First Potomac Realty Trust (FPO) Inactive 10-Q4 Nov 132013 Q3 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2013	Nov. 01, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Entity Registrant Name	'FIRST POTOMAC REALTY TRUST	'
Entity Central Index Key	'0001254595	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	58,701,632

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets:	'	'
Rental property, net	$1,218,364	$1,450,679
Assets held-for-sale	3,447	'
Cash and cash equivalents	16,971	9,374
Escrows and reserves	38,089	13,421
Accounts and other receivables, net of allowance for doubtful accounts of $1,698 and $1,799, respectively	12,309	15,271
Accrued straight-line rents, net of allowance for doubtful accounts of $168 and $530, respectively	29,838	28,133
Notes receivable, net	54,722	54,730
Investment in affiliates	49,229	50,596
Deferred costs, net	39,706	40,370
Prepaid expenses and other assets	11,064	8,597
Intangible assets, net	37,544	46,577
Total assets	1,511,283	1,717,748
Liabilities:	'	'
Mortgage loans	275,974	418,864
Secured term loan	'	10,000
Unsecured term loan	300,000	300,000
Unsecured revolving credit facility	83,000	205,000
Accounts payable and other liabilities	44,704	64,920
Accrued interest	1,697	2,653
Rents received in advance	6,969	9,948
Tenant security deposits	5,799	5,968
Deferred market rent, net	1,746	3,535
Total liabilities	719,889	1,020,888
Noncontrolling interests in the Operating Partnership	33,972	34,367
Equity:	'	'
Preferred Shares, $0.001 par value, 50,000 shares authorized; Series A Preferred Shares, $25 per share liquidation preference, 6,400 shares issued and outstanding	160,000	160,000
Common shares, $0.001 par value, 150,000 shares authorized; 58,772 and 51,047 shares issued and outstanding, respectively	59	51
Additional paid-in capital	912,444	804,584
Noncontrolling interests in consolidated partnerships	3,957	3,728
Accumulated other comprehensive loss	-5,150	-10,917
Dividends in excess of accumulated earnings	-313,888	-294,953
Total equity	757,422	662,493
Total liabilities, noncontrolling interests and equity	$1,511,283	$1,717,748

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Statement Of Financial Position [Abstract]	'	'
Allowance for doubtful accounts, accounts receivable and other	$1,698	$1,799
Allowance for doubtful accounts, Accrued straight-line rents	$168	$530
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	50,000	50,000
Series A Preferred Shares, liquidation preference	$25	$25
Series A Preferred Shares, shares issued	6,400	6,400
Series A Preferred Shares, shares outstanding	6,400	6,400
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000	150,000
Common stock, shares issued	58,772	58,772
Common stock, shares outstanding	51,047	51,047

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:	'	'	'	'
Rental	$32,424	$31,516	$96,742	$93,689
Tenant reimbursements and other	8,413	7,270	25,229	23,585
Total revenues	40,837	38,786	121,971	117,274
Operating expenses:	'	'	'	'
Property operating	10,878	10,035	31,529	27,697
Real estate taxes and insurance	4,240	3,741	13,104	12,253
General and administrative	6,346	5,645	16,598	17,787
Acquisition costs	173	8	173	49
Depreciation and amortization	14,812	14,144	43,891	41,247
Impairment of real estate assets	'	496	'	2,444
Contingent consideration related to acquisition of property	'	112	75	112
Total operating expenses	36,449	34,181	105,370	101,589
Operating income	4,388	4,605	16,601	15,685
Other expenses, net:	'	'	'	'
Interest expense	7,726	9,974	27,036	30,909
Interest and other income	-1,696	-1,521	-4,801	-4,528
Equity in (earnings) losses of affiliates	-19	30	-54	52
Gain on sale of investment	'	-2,951	'	-2,951
Loss on debt extinguishment / modification	123	'	324	13,221
Total other expenses, net	6,134	5,532	22,505	36,703
Loss from continuing operations before income taxes	-1,746	-927	-5,904	-21,018
Benefit from income taxes	'	4,304	'	4,142
(Loss) income from continuing operations	-1,746	3,377	-5,904	-16,876
Discontinued operations:	'	'	'	'
(Loss) income from operations	-387	4,058	5,677	7,454
Loss on debt extinguishment	'	'	-4,414	'
Gain on sale of real estate property	416	'	19,363	161
Income from discontinued operations	29	4,058	20,626	7,615
Net (loss) income	-1,717	7,435	14,722	-9,261
Less: Net loss (income) attributable to noncontrolling interests	211	-232	-196	876
Net (loss) income attributable to First Potomac Realty Trust	-1,506	7,203	14,526	-8,385
Less: Dividends on preferred shares	-3,100	-3,100	-9,300	-8,864
Net (loss) income attributable to common shareholders	($4,606)	$4,103	$5,226	($17,249)
Basic and diluted earnings per common share:	'	'	'	'
Loss from continuing operations	($0.08)	'	($0.28)	($0.49)
Income from discontinued operations	'	$0.08	$0.37	$0.14
Net (loss) income	($0.08)	$0.08	$0.09	($0.35)
Weighted average common shares outstanding:	'	'	'	'
Basic	57,969	50,267	54,014	50,049
Diluted	57,969	50,346	54,014	50,049

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]	'	'	'	'
Net (loss) income	($1,717)	$7,435	$14,722	($9,261)
Unrealized gain on derivative instruments	157	66	6,051	139
Unrealized loss on derivative instruments	-1,164	-2,456	'	-6,545
Total comprehensive (loss) income	-2,724	5,045	20,773	-15,667
Net loss (income) attributable to noncontrolling interests	211	-232	-196	876
Net unrealized loss (gain) from derivative instruments attributable to noncontrolling interests	43	116	-284	318
Comprehensive (loss) income attributable to First Potomac Realty Trust	($2,470)	$4,929	$20,293	($14,473)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:	'	'
Net income (loss)	$14,722	($9,261)
Discontinued operations:	'	'
Gain on sale of real estate property	-19,363	-161
Loss on debt extinguishment / modification	4,414	'
Depreciation and amortization	3,928	7,728
Impairment of real estate assets	1,921	1,072
Depreciation and amortization	44,642	42,003
Stock based compensation	3,696	2,301
Bad debt expense	557	583
Deferred income taxes	'	-3,533
Amortization of deferred market rent	29	268
Amortization of financing costs and discounts	2,328	1,643
Equity in (earnings) losses of affiliates	-54	52
Distributions from investments in affiliates	1,813	1,208
Gain on sale of investment	'	-2,951
Contingent consideration related to acquisition of property	75	112
Contingent consideration payments in excess of fair value at acquisition date	-987	'
Loss on debt extinguishment / modification	324	2,379
Impairment of real estate assets	'	2,444
Changes in assets and liabilities:	'	'
Escrows and reserves	4,003	4,414
Accounts and other receivables	2,078	-3,087
Accrued straight-line rents	-6,267	-7,645
Prepaid expenses and other assets	418	-1,353
Tenant security deposits	876	317
Accounts payable and accrued expenses	-1,605	3,191
Accrued interest	-956	-430
Rents received in advance	-2,927	-1,749
Deferred costs	-8,242	-9,394
Total adjustments	30,701	39,412
Net cash provided by operating activities	45,423	30,151
Cash flows from investing activities:	'	'
Purchase deposit on future acquisition	-2,000	'
Proceeds from sale of real estate assets	213,145	10,838
Proceeds from sale of investment	'	25,705
Principal payments from note receivable	60	'
Change in escrow and reserve accounts	-28,175	-36
Additions to rental property and furniture, fixtures and equipment	-33,477	-42,034
Additions to construction in progress	-14,252	-6,384
Investment in affiliates	-391	-2,534
Net cash provided by (used in) investing activities	134,910	-14,445
Cash flows from financing activities:	'	'
Financing costs	-2,324	-3,502
Issuance of preferred shares, net	'	43,518
Issuance of common shares, net	105,085	3,599
Issuance of debt	132,199	361,400
Payment of deferred acquisition costs and contingent consideration	-9,036	'
Contributions from consolidated joint venture partners	250	'
Repayments of debt	-364,367	-384,731
Dividends to common shareholders	-24,128	-30,513
Dividends to preferred shareholders	-9,300	-8,603
Distributions to noncontrolling interests	-1,168	-1,639
Operating partnership unit redemption	-95	'
Proceeds from stock option exercises	148	56
Net cash used in financing activities	-172,736	-20,415
Net increase (decrease) in cash and cash equivalents	7,597	-4,709
Cash and cash equivalents, beginning of period	9,374	16,749
Cash and cash equivalents, end of period	16,971	12,040
Cash paid for interest, net	26,489	31,162
Cash paid for income based franchise taxes	'	714
Non-cash investing and financing activities:	'	'
Settlements of common shares	537	887
Change in fair value of the outstanding common Operating Partnership units	332	441
Conversion of common Operating Partnership units into common shares	'	3,513
Changes in accruals:	'	'
Additions to rental property and furniture, fixtures and equipment	-3,206	1,068
Additions to development and redevelopment	($974)	$1,798

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (Parenthetical) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
	OperatingPartnershipUnits	Sep. 30, 2012
Capitalized interest on indebtedness paid in cash	$1.50	$2.10
Surrendered common shares to satisfy statutory minimum federal income tax obligations	0.5	0.9
Change in redemption value, noncontrolling interest	3.9	4
Number of operating partnership units redeemed	0	'
Furniture and Fixtures [Member]	'	'
Accrued capital expenditure	9.9	12.8
Development and Redevelopment [Member]	'	'
Accrued capital expenditure	$3.60	$2.30
Number of operating partnership units redeemed	0	322,302

Description_of_Business

Description of Business	9 Months Ended
Description of Business	Sep. 30, 2013
Accounting Policies [Abstract]	'
Description of Business	'
	(1) Description of Business
	First Potomac Realty Trust (the “Company”) is a leader in the ownership, management, development and redevelopment of office and business park properties in the greater Washington, D.C. region. The Company separates its properties into four distinct reporting segments, which it refers to as the Washington, D.C., Maryland, Northern Virginia and Southern Virginia reporting segments. The Company strategically focuses on acquiring and redeveloping properties that it believes can benefit from its intensive property management and seeks to reposition these properties to increase their profitability and value. The Company’s portfolio primarily contains a mix of single-tenant and multi-tenant office properties and business parks. Office properties are single-story and multi-story buildings that are primarily for office use; and business parks contain buildings with office features combined with some industrial property space.
	References in these unaudited condensed consolidated financial statements to “we,” “our” or “First Potomac,” refer to the Company and its subsidiaries, on a consolidated basis, unless the context indicates otherwise.
	The Company conducts its business through First Potomac Realty Investment Limited Partnership, the Company’s operating partnership (the “Operating Partnership”). The Company is the sole general partner of, and, as of September 30, 2013, owned a 95.8% interest in, the Operating Partnership. The remaining interests in the Operating Partnership, which are presented as noncontrolling interests in the Operating Partnership in the accompanying unaudited condensed consolidated financial statements, are limited partnership interests, some of which are owned by several of the Company’s executive officers who contributed properties and other assets to the Company upon its formation, and the remainder of which are owned by other unrelated parties.
	At September 30, 2013, the Company wholly-owned or had a controlling interest in properties totaling 9.1 million square feet and had a noncontrolling ownership interest in properties totaling an additional 0.9 million square feet through five unconsolidated joint ventures. The Company also owned land that can support approximately 1.5 million square feet of additional development. The Company’s consolidated properties were 85.1% occupied by 570 tenants at September 30, 2013. The Company did not include square footage that was in development or redevelopment, which totaled 0.1 million square feet at September 30, 2013, in its occupancy calculation. The Company derives substantially all of its revenue from leases of space within its properties. As of September 30, 2013, the Company’s largest tenant was the U.S. Government, which along with government contractors, accounted for 24% of the Company’s total annualized cash basis rent. The U.S. Government accounted for 30% of the Company’s outstanding accounts receivable at September 30, 2013. The Company operates so as to qualify as a real estate investment trust (“REIT”) for federal income tax purposes.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	(2) Summary of Significant Accounting Policies
	(a) Principles of Consolidation
	The unaudited condensed consolidated financial statements of the Company include the accounts of the Company, the Operating Partnership and the subsidiaries in which the Company or Operating Partnership has a controlling interest, which includes First Potomac Management LLC, a wholly-owned subsidiary that manages the majority of the Company’s properties. All intercompany balances and transactions have been eliminated in consolidation.
	The Company has condensed or omitted certain information and note disclosures normally included in financial statements presented in accordance with U.S. generally accepted accounting principles (“GAAP”) in the accompanying unaudited condensed consolidated financial statements. The Company believes the disclosures made are adequate to prevent the information presented from being misleading. However, the unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s annual report on Form 10-K for the year ended December 31, 2012 and as updated from time to time in other filings with the U.S. Securities and Exchange Commission (the “SEC”).
	In the Company’s opinion, the accompanying unaudited condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments and accruals necessary to present fairly the Company’s financial position as of September 30, 2013, the results of its operations and its comprehensive (loss) income for the three and nine months ended September 30, 2013 and 2012 and its cash flows for the nine months ended September 30, 2013 and 2012. Interim results are not necessarily indicative of full-year performance due, in part, to the timing of transactions and the impact of acquisitions and dispositions throughout the year as well as the seasonality of certain operating expenses such as utilities expense and snow and ice removal costs.

	(b) Use of Estimates
	The preparation of condensed consolidated financial statements in conformity with GAAP requires management of the Company to make a number of estimates and assumptions relating to the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the period. Estimates include the amount of accounts receivable that may be uncollectible; recoverability of notes receivable, future cash flows, discount and capitalization rate assumptions used to fair value acquired properties and to test impairment of certain long-lived assets and goodwill; derivative valuations; market lease rates, lease-up periods, leasing and tenant improvement costs used to fair value intangible assets acquired and probability weighted cash flow analysis used to fair value contingent liabilities. Actual results could differ from those estimates.
	(c) Rental Property
	Rental property is initially recorded at fair value, if acquired in a business combination, or initial cost when constructed or acquired in an asset purchase, less accumulated depreciation and, when appropriate, impairment losses. Improvements and replacements are capitalized at cost when they extend the useful life, increase capacity or improve the efficiency of the asset. Repairs and maintenance are charged to expense when incurred. Depreciation and amortization are recorded on a straight-line basis over the estimated useful lives of the assets. The estimated useful lives of the Company’s assets, by class, are as follows:


	Buildings	39 years
	Building improvements	5 to 20 years
	Furniture, fixtures and equipment	5 to 15 years
	Lease related intangible assets	The term of the related lease
	Tenant improvements	Shorter of the useful life of the asset or the term of the related lease
	The Company regularly reviews market conditions for possible impairment of a property’s carrying value. When circumstances such as adverse market conditions, changes in management’s intended holding period or potential sale to a third party indicate a possible impairment of the fair value of a property, an impairment analysis is performed. The Company assesses potential impairments based on an estimate of the future undiscounted cash flows (excluding interest charges) expected to result from the property’s use and eventual disposition. This estimate is based on projections of future revenues, expenses, capital improvement costs, expected holding periods and capitalization rates. These cash flows consider factors such as expected market trends and leasing prospects, as well as the effects of leasing demand, competition and other factors. If impairment exists due to the inability to recover the carrying value of a real estate investment based on forecasted undiscounted cash flows, an impairment loss is recorded to the extent that the carrying value exceeds the estimated fair value of the property. The Company is required to make estimates as to whether there are impairments in the carrying values of its investments in real estate. Further, the Company will record an impairment loss if it expects to dispose of a property, in the near term, at a price below carrying value. In such an event, the Company will record an impairment loss based on the difference between a property’s carrying value and its projected sales price less any estimated costs to sell.
	The Company will classify a building as held-for-sale in accordance with GAAP in the period in which it has made the decision to dispose of the building, the Company’s Board of Trustees or a designated delegate has approved the sale, there is a high likelihood a binding agreement to purchase the property will be signed under which the buyer will be required to commit a significant amount of nonrefundable cash and no significant financing contingencies exist that could cause the transaction not to be completed in a timely manner. If these criteria are met, the Company will cease depreciation of the asset. The Company will classify any impairment loss, together with the building’s operating results, as discontinued operations in its consolidated statements of operations for all periods presented and classify the assets and related liabilities as held-for-sale in its consolidated balance sheets in the period the held-for-sale criteria are met. Interest expense is reclassified to discontinued operations only to the extent the held-for-sale property is secured by specific mortgage debt and the mortgage debt will not be assigned to another property owned by the Company after the disposition.
	The Company recognizes the fair value, if sufficient information exists to reasonably estimate the fair value, of any liability for conditional asset retirement obligations when incurred, which is generally upon acquisition, construction, development or redevelopment and/or through the normal operation of the asset.

	The Company capitalizes interest costs incurred on qualifying expenditures for real estate assets under development or redevelopment, which include its investment in assets owned through unconsolidated joint ventures that are under development or redevelopment, while being readied for their intended use in accordance with accounting requirements regarding capitalization of interest. The Company will capitalize interest when qualifying expenditures for the asset have been made, activities necessary to get the asset ready for its intended use are in progress and interest costs are being incurred. Capitalized interest also includes interest associated with expenditures incurred to acquire developable land while development activities are in progress. The Company also capitalizes direct compensation costs of the Company’s construction personnel who manage the development and redevelopment projects, but only to the extent the employee’s time can be allocated to a project. Any portion of construction management costs not directly attributable to a specific project are recognized as general and administrative expense in the period incurred. The Company does not capitalize any other general administrative costs such as office supplies, office rent expense or an overhead allocation to its development or redevelopment projects. Capitalized compensation costs were immaterial for the three and nine months ended September 30, 2013 and 2012. Capitalization of interest will end when the asset is substantially complete and ready for its intended use, but no later than one year from completion of major construction activity, if the property is not occupied. The Company will also place redevelopment and development assets into service at this time and commence depreciation upon the substantial completion of tenant improvements and the recognition of revenue. Capitalized interest is depreciated over the useful life of the underlying assets, commencing when those assets are placed into service.
	(d) Notes Receivable
	The Company provides loans to the owners of real estate properties, which can be collateralized by interest in the real estate property. The Company records these loans as “Notes receivable, net” in its consolidated balance sheets. The loans are recorded net of any discount or issuance costs, which are amortized over the life of the respective note receivable using the effective interest method. The Company records interest earned from notes receivable and amortization of any discount or issuance costs within “Interest and other income” in its consolidated statements of operations.
	The Company will establish a provision for anticipated credit losses associated with its notes receivable when it anticipates that it may be unable to collect any contractually due amounts. This determination is based upon such factors as delinquencies, loss experience, collateral quality and current economic or borrower conditions. The Company’s collectability of its notes receivable may be adversely impacted by the financial stability of the Washington, D.C. region and the ability of its underlying assets to keep current tenants or attract new tenants. Estimated losses are recorded as a charge to earnings to establish an allowance for credit losses that the Company estimates to be adequate based on these factors. Based on the review of the above criteria, the Company did not record an allowance for credit losses for its notes receivable during the three and nine months ended September 30, 2013 and 2012.
	(e) Reclassifications
	Certain prior year amounts have been reclassified to conform to the current year presentation, primarily as a result of reclassifying the operating results of several properties as discontinued operations. For more information, see note 7, Discontinued Operations.
	(f) Application of New Accounting Standards
	In January 2013, the FASB issued Accounting Standards Update 2013-02, Reporting of Amounts Reclassified Out of Accumulated Comprehensive Income (“ASU 2013-02”), which requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income. For other amounts that are not required under GAAP to be reclassified in their entirety to net income within the same reporting period, an entity is required to cross-reference other disclosures that provide additional detail about the reclassified amounts. The Company adopted the provisions of ASU 2013-02 on January 1, 2013, and the adoption of this update did not have a significant impact on its condensed consolidated financial statements or notes thereto.

