158,000		'		'	'
Building and Land Improvements	10,709,000		'		'	'
Total	12,867,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,381,000	[4]	'		'	'
8621 Robert Fulton Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	11,000,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,317,000		'		'	'
Building and Land Improvements	12,642,000		'		'	'
Costs Capitalized Subsequent to Acquisition	199,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,317,000		'		'	'
Building and Land Improvements	12,841,000		'		'	'
Total	15,158,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,664,000	[4]	'		'	'
8661 Robert Fulton Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	6,200,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,510,000		'		'	'
Building and Land Improvements	3,764,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,042,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,510,000		'		'	'
Building and Land Improvements	4,806,000		'		'	'
Total	6,316,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,662,000	[4]	'		'	'
8671 Robert Fulton Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	7,600,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,718,000		'		'	'
Building and Land Improvements	4,280,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,941,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,718,000		'		'	'
Building and Land Improvements	6,221,000		'		'	'
Total	7,939,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,451,000	[4]	'		'	'
870 Elkridge Landing Road	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	18,900,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	2,003,000		'		'	'
Building and Land Improvements	9,442,000		'		'	'
Costs Capitalized Subsequent to Acquisition	6,764,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,003,000		'		'	'
Building and Land Improvements	16,206,000		'		'	'
Total	18,209,000	[2],[3]	'		'	'
Accumulated Depreciation	-7,553,000	[4]	'		'	'
891 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,165,000		'		'	'
Building and Land Improvements	4,772,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,000,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,165,000		'		'	'
Building and Land Improvements	6,772,000		'		'	'
Total	7,937,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,965,000	[4]	'		'	'
900 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,993,000		'		'	'
Building and Land Improvements	7,972,000		'		'	'
Costs Capitalized Subsequent to Acquisition	3,350,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,993,000		'		'	'
Building and Land Improvements	11,322,000		'		'	'
Total	13,315,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,230,000	[4]	'		'	'
901 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,156,000		'		'	'
Building and Land Improvements	4,437,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,985,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,156,000		'		'	'
Building and Land Improvements	6,422,000		'		'	'
Total	7,578,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,386,000	[4]	'		'	'
911 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,215,000		'		'	'
Building and Land Improvements	4,861,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,024,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,215,000		'		'	'
Building and Land Improvements	6,885,000		'		'	'
Total	8,100,000	[2],[3]	'		'	'
Accumulated Depreciation	-3,014,000	[4]	'		'	'
921 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,044,000		'		'	'
Building and Land Improvements	4,176,000		'		'	'
Costs Capitalized Subsequent to Acquisition	718,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,044,000		'		'	'
Building and Land Improvements	4,894,000		'		'	'
Total	5,938,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,114,000	[4]	'		'	'
938 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,163,000		'		'	'
