First Potomac Realty Trust (FPO) 10-K 22 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 18, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Entity Registrant Name	FIRST POTOMAC REALTY TRUST
Entity Central Index Key	1,254,595
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		58,101,756
Entity Public Float			$ 593,839,177

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Assets:
Rental property, net		$ 1,130,266	$ 1,288,873
Assets held-for-sale		90,674	59,717
Cash and cash equivalents		13,527	13,323
Escrows and reserves		2,514	2,986
Accounts and other receivables, net of allowance for doubtful accounts of $876 and $1,207, respectively		9,868	10,587
Accrued straight-line rents, net of allowance for doubtful accounts of $105 and $104, respectively		36,888	34,226
Notes receivable, net		34,000	63,679
Investment in affiliates		48,223	47,482
Deferred costs, net		44,502	43,991
Prepaid expenses and other assets		6,950	7,712
Intangible assets, net		32,959	45,884
Total assets	[1],[2]	1,450,371	1,618,460
Liabilities:
Mortgage loans		312,003	305,139
Unsecured term loan		300,000	300,000
Unsecured revolving credit facility		120,000	205,000
Liabilities held-for-sale		1,513	4,562
Accounts payable and other liabilities		47,972	41,113
Accrued interest		1,603	1,720
Rents received in advance		6,003	7,971
Tenant security deposits		4,982	5,891
Deferred market rent, net		2,154	2,827
Total liabilities		796,230	874,223
Noncontrolling interests in the Operating Partnership		28,813	33,332
Equity:
Common shares, $0.001 par value, 150,000 shares authorized; 57,718 and 58,704 shares issued and outstanding, respectively		58	59
Additional paid-in capital		907,220	913,282
Noncontrolling interests in a consolidated partnership		800	898
Accumulated other comprehensive loss		(2,360)	(3,268)
Dividends in excess of accumulated earnings		(440,390)	(360,066)
Total equity		625,328	710,905
Total liabilities, noncontrolling interests and equity		1,450,371	1,618,460
Series A Preferred Shares [Member]
Equity:
Preferred Shares		$ 160,000	$ 160,000
[1]	Corporate assets not allocated to any of our reportable segments totaled $45,088, $84,009 and $73,209 at December 31, 2015, 2014 and 2013, respectively.
[2]	Total assets include our investment in properties that are owned through joint ventures that are not consolidated within our consolidated financial statements. For more information on our unconsolidated investments, including locations within our reportable segments, see note 5, Investment in Affiliates.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Allowance for doubtful accounts, accounts receivable and other	$ 876	$ 1,207
Allowance for doubtful accounts, Accrued straight-line rents	$ 105	$ 104
Preferred stock, par value, per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	50,000	50,000
Series A Preferred Shares, liquidation preference, per share	$ 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	$ 0.001	$ 0.001
Common Stock, shares authorized	150,000	150,000
Common Stock, shares issued	57,718	58,704
Common Stock, shares outstanding	57,718	58,704

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Rental	$ 139,006	$ 128,226	$ 118,337
Tenant reimbursements and other	33,840	33,426	30,478
Total revenues	172,846	161,652	148,815
Operating expenses:
Property operating	44,093	43,252	38,280
Real estate taxes and insurance	19,745	17,360	16,074
General and administrative	25,450	21,156	21,979
Acquisition costs	0	2,681	602
Depreciation and amortization	66,624	61,796	54,567
Impairment of rental property	60,826	3,956	0
Contingent consideration related to acquisition of property	0	0	(213)
Total operating expenses	216,738	150,201	131,289
Operating (loss) income	(43,892)	11,451	17,526
Other expenses, net:
Interest expense	26,797	24,696	32,803
Interest and other income	(6,794)	(6,799)	(6,373)
Equity in (earnings) losses of affiliates	(1,825)	(775)	47
Loss on debt extinguishment / modification	1,824	0	1,810
Gain on sale of rental property	(29,477)	(21,230)	0
Total other (income) expenses	(9,475)	(4,108)	28,287
(Loss) income from continuing operations	(34,417)	15,559	(10,761)
Discontinued operations:
(Loss) income from operations	(975)	146	6,793
Loss on debt extinguishment	(489)	0	(4,414)
Gain on sale of rental property	857	1,338	19,363
(Loss) income from discontinued operations	(607)	1,484	21,742
Net (loss) income	(35,024)	17,043	10,981
Less: Net loss (income) attributable to noncontrolling interests	2,058	(199)	93
Net (loss) income attributable to First Potomac Realty Trust	(32,966)	16,844	11,074
Less: Dividends on preferred shares	(12,400)	(12,400)	(12,400)
Net (loss) income attributable to common shareholders	$ (45,366)	$ 4,444	$ (1,326)
Basic and diluted earnings per common share:
(Loss) income from continuing operations	$ (0.78)	$ 0.05	$ (0.41)
(Loss) income from discontinued operations	(0.01)	0.02	0.38
Net (loss) income	$ (0.79)	$ 0.07	$ (0.03)
Weighted Average Number of Shares Outstanding, Basic	57,982	58,150	55,034
Weighted average common shares outstanding – diluted	57,982	58,220	55,034

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (35,024)	$ 17,043	$ 10,981
Unrealized gain on derivative instruments	1,317	1,289	7,423
Unrealized loss on derivative instruments	(367)	(696)	0
Total comprehensive (loss) income	(34,074)	17,636	18,404
Net loss (income) attributable to noncontrolling interests	2,058	(199)	93
Net gain from derivative instruments attributable to noncontrolling interests	(42)	(25)	(342)
Comprehensive (loss) income attributable to First Potomac Realty Trust	$ (32,058)	$ 17,412	$ 18,155

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Series A Preferred Shares	Common Shares [Member]	Additional Paid-in Capital [Member]	Noncontrolling Interests in Consolidated Partnerships [Member]	Accumulated Other Comprehensive Loss [Member]	Dividends in Excess of Accumulated Earnings [Member]
Beginning balance at Dec. 31, 2012	$ 662,493	$ 160,000	$ 51	$ 804,584	$ 3,728	$ (10,917)	$ (294,953)
Net (loss) income	10,981						10,981
Net unrealized gain (loss) on derivative instruments	7,423					7,423
Net (income) loss attributable to noncontrolling interests	(249)					(342)	93
Dividends paid to common shareholders	(32,917)						(32,917)
Dividends on preferred shares	(12,400)						(12,400)
Accrued common dividends	50						50
Restricted stock expense	3,863			3,863
Exercise of stock options	163			163
Stock option and employee stock purchase plan expense	549			549
Issuance of common stock, net of net settlements	(103,589)		(8)	(103,581)
Acquisition Of Remaining Interests In Consolidated Joint Venture	(4,565)			(1,387)	(3,178)
Adjustment of common Operating Partnership units to fair value	180			180
Noncontrolling interest in consolidated joint ventures, at acquisition	250				250
Income (loss) attributable to noncontrolling interest in consolidated joint ventures	(19)				(19)
Ending balance at Dec. 31, 2013	739,291	160,000	59	911,533	781	(3,836)	(329,246)
Net (loss) income	17,043						17,043
Net unrealized gain (loss) on derivative instruments	593					593
Net (income) loss attributable to noncontrolling interests	(224)					(25)	(199)
Dividends paid to common shareholders	(35,198)						(35,198)
Dividends on preferred shares	(12,400)						(12,400)
Shares issued in exchange for common Operating Partnership units	(66)						(66)
Restricted stock expense	2,860			2,860
Exercise of stock options	174			174
Stock option and employee stock purchase plan expense	536			536
Issuance of common stock, net of net settlements	397			397
Adjustment of common Operating Partnership units to fair value	(1,424)			(1,424)
Net distributions from / contributions to noncontrolling interest in consolidated joint ventures	117				117
Ending balance at Dec. 31, 2014	710,905	160,000	$ 59	913,282	898	(3,268)	(360,066)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	(35,026)				(2)
Net (loss) income	(35,024)						(35,024)
Net unrealized gain (loss) on derivative instruments	950					950
Net (income) loss attributable to noncontrolling interests	2,016					(42)	2,058
Dividends paid to common shareholders	(35,080)						(35,080)
Dividends on preferred shares	(12,400)						(12,400)
Accrued common dividends	117						117
Restricted stock expense	3,447			3,442			5
Exercise of stock options	$ 26			$ 26
Repurchases of common shares	(924,198)		(1,000)	(10,179,000)
Stock Repurchased and Retired During Period, Value	$ (10,180)
Stock option and employee stock purchase plan expense	1,245			$ 1,245
Issuance of common stock, net of net settlements	(1,393)			(1,393)
Adjustment of common Operating Partnership units to fair value	797			797
Net distributions from / contributions to noncontrolling interest in consolidated joint ventures	(96)				(96)
Ending balance at Dec. 31, 2015	$ 625,328	$ 160,000	$ 58	$ 907,220	$ 800	$ (2,360)	$ (440,390)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flow from operating activities:
Net (loss) income	$ (35,024)	$ 17,043	$ 10,981
Discontinued operations:
Gain on sale of rental property	(857)	(1,338)	(19,363)
Loss on debt extinguishment / modification	0	0	192
Depreciation and amortization	1,222	3,665	8,937
Impairment of rental property	0	0	4,092
Depreciation and amortization	67,729	62,843	55,581
Stock based compensation	4,865	3,731	4,412
Bad debt expense	580	1,110	800
Amortization of deferred market rent	138	(14)	76
Amortization of financing costs and discounts	1,482	1,445	2,851
Equity in (earnings) losses of affiliates	(1,825)	(775)	47
Distributions from investments in affiliates	1,490	1,356	2,064
Contingent consideration related to acquisition of property	0	0	(213)
Contingent consideration payments in excess of fair value at acquisition date	0	0	(987)
Impairment of rental property	60,826	3,956	0
Gain on sale of rental property	(29,477)	(21,230)	0
Loss on debt extinguishment / modification	664	0	223
Changes in assets and liabilities:
Escrows and reserves	296	4,693	6,256
Accounts and other receivables	(7)	1,475	1,763
Accrued straight-line rents	(8,722)	(7,968)	(8,078)
Prepaid expenses and other assets	285	326	1,074
Tenant security deposits	(849)	677	1,022
Accounts payable and accrued expenses	7,921	1,227	(2,340)
Accrued interest	(115)	56	(990)
Rents received in advance	(1,767)	1,984	(3,616)
Deferred costs	(8,473)	(11,309)	(9,492)
Total adjustments	95,406	45,910	44,311
Net cash provided by operating activities	60,382	62,953	55,292
Cash flows from investing activities:
Investment in note receivable	0	(9,000)	0
Principal payments from note receivable	29,720	176	104
Proceeds from sale of rental property	129,247	97,701	263,469
Change in escrow and reserve accounts	176	0	(10)
Additions to rental property and furniture, fixtures and equipment	(52,955)	(39,338)	(48,125)
Additions to construction in progress	(20,895)	(11,451)	(19,877)
Acquisition of rental property and associated intangible assets	0	(150,731)	(30,000)
Acquisition of noncontrolling interest in consolidated joint venture	0	0	(4,565)
Investment in affiliates	(405)	(1,988)	(665)
Distributions from investments in affiliates	0	3,075	0
Net cash provided by (used in) investing activities	84,888	(111,556)	160,331
Cash flows from financing activities:
Financing costs	(4,476)	(870)	(5,568)
Issuance of debt	195,956	250,518	152,199
Issuance of common shares, net	0	0	105,085
Payment of deferred acquisition costs and contingent consideration	0	0	(9,036)
Contributions from consolidated joint venture partners	0	213	250
Distributions to consolidated joint venture partners	(96)	(96)	0
Repayments of debt	(277,108)	(147,577)	(412,381)
Dividends to common shareholders	(35,080)	(35,198)	(32,917)
Dividends to preferred shareholders	(12,400)	(12,400)	(12,400)
Distributions to noncontrolling interests	(1,574)	(1,578)	(1,557)
Payments for Repurchase of Common Stock	(10,180)	0	0
Operating partnership unit redemptions	(134)	0	(95)
Proceeds from stock option exercises	26	174	163
Net cash (used in) provided by financing activities	(145,066)	53,186	(216,257)
Net increase (decrease) in cash and cash equivalents	204	4,583	(634)
Cash and cash equivalents, beginning of year	13,323	8,740	9,374
Cash and cash equivalents, end of year	13,527	13,323	8,740
Cash paid for interest, net	25,129	23,083	32,116
Non-cash investing and financing activities:
Debt assumed in connection with the acquisition of rental property	0	37,269	0
Surrendered common shares to satisfy statutory minimum federal income tax obligations	1,781	487	1,348
Change in fair value of the outstanding common Operating Partnership units	(797)	1,424	(215)
Issuance of common Operating Partnership units in connection with the acquisition of rental property	0	40	418
Change in accruals:
Additions to rental property and furniture, fixtures and equipment	795	653	(4,959)
Additions to development and redevelopment	$ 4,408	$ (275)	$ (3,118)

Consolidated Statements of Cas8

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capitalized interest on indebtedness paid in cash	$ 1,900	$ 3,200	$ 2,500
Surrendered common shares to satisfy statutory minimum federal income tax obligations	$ 1,781	487	1,348
Change in redemption value, noncontrolling interest		4,700
Partners' Capital Account, Units, Acquisitions	0
Development and Redevelopment [Member]
Accrued capital expenditure	$ 5,700	1,300	1,500
Furniture and Fixtures [Member]
Accrued capital expenditure	$ 9,900	$ 9,300	$ 8,500
Eight Four Zero First Street Ne [Member]
Partners' Capital Account, Units, Acquisitions		3,125	35,911
Operating Partnership Units Fair Valued		$ 40	$ 400