Earnings_Per_Common_Share

Earnings Per Common Share	9 Months Ended
Earnings Per Common Share	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings Per Common Share	'
	(3) Earnings Per Common Share
	Basic earnings or loss per common share (“EPS”) is calculated by dividing net income or loss attributable to common shareholders by the weighted average common shares outstanding for the periods presented. Diluted EPS is computed after adjusting the basic EPS computation for the effect of dilutive common equivalent shares outstanding during the periods presented, which include stock options, non-vested shares and preferred shares. The Company applies the two-class method for determining EPS as its outstanding unvested shares with non-forfeitable dividend rights are considered participating securities. The Company’s excess of distributions over earnings related to participating securities are shown as a reduction in total earnings attributable to common shareholders in the Company’s computation of EPS.

	The following table sets forth the computation of the Company’s basic and diluted earnings per common share (amounts in thousands, except per share amounts):


			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
	Numerator for basic and diluted earnings per common share:
	(Loss) income from continuing operations		$	(1,746	)	$	3,377		$	(5,904	)	$	(16,876	)
	Income from discontinued operations			29			4,058			20,626			7,615

	Net (loss) income			(1,717	)		7,435			14,722			(9,261	)
	Less: Net loss (income) from continuing operations attributable to noncontrolling interests			202			(35	)		693			1,263
	Less: Net loss (income) from discontinued operations attributable to noncontrolling interests			9			(197	)		(889	)		(387	)

	Net (loss) income attributable to First Potomac Realty Trust			(1,506	)		7,203			14,526			(8,385	)
	Less: Dividends on preferred shares			(3,100	)		(3,100	)		(9,300	)		(8,864	)

	Net (loss) income attributable to common shareholders			(4,606	)		4,103			5,226			(17,249	)
	Less: Allocation to participating securities			(103	)		(162	)		(309	)		(468	)

	Net (loss) income attributable to common shareholders		$	(4,709	)	$	3,941		$	4,917		$	(17,717	)

	Denominator for basic and diluted earnings per common share:
	Weighted average common shares outstanding:
	Basic			57,969			50,267			54,014			50,049
	Diluted			57,969			50,346			54,014			50,049
	Basic and diluted earnings per common share:
	Loss from continuing operations		$	(0.08	)	$	—		$	(0.28	)	$	(0.49	)
	Income from discontinued operations			—			0.08			0.37			0.14

	Net (loss) income		$	(0.08	)	$	0.08		$	0.09		$	(0.35	)

	In accordance with GAAP regarding earnings per common share, the Company did not include the following potential weighted average common shares in its calculation of diluted earnings per common share as they are anti-dilutive for the periods presented (amounts in thousands):


			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
	Stock option awards			1,397			1,451			1,455			1,473
	Non-vested share awards			513			428			528			454
	Series A Preferred Shares(1)			12,183			13,067			11,613			11,816

				14,093			14,946			13,596			13,743


	(1)	The Company’s Series A Preferred Shares are only convertible into the Company’s common shares upon certain changes in control of the Company. The dilutive shares are calculated as the daily average of the face value of the Series A Preferred Shares divided by the outstanding common share price.

Rental_Property

Rental Property	9 Months Ended
Rental Property	Sep. 30, 2013
Text Block [Abstract]	'
Rental Property	'
	(4) Rental Property
	Rental property represents buildings and related improvements, net of accumulated depreciation, and developable land that are wholly-owned or owned by an entity in which the Company has a controlling interest. All of the Company’s rental properties are located within the greater Washington, D.C. region.

	Rental property consists of the following (amounts in thousands):


		September 30,			December 31,
		2013			2012
	Land and land improvements	$	293,010		$	387,047
	Buildings and improvements		876,086			1,086,694
	Construction in process		105,797			56,614
	Tenant improvements		143,666			145,910
	Furniture, fixtures and equipment		5,158			5,498

			1,423,717			1,681,763
	Less: accumulated depreciation		(205,353	)		(231,084	)

		$	1,218,364		$	1,450,679

	Development and Redevelopment Activity
	The Company constructs office buildings and/or business parks on a build-to-suit basis or with the intent to lease upon completion of construction. The Company owns developable land that can accommodate 1.5 million square feet of additional building space, of which, 0.7 million is located in the Washington, D.C. reporting segment, 0.1 million in the Maryland reporting segment, 0.6 million in the Northern Virginia reporting segment and 0.1 million in the Southern Virginia reporting segment.
	On August 4, 2011, the Company formed a joint venture with an affiliate of Perseus Realty, LLC to acquire 1005 First Street, NE in the Company’s Washington, D.C. reporting segment. The site was leased to Greyhound Lines, Inc. (“Greyhound”), which relocated its operations. Greyhound’s lease expired on August 31, 2013, at which time, the property was placed into development. The joint venture anticipates developing a mixed-used project on the 1.6 acre site, which can accommodate up to 712,000 square feet of office space. At September 30, 2013, the Company’s total investment in the development project was $46.4 million, which included the original cost basis of the property of $43.3 million.
	On December 28, 2010, the Company acquired 440 First Street, NW, a vacant eight-story office building in the Company’s Washington, D.C. reporting segment. In 2011, the Company purchased 30,000 square feet of transferable development rights for $0.3 million. In October 2013, the Company substantially completed the redevelopment of the 138,000 square foot property. At September 30, 2013, the Company’s total investment in the redevelopment project was $52.3 million, which included the original cost basis of the property of $23.6 million.
	During the third quarter of 2013, the Company did not place into service any development or redevelopment efforts.

Notes_Receivable

Notes Receivable	9 Months Ended
Notes Receivable	Sep. 30, 2013
Receivables [Abstract]	'
Notes Receivable	'
	(5) Notes Receivable
	Below is a summary of the Company’s notes receivable at September 30, 2013 (dollars in thousands):


		Balance at September 30, 2013
	Issued	Face Amount		Unamortized			Balance		Interest Rate			Property
	Issued	Face Amount		Origination Fees			Balance		Interest Rate			Property
	Dec-10	$	25,000	$	(140	)	$	24,860		12.5	%		950 F Street, NW
	Apr-11		29,940		(78	)		29,862		9	%		America’s Square

		$	54,940	$	(218	)	$	54,722



		Balance at December 31, 2012
	Issued	Face Amount		Unamortized			Balance		Interest Rate			Property
	Issued	Face Amount		Origination Fees			Balance		Interest Rate			Property
	Dec-10	$	25,000	$	(171	)	$	24,829		12.5	%	950 F Street, NW
	Apr-11		30,000		(99	)		29,901		9	%	America’s Square

		$	55,000	$	(270	)	$	54,730

	The Company recorded interest income of $1.5 million for both the three months ended September 30, 2013 and 2012 and $4.4 million for both the nine months ended September 30, 2013 and 2012 related to its notes receivable, which is included within “Interest and other income” in the Company’s consolidated statements of operations.
	The $25.0 million subordinated loan provided to the owners of 950 F Street, NW requires monthly interest-only payments to the Company. The loan matures on April 1, 2017; however, it is repayable in full on or after December 21, 2013. The $30.0 million subordinated loan provided to the owners of America’s Square is repayable in full at any time, subject to yield maintenance. The America’s Square loan matures on May 1, 2016 and required monthly interest-only payments until May 2013, at which time the loan began requiring principal and interest payments through its maturity date. The interest rate on the loan is constant throughout the life of the loan. The Company recorded income from the amortization of origination fees of $17 thousand for both the three months ended September 30, 2013 and 2012 and $52 thousand for both the nine months ended September 30, 2013 and 2012. The amortization of origination fees are recorded within “Interest and other income” in the Company’s consolidated statements of operations.

Investment_in_Affiliates

Investment in Affiliates	9 Months Ended
Investment in Affiliates	Sep. 30, 2013
Equity Method Investments And Joint Ventures [Abstract]	'
Investment in Affiliates	'
	(6) Investment in Affiliates
	The Company owns an interest in several joint ventures that own properties. The Company does not control the activities that are most significant to the joint ventures. As a result, the assets, liabilities and operating results of these noncontrolled joint ventures are not consolidated within the Company’s unaudited condensed consolidated financial statements. The Company’s investments in these joint ventures are recorded as “Investment in affiliates” in its consolidated balance sheets. The Company’s investment in affiliates consisted of the following (dollars in thousands):


			Reporting Segment		Ownership				September 30,				December 31,
			Reporting Segment		Interest				2013				2012
	Prosperity Metro Plaza		Northern Virginia			51	%		$	25,032			$	26,679
	1750 H Street, NW		Washington, D.C.			50	%			16,449				16,130
	Aviation Business Park		Maryland			50	%			5,028				4,713
	RiversPark I and II		Maryland			25	%			2,720				3,074

									$	49,229			$	50,596

	The net assets of the Company’s unconsolidated joint ventures consisted of the following (amounts in thousands):


			September 30,				December 31,
			2013				2012
	Assets:
	Rental property, net		$	194,749			$	198,411
	Cash and cash equivalents			4,215				6,224
	Other assets			16,097				17,377

	Total assets			215,061				222,012

	Liabilities:
	Mortgage loans(1)			107,155				109,427
	Other liabilities			5,469				6,687

	Total liabilities			112,624				116,114

	Net assets		$	102,437			$	105,898


	(1)	Of the total mortgage debt that encumbers the Company’s unconsolidated properties, $7.0 million is recourse to the Company. The recourse mortgage loan was scheduled to mature in September 2013; however, the Company extended the loan’s maturity date to March 2014. Management believes the fair value of the potential liability to the Company is inconsequential as the likelihood of the Company’s need to perform under the debt agreement is remote.

	The Company’s share of earnings or losses related to its unconsolidated joint ventures is recorded in its consolidated statements of operations as “Equity in (earnings) losses of affiliates.” The following table summarizes the results of operations of the Company’s unconsolidated joint ventures, which due to its varying ownership interests in the joint ventures and the varying operations of the joint ventures may or may not be reflective of the amounts recorded in its consolidated statements of operations (amounts in thousands):


			Three Months Ended								Nine Months Ended
			September 30,								September 30,
			2013				2012				2013				2012
	Total revenues		$	6,035			$	6,254			$	18,046			$	18,575
	Total operating expenses			(1,879	)			(1,883	)			(5,649	)			(5,459	)

	Net operating income			4,156				4,371				12,397				13,116
	Depreciation and amortization			(2,887	)			(3,174	)			(8,681	)			(9,510	)
	Other expenses, net			(1,091	)			(1,070	)			(3,254	)			(3,235	)

	Net income		$	178			$	127			$	462			$	371

	The Company earns various fees from several of its joint ventures, which include management fees, leasing commissions and construction management fees. The Company recognizes fees only to the extent of the third party ownership interest in its unconsolidated joint ventures. The Company recognized fees from its unconsolidated joint ventures of $0.2 million and $0.5 million for the three and nine months ended September 30, 2013, respectively, and $0.1 million and $0.3 million for the three and nine months ended September 30, 2012, respectively, which are reflected within “Tenant reimbursements and other revenues” in its consolidated statements of operations.

Discontinued_Operations

Discontinued Operations

9 Months Ended

Sep. 30, 2013

Discontinued Operations And Disposal Groups [Abstract]

Discontinued Operations

(7) Discontinued Operations

On August 15, 2013, the Company sold 4200 Tech Court, a 34,000 square foot office building located in Chantilly, Virginia for net proceeds of $3.2 million. The Company reported a gain on the sale of the property of $0.4 million in its third quarter results. On September 27, 2013, the Company sold Triangle Business Center, a four-building, 74,000 square foot business park property located in Baltimore, Maryland for net proceeds of $2.7 million. As previously disclosed, the Company recorded an impairment charge of $1.4 million on Triangle Business Center in the second quarter of 2013.

On September 24, 2013, the Company entered into a contract to sell Worman’s Mill Court, a 40,000 square foot office building located in Frederick, Maryland. Based on the anticipated sales price, the Company recorded an impairment charge of $0.5 million in the third quarter of 2013. The sale is expected to be completed in the fourth quarter of 2013. At September 30, 2013, the building met the Company’s held-for-sale criteria (described in note 2(c), Rental Property) and, therefore, the assets of the building were classified within “Assets held-for-sale” and the liabilities of the building were classified within “Accounts payable and other liabilities” in the Company’s consolidated balance sheet. The operating results of the building are reflected as discontinued operations in the Company’s consolidated statements of operations for the periods presented.

The following table is a summary of property dispositions whose operating results are reflected as discontinued operations in the Company’s consolidated statements of operations for the periods presented (dollars in thousands):

Reporting Segment

Disposition Date

Property Type

Square Feet

Worman’s Mill Court(1)

Maryland

November 2013

Office

40,099

Triangle Business Center

Maryland

9/27/13

Business Park

74,429

4200 Tech Court

Northern Virginia

8/15/13

Office

33,875

Industrial Portfolio

Various

6/18/13

Industrial

4,044,903

4212 Tech Court

Northern Virginia

6/5/13

Office

32,055

I-66 Commerce Center

Northern Virginia

5/7/13

Industrial

236,082

Owings Mills Business Park(2)

Maryland

11/7/12

Business Park

38,779

Goldenrod Lane

Maryland

5/31/12

Office

23,518

Woodlands Business Center

Maryland

5/8/12

Office

37,887

Airpark Place Business Center

Maryland

3/22/12

Business Park

82,429

(1)

The Company anticipates selling the property in the fourth quarter of 2013 and classified the property as held-for-sale at September 30, 2013; however, the Company can provide no assurances regarding the timing or pricing of the sale of the property, or that such sale will occur at all.

(2)

In November 2012, the Company sold two of the six buildings at Owings Mills Business Park.

The Company has had, and will have, no continuing involvement with any of its disposed properties subsequent to their disposal. The operations of the disposed properties were not subject to any income based taxes. The Company did not dispose of or enter into any binding agreements to sell any other properties during the nine months ended September 30, 2013 and 2012.

The following table summarizes the components of net income from discontinued operations (amounts in thousands):

Three Months Ended

Nine Months Ended

September 30,

2013

2012

2013

2012

Revenues

319

9,965

17,350

26,531

Net (loss) income, before taxes

(387

)

4,058

1,263

7,454

Gain on sale of real estate property

416

—

19,363

161

Debt

Debt	9 Months Ended
Debt	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Debt	'
	(8) Debt
	The Company’s borrowings consisted of the following (amounts in thousands):


			September 30,				December 31,
			2013				2012
	Mortgage loans, effective interest rates ranging from 4.40% to 6.63%, maturing at various dates through July 2022		$	275,974			$	418,864
	Secured term loan, effective interest rate of LIBOR plus 5.50%(1)			—				10,000
	Unsecured term loan, effective interest rates ranging from LIBOR plus 2.15% to LIBOR plus 2.30%, with staggered maturity dates ranging from July 2016 to July 2018(2)(3)(4)			300,000				300,000
	Unsecured revolving credit facility, effective interest rate of LIBOR plus 2.25%, maturing January 2015(2)(3)(4)			83,000				205,000

			$	658,974			$	933,864


	(1)	The Company repaid its $10.0 million secured term loan and its $37.5 million senior secured multi-tranche term loan facility, which was entered into in February 2013, with proceeds from its May 2013 equity offering.
	(2)	At September 30, 2013, LIBOR was 0.18%.
	(3)	Based on the Company’s leverage ratio at September 30, 2013, the applicable interest rate spread on both the unsecured revolving credit facility and the unsecured term loan tranches decreased on October 16, 2013. For more information see notes 8(b) Debt – Unsecured Term Loan, 8(c) Debt – Unsecured Revolving Credit Facility, and 8(e) Debt – Financial Covenants.
	(4)	On October 16, 2013, the Company amended and restated its unsecured revolving credit facility and unsecured term loan. For more information see notes 8(b) Debt – Unsecured Term Loan, 8(c) Debt – Unsecured Revolving Credit Facility, and 8(e) Debt – Financial Covenants.

	(a) Mortgage Loans
	The following table provides a summary of the Company’s mortgage debt at September 30, 2013 and December 31, 2012 (dollars in thousands):


	Encumbered Property		Contractual		Effective				Maturity		September 30,			December 31,
			Interest Rate		Interest				Date		2013			2012
					Rate
	Prosperity Business Center(1)		6.25%			5.75	%			January 2013	$	—		$	3,242
	Cedar Hill(2)		6.00%			6.58	%			February 2013		—			15,404
	10320 Little Patuxent Parkway(2)		6.00%			7.29	%			Feb-13		—			13,291
	1434 Crossways Blvd Building I(2)		6.25%			5.38	%			Mar-13		—			7,650
	Cloverleaf Center(3)		6.75%			6.75	%			Oct-14		—			16,595
	Mercedes Center– Note 1(3)		4.67%			6.04	%			Jan-16		—			4,677
	Mercedes Center – Note 2(3)		6.57%			6.3	%			Jan-16		—			9,498
	Linden Business Center(4)		6.01%			5.58	%			Oct-13		—			6,747
	840 First Street, NE(5)		5.18%			6.05	%			Oct-13		—			54,704
	Annapolis Business Center		5.74%			6.25	%			Jun-14		8,114			8,223
	1005 First Street, NE(6)(7)		LIBOR + 2.75%			5.8	%			Oct-14		22,000			22,000
	Jackson National Life Loan(8)		5.19%			5.19	%			Aug-15		66,400			96,132
	Hanover Business Center Building D		8.88%			6.63	%			Aug-15		288			391
	Chesterfield Business Center Buildings C,D,G and H		8.50%			6.63	%			Aug-15		772			1,036
	440 First Street, NW Construction Loan(7)(9)		LIBOR + 2.50%			5	%			May-16		21,699			—
	Gateway Centre Manassas Building I		7.35%			5.88	%			Nov-16		688			833
	Hillside Center		5.75%			4.62	%			Dec-16		13,448			13,741
	Redland Corporate Center		4.20%			4.64	%			November 2017		67,336			68,209
	Hanover Business Center Building C		7.88%			6.63	%			Dec-17		688			791
	840 First Street, NE / 500 First Street, NW(10)		5.72%			6.01	%			Jul-20		37,298			37,730
	Battlefield Corporate Center		4.26%			4.4	%			Nov-20		3,889			4,003
	Chesterfield Business Center Buildings A,B,E and F		7.45%			6.63	%			Jun-21		1,921			2,060
	Airpark Business Center		7.45%			6.63	%			Jun-21		1,048			1,123
	1211 Connecticut Avenue, NW		4.22%			4.47	%			Jul-22		30,385			30,784

						5.14	%(11)					275,974			418,864
	Unamortized fair value adjustments											(714	)		(696	)

	Total contractual principal balance										$	275,260		$	418,168


	-1	The loan was repaid at maturity with borrowings under the Company’s unsecured revolving credit facility.
	-2	The loans were repaid in February 2013 with borrowings under a $37.5 million senior secured multi-tranche term loan facility, which was subsequently repaid in May 2013 with proceeds from the Company’s May 2013 equity offering. 10320 Little Patuxent Parkway was previously referred to as the Merrill Lynch Building.
	(3)	In June 2013, the Company sold the majority of its industrial portfolio, which included Mercedes Center. The debt instrument that encumbered Mercedes Center was repaid at the time of sale. In addition, the Company used a portion of the net proceeds received from the sale of its industrial portfolio to repay the mortgage loan that encumbered Cloverleaf Center.
	-4	The loan was repaid in September 2013 with available cash.
	(5)	On September 30, 2013, the Company repaid a $53.9 million mortgage loan that encumbered 840 First Street, NE, which was scheduled to mature on October 1, 2013.
	(6)	The loan incurs interest at a variable rate of LIBOR plus a spread of 2.75% (with a floor of 5.0%) and matures in October 2014, with a one-year extension at the Company’s option.
-7	At September 30, 2013, LIBOR was 0.18%.
(8)	At September 30, 2013, the loan was secured by the following properties: Plaza 500, Van Buren Office Park, Rumsey Center, Snowden Center, Greenbrier Technology Center II and Norfolk Business Center. The terms of the loan allow the Company to substitute collateral, as long as certain debt-service coverage and loan-to-value ratios are maintained, or to prepay a portion of the loan, with a prepayment penalty, subject to a debt-service yield.
(9)	At September 30, 2013, the principal balance and the unpaid accrued interest on the 440 First Street, NW construction loan were recourse to the Company.
(10)	On September 30, 2013, the Company repaid a $53.9 million mortgage loan that encumbered 840 First Street, NE, which was scheduled to mature on October 1, 2013. Simultaneously with the repayment of the mortgage debt, the Company encumbered 840 First Street, NE with a $37.3 million mortgage loan that had previously encumbered 500 First Street, NW.
-11	Weighted average interest rate on total mortgage debt.
On September 30, 2013, the Company repaid a $53.9 million mortgage loan that encumbered 840 First Street, NE, which was scheduled to mature on October 1, 2013. 840 First Street, NE is subject to a tax protection agreement, which requires that the Company maintain a specified minimum amount of debt on the property through March 2018. As a result of this requirement, simultaneously with the repayment of the mortgage debt, the Company encumbered 840 First Street, NE with a $37.3 million mortgage loan that had previously encumbered 500 First Street, NW. The transfer of the mortgage loan did not impact any material terms of the agreement. During the third quarter of 2013, the Company incurred $0.1 million in debt extinguishment charges related to the transfer of the loan and the collateral under such loan.