Building and Land Improvements	4,748,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,131,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,163,000		'		'	'
Building and Land Improvements	5,879,000		'		'	'
Total	7,042,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,757,000	[4]	'		'	'
939 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	939,000		'		'	'
Building and Land Improvements	3,756,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,036,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	939,000		'		'	'
Building and Land Improvements	5,792,000		'		'	'
Total	6,731,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,677,000	[4]	'		'	'
940 Elkridge Landing Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,104,000	[10]	'		'	'
Building and Land Improvements	4,725,000	[10]	'		'	'
Costs Capitalized Subsequent to Acquisition	170,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,104,000	[10]	'		'	'
Building and Land Improvements	4,895,000	[10]	'		'	'
Total	5,999,000	[10],[2],[3]	'		'	'
Accumulated Depreciation	-4,884,000	[10],[4]	'		'	'
9651 Hornbaker Road	'		'		'	'
Initial Cost	'		'		'	'
Land	6,050,000		'		'	'
Building and Land Improvements	203,609,000		'		'	'
Costs Capitalized Subsequent to Acquisition	844,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	6,050,000		'		'	'
Building and Land Improvements	204,453,000		'		'	'
Total	210,503,000	[2],[3]	'		'	'
Accumulated Depreciation	-6,637,000	[4]	'		'	'
9690 Deereco Road	'		'		'	'
Initial Cost	'		'		'	'
Land	3,415,000		'		'	'
Building and Land Improvements	13,723,000		'		'	'
Costs Capitalized Subsequent to Acquisition	6,100,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	3,415,000		'		'	'
Building and Land Improvements	19,823,000		'		'	'
Total	23,238,000	[2],[3]	'		'	'
Accumulated Depreciation	-8,717,000	[4]	'		'	'
9900 Franklin Square Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	979,000		'		'	'
Building and Land Improvements	3,466,000		'		'	'
Costs Capitalized Subsequent to Acquisition	361,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	979,000		'		'	'
Building and Land Improvements	3,827,000		'		'	'
Total	4,806,000	[2],[3]	'		'	'
Accumulated Depreciation	-854,000	[4]	'		'	'
9910 Franklin Square Drive	'		'		'	'
Real Estate and Accumulated Depreciation	'		'		'	'
Encumbrances	4,870,000	[1]	'		'	'
Initial Cost	'		'		'	'
Land	1,219,000		'		'	'
Building and Land Improvements	6,590,000		'		'	'
Costs Capitalized Subsequent to Acquisition	209,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,219,000		'		'	'
Building and Land Improvements	6,799,000		'		'	'
Total	8,018,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,705,000	[4]	'		'	'
9920 Franklin Square Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,058,000		'		'	'
Building and Land Improvements	5,293,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,429,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,058,000		'		'	'
Building and Land Improvements	6,722,000		'		'	'
Total	7,780,000	[2],[3]	'		'	'
Accumulated Depreciation	-1,789,000	[4]	'		'	'
9930 Franklin Square Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,137,000		'		'	'
Building and Land Improvements	3,921,000		'		'	'
Costs Capitalized Subsequent to Acquisition	225,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,137,000		'		'	'
Building and Land Improvements	4,146,000		'		'	'
Total	5,283,000	[2],[3]	'		'	'
Accumulated Depreciation	-890,000	[4]	'		'	'
9940 Franklin Square Drive	'		'		'	'
Initial Cost	'		'		'	'
Land	1,052,000		'		'	'
Building and Land Improvements	3,382,000		'		'	'
Costs Capitalized Subsequent to Acquisition	281,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,052,000		'		'	'
Building and Land Improvements	3,663,000		'		'	'
Total	4,715,000	[2],[3]	'		'	'
Accumulated Depreciation	-853,000	[4]	'		'	'
Aerotech Commerce	'		'		'	'
Initial Cost	'		'		'	'
Land	900,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	900,000	[10],[2],[3]	'		'	'