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Description of Business	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 strategically focuses on acquiring and redeveloping properties that it believes can benefit from its intensive property management, leasing expertise, market knowledge and established relationships, 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. 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. References in these consolidated financial statements to “we,” “our,” “us,” “the Company” or “First Potomac,” refer to the Company and its subsidiaries, on a consolidated basis, unless the context indicates otherwise. We conduct our business through First Potomac Realty Investment Limited Partnership, our operating partnership (the “Operating Partnership”). We are the sole general partner of, and, as of December 31, 2015 , owned 100% of the preferred interest and 95.7% of the common interest in the Operating Partnership. The remaining common interests in the Operating Partnership, which are presented as noncontrolling interests in the Operating Partnership in the accompanying consolidated financial statements, are limited partnership interests that are owned by unrelated parties. At December 31, 2015 , we wholly owned or had a controlling interest in properties totaling 7.5 million square feet and had a noncontrolling ownership interest in properties totaling an additional 0.9 million square feet through five unconsolidated joint ventures. We also owned land that can support 1.3 million square feet of additional development. Our consolidated properties were 90.3% occupied by 454 tenants at December 31, 2015 . We did not include square footage that was in development or redevelopment, which totaled 0.2 million square feet at December 31, 2015 , in our occupancy calculation. We derive substantially all of our revenue from leases of space within our properties. As of December 31, 2015 , our largest tenant was the U.S. Government, which accounted for 12% of our total annualized cash basis rent, and the U.S. Government combined with government contractors accounted for 24% of our total annualized cash basis rent as of December 31, 2015 . We operate so as to qualify as a real estate investment trust (“REIT”) for federal income tax purposes. For the year ended December 31, 2015 , we had consolidated total revenues of $ 172.8 million and consolidated total assets of $1.5 billion . Financial information related to our four reporting segments is set forth in note 17 , Segment Information , to our consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (a) Principles of Consolidation Our consolidated financial statements include our accounts and the accounts of our Operating Partnership and the subsidiaries in which we or our Operating Partnership has a controlling interest, which includes First Potomac Management LLC, a wholly owned subsidiary that manages the majority of our properties. All intercompany balances and transactions have been eliminated in consolidation. (b) Use of Estimates The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires our management team 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 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) Revenue Recognition and Accounts Receivable We generate substantially all of our revenue from leases on our properties. We recognize rental revenue on a straight-line basis over the term of our leases, which includes fixed-rate renewal periods leased at below market rates at acquisition or inception. Accrued straight-line rents represent the difference between rental revenue recognized on a straight-line basis over the term of the respective lease agreements and the rental payments contractually due for leases that contain abatement or fixed periodic increases. We consider current information, credit quality, historical trends, economic conditions and other events regarding the tenants’ ability to pay their obligations in determining if amounts due from tenants, including accrued straight-line rents, are ultimately collectible. The uncollectible portion of the amounts due from tenants, including accrued straight-line rents, is charged to “Property operating expense” in our consolidated statements of operations in the period in which the determination is made and to allowance for doubtful accounts in “Accounts and other receivables” and/or “Accrued straight-line rents” on our consolidated balance sheets. During 2015 , 2014 and 2013 , we incurred charges of $0.6 million , $1.1 million and $0.8 million , respectively, related to anticipated uncollectible amounts from tenants, including accrued straight-line rents. We consider similar criteria in assessing impairment associated with outstanding loans or notes receivable and whether any allowance for anticipated credit loss is appropriate. Tenant leases generally contain provisions under which the tenants reimburse us for a portion of property operating expenses and real estate taxes incurred by us. Such reimbursements are recognized in the period in which the expenses are incurred. We record a provision for losses on estimated uncollectible accounts receivable based on our analysis of risk of loss on specific accounts. Lease termination fees are recognized on the date of termination when the related lease or portion thereof is cancelled, the collectability of the fee is reasonably assured and we have possession of the terminated space. We recognized lease termination fees included in “Tenant reimbursements and other revenues” in our consolidated statements of operations of $0.1 million , $1.1 million and $1.0 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. (d) Cash and Cash Equivalents We consider all highly liquid investments with a maturity of 90 days or less at the date of purchase to be cash equivalents. (e) Escrows and Reserves Escrows and reserves represent cash restricted for debt service, real estate taxes, insurance, leasing commissions and tenant improvements. We reflect cash inflows and outflows from our escrows and reserves accounts related to debt service, real estate taxes, insurance and leasing commissions within net cash provided by operating activities and our cash inflows and outflows related to tenant improvements within net cash used by investing activities on our consolidated statements of cash flows. (f) Deferred Costs Financing costs related to long-term debt are deferred and amortized over the remaining life of the debt using the effective interest method. Leasing costs related to the execution of tenant leases and lease incentives are deferred and amortized ratably over the term of the related leases. Accumulated amortization of these combined costs was $30.1 million and $24.8 million at December 31, 2015 and 2014 , respectively. The following table sets forth scheduled future amortization for deferred financing and leasing costs at December 31, 2015 (amounts in thousands): Deferred Financing (1) Deferred Leasing (1)(2) Deferred Lease Incentive 2016 $ 1,935 $ 2,979 $ 645 2017 1,557 5,033 868 2018 1,347 4,482 834 2019 1,313 3,673 761 2020 379 2,986 691 Thereafter 1,423 8,028 2,519 $ 7,954 $ 27,181 $ 6,318 (1) Includes amounts from properties that were classified as held-for-sale at December 31, 2015 . (2) Excludes the amortization of $3.1 million of leasing costs that have yet to be placed in-service as the associated tenants have not moved into their related spaces and, therefore, the period over which the leasing costs will be amortized has yet to be determined. (g) Rental Property Rental property is initially recorded at fair value, when acquired in a business combination, or initial cost when constructed or acquired in an asset purchase. 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 our assets, by class, are as follows: Buildings 39 years Building improvements 5 to 20 years Furniture, fixtures and equipment 5 to 15 years Tenant improvements Shorter of the useful life of the asset or the term of the related lease We regularly review 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 carrying value of a property, an impairment analysis is performed. We assess 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 to maintain the operating capacity, 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. Further, we will record an impairment loss if we expect to dispose of a property in the near term, at a price below carrying value. In such an event, we 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. We will classify a building as held-for-sale in accordance with GAAP in the period in which we have made the decision to dispose of the building, our 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. We will cease recording depreciation on a building once it has been classified as held-for-sale. In the second quarter of 2014, we prospectively adopted Accounting Standards Update No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity (“ASU 2014-08”), which impacts the presentation of operations and gains or losses from disposed properties and properties classified as held-for-sale. ASU 2014-08 states that a disposal of a component of an entity or a group of components of an entity is required to be reported in discontinued operations only if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations or financial results. The operations of all properties that were sold prior to the adoption of ASU 2014-08, two properties (West Park and Patrick Center) that were classified as held-for-sale in previously issued financial statements prior to our adoption of ASU 2014-08 and were subsequently sold, as well as our Richmond, Virginia portfolio, which included Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land (the “Richmond Portfolio”), are reflected within discontinued operations in our consolidated statements of operations for all periods presented. If the building does not qualify as a discontinued operation under ASU 2014-08, we will classify the building’s operating results, together with any impairment charges and any gains or losses on the sale of the building, in continuing operations for all periods presented in our consolidated statements of operations. We will classify the assets and liabilities related to the building as held-for-sale in our consolidated balance sheet for the period the held-for-sale criteria were met. If the building does qualify as a discontinued operation under ASU 2014-08, we will classify the building’s operating results, together with any impairment charges and any gains or losses on the sale of the building, in discontinued operations in our consolidated statements of operations for all periods presented and classify the assets and liabilities related to the building as held-for-sale in our consolidated balance sheets for the periods presented. Interest expense is reclassified to discontinued operations only to the extent the disposed or held-for-sale property is secured by specific mortgage debt and the mortgage debt will not be assigned to another property owned by us after the disposition. We recognize the fair value, if sufficient information exists to reasonably estimate the fair value, of any liability for conditional asset retirement obligations when assumed or incurred, which is generally upon acquisition, construction, development or redevelopment and/or through the normal operation of the asset. We capitalize interest costs incurred on qualifying expenditures for real estate assets under development or redevelopment, which include our investments 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. We 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. We also capitalize direct compensation costs of our 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. We do not capitalize any other general and administrative costs such as office supplies, office rent expense or an overhead allocation to our development or redevelopment projects. Capitalized compensation costs were immaterial during 2015 , 2014 and 2013 . Capitalization of interest ends 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. We 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. (h) Purchase Accounting Acquisitions of rental property, including any associated intangible assets, are measured at fair value at the date of acquisition. Any liabilities assumed or incurred are recorded at their fair value at the time of acquisition. The fair value of the acquired property is allocated between land and building (on an as-if vacant basis) based on management’s estimate of the fair value of those components for each type of property and to tenant improvements based on the depreciated replacement cost of the tenant improvements, which approximates their fair value. The fair value of the in-place leases is recorded as follows: • the fair value of leases in-place on the date of acquisition is based on absorption costs for the estimated lease-up period in which vacancy and foregone revenue are avoided due to the presence of the acquired leases; • the fair value of above and below-market in-place leases based on the present value (using a discount rate that reflects the risks associated with the acquired leases) of the difference between the contractual rent amounts to be paid under the assumed lease and the estimated market lease rates for the corresponding spaces over the remaining non-cancelable terms of the related leases, which range from one to fourteen years; and • the fair value of intangible tenant or customer relationships. Our determination of these fair values requires us to estimate market rents for each of the leases and make certain other assumptions. These estimates and assumptions affect the rental revenue, and depreciation and amortization expense recognized for these leases and associated intangible assets and liabilities. (i) Investment in Affiliates We may continue to grow our portfolio by entering into ownership arrangements with third parties for which we do not have a controlling interest. The structure of the arrangement may affect our accounting treatment as the entities may qualify as variable interest entities (“VIE”) based on disproportionate voting to equity interests, or other factors . In determining whether to consolidate an entity, we assess the structure and intent of the entity relationship as well its power to direct major decisions regarding the entity’s operations. When our investment in an entity meets the requirements for the equity method of accounting, we will record our initial investment in our consolidated balance sheets as “Investment in affiliates.” The initial investment in the entity is adjusted to recognize our share of earnings, losses, distributions received from the entity or additional contributions. Basis differences, if any, are recognized over the life of the venture as an adjustment to “Equity in (earnings) losses of affiliates” in our consolidated statements of operations. Our respective share of all earnings or losses from the entity will be recorded in our consolidated statements of operations as “Equity in (earnings) losses of affiliates.” When we are deemed to have a controlling interest in a partially-owned entity, we will consolidate all of the entity’s assets, liabilities, operating results and cash flows within our consolidated financial statements. The cash contributed to the consolidated entity by the third party, if any, will be reflected in the permanent equity section of our consolidated balance sheets to the extent the associated ownership interests 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 for any distributions received or additional contributions made by the third party. The earnings or losses from the entity attributable to the third party will be recorded in our consolidated statements of operations as a component of “Net loss (income) attributable to noncontrolling interests.” ( j) Sales of Rental Property We account for sales of rental property in accordance with the requirements for full profit recognition, which occurs when the sale is consummated, the buyer has made adequate initial and continuing investments in the property, our receivable is not subject to future subordination, and we do not have substantial continuing involvement with the property. Once the requirements for full profit recognition are achieved, the related assets and liabilities are removed from the balance sheet and the resultant gain or loss is recorded in the period the sale is consummated. For sales transactions that do not meet the criteria for full profit recognition, we account for the transactions as partial sales or financing arrangements required by GAAP. For sales transactions with continuing involvement after the sale, if the continuing involvement with the property is limited by the terms of the sales contract, profit is recognized at the time of sale and is reduced by the maximum exposure to loss related to the nature of the continuing involvement. Sales to entities in which we have or receive an interest are accounted for as partial sales. For sales transactions that do not meet sale criteria, we evaluate the nature of the continuing involvement, including put and call provisions, if present, and accounts for the transaction as a financing arrangement, profit-sharing arrangement, leasing arrangement or other alternate method of accounting rather than as a sale, based on the nature and extent of the continuing involvement. Some transactions may have numerous forms of continuing involvement. In those cases, we determine which method is most appropriate based on the substance of the transaction. (k) Intangible Assets Intangible assets include the fair value of acquired tenant or customer relationships and the fair value of in-place leases at acquisition. Customer relationship fair values are determined based on our evaluation of the specific characteristics of each tenant’s lease and our overall relationship with the tenant. Characteristics we consider include the nature and extent of our existing business relationships with the tenant, growth prospects for developing new business with the tenant, the tenant’s credit quality and expectations of lease renewals. The fair value of customer relationship intangible assets is amortized to expense over the lesser of the initial lease term and any expected renewal periods or the remaining useful life of the building. We determine the fair value of the in-place leases at acquisition by estimating the leasing commissions avoided by having in-place tenants and the operating income that would have not been recognized during the estimated time required to lease the space occupied by existing tenants at the acquisition date. The fair value attributable to existing tenants is amortized to expense over the initial term of the respective leases. Should a tenant terminate its lease, the unamortized portion of the in-place lease fair value is charged to expense by the date of termination. Deferred market rent liability consists of the acquired leases with below-market rents at the date of acquisition. The fair value attributed to deferred market rent assets, which consist of above-market rents at the date of acquisition, is recorded as a component of deferred costs. Above and below-market lease fair values are determined on a lease-by-lease basis based on the present value (using a discounted rate that reflects the risks associated with the acquired leases) of the difference between the contractual rent amounts to be paid under the lease and the estimated market lease rates for the corresponding spaces over the remaining non-cancelable terms of the related leases including any below-market fixed rate renewal periods. The capitalized below-market lease fair values are amortized as an increase to rental revenue over the initial term and any below-market fixed-rate renewal periods of the related leases. Capitalized above-market lease fair values are amortized as a decrease to rental revenue over the initial term of the related leases. In conjunction with our initial public offering and related formation transactions, First Potomac Management, Inc. contributed all of the capital interests in First Potomac Management LLC. The $2.1 million fair value of the in-place workforce acquired has been classified as goodwill and is included as a component of “Intangible assets, net” on the consolidated balance sheets. In 2011, we recognized additional goodwill of $4.8 million representing the residual difference between the consideration transferred for the purchase of 840 First Street, NE, which was acquired in March 2011, and the acquisition date fair value of the identifiable assets acquired and liabilities assumed and deferred taxes representing the difference between the fair value of acquired assets at acquisition and the carryover basis used for income tax purposes. In accordance with accounting requirements regarding goodwill and other intangibles, all acquired goodwill that relates to the operations of a reporting unit and is used in determining the fair value of a reporting unit is allocated to our appropriate reporting unit in a reasonable and consistent manner. We assess goodwill for impairment annually at the end of our fiscal year and in interim periods if certain events occur indicating the carrying value may be impaired. We perform our analysis for potential impairment of goodwill in accordance with GAAP and are permitted to make a qualitative assessment of whether it is more likely than not that a reporting unit’s fair value is less than its carrying amount before applying the two-step goodwill impairment test for that reporting unit. We assess the impairment of our goodwill based on such qualitative factors as general economic conditions, industry and market conditions, market competiveness, overall financial performance (such as negative cash flows) and other entity specific events. As of December 31, 2015 , we concluded that it was more likely than not that the fair value of our reporting units exceeded its carrying value, and as a result, we determined that it was unnecessary to perform any additional testing for goodwill impairment. No goodwill impairment losses were recognized during 2015 , 2014 and 2013 . (l) Derivative Instruments We are exposed to certain risks arising from business operations and economic factors. We use derivative financial instruments to manage exposures that arise from business activities in which our 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. We do not use derivatives for trading or speculative purposes and we intend to enter into derivative agreements only with counterparties that we believe have a strong credit rating to mitigate the risk of counterparty default or insolvency. No hedging activity can completely insulate us from the risks associated with changes in interest rates. Moreover, interest rate hedging could fail to protect us or adversely affect us because, among other things: • available interest rate hedging may not correspond directly with the interest rate risk for which we seek 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 our ability to sell or assign its side of the hedging transaction. We may designate a derivative as either a hedge of the cash flows from a debt instrument or anticipated transaction (cash flow hedge) or a hedge of the fair value of a debt instrument (fair value hedge). All derivatives are recognized as assets or liabilities at fair value. For effective hedging relationships, the effective portion of the change in the fair value of the assets or liabilities is recorded within equity (cash flow hedge) or through earnings (fair value hedge). Ineffective portions of derivative transactions will result in changes in fair value recognized in earnings. For a cash flow hedge, we record our proportionate share of unrealized gains or losses on our derivative instruments associated with our unconsolidated joint ventures within equity and “Investment in affiliates” on our consolidated balance sheets. We incorporate credit valuation adjustments to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting any applicable credit enhancements, such as collateral postings, thresholds, mutual inputs and guarantees. (m) Income Taxes We have elected to be taxed as a REIT. To maintain our status as a REIT, we are required to distribute at least 90% of our ordinary taxable income annually to our shareholders and meet other organizational and operational requirements. As a REIT, we will not be subject to federal income tax and any non-deductible excise tax if we distribute at least 100% of our REIT taxable income to our shareholders. If we fail to qualify as a REIT in any taxable year, we will be subject to federal income tax on our taxable income at regular corporate tax rates. We have certain subsidiaries, including a taxable REIT subsidiary (“TRS”) and an entity that has elected to be taxed as a REIT (which indirectly owns 500 First Street, NW) that may be subject to federal, state or local taxes, as applicable. Our subsidiary REIT will not be subject to federal income tax so long as it meets the REIT qualification requirements and distributes 100% of its REIT taxable income to its shareholders. Our TRS was inactive in 2015 , 2014 and 2013 . See note 8 , Income Taxes, for further information. We account for deferred income taxes using the asset and liability method. Under this method, deferred income taxes are recognized for temporary differences between the financial reporting basis of assets and liabilities and their respective tax bases and for operating losses, capital losses and tax credit carryovers based on tax rates to be effective when amounts are realized or settled. We will recognize deferred tax assets only to the extent that it is more likely than not that they will be realized based on available evidence, including future reversals of existing temporary differences, future projected taxable income and tax planning strategies. We may recognize a tax benefit from an uncertain tax position when it is more-likely-than-not (defined as a likelihood of more than 50% ) that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. If a tax position does not meet the more-likely-than-not recognition threshold, despite our belief that our filing position is supportable, the benefit of that tax position is not recognized in the statements of operations. We recognize interest and penalties, as applicable, related to unrecognized tax benefits as a component of income tax expense. We recognize unrecognized tax benefits in the period that the uncertainty is eliminated by either affirmative agreement of the uncertain tax position by the applicable taxing authority, or by expiration of the applicable statute of limitation. For the years ended December 31, 2015 , 2014 and 2013 , we did not have any uncertain tax positions. (n) Share-Based Payments We measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. For options awards, we use a Black-Scholes option-pricing model. Expected volatility is based on an assessment of our realized volatility over the preceding period that is equivalent to the award’s expected life. The expected term represents the period of time the options are anticipated to remain outstanding as well as our historical experience for groupings of employees that have similar behavior and considered separately for valuation purposes. For non-vested share awards that vest over a predetermined time period, we use the outstanding share price at the date of issuance to fair value the awards. For non-vested shares awards that vest based on market conditions, we use a Monte Carlo simulation (risk-neutral approach) to determine the value and derived service period of each tranche. The expense associated with the share-based awards will be recognized over the period during which an employee is required to provide services in exchange for the award – the requisite service period (usually the vesting period). The fair value for all share-based payment transactions are recognized as a component of income or loss from continuing operations. (o) Notes Receivable We provide loans to the owners of real estate properties, which can be collateralized by interest in the real estate property. We record these loans as “Notes receivable, net” in our 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. We record interest earned from notes receivable and amortization of any discount costs or issuance costs within “Interest and other income” in our consolidated statements of operations. We will establish a provision for anticipated credit losses associated with our notes receivable when we anticipate that we 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. Our collectability of our notes receivable may be adversely impacted by the financial stability of the Washington, D.C. region and the ability of the 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 we estimate to be adequate based on these factors. Based on the review of the above criteria, we did not record an allowance for credit losses for our notes receivable during 2015 , 2014 and 2013 . (p) Application of New Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers and will replace most existing revenue recognition guidance when it becomes effective. In July 2015, the FASB deferred by one year the mandatory effective date of ASU 2014-09 from January 1, 2017 to January 1, 2018. Early adoption is permitted, but not prior to the original effective date of January 1, 2017. ASU 2014-09 permits the use of either the retrospective or cumulative effect transition method. We have not yet selected a transition method and are evaluating the impact that ASU 2014-09 will have on our consolidated financial statements and related disclosures. In August 2014, the FASB issued Accounting Standar

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Common Share	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. We apply the two-class method for determining EPS as our outstanding unvested shares with non-forfeitable dividend rights are considered participating securities. Our excess of distributions over earnings related to participating securities is shown as a reduction in total earnings attributable to common shareholders in our computation of EPS. The following table sets forth the computation of our basic and diluted earnings per common share (amounts in thousands, except per share amounts): 2015 2014 2013 Numerator for basic and diluted earnings per common share: (Loss) income from continuing operations $ (34,417 ) $ 15,559 $ (10,761 ) (Loss) income from discontinued operations (607 ) 1,484 21,742 Net (loss) income (35,024 ) 17,043 10,981 Less: Net loss (income) from continuing operations attributable to noncontrolling interests 2,032 (135 ) 1,047 Less: Net loss (income) from discontinued operations attributable to noncontrolling interests 26 (64 ) (954 ) Net (loss) income attributable to First Potomac Realty Trust (32,966 ) 16,844 11,074 Less: Dividends on preferred shares (12,400 ) (12,400 ) (12,400 ) Net (loss) income attributable to common shareholders (45,366 ) 4,444 (1,326 ) Less: Allocation to participating securities (241 ) (314 ) (388 ) Net (loss) income attributable to common shareholders $ (45,607 ) $ 4,130 $ (1,714 ) Denominator for basic and diluted earnings per common share: Weighted average common shares outstanding – basic 57,982 58,150 55,034 Weighted average common shares outstanding – diluted 57,982 58,220 55,034 Basic and diluted earnings per common share: (Loss) income from continuing operations $ (0.78 ) $ 0.05 $ (0.41 ) (Loss) income from discontinued operations (0.01 ) 0.02 0.38 Net (loss) income $ (0.79 ) $ 0.07 $ (0.03 ) In accordance with GAAP regarding earnings per common share, we did not include the following potential weighted average common shares in our calculation of diluted earnings per common share as they are anti-dilutive for the periods presented (amounts in thousands): 2015 2014 2013 Stock option awards 1,020 1,122 1,369 Non-vested share awards 310 398 471 1,330 1,520 1,840

Rental Property

Rental Property	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Rental Property	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 we have a controlling interest. All of our rental properties are located within the greater Washington, D.C. region. Rental property consists of the following at December 31 (dollars in thousands): 2015 (1) 2014 (2) Land and land improvements $ 280,149 $ 325,214 Buildings and improvements 793,184 949,683 Construction in progress 97,361 69,181 Tenant improvements 168,946 159,867 Furniture, fixtures and equipment 410 427 1,340,050 1,504,372 Less: accumulated depreciation (209,784 ) (215,499 ) $ 1,130,266 $ 1,288,873 (1) Excludes rental property totaling $90.6 million at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9 (a), Dispositions ), which was classified as held-for-sale at December 31, 2015. (2) Excludes rental property totaling $57.7 million at December 31, 2014 related to the sale of the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015. Depreciation of rental property is computed on a straight-line basis over the estimated useful lives of the assets. The estimated lives of our assets range from 5 to 39 years or, in the case of tenant improvements, the shorter of the useful life of the asset or the term of the underlying lease. Development and Redevelopment Activity We will place completed development and redevelopment assets in service upon the earlier of one year after major construction activity is deemed to be substantially complete or upon occupancy. We construct office buildings and/or business parks on a build-to-suit basis or with the intent to lease upon completion of construction. We own developable land that can accommodate 1.3 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, 0.4 million in the Northern Virginia reporting segment and 0.1 million in the Southern Virginia reporting segment. During the third quarter of 2014, we signed a lease for 167,000 square feet at a to-be-constructed building in our Northern Virginia reporting segment on vacant land that we had in our portfolio. We currently expect to complete construction of the new building in the first quarter of 2016 and expect to complete the construction of the tenant improvements in the second half of 2016; however, we can provide no assurance regarding the timing, costs or results of the project. At December 31, 2015, our total investment in the development project, excluding tenant improvements and leasing commission costs, was $29.5 million , which included the original cost basis of the applicable portion of the vacant land of $5.2 million . The majority of the costs incurred as of December 31, 2015 in excess of the original cost basis of the land relate to design and permit fees, site preparation costs, foundation work and completion of the building’s core and superstructure. On August 4, 2011, we formed a joint venture, in which we have a 97% interest, with an affiliate of Perseus Realty, LLC to acquire Storey Park in our Washington, D.C. reporting segment. At the time, the site was leased to Greyhound Lines, Inc. (“Greyhound”), which subsequently relocated its operations. Greyhound’s lease expired on August 31, 2013 , at which time the property was placed into development with the anticipation of developing a mixed-use project on the 1.6 acre site, which can accommodate up to 712,000 square feet. At December 31, 2015, our total investment in the development project was $58.0 million , which included the original cost basis of the property of $43.3 million . The majority of the costs in excess of the original cost basis relate to architectural fees and site preparation costs, as well as capitalized interest and taxes. In February 2016, we entered into a contract, subject to a study period, to sell Storey Park. The sale is expected to be completed in the first half of 2016 and we do not anticipate a loss on the sale; however, we can provide no assurances regarding the timing or pricing of the sale, or that such sale will ultimately occur. Due to the uncertainty of the sale, we did not classify the property as held-for-sale at December 31, 2015 . On December 28, 2010, we acquired 440 First Street, NW, a vacant eight-story office building in our Washington, D.C. reporting segment. In October 2013, we substantially completed the redevelopment of the 139,000 square foot property, and at the time of completion, our total investment in the redevelopment project was $55.5 million , which included the original cost basis of the property of $23.6 million . During the fourth quarter of 2014, all vacant space at the property was placed in-service. At December 31, 2015, the property was 71.7% leased and 56.9% occupied. We did no t place in-service any significant completed development or redevelopment space during 2015. At December 31, 2015, we had no completed development or redevelopment space that had yet to be placed in-service.