Construction Loan
On June 5, 2013, the Company entered into a construction loan (the “Construction Loan”) that is collateralized by the Company’s 440 First Street, NW property, which has undergone a major redevelopment since its acquisition. The Construction Loan has a borrowing capacity of up to $43.5 million, of which the Company borrowed $21.7 million in the third quarter. The Construction Loan has a variable interest rate of LIBOR plus a spread of 2.5% and matures in May 2016, with two one-year extension options at the Company’s discretion. The Company can repay all or a portion of the Construction Loan, without penalty, at any time during the term of the loan. At September 30, 2013, per the terms of the loan agreement, the entire outstanding principal balance and all of the outstanding accrued interest was recourse to the Company. The percentage of outstanding principal balance that is recourse to the Company can be reduced upon the property achieving certain operating thresholds. As of September 30, 2013, the Company was in compliance with all the financial covenants of the Construction Loan.
(b) Unsecured Term Loan
The table below shows the outstanding balances and the interest rate of the three tranches of the $300.0 million unsecured term loan at September 30, 2013 (dollars in thousands):


		Maturity Date				Amount				Interest Rate(1)
Tranche A			Jul-16			$	60,000			LIBOR, plus 215 basis points
Tranche B			July 2017				147,500			LIBOR, plus 225 basis points
Tranche C			Jul-18				92,500			LIBOR, plus 230 basis points

						$	300,000


(1)	The interest rate spread is subject to change based on the Company’s maximum total indebtedness ratio. For more information, see note 8(e) Debt – Financial Covenants.
The term loan agreement contains various restrictive covenants substantially identical to those contained in the Company’s unsecured revolving credit facility, including with respect to liens, indebtedness, investments, distributions, mergers and asset sales. In addition, the agreement requires that the Company satisfy certain financial covenants that are also substantially identical to those contained in the Company’s unsecured revolving credit facility. The agreement also includes customary events of default, the occurrence of which, following any applicable cure period, would permit the lenders to, among other things, declare the principal, accrued interest and other obligations of the Company under the agreement to be immediately due and payable.
On October 16, 2013, the Company amended and restated the unsecured term loan, to, among other things, divide the unsecured term loan into three $100 million tranches that mature in October 2018, 2019 and 2020, which added over two years of term from the previous maturity dates set forth above. As part of the amendments, the Company reduced its LIBOR spreads to current market rates, eliminated the prepayment lock-outs, eliminated prepayment penalties associated with two tranches of the unsecured term loan, decreased the capitalization rates used to calculate gross asset value in the covenant calculations, and moved to a covenant package more closely aligned with the Company’s strategic plan. As of September 30, 2013, the Company was in compliance with all the financial covenants of the unsecured term loan, which, pursuant to the terms of the amended and restated term loan, reflect the amendments to the financial covenants and such amended covenants are applicable to the Company with respect to the quarter ended September 30, 2013. Based on the Company’s leverage ratio at September 30, 2013, the LIBOR spreads applicable to Tranche A, Tranche B and Tranche C decreased by 70 basis points, 65 basis points and 40 basis points, respectively, on October 16, 2013.
(c) Unsecured Revolving Credit Facility
During the third quarter of 2013, the Company used a $33.0 million draw under its unsecured revolving credit facility and available cash to repay a mortgage loan that encumbered 840 First Street, NE. For the three and nine months ended September 30, 2013, the Company’s weighted average borrowings under the unsecured revolving credit facility were $50.4 million and $154.9 million, respectively, with a weighted average interest rate of 2.6% and 2.8%, respectively, compared with weighted average borrowings of $227.4 million and $174.1 million for the three and nine months ended September 30, 2012, respectively. For both the three and nine months ended September 30, 2012, the Company’s unsecured revolving credit facility had a weighted average interest rate of 2.9%. At September 30, 2013, outstanding borrowings under the unsecured revolving credit facility were $83.0 million with a weighted average interest rate of 2.4%. The Company is required to pay an annual commitment fee of 0.25% based on the amount of unused capacity under the unsecured revolving credit facility.

On October 16, 2013, the Company amended and restated the unsecured revolving credit facility, to, among other things, increase commitments from $255 million to $300 million. As a result, the available capacity under the unsecured revolving credit facility was $159.2 million as of the date of this filing. The Company’s ability to borrow under the credit facility is subject to its satisfaction of certain financial and restrictive covenants. At September 30, 2013, LIBOR was 0.18% and the applicable spread on the Company’s unsecured revolving credit facility was 225 basis points. As part of the amendment discussed above, the Company reduced its LIBOR spreads to current market rates, decreased the capitalization rates used to calculate gross asset value in the covenant calculations, and moved to a covenant package more closely aligned with the Company’s strategic plan. As of September 30, 2013, the Company was in compliance with all the financial covenants of the unsecured revolving credit facility, which, pursuant to the terms of the amended and restated revolving credit facility, reflect the amendments to the financial covenants and such amended covenants are applicable to the Company with respect to the quarter ended September 30, 2013. Based on the Company’s leverage ratio at September 30, 2013, the applicable interest rate spread on the Company’s unsecured revolving credit facility decreased by 75 basis points on October 16, 2013.
(d) Interest Rate Swap Agreements
At September 30, 2013, the Company had fixed LIBOR, at a weighted average interest rate of 1.5%, on $350.0 million of its variable rate debt through twelve interest rate swap agreements. See note 9, Derivative Instruments, for more information about the Company’s interest rate swap agreements.
(e) Financial Covenants
The Company’s outstanding corporate debt agreements contain specific financial covenants that may impact future financing decisions made by the Company or may be impacted by a decline in operations. These covenants differ by debt instrument and relate to the Company’s allowable leverage, minimum tangible net worth, fixed charge coverage and other financial metrics. As of September 30, 2013, the Company was in compliance with the covenants of its unsecured term loan and unsecured revolving credit facility and any such financial covenants of its mortgage debt (including the Construction Loan), which, pursuant to the terms of the amended and restated revolving credit facility and unsecured term loan, reflect the amendments to the financial covenants and such amended covenants are applicable to the Company with respect to the quarter ended September 30, 2013.
The Company’s continued ability to borrow under the unsecured revolving credit facility is subject to compliance with financial and operating covenants, and a failure to comply with any of these covenants could result in a default under the credit facility. These debt agreements also contain cross-default provisions that would be triggered if the Company is in default under other loans, including mortgage loans, in excess of certain amounts. In the event of a default, the lenders could accelerate the timing of payments under the debt obligations and the Company may be required to repay such debt with capital from other sources, which may not be available on attractive terms, or at all, which would have a material adverse effect on the Company’s liquidity, financial condition, results of operations and ability to make distributions to our shareholders.
The Company’s unsecured revolving credit facility and unsecured term loan are subject to interest rate spreads that float based on the quarterly measurement of the Company’s maximum consolidated total indebtedness to gross asset value ratio. On October 16, 2013, the Company amended and restated its unsecured revolving credit facility and unsecured term loan. The Company increased the size of the unsecured revolving credit facility from $255 million to $300 million and extended the maturity date of the facility to October 2017, with a one-year extension at the Company’s option. The Company divided its unsecured term loan into three $100 million tranches that mature in October 2018, 2019 and 2020, which added over two years of term from the previous maturity dates. As part of the amendments, the Company reduced its LIBOR spreads to current market rates, eliminated the prepayment lock-outs for the unsecured term loan, eliminated prepayment penalties associated with two tranches of the unsecured term loan, decreased the capitalization rates used to calculate gross asset value in the covenant calculations, and moved to a covenant package more closely aligned with the Company’s strategic plan. The amendments to the unsecured revolving credit facility and unsecured term loan reduced the Company’s borrowing costs, and the Company believes such amendments put it in a stronger position to deploy capital in the future.
As a result of the Company’s leverage ratio at June 30, 2013, the applicable interest rate spread on the Company’s unsecured revolving credit facility and unsecured term loan decreased by 50 basis points and 25 basis points, respectively, on August 1, 2013. Based on the Company’s leverage ratio at September 30, 2013, the applicable interest rate spread on the unsecured revolving credit facility decreased by 75 basis points and the applicable interest rate spreads on Tranche A, Tranche B and Tranche C of the unsecured term loan decreased by 70 basis points, 65 basis points and 40 basis points, respectively, on October 16, 2013.

Derivative_Instruments

Derivative Instruments

9 Months Ended

Sep. 30, 2013

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Derivative Instruments

(9) Derivative Instruments

The Company is exposed to certain risks arising from business operations and economic factors. The Company uses derivative financial instruments to manage exposures that arise from business activities in which its future exposure to interest rate fluctuations is unknown. The objective in the use of an interest rate derivative is to add stability to interest expenses and manage exposure to interest rate changes. The Company does not use derivatives for trading or speculative purposes and intends to enter into derivative agreements only with counterparties that it believes have a strong credit rating to mitigate the risk of counterparty default or insolvency. No hedging activity can completely insulate the Company from the risks associated with changes in interest rates. Moreover, interest rate hedging could fail to protect the Company or adversely affect it because, among other things:

•

available interest rate hedging may not correspond directly with the interest rate risk for which the Company seeks protection;

•

the duration of the hedge may not match the duration of the related liability;

•

the party owing money in the hedging transaction may default on its obligation to pay; and

•

the credit quality of the party owing money on the hedge may be downgraded to such an extent that it impairs the Company’s ability to sell or assign its side of the hedging transaction.

The Company enters into interest rate swap agreements to hedge its exposure on its variable rate debt against fluctuations in prevailing interest rates. The interest rate swap agreements fix LIBOR to a specified interest rate; however, the swap agreements do not affect the contractual spreads associated with each variable debt instrument’s applicable interest rate.

At September 30, 2013, the Company had fixed LIBOR at a weighted average interest rate of 1.5% on $350.0 million of its variable rate debt through twelve interest rate swap agreements that are summarized below (dollars in thousands):

Effective Date

Maturity Date

Notional

Interest Rate

Fixed LIBOR

Amount

Contractual

Interest Rate

Component

Jan-11

January 2014

50,000

LIBOR

1.474

Jul-11

Jul-16

35,000

LIBOR

1.754

Jul-11

Jul-16

25,000

LIBOR

1.763

Jul-11

Jul-17

30,000

LIBOR

2.093

Jul-11

Jul-17

30,000

LIBOR

2.093

Sep-11

Jul-18

30,000

LIBOR

1.66

Jan-12

Jul-18

25,000

LIBOR

1.394

Mar-12

Jul-17

25,000

LIBOR

1.129

Mar-12

Jul-17

12,500

LIBOR

1.129

Mar-12

Jul-18

12,500

LIBOR

1.383

Jun-12

Jul-17

50,000

LIBOR

0.955

Jun-12

Jul-18

25,000

LIBOR

1.135

Total/Weighted Average

350,000

1.5

The Company’s interest rate swap agreements are designated as cash flow hedges and the Company records the effective portion of any unrealized gains associated with the change in fair value of the swap agreements within “Accumulated other comprehensive loss” and “Prepaid expenses and other assets” and the effective portion of any unrealized losses within “Accumulated other comprehensive loss” and “Accounts payable and other liabilities” on its consolidated balance sheets. The Company records its proportionate share of any unrealized gains or losses on its cash flow hedges associated with its unconsolidated joint ventures within “Accumulated other comprehensive loss” and “Investment in affiliates” on its consolidated balance sheets. The Company records any gains or losses incurred as a result of each interest rate swap agreement’s fixed rate deviating from its respective loan’s contractual rate within “Interest expense” in its consolidated statements of operations. The Company did not have any material ineffectiveness associated with its cash flow hedges during the three and nine months ended September 30, 2013 and 2012.

Amounts reported in accumulated other comprehensive loss related to derivatives will be reclassified to “Interest expense” on the Company’s consolidated statements of operations as interest payments are made on the Company’s variable-rate debt. The Company reclassified accumulated other comprehensive loss as an increase to interest expense of $1.2 million and $1.1 million for the three months ended September 30, 2013 and 2012, respectively, and $3.5 million and $3.0 million for the nine months ended September 30, 2013 and 2012, respectively. As of September 30, 2013, the Company estimates that $3.8 million of its accumulated other comprehensive loss will be reclassified as an increase to interest expense over the following twelve months.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	(10) Fair Value Measurements
	The Company applies GAAP that outlines a valuation framework and creates a fair value hierarchy, which distinguishes between assumptions based on market data (observable inputs) and a reporting entity’s own assumptions about market data (unobservable inputs). The required disclosures increase the consistency and comparability of fair value measurements and the related disclosures. Fair value is identified, under the standard, as the price that would be received to sell an asset or paid to transfer a liability between willing third parties at the measurement date (an exit price). In accordance with GAAP, certain assets and liabilities must be measured at fair value, and the Company provides the necessary disclosures that are required for items measured at fair value as outlined in the accounting requirements regarding fair value.
	Financial assets and liabilities, as well as those non-financial assets and liabilities requiring fair value measurement, are measured using inputs from three levels of the fair value hierarchy.
	The three levels are as follows:
	Level 1—Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. An active market is defined as a market in which transactions for the assets or liabilities occur with sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2—Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active (markets with few transactions), inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs derived principally from or corroborated by observable market data correlation or other means (market corroborated inputs).
	Level 3—Unobservable inputs, only used to the extent that observable inputs are not available, reflect the Company’s assumptions about the pricing of an asset or liability.
	In accordance with accounting provisions and the fair value hierarchy described above, the following table shows the fair value of the Company’s consolidated assets and liabilities that are measured on a non-recurring and recurring basis as of September 30, 2013 and December 31, 2012 (amounts in thousands):


			Balance at		Level 1		Level 2		Level 3
			September 30, 2013		Level 1		Level 2		Level 3
	Non-recurring Measurements:
	Impaired real estate assets		$	3,297	$	—	$	3,297	$	—
	Recurring Measurements:
	Derivative instrument-swap assets			231		—		231		—
	Derivative instrument-swap liabilities			5,629		—		5,629		—


			Balance at		Level 1		Level 2		Level 3
			December 31, 2012		Level 1		Level 2		Level 3
	Non-recurring Measurements:
	Impaired real estate assets		$	15,955	$	—	$	15,955	$	—
	Recurring Measurements:
	Derivative instrument-swap liabilities			11,464		—		11,464		—
	With the exception of its contingent consideration obligations, which totaled $0.7 million and $2.3 million at September 30, 2013 and December 31, 2012, respectively, the Company did not re-measure or complete any transactions involving non-financial assets or non-financial liabilities that are measured at fair value on a recurring basis during the three and nine months ended September 30, 2013 and 2012. Also, no transfers into or out of fair value measurement levels for assets or liabilities that are measured on a recurring basis occurred during the nine months ended September 30, 2013 and 2012.

	Impairment of Real Estate Assets
	The Company regularly reviews market conditions for possible impairment of a property’s carrying value. When circumstances such as adverse market conditions, changes in management’s intended holding period or potential sale to a third party indicate a possible impairment of a property, an impairment analysis is performed.
	During the third quarter of 2013, the Company was in negotiations with a buyer to sell its Worman’s Mill Court property, which is located in its Maryland reporting segment. Based on the anticipated sales price, the Company recorded an impairment charge of $0.5 million in the third quarter of 2013. The Company signed a contract to sell the property in September 2013 and anticipates the property will be sold in the fourth quarter of 2013. However, the Company can provide no assurances regarding the timing or pricing of the sale of the Worman’s Mill Court property, or that such sale will occur at all.
	In November 2012, the Company sold two of the six buildings at Owings Mills Business Park, which is located in the Company’s Maryland reporting segment. Based on the anticipated sales price of the two buildings that were subsequently sold, the Company recorded an impairment charge of $2.4 million on the four buildings that remained in the Company’s portfolio in the first quarter of 2012.
	Interest Rate Derivatives
	The interest rate derivatives are fair valued based on prevailing market yield curves on the measurement date and also take into consideration the credit valuation adjustment of the counter-party in determining the fair value of counterparty credit risk associated with the Company’s interest rate swap agreements. The Company uses a third party to assist in valuing its interest rate swap agreements. A daily “snapshot” of the market is taken to obtain close of business rates. The snapshot includes over 7,500 rates including LIBOR fixings, Eurodollar futures, swap rates, exchange rates, treasuries, etc. This market data is obtained via direct feeds from Bloomberg and Reuters and from Inter-Dealer Brokers. The selected rates are compared to their historical values. Any rate that has changed by more than normal mean and related standard deviation would be considered an outlier and flagged for further investigation. The rates are then compiled through a valuation process that generates daily valuations, which are used to value the Company’s interest rate swap agreements. The Company’s interest rate swap derivatives are effective cash flow hedges and the effective portion of the change in fair value is recorded in the equity section of the Company’s consolidated balance sheets as “Accumulated other comprehensive loss.”
	Financial Instruments
	The carrying amounts of cash equivalents, accounts and other receivables, accounts payable and other liabilities, with the exception of any items listed above, approximate their fair values due to their short-term maturities. The Company determines the fair value of its notes receivable and debt instruments by discounting future contractual principal and interest payments using prevailing market rates for securities with similar terms and characteristics at the balance sheet date. The Company deems the fair value measurement of its debt instruments as a Level 2 measurement as the Company uses quoted interest rates for similar debt instruments to value its debt instruments. The Company also uses quoted market interest rates to value its notes receivable, which it considers a Level 2 measurement as it does not believe notes receivable trade in an active market.
	The carrying amount and estimated fair value of the Company’s notes receivable and debt instruments at September 30, 2013 and December 31, 2012 are as follows (amounts in thousands):


			September 30, 2013				December 31, 2012
			Carrying		Fair		Carrying		Fair
			Value		Value		Value		Value
	Financial Assets:
	Notes receivable(1)		$	54,722	$	54,940	$	54,730	$	55,000

	Financial Liabilities:
	Mortgage debt		$	275,974	$	267,606	$	418,864	$	427,851
	Secured term loan(2)			—		—		10,000		10,000
	Unsecured term loan			300,000		309,723		300,000		300,000
	Unsecured revolving credit facility			83,000		85,436		205,000		205,000

	Total		$	658,974	$	662,765	$	933,864	$	942,851


	(1)	The face value of the Company’s notes receivable was $54.9 million and $55.0 million at September 30, 2013 and December 31, 2012.
	(2)	The Company repaid its $10.0 million secured term loan with net proceeds from an equity offering.