Total	900,000	[10],[2],[3]	'		'	'
Arborcrest	'		'		'	'
Initial Cost	'		'		'	'
Land	21,968,000		'		'	'
Building and Land Improvements	96,992,000		'		'	'
Costs Capitalized Subsequent to Acquisition	1,194,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	21,968,000	[2],[3]	'		'	'
Building and Land Improvements	98,186,000	[2],[3]	'		'	'
Total	120,154,000	[2],[3]	'		'	'
Accumulated Depreciation	-5,842,000	[4]	'		'	'
Arundel Preserve	'		'		'	'
Initial Cost	'		'		'	'
Land	5,425,000	[10]	'		'	'
Building and Land Improvements	7,125,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	5,425,000	[10],[2],[3]	'		'	'
Building and Land Improvements	7,125,000	[10],[2],[3]	'		'	'
Total	12,550,000	[10],[2],[3]	'		'	'
Ashburn Crossing	'		'		'	'
Initial Cost	'		'		'	'
Land	4,311,000	[10]	'		'	'
Building and Land Improvements	2,646,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	4,311,000	[10],[2],[3]	'		'	'
Building and Land Improvements	2,646,000	[10],[2],[3]	'		'	'
Total	6,957,000	[10],[2],[3]	'		'	'
Canton Crossing Land	'		'		'	'
Initial Cost	'		'		'	'
Land	16,085,000	[10]	'		'	'
Building and Land Improvements	490,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	16,085,000	[10],[2],[3]	'		'	'
Building and Land Improvements	490,000	[10],[2],[3]	'		'	'
Total	16,575,000	[10],[2],[3]	'		'	'
Canton Crossing Util Distr Ctr	'		'		'	'
Initial Cost	'		'		'	'
Land	7,300,000		'		'	'
Building and Land Improvements	15,556,000		'		'	'
Costs Capitalized Subsequent to Acquisition	878,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	7,300,000	[2],[3]	'		'	'
Building and Land Improvements	16,434,000	[2],[3]	'		'	'
Total	23,734,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,183,000	[4]	'		'	'
Columbia Gateway - Southridge	'		'		'	'
Initial Cost	'		'		'	'
Land	6,387,000	[10]	'		'	'
Building and Land Improvements	2,940,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	6,387,000	[10],[2],[3]	'		'	'
Building and Land Improvements	2,940,000	[10],[2],[3]	'		'	'
Total	9,327,000	[10],[2],[3]	'		'	'
Dahlgren Technology Center	'		'		'	'
Initial Cost	'		'		'	'
Land	978,000	[10]	'		'	'
Building and Land Improvements	178,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	978,000	[10],[2],[3]	'		'	'
Building and Land Improvements	178,000	[10],[2],[3]	'		'	'
Total	1,156,000	[10],[2],[3]	'		'	'
Expedition VII	'		'		'	'
Initial Cost	'		'		'	'
Land	705,000	[10]	'		'	'
Building and Land Improvements	726,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	705,000	[10],[2],[3]	'		'	'
Building and Land Improvements	726,000	[10],[2],[3]	'		'	'
Total	1,431,000	[10],[2],[3]	'		'	'
Indian Head	'		'		'	'
Initial Cost	'		'		'	'
Land	6,436,000	[10]	'		'	'
Building and Land Improvements	0	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	6,436,000	[10],[2],[3]	'		'	'
Building and Land Improvements	0	[10],[2],[3]	'		'	'
Total	6,436,000	[10],[2],[3]	'		'	'
InterQuest	'		'		'	'
Initial Cost	'		'		'	'
Land	14,382,000	[10]	'		'	'
Building and Land Improvements	8,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	14,382,000	[10],[2],[3]	'		'	'
Building and Land Improvements	8,000	[10],[2],[3]	'		'	'
Total	14,390,000	[10],[2],[3]	'		'	'
M Square Research Park	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	4,311,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	4,311,000	[10],[2],[3]	'		'	'
Total	4,311,000	[10],[2],[3]	'		'	'
National Business Park	'		'		'	'
Initial Cost	'		'		'	'
Land	2,372,000	[10]	'		'	'
Building and Land Improvements	7,391,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,372,000	[10],[2],[3]	'		'	'
Building and Land Improvements	7,391,000	[10],[2],[3]	'		'	'
Total	9,763,000	[10],[2],[3]	'		'	'
National Business Park North	'		'		'	'
Initial Cost	'		'		'	'
Land	27,766,000	[10]	'		'	'
Building and Land Improvements	28,000,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	27,766,000	[10],[2],[3]	'		'	'