Investment in Affiliates

Investment in Affiliates	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Investment in Affiliates	Investment in Affiliates We own an interest in several joint ventures that own properties. We do 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 our consolidated financial statements. Our investments in these joint ventures are recorded as “Investment in affiliates” in our consolidated balance sheets. Our investment in affiliates consisted of the following at December 31 (dollars in thousands): 2015 Reporting Segment Ownership Interest Company Investment Debt Recourse Debt (1) Prosperity Metro Plaza Northern Virginia 51 % $ 24,909 $ 50,000 $ — 1750 H Street, NW Washington, D.C. 50 % 15,168 32,000 — Aviation Business Park Maryland 50 % 5,899 — — Rivers Park I and II (2) Maryland 25 % 2,247 28,000 2,800 $ 48,223 $ 110,000 $ 2,800 2014 Reporting Segment Ownership Interest Company Investment Debt Recourse Debt (1) Prosperity Metro Plaza Northern Virginia 51 % $ 24,651 $ 50,000 $ — 1750 H Street, NW Washington, D.C. 50 % 14,834 32,000 — Aviation Business Park Maryland 50 % 5,748 — — Rivers Park I and II (2) Maryland 25 % 2,249 28,000 2,800 $ 47,482 $ 110,000 $ 2,800 (1) We believe the fair value of the potential liability to us related to the recourse debt is inconsequential as the likelihood of our need to perform under the debt agreement is remote. (2) Rivers Park I and Rivers Park II are owned through two separate joint ventures. On November 12, 2014, our 51% owned unconsolidated joint venture repaid a $48.3 million mortgage loan that encumbered Prosperity Metro Plaza, a two-building, 327,000 square-foot office building located in Merrifield, Virginia. Simultaneously with the repayment, the joint venture entered into a new $50.0 million mortgage loan that has a fixed-interest rate of 3.91% . The new loan requires interest only payments through December 2024 , at which time the loan requires principal and interest payments through its maturity date. The loan has a maturity date of December 1, 2029 and is repayable in full without penalty on or after June 1, 2029 . On September 26, 2014, our two 25% owned unconsolidated joint ventures amended a $28.0 million mortgage loan that encumbers Rivers Park I and II, a six-building, 308,000 square-foot business park located in Columbia, Maryland. The amended mortgage loan reduced the variable interest rate spread by 60 basis points and reduced the amount of outstanding principal recourse to us from 25% to 10% . The amended loan matures on September 26, 2017 and is repayable in full without penalty at any time during the term of the loan. On July 10, 2014, an unconsolidated joint venture, in which we have a 50% ownership interest, repaid a $27.9 million mortgage loan that encumbered 1750 H Street, NW, a ten-story, 113,000 square-foot office building located in Washington, D.C. Simultaneously with the repayment, the joint venture entered into a new $32.0 million mortgage loan that has a fixed interest rate of 3.92% , a maturity date of August 1, 2024 , and is repayable in full without penalty on or after August 1, 2021 . The new loan requires monthly interest-only payments with a constant interest rate over the life of the loan. The net assets of our unconsolidated joint ventures consisted of the following at December 31 (dollars in thousands): 2015 2014 Assets: Rental property, net $ 193,243 $ 193,533 Cash and cash equivalents 5,992 4,567 Other assets 17,218 16,748 Total assets 216,453 214,848 Liabilities: Mortgage loans 110,000 110,000 Other liabilities 7,215 7,256 Total liabilities 117,215 117,256 Net assets $ 99,238 $ 97,592 Our share of earnings or losses related to our unconsolidated joint ventures is recorded in our consolidated statements of operations as “Equity in (earnings) losses of affiliates.” The following table summarizes the results of operations of our unconsolidated joint ventures at December 31, which, due to our varying ownership interests in the joint ventures and the varying operations of the joint ventures, may not be reflective of the amounts recorded in our consolidated statements of operations (amounts in thousands): 2015 2014 2013 Total revenues $ 24,255 $ 23,285 $ 24,017 Total operating expenses (7,660 ) (7,408 ) (7,753 ) Net operating income 16,595 15,877 16,264 Depreciation and amortization (8,718 ) (9,893 ) (11,551 ) Interest expense, net (3,909 ) (3,890 ) (4,222 ) Provision for income taxes — (63 ) (83 ) Contingent consideration charge — 126 — Net income $ 3,968 $ 2,157 $ 408 We earn various fees from several of our joint ventures, which include management fees, leasing commissions and construction management fees. We recognize fees only to the extent of the third party ownership interest in our unconsolidated joint ventures. We recognized fees from our unconsolidated joint ventures of $0.7 million , $0.7 million and $0.6 million in 2015, 2014 and 2013, respectively, which are reflected within “Tenant reimbursements and other revenues” in our consolidated statements of operations.

Notes Receivable

Notes Receivable	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Notes Receivable	Notes Receivable Below is a summary of our notes receivable for our outstanding mezzanine loans at December 31, 2015 and 2014 (dollars in thousands): Balance at December 31, 2015 Property Face Amount Unamortized Origination Fees Balance Interest Rate 950 F Street, NW $ 34,000 $ — $ 34,000 9.75 % Balance at December 31, 2014 Property Face Amount Unamortized Origination Fees Balance Interest Rate 950 F Street, NW $ 34,000 $ — $ 34,000 9.75 % America’s Square 29,720 (41 ) 29,679 9.00 % $ 63,720 $ (41 ) $ 63,679 On February 24, 2015, the owners of America Square, a 461,000 square foot office complex located in Washington, D.C., prepaid a mezzanine loan that had an outstanding balance of $29.7 million . We provided the owners of America’s Square a $30.0 million loan in April 2011 , which was secured by a portion of the owner’s interest in the property. The loan had a fixed-interest rate of 9.0% and was scheduled to mature on May 1, 2016 . We received a yield maintenance payment of $2.4 million with the repayment of the loan. The yield maintenance payment is recorded within “Interest and other income” in our consolidated statements of operations. The proceeds from the loan repayment, including the yield maintenance payment, were used to pay down a portion of the outstanding balance under our unsecured revolving credit facility. In December 2010 , we provided a $25.0 million mezzanine loan to the owners of 950 F Street, NW, a ten-story, 287,000 square-foot, office/retail building located in Washington, D.C. that is secured by a portion of the owners’ interest in the property. The loan requires monthly interest-only payments with a constant interest rate over the life of the loan. On January 10, 2014, we amended the loan to increase the outstanding balance to $34.0 million and reduce the fixed interest rate from 12.50% to 9.75% . The amended mezzanine loan matures on April 1, 2017 and, as of December 21, 2015, is repayable in full with 30 days’ prior written notice. As a result of the amendment, we wrote-off $0.1 million of unamortized fees related to the original 950 F Street, NW mezzanine loan. The $9.0 million increase in the loan was provided by a draw under our unsecured revolving credit facility. We recorded interest income related to our notes receivable of $3.7 million , $6.1 million and $5.9 million during 2015, 2014, and 2013, respectively, which is included within “Interest and other income” in our consolidated statements of operations. Payments under the outstanding loan were current at December 31, 2015. The amortization of origination fees associated with our notes receivable was immaterial for 2015, 2014 and 2013.

Intangible Assets and Deferred

Intangible Assets and Deferred Market Rent Liabilities	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Deferred Market Rent Liabilities	Intangible Assets and Deferred Market Rent Liabilities Intangible assets and deferred market rent liabilities consisted of the following at December 31 (amounts in thousands): 2015 (1) 2014 (1) Gross Intangibles Accumulated Amortization Net Intangibles Gross Intangibles Accumulated Amortization Net Intangibles In-place leases $ 45,901 $ (26,961 ) 18,940 $ 51,258 $ (22,443 ) $ 28,815 Customer relationships 663 (601 ) 62 906 (654 ) 252 Leasing commissions 10,612 (5,485 ) 5,127 11,335 (4,272 ) 7,063 Legal leasing fees 344 (177 ) 167 377 (118 ) 259 Deferred market rent assets 3,558 (1,825 ) 1,733 3,906 (1,309 ) 2,597 Goodwill 6,930 — 6,930 6,930 — 6,930 $ 68,008 $ (35,049 ) $ 32,959 $ 74,712 $ (28,796 ) $ 45,916 Deferred market rent liability $ 4,869 $ (2,715 ) $ 2,154 $ 5,193 $ (2,348 ) $ 2,845 (1) The 2014 balances include amounts from properties that were classified as held-for-sale at December 31, 2014. There were no intangible assets or deferred market rent liabilities classified as held-for-sale at December 31, 2015. We recognized $10.6 million , $10.3 million and $8.3 million of amortization expense on intangible assets for the years ended December 31, 2015, 2014 and 2013, respectively. Through the net amortization of deferred market rent assets and deferred market rent liabilities, we recognized a $0.1 million reduction of rental revenue in 2015, an additional $14 thousand of revenue in 2014 and a $0.1 million reduction of revenue in 2013. Losses due to the termination of tenant leases and defaults, which resulted in the write-offs of all related lease-level and intangible assets, were $0.5 million , $1.1 million and $1.0 million during 2015, 2014 and 2013, respectively. The projected net amortization of intangible assets and deferred market liabilities as of December 31, 2015 are as follows (amounts in thousands): 2016 $ 7,318 2017 4,203 2018 2,700 2019 2,388 2020 2,146 Thereafter 5,120 $ 23,875

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We own properties in Washington, D.C. that are subject to income-based franchise taxes at an effective rate of 9.975% as a result of conducting business in Washington, D.C. Our deferred tax assets and liabilities associated with our properties were primarily associated with differences in the GAAP and tax basis of rental property, particularly acquisition costs, but also included intangible assets and deferred market rent assets and liabilities that were associated with properties located in Washington, D.C. We will recognize deferred tax assets only to the extent that it is more likely than not that deferred tax assets will be realized based on consideration of available evidence, including future reversals of existing taxable temporary differences, future projected taxable income and tax planning strategies. During the third quarter of 2012, there was a change in tax regulations in Washington, D.C. that required us to file a unitary tax return, which allowed for a deduction for dividends paid to shareholders. The change in tax regulations resulted in us prospectively measuring all of our deferred tax assets and deferred tax liabilities using the effective tax rate ( 0% ) expected to be in effect as these timing differences reverse; therefore, we did not record a benefit from income taxes during 2015, 2014 or 2013. At December 31, 2015 and 2014, we recorded an estimated $1.2 million receivable within “Accounts and other receivables” in our consolidated balance sheets for an expected tax refund associated with our 2011 tax payments and the estimated payments made in 2012 arising from the change in regulations in 2012. At December 31, 2015 and 2014, we did not have any recorded deferred tax assets or deferred tax liabilities. We also have interests in an unconsolidated joint venture that owns rental property in Washington, D.C. that is subject to the franchise tax. The impact for income taxes related to this unconsolidated joint venture is reflected within “Equity in (earnings) losses of affiliates” in our consolidated statements of operations. We did not record a valuation allowance against our deferred tax assets for any period presented. We did not recognize any deferred tax assets or liabilities as a result of uncertain tax positions and had no material net operating loss, capital loss or alternative minimum tax carryovers for any of the periods presented. There was no benefit or provision for income taxes associated with our discontinued operations for any of the periods presented. As we believe we both qualify as a REIT and will not be subject to federal income tax, a reconciliation between the income tax provision calculated at the statutory federal income tax rate and the actual income tax provision has not been provided.

Dispositions

Dispositions	12 Months Ended
	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Dispositions During the second quarter of 2014, we prospectively adopted ASU 2014-08, which states that a component of an entity or a group of components of an entity is required to be reported in discontinued operations only if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations and financial results. All other disposed properties will have their operating results reflected within continuing operations on our consolidated statements of operations for all periods presented. We have had, and will have, no continuing involvement with any of our disposed properties subsequent to their disposal. The operations of the disposed properties were not subject to any income based taxes. Other than the properties discussed below in this note 9 , Dispositions , we did not dispose of or enter into any agreements to sell any other properties during 2015, 2014 and 2013. (a) Disposed or Held-for-Sale Properties within Continuing Operations The following table is a summary of property dispositions or held-for-sale properties whose operating results are included in continuing operations in our consolidated statements of operations for the periods presented (dollars in thousands): Reporting Disposition Date Property Type Square Feet Net Sale Proceeds NOVA Non-Core Portfolio (1) Northern Virginia TBD Various 945,745 $ 90,600 (2) Cedar Hill I and III Northern Virginia 12/23/2015 Office 102,632 25,939 Newington Business Park Center Northern Virginia 12/17/2015 Industrial 255,600 31,409 Rumsey Center Maryland 7/28/2015 Business Park 135,015 14,956 Owings Mills Business Park Maryland 10/16/2014 Business Park 180,475 12,417 Corporate Campus at Ashburn Center Northern Virginia 6/26/2014 Business Park 194,184 39,910 (1) The NOVA Non-Core Portfolio (defined below) was classified as held-for-sale at December 31, 2015. The sale is expected to occur in the first half of 2016; however, we can provide no assurances regarding the timing or pricing of the sale, or that such sale will occur at all. (2) The net sales proceeds are an estimate based on the contract in place at the time of this filing. We can provide no assurances regarding the timing or pricing of the sale, or that such sale will occur at all. In late January 2016, we entered into a binding contract to sell a portfolio of properties located in our Northern Virginia reporting segment that consists of Van Buren Office Park, Herndon Corporate Center, Windsor at Battlefield, Reston Business Campus, Enterprise Center, Gateway Centre Manassas, Linden Business Center and Prosperity Business Center (collectively, the “NOVA Non-Core Portfolio”). The NOVA Non-Core Portfolio is comprised of eight properties totaling 945,745 square feet. The sale is expected to be completed in the first half of 2016; however, we can provide no assurances regarding the timing or pricing of the sale, or that such sale will occur at all. Coinciding with our review of year-end results and assessment of overall market conditions, we incurred an impairment charge of $26.9 million based on the fair value of the portfolio, less estimated selling costs. At December 31, 2015 , the NOVA Non-Core Portfolio met our held-for-sale criteria, and, therefore, the assets of the buildings were classified within “Assets held-for-sale” and the liabilities of the buildings, which include one mortgage that will be repaid, were classified within “Liabilities held-for-sale” in our consolidated balance sheet. The majority of the assets classified within assets held-for-sale as of December 31, 2015 consisted of $25.2 million in land and land improvements, $88.0 million in buildings and building improvements, $14.4 million in tenant improvements and $37.0 million of accumulated depreciation. Assets held-for-sale also consisted of immaterial amounts of accrued straight-line rents, net of allowance for doubtful accounts, deferred costs, net of accumulated amortization, and prepaid expenses and other assets. The operating results of the NOVA Non-Core Portfolio, Cedar Hill I and III, Newington Business Park Center, Rumsey Center, Corporate Campus at Ashburn Center and Owings Mills Business Park are reflected in continuing operations in our consolidated statements of operations for the periods the respective properties were owned by us. The following table summarizes the aggregate results of operations for the disposed or held-for-sale properties that are included in continuing operations for the periods presented (dollars in thousands): 2015 2014 2013 Revenues $ 21,826 $ 26,037 $ 29,016 Property operating expenses (7,745 ) (9,664 ) (10,249 ) Depreciation and amortization (7,037 ) (9,114 ) (9,697 ) Interest expense, net of interest income (465 ) (842 ) (1,258 ) Impairment of rental property (26,929 ) (3,956 ) — (Loss) income from operations of disposed property (20,350 ) 2,461 7,812 Gain on sale of rental property 29,477 21,230 — Net income from continuing operations $ 9,127 $ 23,691 $ 7,812 (b) Discontinued Operations The following table is a summary of property dispositions whose operating results are reflected as discontinued operations in our consolidated statements of operations for the periods presented (dollars in thousands): Reporting Segment Disposition Date Property Type Square Feet Net Sale Proceeds Richmond Portfolio (1) Southern Virginia 3/19/2015 Business Park 827,900 $ 53,768 Patrick Center Maryland 4/16/2014 Office 66,269 10,888 West Park Maryland 4/2/2014 Office 28,333 2,871 Girard Business Center and Gateway Center Maryland 1/29/2014 Business Park and Office 341,973 31,616 Worman’s Mill Court Maryland 11/19/2013 Office 40,099 3,362 Triangle Business Center Maryland 9/27/2013 Business Park 74,429 2,732 4200 Tech Court Northern Virginia 8/15/2013 Office 33,875 3,210 Industrial Portfolio (2) Various May/June 2013 Industrial 4,280,985 176,569 4212 Tech Court Northern Virginia 6/5/2013 Office 32,055 2,469 (1) The Richmond Portfolio includes 19 buildings totaling 827,900 square feet and a three-acre parcel of undeveloped land. (2) During the second quarter of 2013, we sold 24 industrial properties, which consisted of two separate transactions. On May 7, 2013, we sold I-66 Commerce Center, a 236,000 square foot industrial property in Haymarket, Virginia. On June 18, 2013, we completed the sale of the remaining 23 industrial properties. All properties sold prior to our adoption of ASU 2014-08, or classified as held-for-sale in previously issued consolidated financial statements prior to our adoption of ASU 2014-08, are classified within discontinued operations. In March 2015 , we sold our Richmond, Virginia portfolio, which was located in our Southern Virginia reporting segment. The Richmond Portfolio consisted of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land, and in the aggregate was comprised of 19 buildings totaling 827,900 square feet. With the sale of our Richmond Portfolio, we no longer owned any properties in the Richmond, Virginia area and had strategically exited the Richmond market. As such, in accordance with ASU 2014-08, our Richmond Portfolio was classified as held-for-sale at December 31, 2014 and the operating results of the Richmond Portfolio are reflected within discontinued operations for each of the periods presented. At December 31, 2014, the Richmond Portfolio met our held-for-sale criteria and, therefore, the assets of the buildings were classified within “Assets held-for-sale” and the liabilities of the buildings, along with five mortgage loans that were repaid, were classified within “Liabilities-held-for-sale” in our consolidated balance sheet. The majority of the assets classified within “Assets held-for sale” at December 31, 2014, consisted of $7.7 million in land, $62.0 million in buildings, $8.5 million in tenant improvements, $0.1 million in construction in progress and $20.6 million of accumulated depreciation. The remaining $2.0 million classified within “Assets held-for sale” consisted of accrued straight-line rents, net of allowance for doubtful accounts, deferred costs, net of accumulated amortization, prepaid expenses and other assets, and intangible assets, net of accumulated amortization. The majority of “Liabilities held-for-sale” at December 31, 2014 consisted of $3.5 million of mortgage debt. The remaining $1.1 million classified within “Liabilities held-for-sale” consisted of prepaid rent and security deposits. The following table summarizes the results of operations of properties included in discontinued operations for the years ended December 31 (dollars in thousands): 2015 2014 2013 Revenues $ 877 $ 7,688 $ 31,654 Property operating expenses (638 ) (3,612 ) (10,564 ) Depreciation and amortization (1,222 ) (3,662 ) (8,937 ) Net interest income (expense) 8 (268 ) (1,268 ) Impairment of rental property — — (4,092 ) (Loss) income from operations of disposed property (975 ) 146 6,793 Loss on debt extinguishment (489 ) — (4,414 ) Gain on sale of rental property 857 1,338 19,363 Net (loss) income from discontinued operations $ (607 ) $ 1,484 $ 21,742