Equity

Equity	9 Months Ended
Equity	Sep. 30, 2013
Equity [Abstract]	'
Equity	'
	(11) Equity
	On July 23, 2013, the Company declared a dividend of $0.15 per common share, equating to an annualized dividend of $0.60 per common share. The dividend was paid on August 15, 2013 to common shareholders of record as of August 6, 2013. The Company also declared a dividend of $0.484375 per share on its Series A Preferred Shares. The dividend was paid on August 15, 2013 to preferred shareholders of record as of August 6, 2013.
	On October 22, 2013, the Company declared a dividend of $0.15 per common share, equating to an annualized dividend of $0.60 per common share. The dividend will be paid on November 15, 2013 to common shareholders of record as of November 6, 2013. The Company also declared a dividend of $0.484375 per share on its Series A Preferred Shares. The dividend will be paid on November 15, 2013 to preferred shareholders of record as of November 6, 2013. Dividends on all non-vested share awards are recorded as a reduction of shareholders’ equity. For each dividend paid by the Company on its common and preferred shares, the Operating Partnership distributes an equivalent distribution on its common and preferred Operating Partnership units, respectively.
	The Company’s unsecured revolving credit facility, unsecured term loan and the Construction Loan contain certain restrictions that include, among other things, requirements to maintain specified coverage ratios and other financial covenants, which may limit the Company’s ability to make distributions to its common and preferred shareholders. Further, distributions with respect to the Company’s common shares are subject to its ability to first satisfy its obligations to pay distributions to the holders of its Series A Preferred Shares.
	As a result of the redemption feature of the Operating Partnership units, the noncontrolling interests associated with the Operating Partnership are recorded outside of permanent equity. The Company’s equity and redeemable noncontrolling interests are as follows (amounts in thousands):


		First			Non-redeemable			Total			Redeemable
		Potomac			noncontrolling			Equity			noncontrolling
		Realty Trust			interests						interests
	Balance at December 31, 2012	$	658,765		$	3,728		$	662,493		$	34,367
	Net income (loss)		14,526			(20	)		14,506			216
	Changes in ownership, net		107,836			249			108,085			273
	Distributions to owners		(33,428	)		—			(33,428	)		(1,168	)
	Other comprehensive income		5,767			—			5,767			284

	Balance at September 30, 2013	$	753,466		$	3,957		$	757,423		$	33,972



		First			Non-redeemable			Total			Redeemable
		Potomac			noncontrolling			Equity			noncontrolling
		Realty Trust			interests						interests
	Balance at December 31, 2011	$	672,246		$	4,245		$	676,491		$	39,981
	Net (loss) income		(8,385	)		68			(8,317	)		(944	)
	Changes in ownership, net		49,846			8			49,854			(1,697	)
	Distributions to owners		(38,943	)		—			(38,943	)		(1,639	)
	Other comprehensive loss		(6,088	)		—			(6,088	)		(318	)

	Balance at September 30, 2012	$	668,676		$	4,321		$	672,997		$	35,383

	A summary of the Company’s accumulated other comprehensive loss is as follows (amounts in thousands):


		2013			2012
	Beginning balance at January1,	$	(10,917	)	$	(5,849	)
	Net unrealized gain (loss) on derivative instruments		6,051			(6,406	)
	Net (gain) loss attributable to noncontrolling interests		(284	)		318

	Ending balance at September 30,	$	(5,150	)	$	(11,937	)

Noncontrolling_Interests

Noncontrolling Interests

9 Months Ended

Sep. 30, 2013

Noncontrolling Interest [Abstract]

Noncontrolling Interests

(12) Noncontrolling Interests

(a) Noncontrolling Interests in the Operating Partnership

Noncontrolling interests relate to the common interests in the Operating Partnership not owned by the Company. Interests in the Operating Partnership are owned by limited partners who contributed buildings and other assets to the Operating Partnership in exchange for common Operating Partnership units. Limited partners have the right to tender their units for redemption in exchange for, at the Company’s option, common shares of the Company on a one-for-one basis or cash based on the fair value of the Company’s common shares at the date of redemption. Unitholders receive a distribution per unit equivalent to the dividend per common share. Differences between amounts paid to redeem noncontrolling interests and their carrying values are charged or credited to equity. As a result of the redemption feature of the Operating Partnership units, the noncontrolling interests are recorded outside of permanent equity.

Noncontrolling interests are presented at the greater of their fair value or their cost basis, which is comprised of their fair value at issuance, subsequently adjusted for the noncontrolling interests’ share of net income or losses available to common shareholders, other comprehensive income or losses, distributions received or additional contributions. The Company accounts for issuances of common Operating Partnership units individually, which could result in some portion of its noncontrolling interests being carried at fair value with the remainder being carried at historical cost. Based on the closing share price of the Company’s common stock at September 30, 2013, the cost to acquire, through cash purchase or issuance of the Company’s common shares, all of the outstanding common Operating Partnership units not owned by the Company would be approximately $32.6 million. At September 30, 2013, the Company recorded an adjustment of $3.9 million to present certain common Operating Partnership units at the greater of their carrying value or redemption value.

At December 31, 2012, 2,598,259 of the total common Operating Partnership units, or 4.8%, were not owned by the Company. In May 2013, the Company issued 7,475,000 common shares, which resulted in the Operating Partnership issuing an equivalent number of common Operating Partnership units. During the nine months ended September 30, 2013, 6,718 common Operating Partnership units were redeemed with available cash. As a result, 2,591,541 of the total common Operating Partnership units, or 4.2%, were not owned by the Company at September 30, 2013. There were no common Operating Partnership units redeemed for common shares during the nine months ended September 30, 2013.

(b) Noncontrolling Interests in the Consolidated Partnerships

When the Company is deemed to have a controlling interest in a partially-owned entity, it will consolidate all of the entity’s assets, liabilities and operating results within its condensed consolidated financial statements. The net assets contributed to the consolidated entity by the third party, if any, will be reflected within permanent equity in the Company’s consolidated balance sheets to the extent they are not mandatorily redeemable. The amount will be recorded based on the third party’s initial investment in the consolidated entity and will be adjusted to reflect the third party’s share of earnings or losses in the consolidated entity and any distributions received or additional contributions made by the third party. The earnings or losses from the entity attributable to the third party are recorded as a component of “Net loss (income) attributable to noncontrolling interests” in the Company’s consolidated statements of operations.

At September 30, 2013, the Company’s consolidated joint ventures had a controlling interest in the following properties:

Property

Acquisition Date

Reporting Segment

First Pot

Square

omac

Footage

Controlling

Interest

1005 First Street, NE

August 2011

Washington, D.C.

—

(1)

Redland Corporate Center

November 2010

Maryland

349,267

(1)

The property was placed into development on September 1, 2013.

ShareBased_Compensation

Share-Based Compensation	9 Months Ended
Share-Based Compensation	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Share-Based Compensation	'
	(13) Share-Based Compensation
	The Company records costs related to its share-based compensation based on the grant-date fair value calculated in accordance with GAAP. The Company recognizes share-based compensation costs on a straight-line basis over the requisite service period for each award and these costs are recorded within “General and administrative expense” or “Property operating expense” in the Company’s consolidated statements of operations based on the employee’s job function.

	Non-Vested Share Awards
	The Company issues non-vested common share awards that either vest over a specific time period that is identified at the time of issuance or vest upon the achievement of specific performance goals that are identified at the time of issuance. The Company issues new common shares, subject to restrictions, upon each grant of non-vested common share awards. In July 2013, the Company’s Board of Trustees increased the size of the Board and appointed a new non-employee trustee. On July 29, 2013, the Company granted 3,210 non-vested common shares to the new trustee. The non-vested common shares will vest on the earlier of May 22, 2014 or the date of the 2014 annual meeting of shareholders of the Company, subject to continued service by the trustee until that date. The fair value of the award was determined based on the share price of the underlying common shares on the date of issuance.
	As previously disclosed on the Company’s Current Report on Form 8-K filed on September 6, 2013, in September 2013, the Company provided notice to its then-Chief Operating Officer that he would no longer serve as the Company’s Chief Operating Officer and his last day of employment with the Company would be October 3, 2013. Pursuant to the former officer’s employment agreement dated October 8, 2003, as amended (the “Employment Agreement”), all of the former officer’s non-vested restricted share awards, which totaled 130,464 restricted shares, vested on October 3, 2013, his date of separation. The Company incurred $1.2 million of expense related to the accelerated vesting of the restricted share awards. Also, pursuant to the Employment Agreement, the former officer will receive an aggregate of $0.6 million in salary and incentive bonus that will be paid ratably over the next year. The officer ceased to perform his duties to the Company in September 2013 and, as a result, the Company recognized $1.8 million of personnel separation costs in the third quarter of 2013, which is recorded in “General and administrative expense” in the Company’s consolidated statements of operations for the three and nine months ended September 30, 2013.
	The Company recognized $1.9 million and $3.2 million of compensation expense associated with its non-vested share awards during the three and nine months ended September 30, 2013, respectively, and $0.7 million and $1.9 million during the three and nine months ended September 30, 2012, respectively. Compensation expense associated with its non-vested shares for the three and nine months ended September 30, 2013 included $1.2 million of expense related to the accelerated vesting of the restricted shares associated with the departure of a former officer (as discussed above). Dividends on all non-vested share awards are recorded as a reduction of equity. The Company applies the two-class method for determining EPS as its outstanding non-vested shares with non-forfeitable dividend rights are considered participating securities. The Company’s excess of dividends over earnings related to participating securities are shown as a reduction in net (loss) income attributable to common shareholders in the Company’s computation of EPS.

Segment_Information

Segment Information	9 Months Ended
Segment Information	Sep. 30, 2013
Segment Reporting [Abstract]	'
Segment Information	'
	(14) Segment Information
	The Company’s reportable segments consist of four distinct reporting and operational segments within the greater Washington, D.C. region in which it operates: Maryland, Washington, D.C., Northern Virginia and Southern Virginia. The Company evaluates the performance of its segments based on the operating results of the properties located within each segment, which excludes large non-recurring gains and losses, gains from sale of real estate assets, interest expense, general and administrative costs, acquisition costs or any other indirect corporate expense to the segments. In addition, the segments do not have significant non-cash items other than straight-line and deferred market rent amortization reported in their operating results. There are no inter-segment sales or transfers recorded between segments.

	The results of operations for the Company’s four reporting segments for the three and nine months ended September 30, 2013 and 2012 are as follows (dollars in thousands):


			Three Months Ended September 30, 2013
			Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
	Number of buildings			3	(1)			53				51				38				145
	Square feet			502,690	(1)			2,544,481				3,085,740				2,852,240				8,985,151
	Total revenues		$	7,151			$	11,607			$	13,231			$	8,848			$	40,837
	Property operating expense			(1,779	)			(3,034	)			(3,088	)			(2,977	)			(10,878	)
	Real estate taxes and insurance			(1,151	)			(1,015	)			(1,372	)			(702	)			(4,240	)

	Total property operating income		$	4,221			$	7,558			$	8,771			$	5,169			$	25,719

	Depreciation and amortization expense																			(14,812	)
	General and administrative																			(6,346	)
	Acquisition costs																			(173	)
	Other expenses, net																			(6,134	)
	Income from discontinued operations																			29

	Net loss																		$	(1,717	)

	Capital expenditures(2)		$	4,758			$	2,662			$	2,798			$	1,979			$	12,609



			Three Months Ended September 30, 2012
			Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
	Number of buildings			4	(1)			64				55				57				180
	Square feet			531,714	(1)			3,816,878				3,655,536				5,649,203				13,653,331
	Total revenues		$	6,977			$	11,404			$	11,859			$	8,546			$	38,786
	Property operating expense			(1,388	)			(2,910	)			(3,076	)			(2,661	)			(10,035	)
	Real estate taxes and insurance			(935	)			(877	)			(1,269	)			(660	)			(3,741	)

	Total property operating income		$	4,654			$	7,617			$	7,514			$	5,225				25,010

	Depreciation and amortization expense																			(14,144	)
	General and administrative																			(5,645	)
	Acquisition costs																			(8	)
	Impairment of real estate assets																			(496	)
	Contingent consideration related to acquisition of property																			(112	)
	Other expenses, net																			(5,532	)
	Benefit from income taxes																			4,304
	Income from discontinued operations																			4,058

	Net income																		$	7,435

	Capital expenditures(2)		$	3,836			$	3,328			$	2,877			$	3,214			$	13,429



			Nine Months Ended September 30, 2013
			Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
	Total revenues		$	22,307			$	34,982			$	38,589			$	26,093			$	121,971
	Property operating expense			(5,408	)			(8,650	)			(9,222	)			(8,249	)			(31,529	)
	Real estate taxes and insurance			(3,746	)			(3,029	)			(4,302	)			(2,027	)			(13,104	)

	Total property operating income		$	13,153			$	23,303			$	25,065			$	15,817				77,338

	Depreciation and amortization expense																			(43,891	)
	General and administrative																			(16,598	)
Acquisition costs																			(173	)
Contingent consideration related to acquisition of property																			(75	)
Other expenses, net																			(22,505	)
Income from discontinued operations																			20,626

Net income																		$	14,722

Total assets(3)(4)		$	334,427			$	406,789			$	426,839			$	230,390			$	1,511,283

Capital expenditures(2)		$	17,543			$	10,597			$	11,100			$	7,513			$	47,729


		Nine Months Ended September 30, 2012
		Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
Total revenues		$	20,968			$	36,007			$	35,245			$	25,054			$	117,274
Property operating expense			(3,842	)			(8,065	)			(8,477	)			(7,313	)			(27,697	)
Real estate taxes and insurance			(2,945	)			(3,497	)			(3,799	)			(2,012	)			(12,253	)

Total property operating income		$	14,181			$	24,445			$	22,969			$	15,729				77,324

Depreciation and amortization expense																			(41,247	)
General and administrative																			(17,787	)
Acquisition costs																			(49	)
Impairment of real estate assets																			(2,444	)
Contingent consideration related to acquisition of property																			(112	)
Other expenses, net																			(36,703	)
Benefit from income taxes																			4,142
Income from discontinued operations																			7,615

Net loss																		$	(9,261	)

Total assets(3)(4)		$	313,513			$	497,966			$	459,153			$	365,687			$	1,714,237

Capital expenditures(2)		$	5,541			$	6,359			$	15,354			$	10,050			$	48,418


-1	Excludes 1005 First Street, NE, which was place in development in the third quarter of 2013 and 440 First Street, NW, which has been in redevelopment since its acquisition in December 2010.
(2)	Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $412 and $174 for the three months ended September 30, 2013 and 2012, respectively, and $976 and $1,114 for the nine months ended September 30, 2013 and 2012, respectively.
(3)	Total assets include the Company’s investment in properties that are owned through joint ventures that are not consolidated within the Company’s condensed consolidated financial statements. For more information on the Company’s unconsolidated investments, including location within the Company’s reportable segments, see note 6, Investment in Affiliates.
(4)	Corporate assets not allocated to any of our reportable segments totaled $112,838 and $77,918 at September 30, 2013 and 2012, respectively.