Building and Land Improvements	28,000,000	[10],[2],[3]	'		'	'
Total	55,766,000	[10],[2],[3]	'		'	'
North Gate Business Park	'		'		'	'
Initial Cost	'		'		'	'
Land	6,486,000	[10]	'		'	'
Building and Land Improvements	10,910,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	6,486,000	[10],[2],[3]	'		'	'
Building and Land Improvements	10,910,000	[10],[2],[3]	'		'	'
Total	17,396,000	[10],[2],[3]	'		'	'
Northwest Crossroads	'		'		'	'
Initial Cost	'		'		'	'
Land	7,430,000	[10]	'		'	'
Building and Land Improvements	836,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	7,430,000	[10],[2],[3]	'		'	'
Building and Land Improvements	836,000	[10],[2],[3]	'		'	'
Total	8,266,000	[10],[2],[3]	'		'	'
NOVA Office A	'		'		'	'
Initial Cost	'		'		'	'
Land	2,096,000	[9]	'		'	'
Building and Land Improvements	9,963,000	[9]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	2,096,000	[9]	'		'	'
Building and Land Improvements	9,963,000	[9]	'		'	'
Total	12,059,000	[2],[3],[9]	'		'	'
Old Annapolis Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,637,000		'		'	'
Building and Land Improvements	5,500,000		'		'	'
Costs Capitalized Subsequent to Acquisition	2,103,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,637,000	[2],[3]	'		'	'
Building and Land Improvements	7,603,000	[2],[3]	'		'	'
Total	9,240,000	[2],[3]	'		'	'
Accumulated Depreciation	-2,546,000	[4]	'		'	'
Patriot Park	'		'		'	'
Initial Cost	'		'		'	'
Land	8,768,000	[10]	'		'	'
Building and Land Improvements	248,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	8,768,000	[10],[2],[3]	'		'	'
Building and Land Improvements	248,000	[10],[2],[3]	'		'	'
Total	9,016,000	[10],[2],[3]	'		'	'
Patriot Ridge	'		'		'	'
Initial Cost	'		'		'	'
Land	18,517,000	[10]	'		'	'
Building and Land Improvements	14,166,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	18,517,000	[10],[2],[3]	'		'	'
Building and Land Improvements	14,166,000	[10],[2],[3]	'		'	'
Total	32,683,000	[10],[2],[3]	'		'	'
Redstone Gateway	'		'		'	'
Initial Cost	'		'		'	'
Building and Land Improvements	13,974,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Building and Land Improvements	13,974,000	[10],[2],[3]	'		'	'
Total	13,974,000	[10],[2],[3]	'		'	'
Route 15/Biggs Ford Road	'		'		'	'
Initial Cost	'		'		'	'
Land	8,703,000	[10]	'		'	'
Building and Land Improvements	501,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	8,703,000	[10],[2],[3]	'		'	'
Building and Land Improvements	501,000	[10],[2],[3]	'		'	'
Total	9,204,000	[10],[2],[3]	'		'	'
Sentry Gateway	'		'		'	'
Initial Cost	'		'		'	'
Land	8,275,000	[10]	'		'	'
Building and Land Improvements	3,645,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	8,275,000	[10],[2],[3]	'		'	'
Building and Land Improvements	3,645,000	[10],[2],[3]	'		'	'
Total	11,920,000	[10],[2],[3]	'		'	'
West Nursery Road	'		'		'	'
Initial Cost	'		'		'	'
Land	1,441,000	[10]	'		'	'
Building and Land Improvements	88,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	1,441,000	[10],[2],[3]	'		'	'
Building and Land Improvements	88,000	[10],[2],[3]	'		'	'
Total	1,529,000	[10],[2],[3]	'		'	'
Westfields - Park Center	'		'		'	'
Initial Cost	'		'		'	'
Land	23,745,000	[10]	'		'	'
Building and Land Improvements	3,902,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	23,745,000	[10],[2],[3]	'		'	'
Building and Land Improvements	3,902,000	[10],[2],[3]	'		'	'
Total	27,647,000	[10],[2],[3]	'		'	'
Westfields Corporate Center	'		'		'	'
Initial Cost	'		'		'	'
Land	7,141,000	[10]	'		'	'
Building and Land Improvements	1,379,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	7,141,000	[10],[2],[3]	'		'	'
Building and Land Improvements	1,379,000	[10],[2],[3]	'		'	'
Total	8,520,000	[10],[2],[3]	'		'	'
White Marsh	'		'		'	'
Initial Cost	'		'		'	'
Land	26,589,000	[10]	'		'	'
Building and Land Improvements	12,492,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	26,589,000	[10],[2],[3]	'		'	'
Building and Land Improvements	12,492,000	[10],[2],[3]	'		'	'