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	Debt Our borrowings consisted of the following at December 31 (dollars in thousands): 2015 2014 Mortgage loans, effective interest rates ranging from 4.22% to 6.01%, maturing at various dates through September 2030 (1)(2) $ 312,216 $ 308,637 Unsecured term loan, effective interest rates ranging from LIBOR plus 1.45% to LIBOR plus 1.80%, with staggered maturity dates ranging from December 2020 to December 2022 (1) 300,000 300,000 Unsecured revolving credit facility, effective interest rate of LIBOR plus 1.50%, maturing December 2019 (1) 120,000 205,000 $ 732,216 $ 813,637 (1) At December 31, 2015 , LIBOR was 0.43% . All references to LIBOR in the consolidated financial statements refer to one-month LIBOR. (2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9 , Dispositions , for further discussion. (a) Mortgage Loans The following table provides a summary of our mortgage debt at December 31, 2015 and 2014 (dollars in thousands): Encumbered Property Contractual Interest Rate Effective Interest Rate Maturity Date December 31, 2015 December 31, 2014 Jackson National Life Loan (1) 5.19 % 5.19 % August 2015 $ — $ 64,943 440 First Street, NW Construction Loan (2) LIBOR + 2.50% LIBOR + 2.50% May 2016 32,216 32,216 Storey Park Land Loan (2) LIBOR + 2.50% LIBOR + 2.50% October 2016 22,000 22,000 Gateway Centre Manassas Building I (3) 7.35 % 5.88 % November 2016 — 432 Hillside I and II 5.75 % 4.62 % December 2016 12,540 12,949 Redland Corporate Center Buildings II & III 4.20 % 4.64 % November 2017 64,543 65,816 Northern Virginia Construction Loan (2) LIBOR + 1.85% LIBOR + 1.85% September 2019 9,176 — 840 First Street, NE 5.72 % 6.01 % July 2020 35,888 36,539 Battlefield Corporate Center 4.26 % 4.40 % November 2020 3,526 3,692 1211 Connecticut Avenue, NW 4.22 % 4.47 % July 2022 29,110 29,691 1401 K Street, NW 4.80 % 4.93 % June 2023 36,224 36,861 11 Dupont Circle, NW 4.05 % 4.22 % September 2030 66,780 — 4.58 % (4) 312,003 305,139 Unamortized fair value adjustments (172 ) (370 ) Principal balance 311,831 304,769 Debt Classified within Liabilities Held-for-Sale Gateway Centre Manassas Building I (3) 7.35 % 5.88 % November 2016 213 — Richmond Portfolio (5) Hanover Business Center Building D 8.88 % 6.63 % August 2015 — 104 Chesterfield Business Center Buildings C,D,G and H 8.50 % 6.63 % September 2015 — 302 Hanover Business Center Building C 7.88 % 6.63 % December 2017 — 505 Chesterfield Business Center Buildings A,B,E and F 7.45 % 6.63 % June 2021 — 1,674 Airpark Business Center 7.45 % 6.63 % June 2021 — 913 213 3,498 Total unamortized fair value adjustments (1 ) (73 ) Principal balance 212 3,425 Total principal balance $ 312,043 $ 308,194 (1) On July 21, 2015, we prepaid, without penalty, the $64.2 million outstanding balance on our Jackson National Life Loan, which was scheduled to mature in August 2015 and was secured by the following properties: Plaza 500, Van Buren Office Park, Greenbrier Technology Center II, Norfolk Business Center, Snowden Center and Rumsey Center, which was subsequently sold on July 28, 2015. (2) At December 31, 2015 , LIBOR was 0.43% . (3) Gateway Centre Manassas is included in the NOVA Non-Core Portfolio, which was classified as held-for-sale at December 31, 2015. The mortgage loan that encumbers Gateway Centre Manassas was classified within “ Liabilities held-for-sale ” on our December 31, 2015 consolidated balance sheet. (4) Weighted average interest rate on total mortgage debt. (5) The mortgage loans that encumbered properties within the Richmond Portfolio and related unamortized fair value adjustments were classified within “Liabilities held-for-sale” on our December 31, 2014 consolidated balance sheet and were repaid upon the sale of the Richmond Portfolio in March 2015. Land Loan On October 16, 2014, our 97% owned consolidated joint venture that owns Storey Park repaid a $22.0 million loan that encumbered the Storey Park land and was subject to a 5.0% interest rate floor. Simultaneously with the repayment, the joint venture entered into a new $22.0 million land loan (the “Storey Park Land Loan”) with a variable interest rate of LIBOR plus a spread of 2.50% . The new loan matures on October 16, 2016 , with a one-year extension at our option, and is repayable in full without penalty at any time during the term of the loan. Per the terms of the loan agreement, $6.0 million of the outstanding principal balance and all of the outstanding accrued interest is recourse to us. As of December 31, 2015 , we were in compliance with all the financial covenants of the Storey Park Land Loan. Construction Loans On September 1, 2015, we entered into a construction loan (the “Northern Virginia Construction Loan”) that is collateralized by a 167,000 square foot office building that is currently in development in Northern Virginia. We currently expect to complete construction of the new building in early 2016 and expect to complete the construction of the tenant improvements in the second half of 2016. The loan has a borrowing capacity of up to $43.7 million , of which we borrowed $9.2 million as of December 31, 2015 . The loan has a variable interest rate of LIBOR plus a spread of 1.85% and matures on September 1, 2019 . We can repay all or a portion of the Northern Virginia Construction Loan, without penalty, at any time during the term of the loan. As of December 31, 2015 , we were in compliance with all of the financial covenants of the Northern Virginia Construction Loan. On June 5, 2013, we entered into a construction loan (the “440 First Street, NW Construction Loan”) that is collateralized by our 440 First Street, NW property, which underwent a major redevelopment that was substantially completed in October 2013. The 440 First Street, NW Construction Loan has a borrowing capacity of up to $43.5 million , of which we initially borrowed $21.7 million in the second quarter of 2013 and borrowed an additional $10.5 million in 2014. The 440 First Street, NW Construction Loan has a variable interest rate of LIBOR plus a spread of 2.50% and matures in May 2016 , with two one -year extension options at our discretion. We can repay all or a portion of the 440 First Street, NW Construction Loan, without penalty, at any time during the term of the loan. At December 31, 2015 , per the terms of the loan agreement, 50% of the outstanding principal balance and all of the outstanding accrued interest were recourse to us. The percentage of outstanding principal balance that is recourse to us can be reduced upon the property achieving certain operating thresholds. As of December 31, 2015 , we were in compliance with all of the financial covenants of the 440 First Street, NW Construction Loan. With the exception of the 440 First Street, NW Construction Loan, our mortgage debt is recourse solely to specific assets. We had 11 and 18 consolidated properties that secured mortgage debt at December 31, 2015 and 2014 , respectively. We have originated or assumed the following mortgage loans since January 1, 2014 (dollars in thousands): Month Year Property Effective Interest Rate Principal Amount September 2015 Northern Virginia Construction Loan LIBOR + 1.85% (1) $ 9,176 August 2015 11 Dupont Circle, NW 4.22% 66,780 October 2014 Storey Park Land Loan LIBOR + 2.50% (1) 22,000 (2) April 2014 1401 K Street, NW 4.93% 37,269 (1) At December 31, 2015, LIBOR was 0.43% . (2) We have a 97% ownership interest in the property through a consolidated joint venture. The loan balance in the chart above reflects the entire loan balance, which is reflected in our consolidated balance sheets. We have repaid the following mortgage loans since January 1, 2014 (dollars in thousands): Month Year Property Effective Interest Rate Principal Balance Repaid July 2015 Jackson National Life Loan 5.19 % $ 64,230 March 2015 Hanover Business Center Building D 6.63 % 65 March 2015 Chesterfield Business Center Buildings C,D,G and H 6.63 % 202 March 2015 Hanover Business Center Building C 6.63 % 460 March 2015 Chesterfield Business Center Buildings A,B,E and F 6.63 % 1,584 March 2015 Airpark Business Center 6.63 % 864 October 2014 Storey Park Land Loan 5.80 % 22,000 May 2014 Annapolis Business Center 6.25 % 8,027 (b) Unsecured Term Loan On December 4, 2015, we amended, restated and consolidated our unsecured revolving credit facility and our unsecured term loan. The amendments extended the maturity date of the unsecured term loan’s three $100 million tranches to December 2020 , June 2021 and December 2022 from October 2018 , October 2019 and October 2020, respectively. As part of the amendments, we reduced the interest rate spreads on our unsecured term loan, reduced the capitalization rates used to calculate gross asset value in the financial covenants and amended the covenant package to more closely align with our corporate goals. During the fourth quarter of 2015, we incurred $1.7 million of debt modification charges related to amending and restating our unsecured term loan. The table below shows the outstanding balances and the interest rates of the three tranches of the $300.0 million unsecured term loan at December 31, 2015 (dollars in thousands): Maturity Date Amount Interest Rate (1) Tranche A December 2020 $ 100,000 LIBOR, plus 145 basis points Tranche B June 2021 100,000 LIBOR, plus 145 basis points Tranche C December 2022 100,000 LIBOR, plus 180 basis points $ 300,000 (1) At December 31, 2015 , LIBOR was 0.43% . The interest rate spread is subject to change based on our maximum total indebtedness ratio. For more information, see note 10 (e), Debt – Financial Covenants . The credit agreement governing our unsecured revolving credit facility and consolidated term loan contains various restrictive covenants, including with respect to liens, indebtedness, investments, distributions, mergers and asset sales. In addition, the agreement requires that we satisfy certain financial covenants that are also substantially identical to those contained in our 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 our Company under the agreement to be immediately due and payable. As of December 31, 2015 , we were in compliance with all the financial covenants of the unsecured term loan. (c) Unsecured Revolving Credit Facility On December 4, 2015, we amended, restated and consolidated our unsecured revolving credit facility and our unsecured term loan. The amendments extended the maturity date of the unsecured revolving credit facility to December 2019 from October 2017, with two, six-month extensions at our option. As part of the amendments, we reduced the interest rate spreads on our unsecured revolving credit facility, reduced the capitalization rates used to calculate gross asset value in the financial covenants and amended the covenant package to more closely align with our corporate goals. During the fourth quarter of 2015, we incurred $0.1 million of debt modification charges related to amending and restating the unsecured revolving credit facility. The weighted average borrowings outstanding under the unsecured revolving credit facility were $165.5 million with a weighted average interest rate of 1.9% during 2015 compared with $136.1 million and 1.7% , respectively, during 2014 . Our maximum outstanding borrowings were $218.0 million and $216.0 million during 2015 and 2014 , respectively. At December 31, 2015 , outstanding borrowings under the unsecured revolving credit facility were $120.0 million with a weighted average interest rate of 1.8% . At December 31, 2015 , LIBOR was 0.43% and the applicable spread on our unsecured revolving credit facility was 150 basis points. The available capacity under the unsecured revolving credit facility was $114.0 million as of the date of this filing. We are required to pay a commitment fee at an annual rate of 0.15% of the unused capacity if our usage exceeds 50% of our total capacity under the revolving credit facility, or 0.25% if our usage does not exceed 50%. For more information, see note 10 (e) Debt – Financial Covenants . As of December 31, 2015 , we were in compliance with all the financial covenants of the unsecured revolving credit facility. (d) Interest Rate Swap Agreements At December 31, 2015 , we fixed LIBOR, at a weighted average interest rate of 1.5% , on $300.0 million of our variable rate debt through eleven interest rate swap agreements. In January 2014, an interest rate swap that fixed LIBOR on $50.0 million of variable rate debt expired. See note 11 , Derivative Instruments , for more information about our interest rate swap agreements. (e) Financial Covenants Our outstanding corporate debt agreements contain specific financial covenants that may impact future financing decisions made by us or may be impacted by a decline in operations. These covenants relate to our allowable leverage, minimum tangible net worth, fixed charge coverage and other financial metrics. As of December 31, 2015 , we were in compliance with the covenants of our unsecured term loan and unsecured revolving credit facility and any such financial covenants of our mortgage debt (including the 440 First Street, NW Construction Loan and the Storey Park land loan). Our 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 we were 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 we 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 our liquidity, financial condition, results of operations and ability to make distributions to our shareholders. Our unsecured revolving credit facility and unsecured term loan are subject to interest rate spreads that float based on the quarterly measurement of our maximum consolidated total indebtedness to gross asset value ratio. Based on our leverage ratio at December 31, 2015 , beginning on March 30, 2016, the applicable interest rate spreads on the unsecured revolving credit facility and tranches A and B of the unsecured term loan will decrease by 15 basis points, and the applicable interest rate spread on tranche C of the unsecured term loan will decrease by 20 basis points. (f) Aggregate Debt Maturities Our aggregate debt maturities as of December 31, 2015 , including amounts from properties that were classified as held-for-sale at December 31, 2015 , are as follows (dollars in thousands): 2016 $ 70,260 2017 65,456 2018 2,354 2019 131,648 2020 137,203 Thereafter 325,122 732,043 Unamortized fair value adjustments 173 Total contractual principal balance $ 732,216