Subsequent_Event

Subsequent Event	9 Months Ended
Subsequent Event	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent Event	'
	(15) Subsequent Event
	On October 1, 2013, the Company acquired 540 Gaither Road (Redland I), a six-story, 134,000 square foot office building in Rockville, Maryland, for $30.0 million. The property is located within Redland Corporate Center, which is comprised of three multi-story, office buildings totaling 483,000 square feet. In late 2010, the Company acquired a 97% interest in Redland II and III through a joint venture with Perseus Realty, LLC. The newly acquired property is 100% leased to the Department of Health and Human Services (HHS) through early 2018. The acquisition was funded with the $28.2 million of proceeds from the sale of its industrial portfolio in June 2013 that was previously placed with a qualified intermediary to facilitate a tax-free exchange, as well as available cash.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Principles of Consolidation	'
	(a) Principles of Consolidation
	The unaudited condensed consolidated financial statements of the Company include the accounts of the Company, the Operating Partnership and the subsidiaries in which the Company or Operating Partnership has a controlling interest, which includes First Potomac Management LLC, a wholly-owned subsidiary that manages the majority of the Company’s properties. All intercompany balances and transactions have been eliminated in consolidation.
	The Company has condensed or omitted certain information and note disclosures normally included in financial statements presented in accordance with U.S. generally accepted accounting principles (“GAAP”) in the accompanying unaudited condensed consolidated financial statements. The Company believes the disclosures made are adequate to prevent the information presented from being misleading. However, the unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s annual report on Form 10-K for the year ended December 31, 2012 and as updated from time to time in other filings with the U.S. Securities and Exchange Commission (the “SEC”).
	In the Company’s opinion, the accompanying unaudited condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments and accruals necessary to present fairly the Company’s financial position as of September 30, 2013, the results of its operations and its comprehensive (loss) income for the three and nine months ended September 30, 2013 and 2012 and its cash flows for the nine months ended September 30, 2013 and 2012. Interim results are not necessarily indicative of full-year performance due, in part, to the timing of transactions and the impact of acquisitions and dispositions throughout the year as well as the seasonality of certain operating expenses such as utilities expense and snow and ice removal costs.
Use of Estimates	'
	(b) Use of Estimates
	The preparation of condensed consolidated financial statements in conformity with GAAP requires management of the Company to make a number of estimates and assumptions relating to the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the period. Estimates include the amount of accounts receivable that may be uncollectible; recoverability of notes receivable, future cash flows, discount and capitalization rate assumptions used to fair value acquired properties and to test impairment of certain long-lived assets and goodwill; derivative valuations; market lease rates, lease-up periods, leasing and tenant improvement costs used to fair value intangible assets acquired and probability weighted cash flow analysis used to fair value contingent liabilities. Actual results could differ from those estimates.
Rental Property	'
	(c) Rental Property
	Rental property is initially recorded at fair value, if acquired in a business combination, or initial cost when constructed or acquired in an asset purchase, less accumulated depreciation and, when appropriate, impairment losses. Improvements and replacements are capitalized at cost when they extend the useful life, increase capacity or improve the efficiency of the asset. Repairs and maintenance are charged to expense when incurred. Depreciation and amortization are recorded on a straight-line basis over the estimated useful lives of the assets. The estimated useful lives of the Company’s assets, by class, are as follows:


	Buildings	39 years
	Building improvements	5 to 20 years
	Furniture, fixtures and equipment	5 to 15 years
	Lease related intangible assets	The term of the related lease
	Tenant improvements	Shorter of the useful life of the asset or the term of the related lease
	The Company regularly reviews market conditions for possible impairment of a property’s carrying value. When circumstances such as adverse market conditions, changes in management’s intended holding period or potential sale to a third party indicate a possible impairment of the fair value of a property, an impairment analysis is performed. The Company assesses potential impairments based on an estimate of the future undiscounted cash flows (excluding interest charges) expected to result from the property’s use and eventual disposition. This estimate is based on projections of future revenues, expenses, capital improvement costs, expected holding periods and capitalization rates. These cash flows consider factors such as expected market trends and leasing prospects, as well as the effects of leasing demand, competition and other factors. If impairment exists due to the inability to recover the carrying value of a real estate investment based on forecasted undiscounted cash flows, an impairment loss is recorded to the extent that the carrying value exceeds the estimated fair value of the property. The Company is required to make estimates as to whether there are impairments in the carrying values of its investments in real estate. Further, the Company will record an impairment loss if it expects to dispose of a property, in the near term, at a price below carrying value. In such an event, the Company will record an impairment loss based on the difference between a property’s carrying value and its projected sales price less any estimated costs to sell.
	The Company will classify a building as held-for-sale in accordance with GAAP in the period in which it has made the decision to dispose of the building, the Company’s Board of Trustees or a designated delegate has approved the sale, there is a high likelihood a binding agreement to purchase the property will be signed under which the buyer will be required to commit a significant amount of nonrefundable cash and no significant financing contingencies exist that could cause the transaction not to be completed in a timely manner. If these criteria are met, the Company will cease depreciation of the asset. The Company will classify any impairment loss, together with the building’s operating results, as discontinued operations in its consolidated statements of operations for all periods presented and classify the assets and related liabilities as held-for-sale in its consolidated balance sheets in the period the held-for-sale criteria are met. Interest expense is reclassified to discontinued operations only to the extent the held-for-sale property is secured by specific mortgage debt and the mortgage debt will not be assigned to another property owned by the Company after the disposition.
	The Company recognizes the fair value, if sufficient information exists to reasonably estimate the fair value, of any liability for conditional asset retirement obligations when incurred, which is generally upon acquisition, construction, development or redevelopment and/or through the normal operation of the asset.

	The Company capitalizes interest costs incurred on qualifying expenditures for real estate assets under development or redevelopment, which include its investment in assets owned through unconsolidated joint ventures that are under development or redevelopment, while being readied for their intended use in accordance with accounting requirements regarding capitalization of interest. The Company will capitalize interest when qualifying expenditures for the asset have been made, activities necessary to get the asset ready for its intended use are in progress and interest costs are being incurred. Capitalized interest also includes interest associated with expenditures incurred to acquire developable land while development activities are in progress. The Company also capitalizes direct compensation costs of the Company’s construction personnel who manage the development and redevelopment projects, but only to the extent the employee’s time can be allocated to a project. Any portion of construction management costs not directly attributable to a specific project are recognized as general and administrative expense in the period incurred. The Company does not capitalize any other general administrative costs such as office supplies, office rent expense or an overhead allocation to its development or redevelopment projects. Capitalized compensation costs were immaterial for the three and nine months ended September 30, 2013 and 2012. Capitalization of interest will end when the asset is substantially complete and ready for its intended use, but no later than one year from completion of major construction activity, if the property is not occupied. The Company will also place redevelopment and development assets into service at this time and commence depreciation upon the substantial completion of tenant improvements and the recognition of revenue. Capitalized interest is depreciated over the useful life of the underlying assets, commencing when those assets are placed into service.
Notes Receivable	'
	(d) Notes Receivable
	The Company provides loans to the owners of real estate properties, which can be collateralized by interest in the real estate property. The Company records these loans as “Notes receivable, net” in its consolidated balance sheets. The loans are recorded net of any discount or issuance costs, which are amortized over the life of the respective note receivable using the effective interest method. The Company records interest earned from notes receivable and amortization of any discount or issuance costs within “Interest and other income” in its consolidated statements of operations.
	The Company will establish a provision for anticipated credit losses associated with its notes receivable when it anticipates that it may be unable to collect any contractually due amounts. This determination is based upon such factors as delinquencies, loss experience, collateral quality and current economic or borrower conditions. The Company’s collectability of its notes receivable may be adversely impacted by the financial stability of the Washington, D.C. region and the ability of its underlying assets to keep current tenants or attract new tenants. Estimated losses are recorded as a charge to earnings to establish an allowance for credit losses that the Company estimates to be adequate based on these factors. Based on the review of the above criteria, the Company did not record an allowance for credit losses for its notes receivable during the three and nine months ended September 30, 2013 and 2012.
Reclassifications	'
	(e) Reclassifications
	Certain prior year amounts have been reclassified to conform to the current year presentation, primarily as a result of reclassifying the operating results of several properties as discontinued operations. For more information, see note 7, Discontinued Operations.
Application of New Accounting Standards	'
	(f) Application of New Accounting Standards
	In January 2013, the FASB issued Accounting Standards Update 2013-02, Reporting of Amounts Reclassified Out of Accumulated Comprehensive Income (“ASU 2013-02”), which requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income. For other amounts that are not required under GAAP to be reclassified in their entirety to net income within the same reporting period, an entity is required to cross-reference other disclosures that provide additional detail about the reclassified amounts. The Company adopted the provisions of ASU 2013-02 on January 1, 2013, and the adoption of this update did not have a significant impact on its condensed consolidated financial statements or notes thereto.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	9 Months Ended
Summary of Significant Accounting Policies (Tables)	Sep. 30, 2013
Accounting Policies [Abstract]	'
Estimated Useful Lives of Company's Assets, by Class	'
	The estimated useful lives of the Company’s assets, by class, are as follows:


		Buildings	39 years
		Building improvements	5 to 20 years
		Furniture, fixtures and equipment	5 to 15 years
		Lease related intangible assets	The term of the related lease
		Tenant improvements	Shorter of the useful life of the asset or the term of the related lease

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	9 Months Ended
Earnings Per Common Share (Tables)	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Computation of Company's Basic and Diluted Earnings Per Share	'
	The following table sets forth the computation of the Company’s basic and diluted earnings per common share (amounts in thousands, except per share amounts):


			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
	Numerator for basic and diluted earnings per common share:
	(Loss) income from continuing operations		$	(1,746	)	$	3,377		$	(5,904	)	$	(16,876	)
	Income from discontinued operations			29			4,058			20,626			7,615

	Net (loss) income			(1,717	)		7,435			14,722			(9,261	)
	Less: Net loss (income) from continuing operations attributable to noncontrolling interests			202			(35	)		693			1,263
	Less: Net loss (income) from discontinued operations attributable to noncontrolling interests			9			(197	)		(889	)		(387	)

	Net (loss) income attributable to First Potomac Realty Trust			(1,506	)		7,203			14,526			(8,385	)
	Less: Dividends on preferred shares			(3,100	)		(3,100	)		(9,300	)		(8,864	)

	Net (loss) income attributable to common shareholders			(4,606	)		4,103			5,226			(17,249	)
	Less: Allocation to participating securities			(103	)		(162	)		(309	)		(468	)

	Net (loss) income attributable to common shareholders		$	(4,709	)	$	3,941		$	4,917		$	(17,717	)

	Denominator for basic and diluted earnings per common share:
	Weighted average common shares outstanding:
	Basic			57,969			50,267			54,014			50,049
	Diluted			57,969			50,346			54,014			50,049
	Basic and diluted earnings per common share:
	Loss from continuing operations		$	(0.08	)	$	—		$	(0.28	)	$	(0.49	)
	Income from discontinued operations			—			0.08			0.37			0.14

	Net (loss) income		$	(0.08	)	$	0.08		$	0.09		$	(0.35	)

Anti-Dilutive Shares Not Included in Calculation of Diluted Earnings Per Share	'
	In accordance with GAAP regarding earnings per common share, the Company did not include the following potential weighted average common shares in its calculation of diluted earnings per common share as they are anti-dilutive for the periods presented (amounts in thousands):


			Three Months Ended						Nine Months Ended
			September 30,						September 30,
			2013			2012			2013			2012
	Stock option awards			1,397			1,451			1,455			1,473
	Non-vested share awards			513			428			528			454
	Series A Preferred Shares(1)			12,183			13,067			11,613			11,816

				14,093			14,946			13,596			13,743


	(1)	The Company’s Series A Preferred Shares are only convertible into the Company’s common shares upon certain changes in control of the Company. The dilutive shares are calculated as the daily average of the face value of the Series A Preferred Shares divided by the outstanding common share price.

Rental_Property_Tables

Rental Property (Tables)	9 Months Ended
Rental Property (Tables)	Sep. 30, 2013
Text Block [Abstract]	'
Summary of Rental Property	'
	Rental property consists of the following (amounts in thousands):


		September 30, 2013			December 31, 2012
	Land and land improvements	$	293,010		$	387,047
	Buildings and improvements		876,086			1,086,694
	Construction in process		105,797			56,614
	Tenant improvements		143,666			145,910
	Furniture, fixtures and equipment		5,158			5,498

			1,423,717			1,681,763
	Less: accumulated depreciation		(205,353	)		(231,084	)

		$	1,218,364		$	1,450,679

Notes_Receivable_Tables

Notes Receivable (Tables)	9 Months Ended
Notes Receivable (Tables)	Sep. 30, 2013
Receivables [Abstract]	'
Summary of Notes Receivable	'
	Below is a summary of the Company’s notes receivable at September 30, 2013 (dollars in thousands):


		Balance at September 30, 2013
	Issued	Face Amount		Unamortized			Balance		Interest Rate			Property
	Issued	Face Amount		Origination Fees			Balance		Interest Rate			Property
	Dec-10	$	25,000	$	(140	)	$	24,860		12.5	%		950 F Street, NW
	Apr-11		29,940		(78	)		29,862		9	%		America’s Square

		$	54,940	$	(218	)	$	54,722



		Balance at December 31, 2012
	Issued	Face Amount		Unamortized			Balance		Interest Rate			Property
	Issued	Face Amount		Origination Fees			Balance		Interest Rate			Property
	Dec-10	$	25,000	$	(171	)	$	24,829		12.5	%	950 F Street, NW
	Apr-11		30,000		(99	)		29,901		9	%	America’s Square

		$	55,000	$	(270	)	$	54,730

Investment_in_Affiliates_Table

Investment in Affiliates (Tables)	9 Months Ended
Investment in Affiliates (Tables)	Sep. 30, 2013
Equity Method Investments And Joint Ventures [Abstract]	'
Components of Investments in Affiliates	'
	The Company’s investment in affiliates consisted of the following (dollars in thousands):


			Reporting Segment		Ownership				September 30,				December 31,
			Reporting Segment		Interest				2013				2012
	Prosperity Metro Plaza		Northern Virginia			51	%		$	25,032			$	26,679
	1750 H Street, NW		Washington, D.C.			50	%			16,449				16,130
	Aviation Business Park		Maryland			50	%			5,028				4,713
	RiversPark I and II		Maryland			25	%			2,720				3,074

									$	49,229			$	50,596
Net Assets of Company's Unconsolidated Joint Ventures	'
	The net assets of the Company’s unconsolidated joint ventures consisted of the following (amounts in thousands):


			September 30,				December 31,
			2013				2012
	Assets:
	Rental property, net		$	194,749			$	198,411
	Cash and cash equivalents			4,215				6,224
	Other assets			16,097				17,377

	Total assets			215,061				222,012

	Liabilities:
	Mortgage loans(1)			107,155				109,427
	Other liabilities			5,469				6,687

	Total liabilities			112,624				116,114

	Net assets		$	102,437			$	105,898


	(1)	Of the total mortgage debt that encumbers the Company’s unconsolidated properties, $7.0 million is recourse to the Company. The recourse mortgage loan was scheduled to mature in September 2013; however, the Company extended the loan’s maturity date to March 2014. Management believes the fair value of the potential liability to the Company is inconsequential as the likelihood of the Company’s need to perform under the debt agreement is remote.
Results of Operations of Company's Unconsolidated Joint Ventures	'
	The following table summarizes the results of operations of the Company’s unconsolidated joint ventures, which due to its varying ownership interests in the joint ventures and the varying operations of the joint ventures may or may not be reflective of the amounts recorded in its consolidated statements of operations (amounts in thousands):


			Three Months Ended								Nine Months Ended
			September 30,								September 30,
			2013				2012				2013				2012
	Total revenues		$	6,035			$	6,254			$	18,046			$	18,575
	Total operating expenses			(1,879	)			(1,883	)			(5,649	)			(5,459	)

	Net operating income			4,156				4,371				12,397				13,116
	Depreciation and amortization			(2,887	)			(3,174	)			(8,681	)			(9,510	)
	Other expenses, net			(1,091	)			(1,070	)			(3,254	)			(3,235	)

	Net income		$	178			$	127			$	462			$	371

Discontinued_Operations_Tables

Discontinued Operations (Tables)

9 Months Ended

Sep. 30, 2013

Discontinued Operations And Disposal Groups [Abstract]

Summary of Property Dispositions

Reporting Segment

Disposition Date

Property Type

Square Feet

Worman’s Mill Court(1)

Maryland

November 2013

Office

40,099

Triangle Business Center

Maryland

9/27/13

Business Park

74,429

4200 Tech Court

Northern Virginia

8/15/13

Office

33,875

Industrial Portfolio

Various

6/18/13

Industrial

4,044,903

4212 Tech Court

Northern Virginia

6/5/13

Office

32,055

I-66 Commerce Center

Northern Virginia

5/7/13

Industrial

236,082

Owings Mills Business Park(2)

Maryland

11/7/12

Business Park

38,779

Goldenrod Lane

Maryland

5/31/12

Office

23,518

Woodlands Business Center

Maryland

5/8/12

Office

37,887

Airpark Place Business Center

Maryland

3/22/12

Business Park

82,429

(1)

(2)

In November 2012, the Company sold two of the six buildings at Owings Mills Business Park.

Net Income from Discontinued Operations

The following table summarizes the components of net income from discontinued operations (amounts in thousands):

Three Months Ended

Nine Months Ended

September 30,

2013

2012

2013

2012

Revenues

319

9,965

17,350

26,531

Net (loss) income, before taxes

(387

)

4,058

1,263

7,454

Gain on sale of real estate property

416

—

19,363

161

Debt_Tables

Debt (Tables)	9 Months Ended
Debt (Tables)	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Schedule of Borrowings	'
	The Company’s borrowings consisted of the following (amounts in thousands):


			September 30,				December 31,
			2013				2012
	Mortgage loans, effective interest rates ranging from 4.40% to 6.63%, maturing at various dates through July 2022		$	275,974			$	418,864
	Secured term loan, effective interest rate of LIBOR plus 5.50%(1)			—				10,000
	Unsecured term loan, effective interest rates ranging from LIBOR plus 2.15% to LIBOR plus 2.30%, with staggered maturity dates ranging from July 2016 to July 2018(2)(3)(4)			300,000				300,000
	Unsecured revolving credit facility, effective interest rate of LIBOR plus 2.25%, maturing January 2015(2)(3)(4)			83,000				205,000

			$	658,974			$	933,864


	(1)	The Company repaid its $10.0 million secured term loan and its $37.5 million senior secured multi-tranche term loan facility, which was entered into in February 2013, with proceeds from its May 2013 equity offering.
	(2)	At September 30, 2013, LIBOR was 0.18%.
	(3)	Based on the Company’s leverage ratio at September 30, 2013, the applicable interest rate spread on both the unsecured revolving credit facility and the unsecured term loan tranches decreased on October 16, 2013. For more information see notes 8(b) Debt – Unsecured Term Loan, 8(c) Debt – Unsecured Revolving Credit Facility, and 8(e) Debt – Financial Covenants.
	(4)	On October 16, 2013, the Company amended and restated its unsecured revolving credit facility and unsecured term loan. For more information see notes 8(b) Debt – Unsecured Term Loan, 8(c) Debt – Unsecured Revolving Credit Facility, and 8(e) Debt – Financial Covenants.
Summary of Company's Mortgage Debt	'
	The following table provides a summary of the Company’s mortgage debt at September 30, 2013 and December 31, 2012 (dollars in thousands):


	Encumbered Property		Contractual		Effective				Maturity			September 30,			December 31,
			Interest Rate		Interest				Date			2013			2012
					Rate
	Prosperity Business Center(1)		6.25%			5.75	%			January 2013		$	—		$	3,242
	Cedar Hill(2)		6.00%			6.58	%			February 2013			—			15,404
	10320 Little Patuxent Parkway(2)		6.00%			7.29	%			Feb-13			—			13,291
	1434 Crossways Blvd Building I(2)		6.25%			5.38	%			Mar-13			—			7,650
	Cloverleaf Center(3)		6.75%			6.75	%			Oct-14			—			16,595
	Mercedes Center– Note 1(3)		4.67%			6.04	%			Jan-16			—			4,677
	Mercedes Center – Note 2(3)		6.57%			6.3	%			Jan-16			—			9,498
	Linden Business Center(4)		6.01%			5.58	%			Oct-13			—			6,747
	840 First Street, NE(5)		5.18%			6.05	%			Oct-13			—			54,704
	Annapolis Business Center		5.74%			6.25	%			Jun-14			8,114			8,223
	1005 First Street, NE(6)(7)		LIBOR + 2.75%			5.8	%			Oct-14			22,000			22,000
	Jackson National Life Loan(8)		5.19%			5.19	%			Aug-15			66,400			96,132
	Hanover Business Center Building D		8.88%			6.63	%			Aug-15			288			391
	Chesterfield Business Center Buildings C,D,G and H		8.50%			6.63	%			Aug-15			772			1,036
	440 First Street, NW Construction Loan(7)(9)		LIBOR + 2.50%			5	%			May-16			21,699			—
	Gateway Centre Manassas Building I		7.35%			5.88	%			Nov-16			688			833
	Hillside Center		5.75%			4.62	%			Dec-16			13,448			13,741
	Redland Corporate Center		4.20%			4.64	%			November 2017			67,336			68,209
	Hanover Business Center Building C		7.88%			6.63	%			Dec-17			688			791
	840 First Street, NE / 500 First Street, NW(10)		5.72%			6.01	%			Jul-20			37,298			37,730
	Battlefield Corporate Center		4.26%			4.4	%			Nov-20			3,889			4,003
	Chesterfield Business Center Buildings A,B,E and F		7.45%			6.63	%			Jun-21			1,921			2,060
	Airpark Business Center		7.45%			6.63	%			Jun-21			1,048			1,123
	1211 Connecticut Avenue, NW		4.22%			4.47	%			Jul-22			30,385			30,784

						5.14	%(11)						275,974			418,864
	Unamortized fair value adjustments												(714	)		(696	)

	Total contractual principal balance											$	275,260		$	418,168


	-1	The loan was repaid at maturity with borrowings under the Company’s unsecured revolving credit facility.
	-2	The loans were repaid in February 2013 with borrowings under a $37.5 million senior secured multi-tranche term loan facility, which was subsequently repaid in May 2013 with proceeds from the Company’s May 2013 equity offering. 10320 Little Patuxent Parkway was previously referred to as the Merrill Lynch Building.
	(3)	In June 2013, the Company sold the majority of its industrial portfolio, which included Mercedes Center. The debt instrument that encumbered Mercedes Center was repaid at the time of sale. In addition, the Company used a portion of the net proceeds received from the sale of its industrial portfolio to repay the mortgage loan that encumbered Cloverleaf Center.
	-4	The loan was repaid in September 2013 with available cash.
	(5)	On September 30, 2013, the Company repaid a $53.9 million mortgage loan that encumbered 840 First Street, NE, which was scheduled to mature on October 1, 2013.
	(6)	The loan incurs interest at a variable rate of LIBOR plus a spread of 2.75% (with a floor of 5.0%) and matures in October 2014, with a one-year extension at the Company’s option.
	-7	At September 30, 2013, LIBOR was 0.18%.
	(8)	At September 30, 2013, the loan was secured by the following properties: Plaza 500, Van Buren Office Park, Rumsey Center, Snowden Center, Greenbrier Technology Center II and Norfolk Business Center. The terms of the loan allow the Company to substitute collateral, as long as certain debt-service coverage and loan-to-value ratios are maintained, or to prepay a portion of the loan, with a prepayment penalty, subject to a debt-service yield.
	(9)	At September 30, 2013, the principal balance and the unpaid accrued interest on the 440 First Street, NW construction loan were recourse to the Company.
	(10)	On September 30, 2013, the Company repaid a $53.9 million mortgage loan that encumbered 840 First Street, NE, which was scheduled to mature on October 1, 2013. Simultaneously with the repayment of the mortgage debt, the Company encumbered 840 First Street, NE with a $37.3 million mortgage loan that had previously encumbered 500 First Street, NW.
	-11	Weighted average interest rate on total mortgage debt.
Unsecured Term Loans	'
	The table below shows the outstanding balances and the interest rate of the three tranches of the $300.0 million unsecured term loan at September 30, 2013 (dollars in thousands):


			Maturity Date				Amount				Interest Rate(1)
	Tranche A			July 2016			$	60,000			LIBOR, plus 215 basis points
	Tranche B			Jul-17				147,500			LIBOR, plus 225 basis points
	Tranche C			Jul-18				92,500			LIBOR, plus 230 basis points

							$	300,000


	(1)	The interest rate spread is subject to change based on the Company’s maximum total indebtedness ratio. For more information, see note 8(e) Debt – Financial Covenants.