Total	39,081,000	[10],[2],[3]	'		'	'
Woodland Park	'		'		'	'
Initial Cost	'		'		'	'
Land	9,614,000	[10]	'		'	'
Building and Land Improvements	81,000	[10]	'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	9,614,000	[10],[2],[3]	'		'	'
Building and Land Improvements	81,000	[10],[2],[3]	'		'	'
Total	9,695,000	[10],[2],[3]	'		'	'
Other Developments, including intercompany eliminations	'		'		'	'
Initial Cost	'		'		'	'
Land	8,000		'		'	'
Building and Land Improvements	-155,000		'		'	'
Costs Capitalized Subsequent to Acquisition	261,000		'		'	'
Gross Amounts Carried at Close of Period	'		'		'	'
Land	8,000	[2],[3]	'		'	'
Building and Land Improvements	106,000	[2],[3]	'		'	'
Total	114,000	[2],[3]	'		'	'
Accumulated Depreciation	-9,000	[4]	'		'	'
Fair value measurement on a nonrecurring basis \| Greater Philadelphia	'		'		'	'
Additional information	'		'		'	'
Impairment losses	'		46,100,000		'	'
Other Properties with Shortened Holding Periods \| Fair value measurement on a nonrecurring basis \| Greater Baltimore	'		'		'	'
Additional information	'		'		'	'
Impairment losses	$5,900,000		'		'	'

[1]	Excludes our term loan facilities of $620.0 million, unsecured senior notes of $592.7 million, exchangeable senior notes of $563,000, unsecured notes payable of $1.7 million, a letter of credit on a mortgage loan of $14.8 million, and net premiums on the remaining loans of $69,000.
[2]	The aggregate cost of these assets for Federal income tax purposes was approximately $3.3 billion at DecemberÂ 31, 2013.
[3]	As discussed in Note 3 to our Consolidated Financial Statements, we recognized impairment losses of $5.9 million in connection with two properties in the Greater Baltimore region that we determined no longer met our strategic investment criteria.
[4]	The estimated lives over which depreciation is recognized follow: Building and land improvements: 10-40 years; and tenant improvements: related lease terms.
[5]	Refer to the paragraphs below for further disclosure.
[6]	As discussed below, we have the ability to borrow an aggregate of an additional $180.0 million under these term loan facilities, provided that there is no default under the facilities and subject to the approval of the lenders.
[7]	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 $69,000 at DecemberÂ 31, 2013 and $1.3 million at DecemberÂ 31, 2012.
[8]	Includes $13.9 million balance on construction loans with maximum available borrowings of $26.2 million.
[9]	Under construction or redevelopment at DecemberÂ 31, 2013.
[10]	Held or under pre-construction at DecemberÂ 31, 2013.

Schedule_III_Real_Estate_and_A2

Schedule III - Real Estate and Accumulated Depreciation (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Changes in cost of properties	'		'	'
Beginning balance	$3,859,960		$4,038,932	$3,948,487
Acquisitions of operating properties	0		33,684	26,887
Building and land improvements	249,639		214,418	304,079
Sales	-141,045		-291,491	-75,315
Impairments	-45,931		-121,557	-165,206
Other dispositions	-110,673		-13,891	0
Other	0		-135	0
Ending balance	3,811,950	[1],[2]	3,859,960	4,038,932
Changes in accumulated depreciation	'		'	'
Beginning balance	568,176		577,601	503,032
Depreciation expense	92,677		93,158	99,173
Sales	-9,542		-40,346	-9,640
Impairments	-14,863		-58,855	-15,039
Other dispositions	-38,799		-3,247	0
Other	0		-135	75
Ending balance	$597,649	[3]	$568,176	$577,601

[1]	The aggregate cost of these assets for Federal income tax purposes was approximately $3.3 billion at DecemberÂ 31, 2013.
[2]	As discussed in Note 3 to our Consolidated Financial Statements, we recognized impairment losses of $5.9 million in connection with two properties in the Greater Baltimore region that we determined no longer met our strategic investment criteria.
[3]	The estimated lives over which depreciation is recognized follow: Building and land improvements: 10-40 years; and tenant improvements: related lease terms.