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments Our interest rate swap agreements are designated as cash flow hedges and we record 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 our consolidated balance sheets. We record our proportionate share of any unrealized gains or losses on our cash flow hedges associated with our unconsolidated joint ventures within “Accumulated other comprehensive loss” and “Investment in affiliates” on our consolidated balance sheets. We record any gains or losses incurred as a result of each interest rate swap agreement’s fixed rate deviating from our respective loan’s contractual rate within “Interest expense” in our consolidated statements of operations. We did not have any material ineffectiveness associated with our cash flow hedges in 2015 , 2014 and 2013 . We enter into interest rate swap agreements to hedge our exposure on our 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 December 31, 2015 , we fixed LIBOR at a weighted average interest rate of 1.5% on $300.0 million of our variable rate debt through eleven interest rate swap agreements that are summarized below (dollars in thousands): Maturity Date Notional Amount Interest Rate Contractual Component Fixed LIBOR Interest Rate July 2016 $ 35,000 LIBOR 1.754 % July 2016 25,000 LIBOR 1.763 % July 2017 30,000 LIBOR 2.093 % July 2017 30,000 LIBOR 2.093 % July 2017 25,000 LIBOR 1.129 % July 2017 12,500 LIBOR 1.129 % July 2017 50,000 LIBOR 0.955 % July 2018 12,500 LIBOR 1.383 % July 2018 30,000 LIBOR 1.660 % July 2018 25,000 LIBOR 1.394 % July 2018 25,000 LIBOR 1.135 % Total/Weighted Average $ 300,000 1.505 % Amounts reported in “Accumulated other comprehensive loss” on our consolidated balance sheet at December 31, 2015 related to derivatives will be reclassified to “Interest expense” on our consolidated statements of operations as interest payments are made on our variable-rate debt. We reclassified accumulated other comprehensive losses as an increase to interest expense of $4.0 million , $4.1 million and $4.6 million in 2015 , 2014 and 2013 , respectively. At December 31, 2015 , we estimated that $2.4 million of our accumulated other comprehensive loss will be reclassified as an increase to interest expense over the following twelve months.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Our application of GAAP 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 we provide 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 we have 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 our 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 our consolidated assets and liabilities that are measured on a non-recurring and recurring basis as of December 31, 2015 and 2014 (amounts in thousands): Balance at December 31, 2015 Level 1 Level 2 Level 3 Non-recurring Measurements: Impaired real estate assets $ 104,625 $ — $ 90,625 $ 14,000 Recurring Measurements: Derivative instrument-swap liabilities 2,491 — 2,491 — Balance at December 31, 2014 Level 1 Level 2 Level 3 Recurring Measurements: Derivative instrument-swap assets $ 133 $ — $ 133 $ — Derivative instrument-swap liabilities 3,569 — 3,569 — We 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 years ended December 31, 2015 and 2014. 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 years ended December 31, 2015 and 2014. Impairment of Rental Property We regularly review 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. In late January 2016, we entered into a binding contract to sell our NOVA Non-Core Portfolio, which is located in our Northern Virginia reporting segment. Based on the anticipated sales price, less estimated selling costs, we recorded an impairment charge of $26.9 million . The sale expected to be completed in the first half of 2016; however, we can provide no assurances regarding the timing or pricing of the sale, or that such sale will occur at all. Our One Fair Oaks office property, which is located in our Northern Virginia reporting segment, is currently fully leased to CACI International. We expect CACI International to vacate the property upon their lease expiration in December 2016, and, as a result of the anticipated loss of cash flow and the anticipated challenges re-leasing the property, we evaluated the recoverability of the property's carry value at December 31, 2015, which coincided with our review of year-end results and assessment of overall market conditions. Based on an analysis of the undiscounted net cash flows from One Fair Oaks, we concluded that the carrying value of the property was not recoverable and recorded an impairment charge of $33.9 million to bring the property to its estimated fair value. We estimated the fair value of the property using a discounted cash flow analysis and comparable sales information. In our analysis, we estimated the future net cash flows from the property using an income-based valuation of the building as vacant. The expected useful life and holding period was based on the age of the property and our current plan for the property as well as experience with similar properties. The capitalization rate was estimated using rates from external market research and comparable market transactions, and the discount rate was estimated using a risk adjusted rate of return. We incurred impairment charges of $60.8 million , $4.0 million and $4.1 million during 2015, 2014 and 2013, respectively. The total impairment charges incurred during 2015 related to the above mentioned NOVA Non-Core Portfolio and our One Fair Oaks property, and are reflected within continuing operations in our consolidated statements of operations. The $4.0 million of impairment charges incurred during 2014 related to disposed properties that are reflected within continuing operations on our consolidated statements of operations. The impairment charges incurred during 2013 related to properties that were subsequently disposed of at December 31, 2014 and are recorded within discontinued operations in our consolidated statements of operations. See note 9 , Dispositions for more information. Interest Rate Derivatives At December 31, 2015 , we had hedged $300.0 million of our variable rate debt through eleven interest rate swap agreements. See note 11 , Derivative Instruments, for more information about our interest rate swap agreements. The interest rate derivatives are fair valued based on prevailing market yield curves on the measurement date and also incorporate credit valuation adjustments to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting any applicable credit enhancements, such as collateral postings, thresholds, mutual inputs and guarantees. We use a third party to assist in valuing our 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 our interest rate swap agreements. Our 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 our 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. We determine the fair value of our 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. We deem the fair value measurement of our debt instruments as a Level 2 measurement as we use quoted interest rates for similar debt instruments to value our debt instruments. We also use quoted market interest rates for similar notes to value our notes receivable, which we consider a Level 2 measurement as we do not believe notes receivable trade in an active market. The carrying amount and estimated fair value of our notes receivable and debt instruments at December 31 are as follows (amounts in thousands): 2015 2014 Carrying Value Fair Value Carrying Value Fair Value Financial Assets: Notes receivable (1) $ 34,000 $ 34,000 $ 63,679 $ 63,720 Financial Liabilities: Mortgage debt (2) $ 312,216 $ 298,541 $ 308,637 $ 292,882 Unsecured term loan 300,000 300,000 300,000 300,000 Unsecured revolving credit facility 120,000 120,000 205,000 205,000 Total $ 732,216 $ 718,541 $ 813,637 $ 797,882 (1) The principal amount of our notes receivable was $34.0 million and $63.7 million at December 31, 2015 and 2014, respectively. On February 24, 2015, the owners of America’s Square, a 461,000 square foot office complex located in Washington, D.C., prepaid the $29.7 million outstanding balance of the $30.0 million mezzanine loan that we provided to them in April 2011. (2) Includes $0.2 million and $3.5 million of mortgage debt that were classified as held-for-sale and included within “Liabilities held-for-sale” on our consolidated balance sheets for December 31, 2015 and 2014, respectively. See note 9 , Dispositions for additional details.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies (a) Operating Leases Our rental properties are subject to non-cancelable operating leases generating future minimum contractual rent payments due from tenants, which as of December 31, 2015 are as follows (dollars in thousands): Future minimum contractual rent payments 2016 $ 129,004 2017 112,800 2018 100,533 2019 87,924 2020 72,606 Thereafter 206,499 $ 709,366 Our consolidated properties were 90.3% occupied by 454 tenants at December 31, 2015 . We did not include square footage that was in development or redevelopment, which totaled 0.2 million square feet at December 31, 2015 , in our occupancy calculation. We rent office space for our corporate headquarters under a non-cancelable operating lease, which we entered into in 2005. The lease agreement for our corporate headquarters will expire on January 31, 2021 . During the fourth quarter of 2012, we subleased 5,000 square feet of our corporate office space to one tenant, which commenced in January 2013 . During the fourth quarter of 2013, the subtenant amended its lease to include an additional 2,700 square feet, which the subtenant occupied in March 2014 . During the third quarter of 2015, the subtenant further amended its lease to expand their office space by an additional 1,321 square feet, which the subtenant occupied in December 2015 . The subtenant’s lease will expire in January 2018 and the lease has a termination option in January 2016 . Rent expense incurred under the terms of the corporate office leases, net of subleased revenue, was $1.6 million for the year ended December 31, 2015 and $1.8 million for both the years ended December 31, 2014 and 2013. Future minimum rental payments under our corporate office leases as of December 31, 2015 are summarized as follows, net of sublease revenue (dollars in thousands): Future minimum rent payments 2016 $ 1,431 2017 1,469 2018 1,906 2019 1,995 2020 2,049 Thereafter 175 $ 9,025 (b) Legal Proceedings We are subject to legal proceedings and claims arising in the ordinary course of our business, for which, we carry various forms of insurance to protect the Company. In the opinion of our management and legal counsel, the amount of ultimate liability with respect to these claims will not have a material impact on our financial position, results of operations or cash flows. (c) Capital Commitments As of December 31, 2015 , we had contractual construction in progress obligations, which included amounts accrued at December 31, 2015 , of $13.7 million . The amount of contractual construction in progress obligations are primarily related to development activities for the to-be-constructed building in our Northern Virginia reporting segment. As of December 31, 2015 , we had contractual rental property and furniture, fixtures and equipment obligations of $27.8 million outstanding, which included amounts accrued at December 31, 2015 . The amount of contractual rental property and furniture, fixtures and equipment obligations at December 31, 2015 included significant tenant improvement costs for the lease at the build-to-suit building in our Northern Virginia reporting segment. We anticipate meeting our contractual obligations related to our construction activities with cash from our operating activities. In the event cash from our operating activities is not sufficient to meet our contractual obligations, we can access additional capital through our unsecured revolving credit facility. We remain liable, solely to the extent of our proportionate ownership percentage, to fund any capital shortfalls or commitments from properties owned through unconsolidated joint ventures. We have various obligations to certain local municipalities associated with our development projects that will require completion of specified site improvements, such as sewer and road maintenance, grading and other general landscaping work. As of December 31, 2015 , we remained liable to those local municipalities for $2.6 million in the event that we do not complete the specified work. We intend to complete the site improvements in satisfaction of these obligations. (d) Insurance We carry insurance coverage on our properties with policy specifications and insured limits that we believe are adequate given the relative risk of loss, cost of the coverage and standard industry practice. However, certain types of losses (such as from terrorism, earthquakes and floods) may be either uninsurable or not economically insurable. Further, certain of the properties are located in areas that are subject to earthquake activity and floods. Should a property sustain damage as a result of a terrorist act, earthquake or flood, we may incur losses due to insurance deductibles, co-payments on insured losses or uninsured losses. Should an uninsured loss occur, we could lose some or all of our capital investment, cash flow and anticipated profits related to one or more properties.

Equity

Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Equity	Equity In December 2015, our Board of Trustees authorized the redemption of some or all of our 6.4 million outstanding shares of our Series A Preferred Shares. On January 19, 2016 , we redeemed 2.2 million shares, representing approximately 34% , of our 6.4 million outstanding Series A Preferred Shares at a redemption price of $25.00 per share, plus accrued dividends. We used proceeds from the sale of Newington Business Park Center and Cedar Hill I and III to partially redeem the Series A Preferred Shares. In July 2015, our Board of Trustees authorized a share repurchase program that allows us to acquire up to five million of our common shares of beneficial interest from time to time through July 2016 in open market transactions at prevailing prices or in negotiated private transactions. We are not obligated to acquire any particular amount of common shares and the share repurchase program may be suspended by the Board of Trustees at any time. During 2015, we repurchased 924,198 shares at a weighted-average share price of $10.99 for a total purchase price of $10.2 million , utilizing a portion of the proceeds from our sale of Rumsey Center. As of the date of this filing, we are authorized to repurchase an additional 4.1 million of our common shares through July 2016. We declared and paid dividends of $0.60 per common share to common shareholders during each of 2015, 2014 and 2013 . We declared and pai d dividends of $1.9375 per share on our Series A Preferred Shares during 2015, 2014 and 2013. On January 26, 2016 , we 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 February 16, 2016 to common shareholders of record as of F ebruary 9, 2016 . We also declared a dividend on January 26, 2016 of $0.484375 per share on our Series A Preferred Shares. The dividend was paid on February 16, 2016 to preferred shareholders of record as of F ebruary 9, 2016 . Dividends on all non-vested share awards are recorded as a reduction of shareholders’ equity. For each dividend paid by us on our common and preferred shares, the Operating Partnership distributes an equivalent distribution on our common and preferred Operating Partnership units, respectively. Our unsecured revolving credit facility, unsecured term loan, the 440 First Street, NW Construction Loan, the Northern Virginia Construction Loan and the Storey Park Land Loan contain certain restrictions that include, among other things, requirements to maintain specified coverage ratios and other financial covenants, which may limit our ability to make distributions to our common and preferred shareholders, except for distributions required to maintain our qualification as a REIT. Further, distributions with respect to our common shares are subject to our ability to first satisfy our obligations to pay distributions to the holders of our Series A Preferred Shares. For federal income tax purposes, dividends paid to shareholders may be characterized as ordinary income, return of capital or capital gains. The characterization of the dividends declared on our common and preferred shares for 2015 , 2014 and 2013 are as follows: Common Shares Preferred Shares 2015 2014 2013 2015 2014 2013 Ordinary income (1) 52.01 % 72.42 % 13.53 % 72.89 % 100.00 % 100.00 % Return of capital 28.64 % 27.58 % 86.47 % — — — Capital gains 19.35 % — — 27.11 % — — (1) The dividends classified above as ordinary income do not represent “qualified dividend income” and, therefore, are not eligible for reduced rates.

Noncontrolling Interests

Noncontrolling Interests	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Noncontrolling Interests	Noncontrolling Interests (a) Noncontrolling Interests in the Operating Partnership Noncontrolling interests relate to the common interests in the Operating Partnership not owned by us. 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 our option, our common shares on a one-for-one basis or cash based on the fair value of our 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. We account for issuances of common Operating Partnership units individually, which could result in some portion of our noncontrolling interests being carried at fair value with the remainder being carried at historical cost. Based on the closing price of our common shares at December 31, 2015, the cost to acquire, through cash purchase or issuance of our common shares, all of the outstanding common Operating Partnership units not owned by us would be $29.9 million . At December 31, 2015 and 2014, we recorded adjustments of $4.0 million and $4.7 million , respectively, to present certain common Operating Partnership units at the greater of their carrying value or redemption value. We owned 95.7% of the outstanding common Operating Partnership units at December 31, 2015 , 2014 , and 2013 . At December 31, 2015, 2,619,069 of the total common Operating Partnership units, or 4.3% , were not owned by us. During 2015, 11,508 common Operating Partnership units were redeemed with available cash, and during 2013, 6,718 common Operating Partnership units were redeemed with available cash. There were no common Operating Partnership units redeemed for cash in 2014. There were no common Operating Partnership units redeemed for common shares in 2015, 2014 or 2013. During the first quarter of 2014, we issued 3,125 common Operating Partnership units to the seller of 840 First Street, NE to satisfy a contingent consideration obligation related to the acquisition of the property. The redeemable noncontrolling interests in the Operating Partnership for the three years ended December 31 are as follows (dollars in thousands): Redeemable noncontrolling interests Balance at December 31, 2013 $ 33,221 Net income 199 Changes in ownership, net 1,465 Distributions to owners (1,578 ) Other comprehensive income 25 Balance at December 31, 2014 33,332 Net loss (2,056 ) Changes in ownership, net (931 ) Distributions to owners (1,574 ) Other comprehensive income 42 Balance at December 31, 2015 $ 28,813 (b) Noncontrolling Interests in the Consolidated Partnerships When we are deemed to have a controlling interest in a partially-owned entity, we will consolidate all of the entity’s assets, liabilities and operating results within our consolidated financial statements. The net assets contributed to the consolidated entity by the third party, if any, will be reflected within permanent equity in our 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 our consolidated statements of operations. On August 4, 2011, we formed a joint venture, in which we have a 97% interest, with an affiliate of Perseus Realty, LLC to acquire Storey Park in our Washington, D.C. reporting segment. At the time, the site was leased to Greyhound Lines, Inc. (“Greyhound”), which subsequently relocated its operations. Greyhound’s lease expired on August 31, 2013 , at which time the property was placed into development with the anticipation of developing a mixed-use project on the 1.6 acre site, which can accommodate up to 712,000 square feet. At December 31, 2015, our total investment in the development project was $58.0 million , which included the original cost basis of the property of $43.3 million . The majority of the costs in excess of the original cost basis relate to architectural fees and site preparation costs, as well as capitalized interest and taxes. In February 2016, we entered into a contract, subject to a study period, to sell Storey Park. The sale is expected to be completed in the first half of 2016 and we do not anticipate a loss on the sale; however, we can provide no assurances regarding the timing or pricing of the sale, or that such sale will ultimately occur. Due to the uncertainty of the sale, we did not classify the property as held-for-sale at December 31, 2015 . On October 16, 2014, our 97% owned consolidated joint venture repaid a $22.0 million loan that was subject to a 5.0% interest rate floor. The loan encumbered the Storey Park land which is located in Washington, D.C. Simultaneously with the repayment, the joint venture entered into a new $22.0 million loan with a variable-interest rate of LIBOR plus 2.50% .