Derivative_Instruments_Tables

Derivative Instruments (Tables)	9 Months Ended
Derivative Instruments (Tables)	Sep. 30, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Summary of Interest Rate Swap Agreements	'
	At September 30, 2013, the Company had fixed LIBOR at a weighted average interest rate of 1.5% on $350.0 million of its variable rate debt through twelve interest rate swap agreements that are summarized below (dollars in thousands):


	Effective Date	Maturity Date	Notional		Interest Rate	Fixed LIBOR
			Amount		Contractual	Interest Rate
					Component
	Jan-11	January 2014	$	50,000	LIBOR		1.474	%
	Jul-11	Jul-16		35,000	LIBOR		1.754	%
	Jul-11	Jul-16		25,000	LIBOR		1.763	%
	Jul-11	Jul-17		30,000	LIBOR		2.093	%
	Jul-11	Jul-17		30,000	LIBOR		2.093	%
	Sep-11	Jul-18		30,000	LIBOR		1.66	%
	Jan-12	Jul-18		25,000	LIBOR		1.394	%
	Mar-12	Jul-17		25,000	LIBOR		1.129	%
	Mar-12	Jul-17		12,500	LIBOR		1.129	%
	Mar-12	Jul-18		12,500	LIBOR		1.383	%
	Jun-12	Jul-17		50,000	LIBOR		0.955	%
	Jun-12	Jul-18		25,000	LIBOR		1.135	%

	Total/Weighted Average		$	350,000			1.5	%

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value of Assets and Liabilities	'
	In accordance with accounting provisions and the fair value hierarchy described above, the following table shows the fair value of the Company’s consolidated assets and liabilities that are measured on a non-recurring and recurring basis as of September 30, 2013 and December 31, 2012 (amounts in thousands):


			Balance at		Level 1		Level 2		Level 3
			September 30, 2013		Level 1		Level 2		Level 3
	Non-recurring Measurements:
	Impaired real estate assets		$	3,297	$	—	$	3,297	$	—
	Recurring Measurements:
	Derivative instrument-swap assets			231		—		231		—
	Derivative instrument-swap liabilities			5,629		—		5,629		—


			Balance at		Level 1		Level 2		Level 3
			December 31, 2012		Level 1		Level 2		Level 3
	Non-recurring Measurements:
	Impaired real estate assets		$	15,955	$	—	$	15,955	$	—
	Recurring Measurements:
	Derivative instrument-swap liabilities			11,464		—		11,464		—
Fair Value of Debt Instruments	'
	The carrying amount and estimated fair value of the Company’s notes receivable and debt instruments at September 30, 2013 and December 31, 2012 are as follows (amounts in thousands):


			September 30, 2013				December 31, 2012
			Carrying		Fair		Carrying		Fair
			Value		Value		Value		Value
	Financial Assets:
	Notes receivable(1)		$	54,722	$	54,940	$	54,730	$	55,000

	Financial Liabilities:
	Mortgage debt		$	275,974	$	267,606	$	418,864	$	427,851
	Secured term loan(2)			—		—		10,000		10,000
	Unsecured term loan			300,000		309,723		300,000		300,000
	Unsecured revolving credit facility			83,000		85,436		205,000		205,000

	Total		$	658,974	$	662,765	$	933,864	$	942,851


	(1)	The face value of the Company’s notes receivable was $54.9 million and $55.0 million at September 30, 2013 and December 31, 2012.
	(2)	The Company repaid its $10.0 million secured term loan with net proceeds from an equity offering.

Equity_Tables

Equity (Tables)	9 Months Ended
Equity (Tables)	Sep. 30, 2013
Equity [Abstract]	'
Company's Allocation between Non-controlling Interests	'
	The Company’s equity and redeemable noncontrolling interests are as follows (amounts in thousands):


		First			Non-redeemable			Total			Redeemable
		Potomac			noncontrolling			Equity			noncontrolling
		Realty Trust			interests						interests
	Balance at December 31, 2012	$	658,765		$	3,728		$	662,493		$	34,367
	Net income (loss)		14,526			(20	)		14,506			216
	Changes in ownership, net		107,836			249			108,085			273
	Distributions to owners		(33,428	)		—			(33,428	)		(1,168	)
	Other comprehensive income		5,767			—			5,767			284

	Balance at September 30, 2013	$	753,466		$	3,957		$	757,423		$	33,972



		First			Non-redeemable			Total			Redeemable
		Potomac			noncontrolling			Equity			noncontrolling
		Realty Trust			interests						interests
	Balance at December 31, 2011	$	672,246		$	4,245		$	676,491		$	39,981
	Net (loss) income		(8,385	)		68			(8,317	)		(944	)
	Changes in ownership, net		49,846			8			49,854			(1,697	)
	Distributions to owners		(38,943	)		—			(38,943	)		(1,639	)
	Other comprehensive loss		(6,088	)		—			(6,088	)		(318	)

	Balance at September 30, 2012	$	668,676		$	4,321		$	672,997		$	35,383

Company's Accumulated Other Comprehensive Loss	'
	A summary of the Company’s accumulated other comprehensive loss is as follows (amounts in thousands):


		2013			2012
	Beginning balance at January1,	$	(10,917	)	$	(5,849	)
	Net unrealized gain (loss) on derivative instruments		6,051			(6,406	)
	Net (gain) loss attributable to noncontrolling interests		(284	)		318

	Ending balance at September 30,	$	(5,150	)	$	(11,937	)

Noncontrolling_Interests_Table

Noncontrolling Interests (Tables)

9 Months Ended

Sep. 30, 2013

Noncontrolling Interest [Abstract]

Property Owned under Consolidated Joint Ventures

At September 30, 2013, the Company’s consolidated joint ventures had a controlling interest in the following properties:

Property

Acquisition Date

Reporting Segment

First Pot

Square

omac

Footage

Controlling

Interest

1005 First Street, NE

August 2011

Washington, D.C.

—

(1)

Redland Corporate Center

November 2010

Maryland

349,267

(1)

The property was placed into development on September 1, 2013.

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
Segment Information (Tables)	Sep. 30, 2013
Segment Reporting [Abstract]	'
Summary of Segment Information	'
	The results of operations for the Company’s four reporting segments for the three and nine months ended September 30, 2013 and 2012 are as follows (dollars in thousands):


			Three Months Ended September 30, 2013
			Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
	Number of buildings			3	(1)			53				51				38				145
	Square feet			502,690	(1)			2,544,481				3,085,740				2,852,240				8,985,151
	Total revenues		$	7,151			$	11,607			$	13,231			$	8,848			$	40,837
	Property operating expense			(1,779	)			(3,034	)			(3,088	)			(2,977	)			(10,878	)
	Real estate taxes and insurance			(1,151	)			(1,015	)			(1,372	)			(702	)			(4,240	)

	Total property operating income		$	4,221			$	7,558			$	8,771			$	5,169			$	25,719

	Depreciation and amortization expense																			(14,812	)
	General and administrative																			(6,346	)
	Acquisition costs																			(173	)
	Other expenses, net																			(6,134	)
	Income from discontinued operations																			29

	Net loss																		$	(1,717	)

	Capital expenditures(2)		$	4,758			$	2,662			$	2,798			$	1,979			$	12,609



			Three Months Ended September 30, 2012
			Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
	Number of buildings			4	(1)			64				55				57				180
	Square feet			531,714	(1)			3,816,878				3,655,536				5,649,203				13,653,331
	Total revenues		$	6,977			$	11,404			$	11,859			$	8,546			$	38,786
	Property operating expense			(1,388	)			(2,910	)			(3,076	)			(2,661	)			(10,035	)
	Real estate taxes and insurance			(935	)			(877	)			(1,269	)			(660	)			(3,741	)

	Total property operating income		$	4,654			$	7,617			$	7,514			$	5,225				25,010

	Depreciation and amortization expense																			(14,144	)
	General and administrative																			(5,645	)
	Acquisition costs																			(8	)
	Impairment of real estate assets																			(496	)
	Contingent consideration related to acquisition of property																			(112	)
	Other expenses, net																			(5,532	)
	Benefit from income taxes																			4,304
	Income from discontinued operations																			4,058

	Net income																		$	7,435

	Capital expenditures(2)		$	3,836			$	3,328			$	2,877			$	3,214			$	13,429



			Nine Months Ended September 30, 2013
			Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
	Total revenues		$	22,307			$	34,982			$	38,589			$	26,093			$	121,971
	Property operating expense			(5,408	)			(8,650	)			(9,222	)			(8,249	)			(31,529	)
	Real estate taxes and insurance			(3,746	)			(3,029	)			(4,302	)			(2,027	)			(13,104	)

	Total property operating income		$	13,153			$	23,303			$	25,065			$	15,817				77,338

	Depreciation and amortization expense																			(43,891	)
	General and administrative																			(16,598	)
	Acquisition costs																			(173	)
	Contingent consideration related to acquisition of property																			(75	)
	Other expenses, net																			(22,505	)
Income from discontinued operations																			20,626

Net income																		$	14,722

Total assets(3)(4)		$	334,427			$	406,789			$	426,839			$	230,390			$	1,511,283

Capital expenditures(2)		$	17,543			$	10,597			$	11,100			$	7,513			$	47,729


		Nine Months Ended September 30, 2012
		Washington, D.C.				Maryland				Northern Virginia				Southern Virginia				Consolidated
Total revenues		$	20,968			$	36,007			$	35,245			$	25,054			$	117,274
Property operating expense			(3,842	)			(8,065	)			(8,477	)			(7,313	)			(27,697	)
Real estate taxes and insurance			(2,945	)			(3,497	)			(3,799	)			(2,012	)			(12,253	)

Total property operating income		$	14,181			$	24,445			$	22,969			$	15,729				77,324

Depreciation and amortization expense																			(41,247	)
General and administrative																			(17,787	)
Acquisition costs																			(49	)
Impairment of real estate assets																			(2,444	)
Contingent consideration related to acquisition of property																			(112	)
Other expenses, net																			(36,703	)
Benefit from income taxes																			4,142
Income from discontinued operations																			7,615

Net loss																		$	(9,261	)

Total assets(3)(4)		$	313,513			$	497,966			$	459,153			$	365,687			$	1,714,237

Capital expenditures(2)		$	5,541			$	6,359			$	15,354			$	10,050			$	48,418


-1	Excludes 1005 First Street, NE, which was place in development in the third quarter of 2013 and 440 First Street, NW, which has been in redevelopment since its acquisition in December 2010.
(2)	Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $412 and $174 for the three months ended September 30, 2013 and 2012, respectively, and $976 and $1,114 for the nine months ended September 30, 2013 and 2012, respectively.
(3)	Total assets include the Company’s investment in properties that are owned through joint ventures that are not consolidated within the Company’s condensed consolidated financial statements. For more information on the Company’s unconsolidated investments, including location within the Company’s reportable segments, see note 6, Investment in Affiliates.
(4)	Corporate assets not allocated to any of our reportable segments totaled $112,838 and $77,918 at September 30, 2013 and 2012, respectively.

Description_of_Business_Additi

Description of Business - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
	Person	sqft
	Project
	Property
	sqft
Real Estate Properties [Line Items]	'	'
Number of separate segments its properties	4	'
Interest in Operating Partnership	95.80%	'
Area of land parcel	8,985,151	13,653,331
Unconsolidated joint ventures	5	'
Square footage of land for additional development	1,500,000	'
Occupancy rate in the Company's consolidated properties	85.10%	'
Number of tenants representing the 84.0% occupancy rate	570	'
Square footage in development or redevelopment not included on occupancy calculation	100,000	'
Share of U.S. Government along with government contractors in Company's total annualized rental revenue	24.00%	'
Percentage of outstanding account receivables accounted by government	30.00%	'
Wholly-owned Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Area of land parcel	9,100,000	'
Unconsolidated Properties [Member]	'	'
Real Estate Properties [Line Items]	'	'
Area of land parcel	900,000	'

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Estimated Useful Lives of Company's Assets, by Class (Detail)	9 Months Ended
	Sep. 30, 2013
Property, Plant and Equipment [Line Items]	'
Lease related intangible assets, Useful life	'The term of the related lease
Tenant improvements, Useful life	'Shorter of the useful life of the asset or the term of the related lease
Buildings [Member]	'
Property, Plant and Equipment [Line Items]	'
Property, plant and equipment, Useful life	'39 years
Minimum [Member] \| Building Improvements [Member]	'
Property, Plant and Equipment [Line Items]	'
Property, plant and equipment, Useful life	'5 years
Minimum [Member] \| Furniture, Fixtures and Equipment [Member]	'
Property, Plant and Equipment [Line Items]	'
Property, plant and equipment, Useful life	'5 years
Maximum [Member] \| Building Improvements [Member]	'
Property, Plant and Equipment [Line Items]	'
Property, plant and equipment, Useful life	'20 years
Maximum [Member] \| Furniture, Fixtures and Equipment [Member]	'
Property, Plant and Equipment [Line Items]	'
Property, plant and equipment, Useful life	'15 years

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accounting Policies [Abstract]	'	'	'	'
Allowance for credit losses for its notes receivable	$0	$0	$0	$0

Earnings_Per_Common_Share_Comp

Earnings Per Common Share - Computation of Company's Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator for basic and diluted earnings per common share:	'	'	'	'
(Loss) income from continuing operations	($1,746)	$3,377	($5,904)	($16,876)
Income from discontinued operations	29	4,058	20,626	7,615
Net (loss) income	-1,717	7,435	14,722	-9,261
Less: Net loss (income) from continuing operations attributable to noncontrolling interests	202	-35	693	1,263
Less: Net loss (income) from discontinued operations attributable to noncontrolling interests	9	-197	-889	-387
Net (loss) income attributable to First Potomac Realty Trust	-1,506	7,203	14,526	-8,385
Less: Dividends on preferred shares	-3,100	-3,100	-9,300	-8,864
Net (loss) income attributable to common shareholders	-4,606	4,103	5,226	-17,249
Less: Allocation to participating securities	-103	-162	-309	-468
Net (loss) income attributable to common shareholders	($4,709)	$3,941	$4,917	($17,717)
Weighted average common shares outstanding:	'	'	'	'
Basic	57,969	50,267	54,014	50,049
Diluted	57,969	50,346	54,014	50,049
Basic and diluted earnings per common share:	'	'	'	'
Loss from continuing operations	($0.08)	'	($0.28)	($0.49)
Income from discontinued operations	'	$0.08	$0.37	$0.14
Net (loss) income	($0.08)	$0.08	$0.09	($0.35)

Earnings_Per_Common_Share_Anti

Earnings Per Common Share - Anti-Dilutive Shares Not Included in Calculation of Diluted Earnings Per Share (Detail)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Anti-dilutive securities excluded from computation of earnings per share, Amount	14,093	14,946	13,596	13,743
Stock Option Awards [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Anti-dilutive securities excluded from computation of earnings per share, Amount	1,397	1,451	1,455	1,473
Non-vested Share Awards [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Anti-dilutive securities excluded from computation of earnings per share, Amount	513	428	528	454
Series A Preferred Shares [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Anti-dilutive securities excluded from computation of earnings per share, Amount	12,183	13,067	11,613	11,816

Rental_Property_Summary_of_Ren

Rental Property - Summary of Rental Property (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Real Estate [Abstract]	'	'
Land and land improvements	$293,010	$387,047
Buildings and improvements	876,086	1,086,694
Construction in process	105,797	56,614
Tenant improvements	143,666	145,910
Furniture, fixtures and equipment	5,158	5,498
Rental property, gross	1,423,717	1,681,763
Less: accumulated depreciation	-205,353	-231,084
Rental property, net	$1,218,364	$1,450,679

Rental_Property_Additional_Inf

Rental Property - Additional Information (Detail) (USD $)

1 Months Ended

9 Months Ended

1 Months Ended

12 Months Ended

Aug. 04, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Aug. 04, 2013

Sep. 30, 2013

Sep. 30, 2012

Aug. 04, 2013

Dec. 31, 2011

Sep. 30, 2013

sqft

Greyhound Lines, Inc. [Member]

Buildings [Member]

Washington, D.C. [Member]

Maryland [Member]

Washington, D.C. [Member]

1005 First Street, NE [Member]

440 First Street, NW [Member]

Northern [Member]

Southern [Member]

sqft

Real Estate Investment [Member]

sqft

acre

sqft

Virginia [Member]

sqft

Segment Reporting Information [Line Items]