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Benefit Plans	Benefit Plans (a) Share-Based Payments We issued share-based payments in the form of stock options and non-vested shares as permitted in our 2003 Equity Compensation Plan (the “2003 Plan”), which was amended in 2005, 2007 and July 2013, and expired in September 2013. We have also issued share-based compensation in the form of stock options and non-vested shares as permitted in our 2009 Equity Compensation Plan (the “2009 Plan”), which was amended in 2010, 2011 and 2013. In 2011, we received shareholder approval to authorize an additional 4.5 million shares for issuance under the 2009 Plan. The compensation plans provide for the issuance of options to purchase common shares, share awards, share appreciation rights, performance units and other equity-based awards. Stock options granted under the plans are non-qualified, and all employees and non-employee trustees are eligible to receive grants. Under the terms of the amendment to the 2009 Plan, every stock option granted by us reduces the awards available for issuance on a one -for-one basis. However, for every restricted award issued, the awards available for issuance are reduced by 3.44 awards. At December 31, 2015 , we had 7.4 million share equity awards authorized under the 2009 Plan and, of those awards, 2.8 million common share equity awards remained available for issuance by us. We record costs related to our share-based compensation based on the grant-date fair value calculated in accordance with GAAP. We recognize 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 our consolidated statements of operations based on the employee’s job function. Stock Options Summary As of December 31, 2015 , 2.3 million stock options have been awarded of which 1.0 million stock options remained outstanding. During the first quarter of 2015, we issued 119,500 stock options to our non-officer employees. The stock options vest 25% on the first anniversary of the date of grant and 6.25% in each subsequent calendar quarter. The awards described above have a ten -year contractual life. We recognized $1.2 million of compensation expense associated with stock option awards for the year ended December 31, 2015 and $0.5 million for both the years ended December 31, 2014 and 2013. Compensation expense associated with our stock option awards for the year ended December 31, 2015 includes a $0.8 million charge related to the accelerated vesting of 0.3 million options in accordance with the separation agreement for our former Chief Executive Officer. A summary of our stock option activity for the three years ended December 31 is presented below: Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2012 1,384,006 $ 15.91 5.9 years $ 174,763 Granted 124,250 12.73 Exercised (14,733 ) 11.05 Expired (298,469 ) 15.00 Forfeited (105,762 ) 16.17 Outstanding at December 31, 2013 1,089,292 15.83 6.6 years $ 109,151 Granted 135,250 11.61 Exercised (17,171 ) 10.10 Expired (57,500 ) 19.08 Forfeited (98,512 ) 14.49 Outstanding at December 31, 2014 1,051,359 15.33 6.3 years $ 181,352 Granted 119,500 12.48 Exercised (2,750 ) 9.30 Expired (59,000 ) 22.44 Forfeited (145,971 ) 15.06 Outstanding at December 31, 2015 963,138 $ 14.59 6.1 years $ 59,002 Exercisable at December 31: 2015 805,259 $ 15.06 5.6 years $ 59,002 2014 552,620 16.49 5.1 years 102,039 2013 521,723 17.25 4.9 years 109,151 Options expected to vest, subsequent to December 31, 2015 142,530 $ 12.29 8.5 years $ — The following table summarizes information about our stock options at December 31, 2015 : Options Outstanding Options Exercisable Year Issued Range of Exercise Prices Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Options Weighted Average Exercise Price 2006 $ 26.60 11,850 0.0 years $ 26.60 11,850 $ 26.60 2007 29.11 - 29.24 24,500 1.1 years 29.14 24,500 29.14 2008 17.29 26,250 2.0 years 17.29 26,250 17.29 2009 9.30 28,096 3.0 years 9.30 28,096 9.30 2010 12.57 33,830 4.0 years 12.57 33,830 12.57 2011 17.12 37,250 5.0 years 17.12 37,250 17.12 2012 13.54 - 15.00 553,001 6.0 years 14.86 549,937 14.87 2013 12.73 63,845 7.0 years 12.73 48,655 12.73 2014 11.61 87,266 8.0 years 11.61 44,891 11.61 2015 12.48 97,250 9.0 years 12.48 — — 963,138 6.1 years 14.60 805,259 15.06 As of December 31, 2015 , we had $0.3 million of unrecognized compensation cost, net of estimated forfeitures, related to stock option awards. We anticipate this cost will be recognized over a weighted-average period of approximately 2.2 years . We calculate the grant date fair value of option awards using a Black-Scholes option-pricing model. Expected volatility is based on an assessment of our realized volatility over the preceding period that is equivalent to the award’s expected life, which in our opinion, gives an accurate indication of future volatility. The expected term represents the period of time the options are anticipated to remain outstanding as well as our historical experience for groupings of employees that have similar behavior and are considered separately for valuation purposes. The risk-free rate is based on the U.S. Treasury rate at the time of grant for instruments of similar term. The weighted average assumptions used in the fair value determination of stock options granted to employees for the years ended December 31 are summarized as follows: 2015 2014 2013 Risk-free interest rate 1.61 % 1.72 % 0.76 % Expected volatility 29.2 % 39.0 % 49.7 % Expected dividend yield 4.79 % 4.66 % 4.92 % Weighted average expected life of options 5.0 years 5.0 years 5.0 years The weighted average grant date fair value of the stock options issued in 2015, 2014 and 2013 was $1.96 , $2.67 and $3.61 , respectively. Option Exercises We received $26 thousand , $174 thousand and $163 thousand from the exercise of stock options during 2015, 2014 and 2013, respectively. Shares issued as a result of stock option exercises are provided by the issuance of new shares. The total intrinsic value of options exercised was $7 thousand in 2015, and $43 thousand in both 2014 and 2013. Non-Vested Share Awards We issue 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. We issue new common shares, subject to restrictions, upon each grant of non-vested common share awards. In February 2015, we granted a total of 121,380 non-vested common shares to our officers, which will vest ratably on an annual basis over a three-year period from the date of grant. In November 2015, we entered into separation agreements with our former Chief Executive Officer and Chief Investment Officer. Pursuant to the terms of their respective separation agreements, all of the former officers’ non-vested restricted share awards, which totaled an aggregate 229,171 restricted shares, vested on November 8, 2015, their date of separation. We incurred $1.2 million of compensation expense related to the accelerated vesting of the former officers’ non-vested restricted share awards. We recognized $3.3 million , $2.8 million and $3.5 million of compensation expense associated with our non-vested common share awards in 2015, 2014 and 2013, respectively. Compensation expense associated with our non-vested common shares for 2015 and 2013 each included $1.2 million of expense related to the accelerated vesting of the restricted shares associated with the departure of two former officers in 2015 and a former officer in 2013. Dividends on all non-vested common share awards are recorded as a reduction of equity. We apply the two-class method for determining EPS as our outstanding non-vested common shares with non-forfeitable dividend rights are considered participating securities. Our excess of dividends over earnings related to participating securities are shown as a reduction in net income or loss attributable to common shareholders in our computation of EPS. Independent members of our Board of Trustees received annual grants of restricted common shares as a component of compensation for serving on our Board of Trustees. In May 2015, we granted 31,218 non-vested common shares to our non-employee trustees, all of which will vest on the earlier of the first anniversary of the grant date or the date of our 2016 annual meetings of our shareholders, subject to continued service by the trustee until that date. We recognized $0.4 million of compensation expense associated with trustee restricted share awards for the years ended December 31, 2015, 2014 and 2013. A summary of our non-vested common share awards at December 31, 2015 is as follows: Non-vested Shares Weighted Average Grant Date Fair Value Non-vested at December 31, 2012 673,828 $ 12.83 Granted 313,086 12.14 Vested (297,778 ) 12.89 Expired (45,049 ) 11.42 Forfeited (6,425 ) 14.01 Non-vested at December 31, 2013 637,662 13.33 Granted 164,675 12.84 Vested (137,924 ) 14.21 Expired (29,514 ) 10.21 Forfeited (11,478 ) 13.04 Non-vested at December 31, 2014 623,421 13.16 Granted 152,598 11.79 Vested (401,888 ) 13.16 Expired (133,371 ) 12.61 Forfeited (48,378 ) 13.30 Non-vested at December 31, 2015 192,382 $ 12.42 As of December 31, 2015 , we had $1.4 million of unrecognized compensation cost related to non-vested common shares. We anticipate this cost will be recognized over a weighted-average period of 1.7 years . We value our non-vested time-based awards issued in 2015, 2014 and 2013 at the grant date fair value, which is the market price of our common shares. For the non-vested performance-based share awards issued in 2013, we used a Monte Carlo Simulation (risk-neutral approach) to determine the number of shares that may be issued pursuant to the award as these awards were deemed to have a market condition. The risk-free interest rate assumptions used in the Monte Carlo Simulation were determined based on the zero coupon risk-free rate for the time frame of 0.25 years to 3.0 years , which ranged from 0.11% to 0.4% , respectively. The volatility used for our common share price in the Monte Carlo Simulation varied between 24.31% and 29.11% . We did not issue any non-vested performance-based awards in 2015 or 2014. The weighted average grant date fair value of the shares issued in 2015, 2014 and 2013 were $11.79 , $12.84 and $12.14 , respectively. The total fair value of shares vested were $5.3 million , $2.0 million and $3.8 million at December 31, 2015, 2014 and 2013, respectively. We issue new shares, subject to restrictions, upon each grant of non-vested common share awards. (b) 401(k) Plan We have a 401(k) defined contribution plan covering all employees in accordance with the Internal Revenue Code. The maximum employer or employee contribution cannot exceed the IRS limits for the plan year. In 2014, we amended the eligibility requirements of the plan, allowing employees to contribute after 60 days of consecutive service. Employee contributions vest immediately. Employer contributions begin one year after the employee’s start of service and vest ratably over four years . For the three years ended December 31, 2015, 2014 and 2013, we matched up to 6% of each employee’s contributions. We pay for administrative expenses and matching contributions with available cash. Our plan does not allow for us to make additional discretionary contributions. Our contributions were $0.6 million for each of the years ended December 31, 2015, 2014 and 2013. The employer match payable to the 401(k) plan was fully funded as of December 31, 2015. (c) Employee Share Purchase Plan In 2009, our common shareholders approved the First Potomac Realty Trust 2009 Employee Share Purchase Plan (“the Plan”). The Plan allows participating employees to acquire our common shares, at a discounted price, through payroll deductions or cash contributions. Under the Plan, a total of 200,000 common shares may be issued and the offering periods of the Plan cannot exceed five years . Currently, each offering period commences on the first day of each calendar quarter (offering date) and ends on the last business day of the calendar quarter (purchase date) in which the offering period commenced. The purchase price at which common shares will be sold in any offering period will be the lower of: a) 85 percent of the fair value of common shares on the offering date or b) 85 percent of the fair value of the common shares on the purchase date. The first offering period began during the fourth quarter of 2009. We issued common shares of 5,843 , 8,950 and 11,007 under the Plan during the years ended December 31, 2015, 2014 and 2013, respectively, which resulted in compensation expense totaling $11 thousand , $20 thousand and $26 thousand , respectively.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information Our reportable segments consist of four distinct reporting and operational segments within the greater Washington, D.C. region in which we operate: Washington, D.C., Maryland, Northern Virginia and Southern Virginia. We evaluate the performance of our segments based on the operating results of the properties located within each segment, which excludes large non-recurring gains and losses, gains or losses from sale of rental property, 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 continuing operations for our four reporting segments for the three years ended December 31 are as follows (dollars in thousands): 2015 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (1) 6 34 40 19 99 Square feet (1) 918,375 1,885,630 2,661,448 2,023,639 7,489,092 Total revenues $ 44,553 $ 44,226 $ 55,230 $ 28,837 $ 172,846 Property operating expense (11,363 ) (11,457 ) (13,540 ) (7,733 ) (44,093 ) Real estate taxes and insurance (8,238 ) (3,540 ) (5,540 ) (2,427 ) (19,745 ) Total property operating income $ 24,952 $ 29,229 $ 36,150 $ 18,677 109,008 Depreciation and amortization expense (66,624 ) General and administrative (25,450 ) Impairment of rental property (60,826 ) Other income 9,475 Loss from discontinued operations (607 ) Net income $ (35,024 ) Total assets (2)(3) $ 521,107 $ 341,898 $ 374,811 $ 167,467 $ 1,450,371 Capital expenditures (4) $ 12,930 $ 9,003 $ 43,125 $ 7,961 $ 73,850 2014 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (1) 6 38 49 38 131 Square feet (1) 917,008 1,999,332 3,021,509 2,852,298 8,790,147 Total revenues $ 33,959 $ 45,767 $ 53,645 $ 28,281 $ 161,652 Property operating expense (9,683 ) (11,482 ) (13,352 ) (8,735 ) (43,252 ) Real estate taxes and insurance (5,583 ) (3,907 ) (5,592 ) (2,278 ) (17,360 ) Total property operating income $ 18,693 $ 30,378 $ 34,701 $ 17,268 101,040 Depreciation and amortization expense (61,796 ) General and administrative (21,156 ) Acquisition costs (2,681 ) Impairment of rental property (3,956 ) Other income 4,108 Income from discontinued operations 1,484 Net income $ 17,043 Total assets (2)(3) $ 505,842 $ 360,470 $ 439,833 $ 228,306 $ 1,618,460 Capital expenditures (4) $ 23,422 $ 10,185 $ 7,816 $ 8,436 $ 50,789 2013 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (1)(5) 4 53 51 38 146 Square feet (1)(5) 522,605 2,638,988 3,086,057 2,852,471 9,100,121 Total revenues $ 28,208 $ 41,735 $ 51,787 $ 27,085 $ 148,815 Property operating expense (6,693 ) (10,579 ) (12,601 ) (8,407 ) (38,280 ) Real estate taxes and insurance (4,792 ) (3,436 ) (5,679 ) (2,167 ) (16,074 ) Total property operating income $ 16,723 $ 27,720 $ 33,507 $ 16,511 94,461 Depreciation and amortization expense (54,567 ) General and administrative (21,979 ) Acquisition costs (602 ) Contingent consideration related to acquisition of property 213 Other expenses (28,287 ) Income from discontinued operations 21,742 Net income $ 10,981 Total assets (2)(3) $ 344,739 $ 430,498 $ 423,839 $ 230,175 $ 1,502,460 Capital expenditures (4) $ 26,910 $ 16,216 $ 13,685 $ 10,106 $ 68,002 (1) Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013. (2) Total assets include our investment in properties that are owned through joint ventures that are not consolidated within our consolidated financial statements. For more information on our unconsolidated investments, including locations within our reportable segments, see note 5 , Investment in Affiliates . (3) Corporate assets not allocated to any of our reportable segments totaled $45,088 , $84,009 and $73,209 at December 31, 2015 , 2014 and 2013 , respectively. (4) Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $831 , $930 and $1,085 at December 31, 2015 , 2014 and 2013 , respectively. (5) Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Quarterly Financial Information (unaudited) 2015 (1) First Second Third Fourth (amounts in thousands, except per share amounts) Quarter Quarter Quarter Quarter Revenues $ 43,849 $ 43,039 $ 42,854 $ 43,104 Operating expenses 40,016 37,268 37,079 102,375 Operating income (loss) 3,833 5,771 5,775 (59,271 ) Income (loss) from continuing operations 1,099 476 3,997 (39,990 ) (Loss) income from discontinued operations (607 ) — — — Less: Net loss (income) attributable to noncontrolling interests 112 114 (38 ) 1,870 Net (loss) income attributable to First Potomac Realty Trust 604 590 3,959 (38,120 ) Less: Dividends on preferred shares (3,100 ) (3,100 ) (3,100 ) (3,100 ) Net (loss) income attributable to common shareholders $ (2,496 ) $ (2,510 ) $ 859 $ (41,220 ) Basic and diluted earnings per common share: (Loss) income from continuing operations $ (0.03 ) $ (0.04 ) $ 0.01 $ (0.72 ) (Loss) income from discontinued operations (0.01 ) — — — Net (loss) income $ (0.04 ) $ (0.04 ) $ 0.01 $ (0.72 ) 2014 (1) First Second Third Fourth (amounts in thousands, except per share amounts) Quarter Quarter Quarter Quarter Revenues $ 39,363 $ 39,307 $ 40,055 $ 42,928 Operating expenses 35,744 39,579 36,283 38,595 Operating income (loss) 3,619 (272 ) 3,772 4,333 (Loss) income from continuing operations (586 ) 16,796 (248 ) (402 ) (Loss) income from discontinued operations (857 ) 1,538 297 505 Less: Net loss (income) attributable to noncontrolling interests 195 (652 ) 131 128 Net (loss) income attributable to First Potomac Realty Trust (1,248 ) 17,682 180 231 Less: Dividends on preferred shares (3,100 ) (3,100 ) (3,100 ) (3,100 ) Net (loss) income attributable to common shareholders $ (4,348 ) $ 14,582 $ (2,920 ) $ (2,869 ) Basic and diluted earnings per common share: (Loss) income from continuing operations $ (0.07 ) $ 0.22 $ (0.05 ) $ (0.06 ) (Loss) income from discontinued operations (0.01 ) 0.03 — 0.01 Net (loss) income $ (0.08 ) $ 0.25 $ (0.05 ) $ (0.05 ) (1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals. We did no t sell any common shares in 2015 or 2014. The sum of the basic and diluted earnings per common share for the four quarters in the periods presented differs from the annual earnings per common share calculation due to the required method of computing the weighted average number of common shares in the respective periods.