Additional Building Space

1,500,000

100,000

Additional Building Space

8,985,151

13,653,331

712,000

700,000

2,544,481

3,816,878

600,000

100,000

Development of area for operations by joint venture

1.6

Lease expiration date

31-Aug-13

Projected incremental investment in development project

$46,400,000

Original cost basis of the property

876,086,000

1,086,694,000

43,300,000

23,600,000

Transferable development rights, purchased

30,000

Acquisition of transferable development rights, value

300,000

Projected incremental investment in redevelopment project

$52,300,000

Anticipated completion of redevelopment

138,000

Notes_Receivable_Summary_of_No

Notes Receivable - Summary of Notes Receivable (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Receivables with Imputed Interest [Line Items]	'	'
Face Amount	$54,940	$55,000
Unamortized Origination Fees	-218	-270
Balance	54,722	54,730
Notes Receivables Issued on December 2010 [Member]	'	'
Receivables with Imputed Interest [Line Items]	'	'
Notes receivable issued date	1-Dec-10	1-Dec-10
Face Amount	25,000	25,000
Unamortized Origination Fees	-140	-171
Balance	24,860	24,829
Interest Rate	12.50%	12.50%
Property	'950 F Street, NW	'950 F Street, NW
Notes Receivables Issued on April 2011 [Member]	'	'
Receivables with Imputed Interest [Line Items]	'	'
Notes receivable issued date	1-Apr-11	1-Apr-11
Face Amount	29,940	30,000
Unamortized Origination Fees	-78	-99
Balance	$29,862	$29,901
Interest Rate	9.00%	9.00%
Property	'America's Square	'America's Square

Notes_Receivable_Additional_In

Notes Receivable - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
Notes Receivable - Additional Information (Detail) (USD $)	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Receivables with Imputed Interest [Line Items]	'	'	'	'
Interest income	$1,500,000	$1,500,000	$4,400,000	$4,400,000
Income from amortization of origination fees	17,000	17,000	52,000	52,000
Notes Receivables Issued on December 2010 [Member]	'	'	'	'
Receivables with Imputed Interest [Line Items]	'	'	'	'
Subordinated loan provided to owners	25,000,000	'	25,000,000	'
Notes Receivables Issued on April 2011 [Member]	'	'	'	'
Receivables with Imputed Interest [Line Items]	'	'	'	'
Subordinated loan provided to owners	$30,000,000	'	$30,000,000	'

Investment_in_Affiliates_Compo

Investment in Affiliates - Components of Investments in Affiliates (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]	'	'
Company Investment	$49,229	$50,596
Prosperity Metro Plaza [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Reporting Segment	'Northern Virginia	'
Ownership Interest	51.00%	'
Company Investment	25,032	26,679
1750 H Street, NW [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Reporting Segment	'Washington, D.C.	'
Ownership Interest	50.00%	'
Company Investment	16,449	16,130
Aviation Business Park [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Reporting Segment	'Maryland	'
Ownership Interest	50.00%	'
Company Investment	5,028	4,713
RiversPark I and II [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Reporting Segment	'Maryland	'
Ownership Interest	25.00%	'
Company Investment	$2,720	$3,074

Investment_in_Affiliates_Net_A

Investment in Affiliates - Net Assets of Company's Unconsolidated Joint Ventures (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Assets:	'	'	'	'
Rental property, net	$1,218,364	$1,450,679	'	'
Cash and cash equivalents	16,971	9,374	12,040	16,749
Total assets	1,511,283	1,717,748	1,714,237	'
Liabilities:	'	'	'	'
Mortgage loans	'	10,000	'	'
Total liabilities	719,889	1,020,888	'	'
Unconsolidated Joint Ventures [Member]	'	'	'	'
Assets:	'	'	'	'
Rental property, net	194,749	198,411	'	'
Cash and cash equivalents	4,215	6,224	'	'
Other assets	16,097	17,377	'	'
Total assets	215,061	222,012	'	'
Liabilities:	'	'	'	'
Mortgage loans	107,155	109,427	'	'
Other liabilities	5,469	6,687	'	'
Total liabilities	112,624	116,114	'	'
Net assets	$102,437	$105,898	'	'

Investment_in_Affiliates_Net_A1

Investment in Affiliates - Net Assets of Company's Unconsolidated Joint Ventures (Parenthetical) (Detail) (Unconsolidated Entities [Member], USD $)	Sep. 30, 2013
In Millions, unless otherwise specified	Sep. 30, 2013
Unconsolidated Entities [Member]	'
Schedule of Equity Method Investments [Line Items]	'
Mortgage debt aggregate fair value	$7

Investment_in_Affiliates_Resul

Investment in Affiliates - Results of Operations of Company's Unconsolidated Joint Ventures (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Total revenues	$40,837	$38,786	$121,971	$117,274
Total operating expenses	-36,449	-34,181	-105,370	-101,589
Net operating income	4,388	4,605	16,601	15,685
Depreciation and amortization	-14,812	-14,144	-43,891	-41,247
Other expenses, net	-6,134	-5,532	-22,505	-36,703
Net income	19	-30	54	-52
Unconsolidated Joint Ventures [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Total revenues	6,035	6,254	18,046	18,575
Total operating expenses	-1,879	-1,883	-5,649	-5,459
Net operating income	4,156	4,371	12,397	13,116
Depreciation and amortization	-2,887	-3,174	-8,681	-9,510
Other expenses, net	-1,091	-1,070	-3,254	-3,235
Net income	$178	$127	$462	$371

Investment_in_Affiliates_Addit

Investment in Affiliates - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Equity Method Investments And Joint Ventures [Abstract]	'	'	'	'
Fees from joint ventures	$0.20	$0.10	$0.50	$0.30

Discontinued_Operation_Additio

Discontinued Operation - Additional Information (Detail) (USD $)

1 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

Sep. 27, 2013

Aug. 15, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 27, 2013

Sep. 30, 2012

Sep. 24, 2013

Aug. 15, 2013

Jun. 30, 2013

Sep. 30, 2013

Maryland [Member]

Virginia Properties [Member]

Triangle Business Center [Member]

Worman's Mill Court [Member]

Buildings

sqft

SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]

Industrial portfolio

74,000

40,000

34,000

Proceeds from sale of building

$2,700,000

$3,200,000

Gain on sale of property

400,000

Number of buildings

Impairment charge on the contractual sale price

$496,000

$2,444,000

$1,400,000

$500,000

Discontinued_Operations_Summar

Discontinued Operations - Summary of Property Dispositions (Detail)

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

sqft

Worman's Mill Court [Member]

Triangle Business Center [Member]

4200 Tech Court [Member]

Industrial Portfolio [Member]

4212 Tech Court [Member]

I-66 Commerce Center [Member]

Owings Mills Business Park [Member]

Goldenrod Lane [Member]

Woodlands Business Center [Member]

Airpark Place Business Center [Member]

sqft

SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]

Reporting Segment

'Maryland

'Northern Virginia

'Various

'Northern Virginia

'Maryland

Disposition Date

30-Nov-13

27-Sep-13

15-Aug-13

18-Jun-13

5-Jun-13

7-May-13

7-Nov-12

31-May-12

8-May-12

22-Mar-12

Property Type

'Office

'Business Park

'Office

'Industrial

'Office

'Industrial

'Business Park

'Office

'Business Park

Square Feet

8,985,151

13,653,331

40,099

74,429

33,875

4,044,903

32,055

236,082

38,779

23,518

37,887

82,429

Discontinued_Operations_Summar1

Discontinued Operations - Summary of Property Dispositions (Parenthetical) (Detail) (Owings Mills Business Park [Member])	1 Months Ended
	Nov. 30, 2012
	Buildings
Owings Mills Business Park [Member]	'
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]	'
Number of building sold	2
Number of buildings	6

Discontinued_Operations_Net_In

Discontinued Operations - Net Income from Discontinued Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Discontinued Operations And Disposal Groups [Abstract]	'	'	'	'
Revenues	$319	$9,965	$17,350	$26,531
Net (loss) income, before taxes	-387	4,058	1,263	7,454
Gain on sale of real estate property	$416	'	$19,363	$161

Debt_Schedule_of_Borrowings_De

Debt - Schedule of Borrowings (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]	'	'
Mortgage loans, effective interest rates ranging from 4.40% to 6.63%, maturing at various dates through July 2022	$275,974	$418,864
Secured term loan, effective interest rate of LIBOR plus 5.50%	'	10,000
Unsecured revolving credit facility, effective interest rate of LIBOR plus 2.25%, maturing January 2015	83,000	205,000
Total long term debt	658,974	933,864
Secured Term Loan [Member]	'	'
Debt Instrument [Line Items]	'	'
Secured term loan, effective interest rate of LIBOR plus 5.50%	'	10,000
Unsecured Term Loan, Effective Interest Rates Ranging from LIBOR Plus 2.15% to LIBOR Plus 2.30%, with Staggered Maturity Dates Ranging from July 2016 to July 2018 [Member]	'	'
Debt Instrument [Line Items]	'	'
Unsecured term loan, effective interest rates ranging from LIBOR plus 2.15% to LIBOR plus 2.30%, with staggered maturity dates ranging from July 2016 to July 2018	$300,000	$300,000

Debt_Schedule_of_Borrowings_Pa

Debt - Schedule of Borrowings (Parenthetical) (Detail) (USD $)	1 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Jun. 05, 2013	Sep. 30, 2013
Debt Instrument [Line Items]	'	'
Effective interest rate on secured term loan	2.50%	2.75%
Effective interest rate on the notes	'	5.14%
Repayment of term loan	'	$10
Debt instrument variable rate basis	'	0.18%
Bridge Loan [Member]	'	'
Debt Instrument [Line Items]	'	'
Repayment of term loan	'	$37.50
Mortgage Loans [Member]	'	'
Debt Instrument [Line Items]	'	'
Debt instrument, interest rate, effective percentage rate range, minimum	'	4.40%
Debt instrument, interest rate, effective percentage rate range, maximum	'	6.63%
Debt instrument maturity date	'	'July 2022
Secured Term Loan [Member]	'	'
Debt Instrument [Line Items]	'	'
Effective interest rate on secured term loan	'	5.50%
Unsecured Term Loan, Effective Interest Rates Ranging from LIBOR Plus 2.15% to LIBOR Plus 2.30%, with Staggered Maturity Dates Ranging from July 2016 to July 2018 [Member]	'	'
Debt Instrument [Line Items]	'	'
Debt instrument maturity date	'	'July 2016 to July 2018
Debt instrument basis spread on variable rate, minimum	'	2.15%
Debt instrument basis spread on variable rate, maximum	'	2.30%
Unsecured Revolving Credit Facility [Member]	'	'
Debt Instrument [Line Items]	'	'
Debt instrument maturity date	'	'January 2015
Effective interest rate on secured term loan	'	0.50%
Effective interest rate on the notes	'	2.25%

Debt_Summary_of_Companys_Mortg

Debt - Summary of Company's Mortgage Debt (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]	'	'
Effective Interest Rate	5.14%	'
Total Mortgage Debt	$275,974	$418,864
Unamortized fair value adjustments	-714	-696
Total contractual principal balance	658,974	933,864
Mortgage Loans [Member]	'	'
Debt Instrument [Line Items]	'	'
Total contractual principal balance	275,260	418,168
Prosperity Business Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'January 2013	'
Contractual Interest Rate	6.25%	'
Effective Interest Rate	5.75%	'
Total Mortgage Debt	'	3,242
Cedar Hill [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'February 2013	'
Contractual Interest Rate	6.00%	'
Effective Interest Rate	6.58%	'
Total Mortgage Debt	'	15,404
10320 Little Patuxent Parkway [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'February 2013	'
Contractual Interest Rate	6.00%	'
Effective Interest Rate	7.29%	'
Total Mortgage Debt	'	13,291
1434 Crossways Blvd Building I [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'March 2013	'
Contractual Interest Rate	6.25%	'
Effective Interest Rate	5.38%	'
Total Mortgage Debt	'	7,650
Cloverleaf Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'October 2014	'
Contractual Interest Rate	6.75%	'
Effective Interest Rate	6.75%	'
Total Mortgage Debt	'	16,595
Mercedes Center - Note 1 [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'January 2016	'
Contractual Interest Rate	4.67%	'
Effective Interest Rate	6.04%	'
Total Mortgage Debt	'	4,677
Mercedes Center - Note 2 [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'January 2016	'
Contractual Interest Rate	6.57%	'
Effective Interest Rate	6.30%	'
Total Mortgage Debt	'	9,498
Linden Business Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'October 2013	'
Contractual Interest Rate	6.01%	'
Effective Interest Rate	5.58%	'
Total Mortgage Debt	'	6,747
840 First Street, NE [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'October 2013	'
Contractual Interest Rate	5.18%	'
Effective Interest Rate	6.05%	'
Total Mortgage Debt	'	54,704
Annapolis Business Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'June 2014	'
Contractual Interest Rate	5.74%	'
Effective Interest Rate	6.25%	'
Total Mortgage Debt	8,114	8,223
1005 First Street, NE [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'October 2014	'
Effective Interest Rate	5.80%	'
Contractual Interest Rate terms	'LIBOR + 2.75%	'
Total Mortgage Debt	22,000	22,000
Jackson National Life Loan [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'August 2015	'
Contractual Interest Rate	5.19%	'
Effective Interest Rate	5.19%	'
Total Mortgage Debt	66,400	96,132
Hanover Business Center Building D [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'August 2015	'
Contractual Interest Rate	8.88%	'
Effective Interest Rate	6.63%	'
Total Mortgage Debt	288	391
Chesterfield Business Center Buildings C,D,G and H [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'August 2015	'
Contractual Interest Rate	8.50%	'
Effective Interest Rate	6.63%	'
Total Mortgage Debt	772	1,036
440 First Street, NW Construction Loan [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'May 2016	'
Effective Interest Rate	5.00%	'
Contractual Interest Rate terms	'LIBOR + 2.50%	'
Total Mortgage Debt	21,699	'
Gateway Centre Manassas Building I [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'November 2016	'
Contractual Interest Rate	7.35%	'
Effective Interest Rate	5.88%	'
Total Mortgage Debt	688	833
Hillside Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'December 2016	'
Contractual Interest Rate	5.75%	'
Effective Interest Rate	4.62%	'
Total Mortgage Debt	13,448	13,741
Redland Corporate Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'November 2017	'
Contractual Interest Rate	4.20%	'
Effective Interest Rate	4.64%	'
Total Mortgage Debt	67,336	68,209
Hanover Business Center Building C [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'December 2017	'
Contractual Interest Rate	7.88%	'
Effective Interest Rate	6.63%	'
Total Mortgage Debt	688	791
840 First Street, NE / 500 First Street, NW [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'July 2020	'
Contractual Interest Rate	5.72%	'
Effective Interest Rate	6.01%	'
Total Mortgage Debt	37,298	37,730
Battlefield Corporate Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'November 2020	'
Contractual Interest Rate	4.26%	'
Effective Interest Rate	4.40%	'
Total Mortgage Debt	3,889	4,003
Chesterfield Business Center Buildings A,B,E and F [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'June 2021	'
Contractual Interest Rate	7.45%	'
Effective Interest Rate	6.63%	'
Total Mortgage Debt	1,921	2,060
Airpark Business Center [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'June 2021	'
Contractual Interest Rate	7.45%	'
Effective Interest Rate	6.63%	'
Total Mortgage Debt	1,048	1,123
1211 Connecticut Avenue, NW [Member]	'	'
Debt Instrument [Line Items]	'	'
Maturity Date	'July 2022	'
Contractual Interest Rate	4.22%	'
Effective Interest Rate	4.47%	'
Total Mortgage Debt	$30,385	$30,784

Debt_Summary_of_Companys_Mortg1

Debt - Summary of Company's Mortgage Debt (Parenthetical) (Detail) (USD $)	1 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Jun. 05, 2013	Sep. 30, 2013
Debt Instrument [Line Items]	'	'
Repayment of term loan	'	$10
Maturity Date	'	31-Oct-14
LIBOR plus interest rate	2.50%	2.75%
LIBOR floor rate	'	5.00%
Debt instrument variable rate basis	'	0.18%
840 First Street, NE [Member]	'	'
Debt Instrument [Line Items]	'	'
Mortgage loan encumbered	'	53.9
Maturity Date	'	1-Oct-13
500 First Street, NW [Member]	'	'
Debt Instrument [Line Items]	'	'
Mortgage loan encumbered	'	37.3
Bridge Loan [Member]	'	'
Debt Instrument [Line Items]	'	'
Repayment of term loan	'	$37.50

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)

1 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

Jun. 05, 2013

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Oct. 16, 2013

Sep. 30, 2013

Tranche A [Member]

Tranche B [Member]

Tranche C [Member]

Subsequent Event [Member]

500 First Street, NW [Member]

Term Loan [Member]

Tranche A [Member]

Tranche B [Member]

Tranche C [Member]

Tranches

Debt Instrument [Line Items]

Debt extinguishment charges

$123,000

$324,000

$13,221,000

Duration of tax protection agreement

31-Mar-18

Mortgage loan encumbered

37,300,000

Borrowing capacity of a construction loan

43,500,000

Amount borrowed

21,700,000

Loan variable interest rate

2.50%

2.75%

Maturity date

'2016-05

'2017-10

Maturity Period

'1 year

Outstanding balance of three tranches

$300,000,000

$60,000,000

$147,500,000

$92,500,000

$100,000,000

$300,000,000

Number of tranches

Term loan maturity date

'2018-10

'2019-10

'2020-10

Libor spread

0.70%

0.65%

0.40%

Debt_Unsecured_Term_Loans_Deta

Debt - Unsecured Term Loans (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Tranche A [Member]	Tranche B [Member]	Tranche C [Member]
Debt Instrument [Line Items]	'	'	'	'	'
Maturity Date	'	'	'July 2016	'July 2017	'July 2018
Unsecured term loan	$300,000	$300,000	$60,000	$147,500	$92,500
Interest Rate	'	'	'LIBOR, plus 215 basis points	'LIBOR, plus 225 basis points	'LIBOR, plus 230 basis points

Debt_Additional_Information_1_

Debt - Additional Information 1 (Detail) (USD $)

1 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

Jun. 05, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Oct. 16, 2013

Oct. 15, 2013

Oct. 16, 2013

Sep. 30, 2013

Oct. 16, 2013

Sep. 30, 2013

Derivative

Tranche A [Member]

Tranche B [Member]

Tranche C [Member]

Revolving Credit Facility [Member]

Subsequent Event [Member]

Unsecured Revolving Credit Facility [Member]

Unsecured Term Loans [Member]

Interest Rate Swap [Member]

Minimum [Member]

Maximum [Member]

Tranche A [Member]

Tranche B [Member]

Tranche C [Member]

Subsequent Event [Member]

Debt Instrument [Line Items]