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2015
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III - Real Estate and Accumulated Depreciation	SCHEDULE III FIRST POTOMAC REALTY TRUST REAL ESTATE AND ACCUMULATED DEPRECIATION December 31, 2015 (Amounts in thousands) Property Location (1) Date Acquired Property Type (2) Encumbrances at December 31, 2015 (3) Maryland Snowden Center Columbia Oct 2002 BP $ — Metro Park North Rockville Dec 2004 Office — Gateway 270 West Clarksburg Jul 2006 BP — Indian Creek Court Beltsville Aug 2006 BP — Ammendale Commerce Center Beltsville Mar 2007 BP — Annapolis Business Center Annapolis Jun 2007 Office — Cloverleaf Center Germantown Oct 2009 Office — Redland Corporate Center Buildings II & III Rockville Nov 2010 Office 64,543 TenThreeTwenty Columbia Feb 2011 Office — Hillside I and II Columbia Nov 2011 Office 12,540 540 Gaither Road (Redland I) Rockville Oct 2013 Office — Total Maryland 77,083 Washington, D.C. 500 First Street, NW Capitol Hill Jun 2010 Office — 440 First Street, NW Capitol Hill Dec 2010 Office 32,216 1211 Connecticut Ave, NW CBD Dec 2010 Office 29,110 840 First Street, NE NoMA Mar 2011 Office 35,888 Storey Park NoMA Aug 2011 Office 22,000 1401 K Street, NW East End Apr 2014 Office 36,224 11 Dupont Circle, NW CBD Sep 2014 Office 66,780 Total Washington, D.C. 222,218 Northern Virginia Plaza 500 Alexandria Dec 1997 I — 403/405 Glenn Drive Sterling Oct 2005 BP — Sterling Park Business Center Sterling Feb 2006 BP — Davis Drive Sterling Aug 2006 BP — Three Flint Hill Oakton Apr 2010 Office — Atlantic Corporate Park Sterling Nov 2010 Office — One Fair Oaks Fairfax Apr 2011 Office — 1775 Wiehle Avenue Reston Jun 2014 Office — Northern Virginia Build-to-Suit Northern Virginia 9,176 Total Northern Virginia 9,176 Southern Virginia Crossways Commerce Center Chesapeake Dec 1999 BP — Greenbrier Technology Center II Chesapeake Oct 2002 BP — Norfolk Business Center Norfolk Oct 2002 BP — Crossways II Chesapeake Oct 2004 BP — Norfolk Commerce Park II Norfolk Oct 2004 BP — 1434 Crossways Boulevard Chesapeake Aug 2005 BP — Crossways I Chesapeake Feb 2006 BP — Crossways Commerce Center IV Chesapeake May 2006 BP — Gateway II Norfolk Nov 2006 BP — Greenbrier Circle Corporate Center Chesapeake Jan 2007 BP — Greenbrier Technology Center I Chesapeake Jan 2007 BP — Battlefield Corporate Center Chesapeake Oct 2010 BP 3,526 Greenbrier Towers Chesapeake Jul 2011 Office — Total Southern Virginia 3,526 Land held for future development — Other — Total Consolidated Portfolio $ 312,003 Initial Costs Gross Amount at End of Year Land Building and Improvements Since Acquisition (4) Land Building and Improvements Total Accumulated Depreciation $ 3,404 $ 12,824 $ 4,569 $ 3,404 $ 17,393 $ 20,797 $ 7,016 9,220 32,056 3,065 9,220 35,121 44,341 9,942 18,302 20,562 8,432 18,302 28,994 47,296 7,176 5,673 17,168 12,937 5,673 30,105 35,778 9,189 2,398 7,659 5,890 2,398 13,549 15,947 5,988 6,101 12,602 556 6,101 13,158 19,259 2,860 7,097 14,211 1,028 7,097 15,239 22,336 2,857 17,272 63,480 14,606 17,720 77,638 95,358 15,561 2,041 5,327 13,640 2,041 18,967 21,008 3,310 3,302 10,926 3,552 3,302 14,478 17,780 1,222 6,458 19,831 256 6,539 20,006 26,545 2,294 81,268 216,646 68,531 81,797 284,648 366,445 67,415 25,806 33,883 542 25,827 34,404 60,231 6,034 — 15,300 49,133 9,121 55,312 64,433 3,853 27,077 17,520 11,227 27,077 28,747 55,824 3,456 16,846 60,905 11,273 16,846 72,178 89,024 10,267 43,672 4,194 10,135 — 58,001 58,001 — 29,506 23,269 4,775 29,506 28,044 57,550 1,921 15,744 64,832 5,343 15,744 70,175 85,919 2,947 158,651 219,903 92,428 124,121 346,861 470,982 28,478 6,265 35,433 6,790 6,268 42,220 48,488 19,056 3,940 12,547 4,367 3,940 16,914 20,854 5,375 14,656 10,750 18,931 15,559 28,778 44,337 8,220 1,614 3,611 3,462 1,646 7,041 8,687 2,081 — 13,653 24,779 4,181 34,251 38,432 7,517 5,895 11,655 18,319 5,895 29,974 35,869 5,093 5,688 43,176 (25,909 ) 1,607 21,348 22,955 9,248 3,542 30,575 48 3,541 30,624 34,165 2,062 5,241 — 33,930 — 39,171 39,171 — 46,841 161,400 84,717 42,637 250,321 292,958 58,652 5,160 23,660 13,801 5,160 37,461 42,621 15,652 1,365 5,119 1,325 1,365 6,444 7,809 2,522 1,323 4,967 1,270 1,324 6,236 7,560 2,487 1,036 6,254 1,843 1,036 8,097 9,133 2,493 1,221 8,693 4,379 1,221 13,072 14,293 4,793 4,447 24,739 4,198 4,815 28,569 33,384 7,691 2,657 11,597 2,892 2,646 14,500 17,146 4,301 1,292 3,899 700 1,292 4,599 5,891 1,561 1,320 2,293 617 1,320 2,910 4,230 947 4,164 18,984 5,817 4,164 24,801 28,965 6,210 2,024 7,960 2,386 2,024 10,346 12,370 3,044 1,860 6,071 798 1,881 6,848 8,729 1,170 2,997 9,173 4,948 2,997 14,121 17,118 2,292 30,866 133,409 44,974 31,245 178,004 209,249 55,163 343 — 6 349 — 349 — — — 67 — 67 67 76 $ 317,969 $ 731,358 $ 290,723 $ 280,149 $ 1,059,901 $ 1,340,050 $ 209,784 (1) CBD=Central Business District; NoMA=North of Massachusetts Avenue (2) I=Industrial; BP=Business Park (3) Includes the unamortized fair value adjustments recorded at acquisition upon the assumption of mortgage loans. (4) We placed Storey Park into development on September 1, 2013. At December 31, 2015, the land and building assets associated with Storey Park are included in construction in progress, which is reflected in Building and Improvements in the above table. Depreciation of rental property is computed on a straight-line basis over the estimated useful lives of the assets. The estimated lives of our assets range from 5 to 39 years or to the term of the underlying lease. The tax basis of our rental property assets was $1,547 million and $1,576 million at December 31, 2015 and 2014, respectively. (a) Reconciliation of Rental Property (1) The following table reconciles the rental property investments for the years ended December 31 (amounts in thousands): 2015 2014 2013 Beginning balance $ 1,504,372 $ 1,330,180 $ 1,605,722 Acquisitions of rental property (2) — 170,823 26,289 Capital expenditures (3) 73,125 49,860 66,808 Impairments (51,521 ) (3,956 ) (4,069 ) Dispositions of rental property (59,652 ) (30,916 ) (290,777 ) Assets held-for-sale (127,907 ) (643 ) (55,767 ) Other (4) 1,633 (10,976 ) (18,026 ) Ending balance $ 1,340,050 $ 1,504,372 $ 1,330,180 (b) Reconciliation of Accumulated Depreciation (1) The following table reconciles the accumulated depreciation on the rental property investments for the years ended December 31 (amounts in thousands): 2015 2014 2013 Beginning balance $ 215,499 $ 185,725 $ 215,154 Depreciation of rental property 49,772 47,625 48,638 Assets held-for-sale (16,400 ) (1,631 ) (13,470 ) Dispositions of rental property (35,964 ) (5,712 ) (54,377 ) Other (4) (3,123 ) (10,508 ) (10,220 ) Ending balance $ 209,784 $ 215,499 $ 185,725 (1) Excludes rental property and applicable accumulated depreciation at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9 (a), Dispositions ), which was classified as held-for-sale at December 31, 2015. The rental property and applicable accumulated depreciation related to the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015, is excluded from all years presented. (2) For more information on our acquisitions, including the assumption of liabilities and other non-cash items, see the supplemental disclosure of cash flow information accompanying our consolidated statements of cash flows. (3) Represents cash paid for capital expenditures. (4) Includes accrued increases to rental property investments, fully depreciated assets that were written-off during the year and other immaterial transactions.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	(a) Principles of Consolidation Our consolidated financial statements include our accounts and the accounts of our Operating Partnership and the subsidiaries in which we or our Operating Partnership has a controlling interest, which includes First Potomac Management LLC, a wholly owned subsidiary that manages the majority of our properties. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	(b) Use of Estimates The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires our management team 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 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.
Revenue Recognition and Accounts Receivable	(c) Revenue Recognition and Accounts Receivable We generate substantially all of our revenue from leases on our properties. We recognize rental revenue on a straight-line basis over the term of our leases, which includes fixed-rate renewal periods leased at below market rates at acquisition or inception. Accrued straight-line rents represent the difference between rental revenue recognized on a straight-line basis over the term of the respective lease agreements and the rental payments contractually due for leases that contain abatement or fixed periodic increases. We consider current information, credit quality, historical trends, economic conditions and other events regarding the tenants’ ability to pay their obligations in determining if amounts due from tenants, including accrued straight-line rents, are ultimately collectible. The uncollectible portion of the amounts due from tenants, including accrued straight-line rents, is charged to “Property operating expense” in our consolidated statements of operations in the period in which the determination is made and to allowance for doubtful accounts in “Accounts and other receivables” and/or “Accrued straight-line rents” on our consolidated balance sheets. During 2015 , 2014 and 2013 , we incurred charges of $0.6 million , $1.1 million and $0.8 million , respectively, related to anticipated uncollectible amounts from tenants, including accrued straight-line rents. We consider similar criteria in assessing impairment associated with outstanding loans or notes receivable and whether any allowance for anticipated credit loss is appropriate. Tenant leases generally contain provisions under which the tenants reimburse us for a portion of property operating expenses and real estate taxes incurred by us. Such reimbursements are recognized in the period in which the expenses are incurred. We record a provision for losses on estimated uncollectible accounts receivable based on our analysis of risk of loss on specific accounts. Lease termination fees are recognized on the date of termination when the related lease or portion thereof is cancelled, the collectability of the fee is reasonably assured and we have possession of the terminated space. We recognized lease termination fees included in “Tenant reimbursements and other revenues” in our consolidated statements of operations of $0.1 million , $1.1 million and $1.0 million for the years ended December 31, 2015 , 2014 and 2013 , respectively.
Cash and Cash Equivalents	(d) Cash and Cash Equivalents We consider all highly liquid investments with a maturity of 90 days or less at the date of purchase to be cash equivalents.
Escrows and Reserves	(e) Escrows and Reserves Escrows and reserves represent cash restricted for debt service, real estate taxes, insurance, leasing commissions and tenant improvements. We reflect cash inflows and outflows from our escrows and reserves accounts related to debt service, real estate taxes, insurance and leasing commissions within net cash provided by operating activities and our cash inflows and outflows related to tenant improvements within net cash used by investing activities on our consolidated statements of cash flows.
Deferred Costs	(f) Deferred Costs Financing costs related to long-term debt are deferred and amortized over the remaining life of the debt using the effective interest method. Leasing costs related to the execution of tenant leases and lease incentives are deferred and amortized ratably over the term of the related leases. Accumulated amortization of these combined costs was $30.1 million and $24.8 million at December 31, 2015 and 2014 , respectively. The following table sets forth scheduled future amortization for deferred financing and leasing costs at December 31, 2015 (amounts in thousands): Deferred Financing (1) Deferred Leasing (1)(2) Deferred Lease Incentive 2016 $ 1,935 $ 2,979 $ 645 2017 1,557 5,033 868 2018 1,347 4,482 834 2019 1,313 3,673 761 2020 379 2,986 691 Thereafter 1,423 8,028 2,519 $ 7,954 $ 27,181 $ 6,318 (1) Includes amounts from properties that were classified as held-for-sale at December 31, 2015 . (2) Excludes the amortization of $3.1 million of leasing costs that have yet to be placed in-service as the associated tenants have not moved into their related spaces and, therefore, the period over which the leasing costs will be amortized has yet to be determined.
Rental Property	(g) Rental Property Rental property is initially recorded at fair value, when acquired in a business combination, or initial cost when constructed or acquired in an asset purchase. 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 our assets, by class, are as follows: Buildings 39 years Building improvements 5 to 20 years Furniture, fixtures and equipment 5 to 15 years Tenant improvements Shorter of the useful life of the asset or the term of the related lease We regularly review 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 carrying value of a property, an impairment analysis is performed. We assess 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 to maintain the operating capacity, 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. Further, we will record an impairment loss if we expect to dispose of a property in the near term, at a price below carrying value. In such an event, we 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. We will classify a building as held-for-sale in accordance with GAAP in the period in which we have made the decision to dispose of the building, our 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. We will cease recording depreciation on a building once it has been classified as held-for-sale. In the second quarter of 2014, we prospectively adopted Accounting Standards Update No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity (“ASU 2014-08”), which impacts the presentation of operations and gains or losses from disposed properties and properties classified as held-for-sale. ASU 2014-08 states that a disposal of a component of an entity or a group of components of an entity is required to be reported in discontinued operations only if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations or financial results. The operations of all properties that were sold prior to the adoption of ASU 2014-08, two properties (West Park and Patrick Center) that were classified as held-for-sale in previously issued financial statements prior to our adoption of ASU 2014-08 and were subsequently sold, as well as our Richmond, Virginia portfolio, which included Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land (the “Richmond Portfolio”), are reflected within discontinued operations in our consolidated statements of operations for all periods presented. If the building does not qualify as a discontinued operation under ASU 2014-08, we will classify the building’s operating results, together with any impairment charges and any gains or losses on the sale of the building, in continuing operations for all periods presented in our consolidated statements of operations. We will classify the assets and liabilities related to the building as held-for-sale in our consolidated balance sheet for the period the held-for-sale criteria were met. If the building does qualify as a discontinued operation under ASU 2014-08, we will classify the building’s operating results, together with any impairment charges and any gains or losses on the sale of the building, in discontinued operations in our consolidated statements of operations for all periods presented and classify the assets and liabilities related to the building as held-for-sale in our consolidated balance sheets for the periods presented. Interest expense is reclassified to discontinued operations only to the extent the disposed or held-for-sale property is secured by specific mortgage debt and the mortgage debt will not be assigned to another property owned by us after the disposition. We recognize the fair value, if sufficient information exists to reasonably estimate the fair value, of any liability for conditional asset retirement obligations when assumed or incurred, which is generally upon acquisition, construction, development or redevelopment and/or through the normal operation of the asset. We capitalize interest costs incurred on qualifying expenditures for real estate assets under development or redevelopment, which include our investments 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. We 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. We also capitalize direct compensation costs of our 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. We do not capitalize any other general and administrative costs such as office supplies, office rent expense or an overhead allocation to our development or redevelopment projects. Capitalized compensation costs were immaterial during 2015 , 2014 and 2013 . Capitalization of interest ends 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. We 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.
Purchase Accounting	(h) Purchase Accounting Acquisitions of rental property, including any associated intangible assets, are measured at fair value at the date of acquisition. Any liabilities assumed or incurred are recorded at their fair value at the time of acquisition. The fair value of the acquired property is allocated between land and building (on an as-if vacant basis) based on management’s estimate of the fair value of those components for each type of property and to tenant improvements based on the depreciated replacement cost of the tenant improvements, which approximates their fair value. The fair value of the in-place leases is recorded as follows: • the fair value of leases in-place on the date of acquisition is based on absorption costs for the estimated lease-up period in which vacancy and foregone revenue are avoided due to the presence of the acquired leases; • the fair value of above and below-market in-place leases based on the present value (using a discount rate that reflects the risks associated with the acquired leases) of the difference between the contractual rent amounts to be paid under the assumed lease and the estimated market lease rates for the corresponding spaces over the remaining non-cancelable terms of the related leases, which range from one to fourteen years; and • the fair value of intangible tenant or customer relationships. Our determination of these fair values requires us to estimate market rents for each of the leases and make certain other assumptions. These estimates and assumptions affect the rental revenue, and depreciation and amortization expense recognized for these leases and associated intangible assets and liabilities.
Investment in Affiliates	(i) Investment in Affiliates We may continue to grow our portfolio by entering into ownership arrangements with third parties for which we do not have a controlling interest. The structure of the arrangement may affect our accounting treatment as the entities may qualify as variable interest entities (“VIE”) based on disproportionate voting to equity interests, or other factors . In determining whether to consolidate an entity, we assess the structure and intent of the entity relationship as well its power to direct major decisions regarding the entity’s operations. When our investment in an entity meets the requirements for the equity method of accounting, we will record our initial investment in our consolidated balance sheets as “Investment in affiliates.” The initial investment in the entity is adjusted to recognize our share of earnings, losses, distributions received from the entity or additional contributions. Basis differences, if any, are recognized over the life of the venture as an adjustment to “Equity in (earnings) losses of affiliates” in our consolidated statements of operations. Our respective share of all earnings or losses from the entity will be recorded in our consolidated statements of operations as “Equity in (earnings) losses of affiliates.” When we are deemed to have a controlling interest in a partially-owned entity, we will consolidate all of the entity’s assets, liabilities, operating results and cash flows within our consolidated financial statements. The cash contributed to the consolidated entity by the third party, if any, will be reflected in the permanent equity section of our consolidated balance sheets to the extent the associated ownership interests 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 for any distributions received or additional contributions made by the third party. The earnings or losses from the entity attributable to the third party will be recorded in our consolidated statements of operations as a component of “Net loss (income) attributable to noncontrolling interests.”
Sales of Real Estate	( j) Sales of Rental Property We account for sales of rental property in accordance with the requirements for full profit recognition, which occurs when the sale is consummated, the buyer has made adequate initial and continuing investments in the property, our receivable is not subject to future subordination, and we do not have substantial continuing involvement with the property. Once the requirements for full profit recognition are achieved, the related assets and liabilities are removed from the balance sheet and the resultant gain or loss is recorded in the period the sale is consummated. For sales transactions that do not meet the criteria for full profit recognition, we account for the transactions as partial sales or financing arrangements required by GAAP. For sales transactions with continuing involvement after the sale, if the continuing involvement with the property is limited by the terms of the sales contract, profit is recognized at the time of sale and is reduced by the maximum exposure to loss related to the nature of the continuing involvement. Sales to entities in which we have or receive an interest are accounted for as partial sales. For sales transactions that do not meet sale criteria, we evaluate the nature of the continuing involvement, including put and call provisions, if present, and accounts for the transaction as a financing arrangement, profit-sharing arrangement, leasing arrangement or other alternate method of accounting rather than as a sale, based on the nature and extent of the continuing involvement. Some transactions may have numerous forms of continuing involvement. In those cases, we determine which method is most appropriate based on the substance of the transaction.
Intangible Assets	(k) Intangible Assets Intangible assets include the fair value of acquired tenant or customer relationships and the fair value of in-place leases at acquisition. Customer relationship fair values are determined based on our evaluation of the specific characteristics of each tenant’s lease and our overall relationship with the tenant. Characteristics we consider include the nature and extent of our existing business relationships with the tenant, growth prospects for developing new business with the tenant, the tenant’s credit quality and expectations of lease renewals. The fair value of customer relationship intangible assets is amortized to expense over the lesser of the initial lease term and any expected renewal periods or the remaining useful life of the building. We determine the fair value of the in-place leases at acquisition by estimating the leasing commissions avoided by having in-place tenants and the operating income that would have not been recognized during the estimated time required to lease the space occupied by existing tenants at the acquisition date. The fair value attributable to existing tenants is amortized to expense over the initial term of the respective leases. Should a tenant terminate its lease, the unamortized portion of the in-place lease fair value is charged to expense by the date of termination. Deferred market rent liability consists of the acquired leases with below-market rents at the date of acquisition. The fair value attributed to deferred market rent assets, which consist of above-market rents at the date of acquisition, is recorded as a component of deferred costs. Above and below-market lease fair values are determined on a lease-by-lease basis based on the present value (using a discounted rate that reflects the risks associated with the acquired leases) of the difference between the contractual rent amounts to be paid under the lease and the estimated market lease rates for the corresponding spaces over the remaining non-cancelable terms of the related leases including any below-market fixed rate renewal periods. The capitalized below-market lease fair values are amortized as an increase to rental revenue over the initial term and any below-market fixed-rate renewal periods of the related leases. Capitalized above-market lease fair values are amortized as a decrease to rental revenue over the initial term of the related leases. In conjunction with our initial public offering and related formation transactions, First Potomac Management, Inc. contributed all of the capital interests in First Potomac Management LLC. The $2.1 million fair value of the in-place workforce acquired has been classified as goodwill and is included as a component of “Intangible assets, net” on the consolidated balance sheets. In 2011, we recognized additional goodwill of $4.8 million representing the residual difference between the consideration transferred for the purchase of 840 First Street, NE, which was acquired in March 2011, and the acquisition date fair value of the identifiable assets acquired and liabilities assumed and deferred taxes representing the difference between the fair value of acquired assets at acquisition and the carryover basis used for income tax purposes. In accordance with accounting requirements regarding goodwill and other intangibles, all acquired goodwill that relates to the operations of a reporting unit and is used in determining the fair value of a reporting unit is allocated to our appropriate reporting unit in a reasonable and consistent manner. We assess goodwill for impairment annually at the end of our fiscal year and in interim periods if certain events occur indicating the carrying value may be impaired. We perform our analysis for potential impairment of goodwill in accordance with GAAP and are permitted to make a qualitative assessment of whether it is more likely than not that a reporting unit’s fair value is less than its carrying amount before applying the two-step goodwill impairment test for that reporting unit. We assess the impairment of our goodwill based on such qualitative factors as general economic conditions, industry and market conditions, market competiveness, overall financial performance (such as negative cash flows) and other entity specific events. As of December 31, 2015 , we concluded that it was more likely than not that the fair value of our reporting units exceeded its carrying value, and as a result, we determined that it was unnecessary to perform any additional testing for goodwill impairment. No goodwill impairment losses were recognized during 2015 , 2014 and 2013 .
Derivative Instruments	(l) Derivative Instruments We are exposed to certain risks arising from business operations and economic factors. We use derivative financial instruments to manage exposures that arise from business activities in which our 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. We do not use derivatives for trading or speculative purposes and we intend to enter into derivative agreements only with counterparties that we believe have a strong credit rating to mitigate the risk of counterparty default or insolvency. No hedging activity can completely insulate us from the risks associated with changes in interest rates. Moreover, interest rate hedging could fail to protect us or adversely affect us because, among other things: • available interest rate hedging may not correspond directly with the interest rate risk for which we seek 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 our ability to sell or assign its side of the hedging transaction. We may designate a derivative as either a hedge of the cash flows from a debt instrument or anticipated transaction (cash flow hedge) or a hedge of the fair value of a debt instrument (fair value hedge). All derivatives are recognized as assets or liabilities at fair value. For effective hedging relationships, the effective portion of the change in the fair value of the assets or liabilities is recorded within equity (cash flow hedge) or through earnings (fair value hedge). Ineffective portions of derivative transactions will result in changes in fair value recognized in earnings. For a cash flow hedge, we record our proportionate share of unrealized gains or losses on our derivative instruments associated with our unconsolidated joint ventures within equity and “Investment in affiliates” on our consolidated balance sheets. We incorporate credit valuation adjustments to appropriately reflect both our own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting any applicable credit enhancements, such as collateral postings, thresholds, mutual inputs and guarantees.
Income Taxes	(m) Income Taxes We have elected to be taxed as a REIT. To maintain our status as a REIT, we are required to distribute at least 90% of our ordinary taxable income annually to our shareholders and meet other organizational and operational requirements. As a REIT, we will not be subject to federal income tax and any non-deductible excise tax if we distribute at least 100% of our REIT taxable income to our shareholders. If we fail to qualify as a REIT in any taxable year, we will be subject to federal income tax on our taxable income at regular corporate tax rates. We have certain subsidiaries, including a taxable REIT subsidiary (“TRS”) and an entity that has elected to be taxed as a REIT (which indirectly owns 500 First Street, NW) that may be subject to federal, state or local taxes, as applicable. Our subsidiary REIT will not be subject to federal income tax so long as it meets the REIT qualification requirements and distributes 100% of its REIT taxable income to its shareholders. Our TRS was inactive in 2015 , 2014 and 2013 . See note 8 , Income Taxes, for further information. We account for deferred income taxes using the asset and liability method. Under this method, deferred income taxes are recognized for temporary differences between the financial reporting basis of assets and liabilities and their respective tax bases and for operating losses, capital losses and tax credit carryovers based on tax rates to be effective when amounts are realized or settled. We will recognize deferred tax assets only to the extent that it is more likely than not that they will be realized based on available evidence, including future reversals of existing temporary differences, future projected taxable income and tax planning strategies. We may recognize a tax benefit from an uncertain tax position when it is more-likely-than-not (defined as a likelihood of more than 50% ) that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. If a tax position does not meet the more-likely-than-not recognition threshold, despite our belief that our filing position is supportable, the benefit of that tax position is not recognized in the statements of operations. We recognize interest and penalties, as applicable, related to unrecognized tax benefits as a component of income tax expense. We recognize unrecognized tax benefits in the period that the uncertainty is eliminated by either affirmative agreement of the uncertain tax position by the applicable taxing authority, or by expiration of the applicable statute of limitation. For the years ended December 31, 2015 , 2014 and 2013 , we did not have any uncertain tax positions.
Share-Based Payments	(n) Share-Based Payments We measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. For options awards, we use a Black-Scholes option-pricing model. Expected volatility is based on an assessment of our realized volatility over the preceding period that is equivalent to the award’s expected life. The expected term represents the period of time the options are anticipated to remain outstanding as well as our historical experience for groupings of employees that have similar behavior and considered separately for valuation purposes. For non-vested share awards that vest over a predetermined time period, we use the outstanding share price at the date of issuance to fair value the awards. For non-vested shares awards that vest based on market conditions, we use a Monte Carlo simulation (risk-neutral approach) to determine the value and derived service period of each tranche. The expense associated with the share-based awards will be recognized over the period during which an employee is required to provide services in exchange for the award – the requisite service period (usually the vesting period). The fair value for all share-based payment transactions are recognized as a component of income or loss from continuing operations.
Notes Receivable	(o) Notes Receivable We provide loans to the owners of real estate properties, which can be collateralized by interest in the real estate property. We record these loans as “Notes receivable, net” in our 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. We record interest earned from notes receivable and amortization of any discount costs or issuance costs within “Interest and other income” in our consolidated statements of operations. We will establish a provision for anticipated credit losses associated with our notes receivable when we anticipate that we 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. Our collectability of our notes receivable may be adversely impacted by the financial stability of the Washington, D.C. region and the ability of the 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 we estimate to be adequate based on these factors. Based on the review of the above criteria, we did not record an allowance for credit losses for our notes receivable during 2015 , 2014 and 2013 .
Application of New Accounting Standards	(p) Application of New Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers and will replace most existing revenue recognition guidance when it becomes effective. In July 2015, the FASB deferred by one year the mandatory effective date of ASU 2014-09 from January 1, 2017 to January 1, 2018. Early adoption is permitted, but not prior to the original effective date of January 1, 2017. ASU 2014-09 permits the use of either the retrospective or cumulative effect transition method. We have not yet selected a transition method and are evaluating the impact that ASU 2014-09 will have on our consolidated financial statements and related disclosures. In August 2014, the FASB issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (“ASU 2014-15”), which requires an entity to evaluate whether conditions or events, in the aggregate, raise substantial doubt about the entity’s ability to continue as a going concern for one year from the date the financial statements are issued or are available to be issued. The guidance will become effective for annual periods ending after December 15, 2016. The adoption of ASU 2014-15 is not expected to have an impact on our consolidated financial statements and related disclosures. In January 2015, the FASB issued Accounting Standards Update No. 2015-01, Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items (“ASU 2015-01”), which eliminates the concept of extraordinary items from GAAP and the requirement that an entity separately report extraordinary items in the income statement. ASU 2015-01 also requires that entities continue to evaluate whether items are unusual in nature or infrequent in occurrence for presentation and disclosure purposes. ASU 2015-01 applies to all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted and the guidance may be applied prospectively or retrospectively to all prior periods presented in the consolidated financial statements. The adoption of ASU 2015-01 is not expected to have a material impact on our consolidated financial statements and related disclosures. In February 2015, the FASB issued Accounting Standards Update No. 2015-02, Amendments to the Consolidation Analysis (“ASU 2015-02”), which makes certain changes to both the variable interest model and the voting model, including changes to the identification of variable interests (fees paid to a decision maker or service provider), the variable interest entity characteristics for a limited partnership or similar entity and the primary beneficiary determination. ASU 2015-02 is effective for periods beginning after December 15, 2015 and is not expected to have a material impact on our consolidated financial statements and related disclosures. In April 2015, the FASB issued Accounting Standards Update No. 2015-03, Simplifying the Presentation of Debt Issuance Costs (“ASU 2015-03”), which requires debt issuance costs to be presented in the balance sheet as a direct deduction from the carrying value of the debt liability. ASU 2015-03 is effective for periods beginning after December 15, 2015 with early adoption permitted and will be applied on a retrospective basis. The guidance is not expected to have a material impact on our consolidated financial statements and related disclosures. In September 2015, the FASB issued Accounting Standards Update No. 2015-16, Simplifying the Accounting for Measurement-Period Adjustments (“ASU 2015-16”), which eliminates the requirement for an acquirer to retrospectively adjust the financial statements for measurement-period adjustments that occur in periods after the acquisition of a business combination. The acquirer would instead recognize measurement-period adjustments in the reporting period in which the adjustment is identified. ASU 2015-16 is effective for periods beginning after December 15, 2015 with early adoption permitted and will be applied on a retrospective basis. The guidance is not expected to have a material impact on our consolidated financial statements and related disclosures. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-01”), which requires, among other things, entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes and eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value disclosed for financial instruments measured at amortized cost on the balance sheet. ASU 2016-01 is effective for periods beginning after December 15, 2017; early adoption is not permitted. The guidance is not expected to have a material impact on our consolidated financial statements and related disclosures.