Unsecured revolving credit facility

$83,000,000

$33,000,000

Weighted average borrowings outstanding on unsecured revolving credit facility

50,400,000

227,400,000

154,900,000

174,100,000

Weighted average interest rate

2.60%

2.90%

2.80%

2.90%

Weighted average interest rate

2.40%

Annual commitment fee

0.25%

Available capacity on the unsecured revolving credit facility

159,200,000

255,000,000

300,000,000

Line of credit facility basis spread on variable rate basis

0.18%

Unsecured term loan, basis points

2.50%

2.75%

0.50%

0.75%

0.25%

Weighted average rate amount on variable rate debt

350,000,000

Fixed effective interest rate

1.50%

Number of interest rate swap agreements

Company's unsecured revolving credit facility

$300,000,000

$255,000,000

Maturity date

'2016-05

'2017-10

Term loan maturity date

'July 2016

'July 2017

'July 2018

'October 2018

'October 2019

'October 2020

'January 2015

Maturity Extension Period

'1 year

Unsecured term loan, basis points

0.70%

0.65%

0.40%

0.75%

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivatives, Fair Value [Line Items]	'	'	'	'
Fixed effective interest rate	1.50%	'	1.50%	'
Weighted average rate amount on variable rate debt	$350,000,000	'	$350,000,000	'
Number of interest rate swap agreements	12	'	12	'
Interest Rate Swap [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Fixed effective interest rate	1.50%	'	1.50%	'
Weighted average rate amount on variable rate debt	350,000,000	'	350,000,000	'
Interest Expense [Member] \| Interest Rate Swap [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Accumulated other comprehensive loss reclassified as an increase in interest expense	1,200,000	1,100,000	3,500,000	3,000,000
Estimated accumulated other comprehensive loss reclassified as an increase in interest expense over the following twelve months	'	'	$3,800,000	'

Derivative_Instruments_Summary

Derivative Instruments - Summary of Interest Rate Swap Agreements (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Derivatives, Fair Value [Line Items]	'
Notional Amount	$350,000
Fixed LIBOR Interest Rate	1.50%
Interest Rate Swap One [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Jan-11
Maturity Date	31-Jan-14
Notional Amount	50,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.47%
Interest Rate Swap Two [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Jul-11
Maturity Date	31-Jul-16
Notional Amount	35,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.75%
Interest Rate Swap Three [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Jul-11
Maturity Date	31-Jul-16
Notional Amount	25,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.76%
Interest Rate Swap Four [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Jul-11
Maturity Date	31-Jul-17
Notional Amount	30,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	2.09%
Interest Rate Swap Five [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Jul-11
Maturity Date	31-Jul-17
Notional Amount	30,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	2.09%
Interest Rate Swap Six [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	30-Sep-11
Maturity Date	31-Jul-18
Notional Amount	30,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.66%
Interest Rate Swap Seven [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Jan-12
Maturity Date	31-Jul-18
Notional Amount	25,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.39%
Interest Rate Swap Eight [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Mar-12
Maturity Date	31-Jul-17
Notional Amount	25,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.13%
Interest Rate Swap Nine [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Mar-12
Maturity Date	31-Jul-17
Notional Amount	12,500
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.13%
Interest Rate Swap Ten [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	31-Mar-12
Maturity Date	31-Jul-18
Notional Amount	12,500
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.38%
Interest Rate Swap Eleven [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	30-Jun-12
Maturity Date	31-Jul-17
Notional Amount	50,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	0.96%
Interest Rate Swap Twelve [Member]	'
Derivatives, Fair Value [Line Items]	'
Effective Date	30-Jun-12
Maturity Date	31-Jul-18
Notional Amount	$25,000
Interest Rate Contractual Component	'LIBOR
Fixed LIBOR Interest Rate	1.14%

Fair_Value_Measurements_Fair_V

Fair Value Measurements - Fair Value of Assets and Liabilities (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Measurements, Non-recurring [Member]	'	'
Non-recurring Measurements:	'	'
Impaired real estate assets	$3,297	$15,955
Fair Value Measurements, Recurring [Member]	'	'
Recurring Measurements:	'	'
Derivative instrument-swap assets	231	'
Derivative instrument-swap liabilities	5,629	11,464
Level 1 [Member] \| Fair Value Measurements, Non-recurring [Member]	'	'
Non-recurring Measurements:	'	'
Impaired real estate assets	'	'
Level 1 [Member] \| Fair Value Measurements, Recurring [Member]	'	'
Recurring Measurements:	'	'
Derivative instrument-swap assets	'	'
Derivative instrument-swap liabilities	'	'
Level 2 [Member] \| Fair Value Measurements, Non-recurring [Member]	'	'
Non-recurring Measurements:	'	'
Impaired real estate assets	3,297	15,955
Level 2 [Member] \| Fair Value Measurements, Recurring [Member]	'	'
Recurring Measurements:	'	'
Derivative instrument-swap assets	231	'
Derivative instrument-swap liabilities	5,629	11,464
Level 3 [Member] \| Fair Value Measurements, Non-recurring [Member]	'	'
Non-recurring Measurements:	'	'
Impaired real estate assets	'	'
Level 3 [Member] \| Fair Value Measurements, Recurring [Member]	'	'
Recurring Measurements:	'	'
Derivative instrument-swap assets	'	'
Derivative instrument-swap liabilities	'	'

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended			9 Months Ended
	Nov. 30, 2012	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013
	Buildings					Worman's Mill Court [Member]	Interest Rate Swap [Member]
							Rate
Derivatives, Fair Value [Line Items]	'	'	'	'	'	'	'
Contingent consideration obligations	'	'	'	$700,000	$2,300,000	'	'
Impairment charges	'	496,000	2,444,000	'	'	500,000	'
Number of buildings with reduced holding period	6	'	'	'	'	'	'
Impairment charge on property	$2,400,000	'	'	'	'	'	'
Number of buildings sold	2	'	'	'	'	'	'
Minimum number of daily snapshot used for valuation of interest rate swap agreements	'	'	'	'	'	'	7,500

Fair_Value_Measurements_Fair_V1

Fair Value Measurements - Fair Value of Debt Instruments (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial Assets:	'	'
Carrying value of notes receivable	$54,722	$54,730
Fair value of notes receivable	54,900	55,000
Carrying Value [Member]	'	'
Financial Assets:	'	'
Carrying value of notes receivable	54,722	54,730
Financial Liabilities:	'	'
Carrying value of the debt instruments	658,974	933,864
Carrying Value [Member] \| Mortgage Debt [Member]	'	'
Financial Liabilities:	'	'
Carrying value of the debt instruments	275,974	418,864
Carrying Value [Member] \| Secured Term Loan [Member]	'	'
Financial Liabilities:	'	'
Carrying value of the debt instruments	'	10,000
Carrying Value [Member] \| Unsecured Term Loan [Member]	'	'
Financial Liabilities:	'	'
Carrying value of the debt instruments	300,000	300,000
Carrying Value [Member] \| Unsecured Revolving Credit Facility [Member]	'	'
Financial Liabilities:	'	'
Carrying value of the debt instruments	83,000	205,000
Fair Value [Member]	'	'
Financial Assets:	'	'
Fair value of notes receivable	54,940	55,000
Financial Liabilities:	'	'
Fair value of the debt instruments	662,765	942,851
Fair Value [Member] \| Mortgage Debt [Member]	'	'
Financial Liabilities:	'	'
Fair value of the debt instruments	267,606	427,851
Fair Value [Member] \| Secured Term Loan [Member]	'	'
Financial Liabilities:	'	'
Fair value of the debt instruments	'	10,000
Fair Value [Member] \| Unsecured Term Loan [Member]	'	'
Financial Liabilities:	'	'
Fair value of the debt instruments	309,723	300,000
Fair Value [Member] \| Unsecured Revolving Credit Facility [Member]	'	'
Financial Liabilities:	'	'
Fair value of the debt instruments	$85,436	$205,000

Fair_Value_Measurements_Fair_V2

Fair Value Measurements - Fair Value of Debt Instruments (Parenthetical) (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]	'	'
Fair value of notes receivable	$54.90	$55
Repayments of secured debt	$10	'

Equity_Additional_Information_

Equity - Additional Information (Detail) (USD $)	9 Months Ended
Equity - Additional Information (Detail) (USD $)	Sep. 30, 2013
Class of Stock [Line Items]	'
Common share dividend per share annualized	$0.60
Dividend declared date	22-Oct-13
Series A Preferred Shares [Member]	'
Class of Stock [Line Items]	'
Common share dividend per share declared	$0.15
Dividends declared on Series A Preferred Shares	$0.48
Dividend paid date	15-Nov-13
Dividend record date	6-Nov-13
Common share [Member]	'
Class of Stock [Line Items]	'
Dividend declared date	23-Jul-13
Dividend paid date	15-Aug-13
Dividend record date	6-Aug-13
Preferred Shares [Member]	'
Class of Stock [Line Items]	'
Dividend paid date	15-Aug-13
Dividend record date	6-Aug-13

Equity_Companys_Allocation_Bet

Equity - Company's Allocation Between Non-controlling Interests (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Noncontrolling Interest [Line Items]	'	'
Beginning Balance	$662,493	$676,491
Net income (loss)	14,506	-8,317
Changes in ownership, net	108,085	49,854
Distributions to owners	-33,428	-38,943
Other comprehensive income/loss	5,767	-6,088
Ending Balance	757,423	672,997
Beginning Balance, Redeemable noncontrolling interests	34,367	39,981
Net income (loss), Redeemable noncontrolling interests	216	-944
Change in ownership, net, Redeemable noncontrolling interests	273	-1,697
Distributions to owners, Redeemable noncontrolling interests	-1,168	-1,639
Other comprehensive income/loss, Redeemable noncontrolling interests	284	-318
Ending Balance, Redeemable noncontrolling interests	33,972	35,383
First Potomac Realty Trust [Member]	'	'
Noncontrolling Interest [Line Items]	'	'
Beginning Balance	658,765	672,246
Net income (loss)	14,526	-8,385
Changes in ownership, net	107,836	49,846
Distributions to owners	-33,428	-38,943
Other comprehensive income/loss	5,767	-6,088
Ending Balance	753,466	668,676
Non-redeemable Noncontrolling Interests [Member]	'	'
Noncontrolling Interest [Line Items]	'	'
Beginning Balance	3,728	4,245
Net income (loss)	-20	68
Changes in ownership, net	249	8
Distributions to owners	'	'
Other comprehensive income/loss	'	'
Ending Balance	$3,957	$4,321

Equity_Companys_Accumulated_Ot

Equity - Company's Accumulated Other Comprehensive Loss (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Partners Capital [Abstract]	'	'	'	'
Balance	'	'	($10,917)	($5,849)
Net Unrealized gain (loss) on derivative instruments	'	'	6,051	-6,406
Net (gain) loss attributable to noncontrolling interests	43	116	-284	318
Balance	($5,150)	($11,937)	($5,150)	($11,937)

Noncontrolling_Interests_Addit

Noncontrolling Interests - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	31-May-13	Sep. 30, 2013	Dec. 31, 2012
	31-May-13	OperatingPartnershipUnits	Dec. 31, 2012
Business Combinations [Abstract]	'	'	'
Conversion ratio for units to common shares	'	1	'
Cost to acquire all of the outstanding common Operating Partnership units not owned by the Company	'	$32.60	'
Fair value adjustment, cost basis	'	$3.90	'
Outstanding Operating Partnership units not owned by the Company	'	2,591,541	2,598,259
Partnership units not owned	'	4.20%	4.80%
Operating Partnership units issued for acquisition	7,475,000	'	'
Operating Partnership units redeemed	'	6,718	'
Number of operating partnership units redeemed	'	0	'

Noncontrolling_Interests_Prope

Noncontrolling Interests - Property Owned under Consolidated Joint Ventures (Detail)	9 Months Ended
	Sep. 30, 2013
	sqft
1005 First Street, NE [Member]	'
Business Acquisition [Line Items]	'
Acquisition Date	1-Aug-11
Reporting Segment	'Washington, D.C.
First Potomac Controlling Interest	97.00%
Square Footage	'
Redland Corporate Center [Member]	'
Business Acquisition [Line Items]	'
Acquisition Date	1-Nov-10
Reporting Segment	'Maryland
First Potomac Controlling Interest	97.00%
Square Footage	349,267

Noncontrolling_Interests_Prope1

Noncontrolling Interests - Property Owned under Consolidated Joint Ventures (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Development placement date	1-Sep-13

ShareBased_Compensation_Additi

Share-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	1 Months Ended		9 Months Ended	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Oct. 03, 2013	Jul. 29, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
	Sep. 30, 2013	Sep. 30, 2013	Subsequent Event [Member]	Non-Vested Common Share Awards [Member]	Non-Vested Common Share Awards [Member]	Non-Vested Share Awards [Member]	Non-Vested Share Awards [Member]	Non-Vested Share Awards [Member]	Non-Vested Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'
Non-vested common shares granted to non-employee trustees	'	'	'	3,210	'	'	'	'	'
Non-vested common shares	'	'	'	'	'May 22, 2014 or the date of the 2014 annual meeting of shareholders of the Company, subject to continued service by the trustee	'	'	'	'
Restricted common shares, granted	'	'	130,464	'	'	'	'	'	'
Expense relating to vesting of shares	$1.20	$1.20	'	'	'	'	'	'	'
Compensation to former employees	0.6	0.6	'	'	'	'	'	'	'
Personnel separation costs	1.8	'	'	'	'	'	'	'	'
Compensation expense associated with share based awards	'	'	'	'	'	$1.90	$0.70	$3.20	$1.90

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	Segment
Segment Reporting [Abstract]	'
Number of distinct operating segments	4

Segment_Information_Summary_of

Segment Information - Summary of Segment Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
	sqft	sqft	sqft	sqft
	Buildings	Buildings	Buildings	Buildings
Segment Reporting Information [Line Items]	'	'	'	'	'
Number of buildings	145	180	145	180	'
Square Feet	8,985,151	13,653,331	8,985,151	13,653,331	'
Total revenues	$40,837	$38,786	$121,971	$117,274	'
Property operating expense	-10,878	-10,035	-31,529	-27,697	'
Real estate taxes and insurance	-4,240	-3,741	-13,104	-12,253	'
Total property operating income	25,719	25,010	77,338	77,324	'
Depreciation and amortization expense	-14,812	-14,144	-43,891	-41,247	'
General and administrative	-6,346	-5,645	-16,598	-17,787	'
Acquisition costs	-173	-8	-173	-49	'
Other expenses, net	-6,134	-5,532	-22,505	-36,703	'
Income from discontinued operations	29	4,058	20,626	7,615	'
Net (loss) income	-1,717	7,435	14,722	-9,261	'
Capital expenditures	12,609	13,429	47,729	48,418	'
Impairment of real estate assets	'	-496	'	-2,444	'
Contingent consideration related to acquisition of property	'	-112	-75	-112	'
Benefit from income taxes	'	4,304	'	4,142	'
Total assets	1,511,283	1,714,237	1,511,283	1,714,237	1,717,748
Washington, D.C. [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Number of buildings	3	4	3	4	'
Square Feet	502,690	531,714	502,690	531,714	'
Total revenues	7,151	6,977	22,307	20,968	'
Property operating expense	-1,779	-1,388	-5,408	-3,842	'
Real estate taxes and insurance	-1,151	-935	-3,746	-2,945	'
Total property operating income	4,221	4,654	13,153	14,181	'
Depreciation and amortization expense	'	'	'	'	'
General and administrative	'	'	'	'	'
Acquisition costs	'	'	'	'	'
Other expenses, net	'	'	'	'	'
Income from discontinued operations	'	'	'	'	'
Net (loss) income	'	'	'	'	'
Capital expenditures	4,758	3,836	17,543	5,541	'
Impairment of real estate assets	'	'	'	'	'
Contingent consideration related to acquisition of property	'	'	'	'	'
Benefit from income taxes	'	'	'	'	'
Total assets	334,427	313,513	334,427	313,513	'
Maryland [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Number of buildings	53	64	53	64	'
Square Feet	2,544,481	3,816,878	2,544,481	3,816,878	'
Total revenues	11,607	11,404	34,982	36,007	'
Property operating expense	-3,034	-2,910	-8,650	-8,065	'
Real estate taxes and insurance	-1,015	-877	-3,029	-3,497	'
Total property operating income	7,558	7,617	23,303	24,445	'
Depreciation and amortization expense	'	'	'	'	'
General and administrative	'	'	'	'	'
Acquisition costs	'	'	'	'	'
Other expenses, net	'	'	'	'	'
Income from discontinued operations	'	'	'	'	'
Net (loss) income	'	'	'	'	'
Capital expenditures	2,662	3,328	10,597	6,359	'
Impairment of real estate assets	'	'	'	'	'
Contingent consideration related to acquisition of property	'	'	'	'	'
Benefit from income taxes	'	'	'	'	'
Total assets	406,789	497,966	406,789	497,966	'
Northern Virginia [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Number of buildings	51	55	51	55	'
Square Feet	3,085,740	3,655,536	3,085,740	3,655,536	'
Total revenues	13,231	11,859	38,589	35,245	'
Property operating expense	-3,088	-3,076	-9,222	-8,477	'
Real estate taxes and insurance	-1,372	-1,269	-4,302	-3,799	'
Total property operating income	8,771	7,514	25,065	22,969	'
Depreciation and amortization expense	'	'	'	'	'
General and administrative	'	'	'	'	'
Acquisition costs	'	'	'	'	'
Other expenses, net	'	'	'	'	'
Income from discontinued operations	'	'	'	'	'
Net (loss) income	'	'	'	'	'
Capital expenditures	2,798	2,877	11,100	15,354	'
Impairment of real estate assets	'	'	'	'	'
Contingent consideration related to acquisition of property	'	'	'	'	'
Benefit from income taxes	'	'	'	'	'
Total assets	426,839	459,153	426,839	459,153	'
Southern Virginia [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Number of buildings	38	57	38	57	'
Square Feet	2,852,240	5,649,203	2,852,240	5,649,203	'
Total revenues	8,848	8,546	26,093	25,054	'
Property operating expense	-2,977	-2,661	-8,249	-7,313	'
Real estate taxes and insurance	-702	-660	-2,027	-2,012	'
Total property operating income	5,169	5,225	15,817	15,729	'
Depreciation and amortization expense	'	'	'	'	'
General and administrative	'	'	'	'	'
Acquisition costs	'	'	'	'	'
Other expenses, net	'	'	'	'	'
Income from discontinued operations	'	'	'	'	'
Net (loss) income	'	'	'	'	'
Capital expenditures	1,979	3,214	7,513	10,050	'
Impairment of real estate assets	'	'	'	'	'
Contingent consideration related to acquisition of property	'	'	'	'	'
Benefit from income taxes	'	'	'	'	'
Total assets	$230,390	$365,687	$230,390	$365,687	'

Segment_Information_Summary_of1

Segment Information - Summary of Segment Information (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]	'	'	'	'
Capital expenditures for corporate assets not allocated to any reportable segments	$412	$174	$976	$1,114
Corporate assets not allocated to any reportable segments	$112,838	$77,918	$112,838	$77,918

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Oct. 01, 2013	Oct. 01, 2013	Oct. 31, 2010
			Subsequent Event [Member]	Redland Corporate Center [Member]	Redland Corporate Center [Member]
			sqft	Subsequent Event [Member]	Subsequent Event [Member]
				sqft
Subsequent Event [Line Items]	'	'	'	'	'
Square foot office building in Rockville	'	'	483,000	134,000	'
Acquisition building in Rockville	$876,086,000	$1,086,694,000	'	$30,000,000	'
Percentage of property leased	'	'	'	100.00%	'
Cost of acquisition funded using sale of industrial portfolio	'	'	$28,200,000	'	'
Lease agreement, year of expiry	'	'	'early 2018	'	'
Percentage of interest acquired by company	'	'	'	'	97.00%