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Scheduled Future Amortization for Deferred Financing and Leasing Costs	The following table sets forth scheduled future amortization for deferred financing and leasing costs at December 31, 2015 (amounts in thousands): Deferred Financing (1) Deferred Leasing (1)(2) Deferred Lease Incentive 2016 $ 1,935 $ 2,979 $ 645 2017 1,557 5,033 868 2018 1,347 4,482 834 2019 1,313 3,673 761 2020 379 2,986 691 Thereafter 1,423 8,028 2,519 $ 7,954 $ 27,181 $ 6,318 (1) Includes amounts from properties that were classified as held-for-sale at December 31, 2015 . (2) Excludes the amortization of $3.1 million of leasing costs that have yet to be placed in-service as the associated tenants have not moved into their related spaces and, therefore, the period over which the leasing costs will be amortized has yet to be determined.
Estimated Useful Lives of Company's Assets, by Class	The estimated useful lives of our assets, by class, are as follows: Buildings 39 years Building improvements 5 to 20 years Furniture, fixtures and equipment 5 to 15 years 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)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Computation of Company's Basic and Diluted Earnings Per Share	The following table sets forth the computation of our basic and diluted earnings per common share (amounts in thousands, except per share amounts): 2015 2014 2013 Numerator for basic and diluted earnings per common share: (Loss) income from continuing operations $ (34,417 ) $ 15,559 $ (10,761 ) (Loss) income from discontinued operations (607 ) 1,484 21,742 Net (loss) income (35,024 ) 17,043 10,981 Less: Net loss (income) from continuing operations attributable to noncontrolling interests 2,032 (135 ) 1,047 Less: Net loss (income) from discontinued operations attributable to noncontrolling interests 26 (64 ) (954 ) Net (loss) income attributable to First Potomac Realty Trust (32,966 ) 16,844 11,074 Less: Dividends on preferred shares (12,400 ) (12,400 ) (12,400 ) Net (loss) income attributable to common shareholders (45,366 ) 4,444 (1,326 ) Less: Allocation to participating securities (241 ) (314 ) (388 ) Net (loss) income attributable to common shareholders $ (45,607 ) $ 4,130 $ (1,714 ) Denominator for basic and diluted earnings per common share: Weighted average common shares outstanding – basic 57,982 58,150 55,034 Weighted average common shares outstanding – diluted 57,982 58,220 55,034 Basic and diluted earnings per common share: (Loss) income from continuing operations $ (0.78 ) $ 0.05 $ (0.41 ) (Loss) income from discontinued operations (0.01 ) 0.02 0.38 Net (loss) income $ (0.79 ) $ 0.07 $ (0.03 )
Anti-Dilutive Shares Not Included in Calculation of Diluted Earnings Per Share	In accordance with GAAP regarding earnings per common share, we did not include the following potential weighted average common shares in our calculation of diluted earnings per common share as they are anti-dilutive for the periods presented (amounts in thousands): 2015 2014 2013 Stock option awards 1,020 1,122 1,369 Non-vested share awards 310 398 471 1,330 1,520 1,840

Rental Property (Tables)

Rental Property (Tables)	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Summary of Rental Property	Rental property consists of the following at December 31 (dollars in thousands): 2015 (1) 2014 (2) Land and land improvements $ 280,149 $ 325,214 Buildings and improvements 793,184 949,683 Construction in progress 97,361 69,181 Tenant improvements 168,946 159,867 Furniture, fixtures and equipment 410 427 1,340,050 1,504,372 Less: accumulated depreciation (209,784 ) (215,499 ) $ 1,130,266 $ 1,288,873 (1) Excludes rental property totaling $90.6 million at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9 (a), Dispositions ), which was classified as held-for-sale at December 31, 2015. (2) Excludes rental property totaling $57.7 million at December 31, 2014 related to the sale of the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015.

Investment in Affiliates (Table

Investment in Affiliates (Tables)	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Components of Investments in Affiliates	Our investment in affiliates consisted of the following at December 31 (dollars in thousands): 2015 Reporting Segment Ownership Interest Company Investment Debt Recourse Debt (1) Prosperity Metro Plaza Northern Virginia 51 % $ 24,909 $ 50,000 $ — 1750 H Street, NW Washington, D.C. 50 % 15,168 32,000 — Aviation Business Park Maryland 50 % 5,899 — — Rivers Park I and II (2) Maryland 25 % 2,247 28,000 2,800 $ 48,223 $ 110,000 $ 2,800 2014 Reporting Segment Ownership Interest Company Investment Debt Recourse Debt (1) Prosperity Metro Plaza Northern Virginia 51 % $ 24,651 $ 50,000 $ — 1750 H Street, NW Washington, D.C. 50 % 14,834 32,000 — Aviation Business Park Maryland 50 % 5,748 — — Rivers Park I and II (2) Maryland 25 % 2,249 28,000 2,800 $ 47,482 $ 110,000 $ 2,800 (1) We believe the fair value of the potential liability to us related to the recourse debt is inconsequential as the likelihood of our need to perform under the debt agreement is remote. (2) Rivers Park I and Rivers Park II are owned through two separate joint ventures.
Net Assets of Company's Unconsolidated Joint Ventures	The net assets of our unconsolidated joint ventures consisted of the following at December 31 (dollars in thousands): 2015 2014 Assets: Rental property, net $ 193,243 $ 193,533 Cash and cash equivalents 5,992 4,567 Other assets 17,218 16,748 Total assets 216,453 214,848 Liabilities: Mortgage loans 110,000 110,000 Other liabilities 7,215 7,256 Total liabilities 117,215 117,256 Net assets $ 99,238 $ 97,592
Results of Operations of Company's Unconsolidated Joint Ventures	The following table summarizes the results of operations of our unconsolidated joint ventures at December 31, which, due to our varying ownership interests in the joint ventures and the varying operations of the joint ventures, may not be reflective of the amounts recorded in our consolidated statements of operations (amounts in thousands): 2015 2014 2013 Total revenues $ 24,255 $ 23,285 $ 24,017 Total operating expenses (7,660 ) (7,408 ) (7,753 ) Net operating income 16,595 15,877 16,264 Depreciation and amortization (8,718 ) (9,893 ) (11,551 ) Interest expense, net (3,909 ) (3,890 ) (4,222 ) Provision for income taxes — (63 ) (83 ) Contingent consideration charge — 126 — Net income $ 3,968 $ 2,157 $ 408

Notes Receivable (Tables)

Notes Receivable (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Summary of Notes Receivable	Below is a summary of our notes receivable for our outstanding mezzanine loans at December 31, 2015 and 2014 (dollars in thousands): Balance at December 31, 2015 Property Face Amount Unamortized Origination Fees Balance Interest Rate 950 F Street, NW $ 34,000 $ — $ 34,000 9.75 % Balance at December 31, 2014 Property Face Amount Unamortized Origination Fees Balance Interest Rate 950 F Street, NW $ 34,000 $ — $ 34,000 9.75 % America’s Square 29,720 (41 ) 29,679 9.00 % $ 63,720 $ (41 ) $ 63,679

Intangible Assets and Deferre34

Intangible Assets and Deferred Market Rent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Deferred Market Rent Liabilities	Intangible assets and deferred market rent liabilities consisted of the following at December 31 (amounts in thousands): 2015 (1) 2014 (1) Gross Intangibles Accumulated Amortization Net Intangibles Gross Intangibles Accumulated Amortization Net Intangibles In-place leases $ 45,901 $ (26,961 ) 18,940 $ 51,258 $ (22,443 ) $ 28,815 Customer relationships 663 (601 ) 62 906 (654 ) 252 Leasing commissions 10,612 (5,485 ) 5,127 11,335 (4,272 ) 7,063 Legal leasing fees 344 (177 ) 167 377 (118 ) 259 Deferred market rent assets 3,558 (1,825 ) 1,733 3,906 (1,309 ) 2,597 Goodwill 6,930 — 6,930 6,930 — 6,930 $ 68,008 $ (35,049 ) $ 32,959 $ 74,712 $ (28,796 ) $ 45,916 Deferred market rent liability $ 4,869 $ (2,715 ) $ 2,154 $ 5,193 $ (2,348 ) $ 2,845 (1) The 2014 balances include amounts from properties that were classified as held-for-sale at December 31, 2014. There were no intangible assets or deferred market rent liabilities classified as held-for-sale at December 31, 2015.
Projected Net Amortization of Intangible Assets and Deferred Market Liabilities Including Amounts from Properties Classified as Held-For-Sale	The projected net amortization of intangible assets and deferred market liabilities as of December 31, 2015 are as follows (amounts in thousands): 2016 $ 7,318 2017 4,203 2018 2,700 2019 2,388 2020 2,146 Thereafter 5,120 $ 23,875

Dispositions (Tables)

Dispositions (Tables)	12 Months Ended
	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Schedule of Disposal Groups Including Not Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	The following table summarizes the aggregate results of operations for the disposed or held-for-sale properties that are included in continuing operations for the periods presented (dollars in thousands): 2015 2014 2013 Revenues $ 21,826 $ 26,037 $ 29,016 Property operating expenses (7,745 ) (9,664 ) (10,249 ) Depreciation and amortization (7,037 ) (9,114 ) (9,697 ) Interest expense, net of interest income (465 ) (842 ) (1,258 ) Impairment of rental property (26,929 ) (3,956 ) — (Loss) income from operations of disposed property (20,350 ) 2,461 7,812 Gain on sale of rental property 29,477 21,230 — Net income from continuing operations $ 9,127 $ 23,691 $ 7,812
Discontinued Operations Square Feet Area	The following table is a summary of property dispositions or held-for-sale properties whose operating results are included in continuing operations in our consolidated statements of operations for the periods presented (dollars in thousands): Reporting Disposition Date Property Type Square Feet Net Sale Proceeds NOVA Non-Core Portfolio (1) Northern Virginia TBD Various 945,745 $ 90,600 (2) Cedar Hill I and III Northern Virginia 12/23/2015 Office 102,632 25,939 Newington Business Park Center Northern Virginia 12/17/2015 Industrial 255,600 31,409 Rumsey Center Maryland 7/28/2015 Business Park 135,015 14,956 Owings Mills Business Park Maryland 10/16/2014 Business Park 180,475 12,417 Corporate Campus at Ashburn Center Northern Virginia 6/26/2014 Business Park 194,184 39,910
Summary of Completed and Anticipated Property Dispositions	The following table is a summary of property dispositions whose operating results are reflected as discontinued operations in our consolidated statements of operations for the periods presented (dollars in thousands): Reporting Segment Disposition Date Property Type Square Feet Net Sale Proceeds Richmond Portfolio (1) Southern Virginia 3/19/2015 Business Park 827,900 $ 53,768 Patrick Center Maryland 4/16/2014 Office 66,269 10,888 West Park Maryland 4/2/2014 Office 28,333 2,871 Girard Business Center and Gateway Center Maryland 1/29/2014 Business Park and Office 341,973 31,616 Worman’s Mill Court Maryland 11/19/2013 Office 40,099 3,362 Triangle Business Center Maryland 9/27/2013 Business Park 74,429 2,732 4200 Tech Court Northern Virginia 8/15/2013 Office 33,875 3,210 Industrial Portfolio (2) Various May/June 2013 Industrial 4,280,985 176,569 4212 Tech Court Northern Virginia 6/5/2013 Office 32,055 2,469 (1) The Richmond Portfolio includes 19 buildings totaling 827,900 square feet and a three-acre parcel of undeveloped land. (2) During the second quarter of 2013, we sold 24 industrial properties, which consisted of two separate transactions. On May 7, 2013, we sold I-66 Commerce Center, a 236,000 square foot industrial property in Haymarket, Virginia. On June 18, 2013, we completed the sale of the remaining 23 industrial properties.
Net Income from Discontinued Operations	The following table summarizes the results of operations of properties included in discontinued operations for the years ended December 31 (dollars in thousands): 2015 2014 2013 Revenues $ 877 $ 7,688 $ 31,654 Property operating expenses (638 ) (3,612 ) (10,564 ) Depreciation and amortization (1,222 ) (3,662 ) (8,937 ) Net interest income (expense) 8 (268 ) (1,268 ) Impairment of rental property — — (4,092 ) (Loss) income from operations of disposed property (975 ) 146 6,793 Loss on debt extinguishment (489 ) — (4,414 ) Gain on sale of rental property 857 1,338 19,363 Net (loss) income from discontinued operations $ (607 ) $ 1,484 $ 21,742

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Borrowings	Our borrowings consisted of the following at December 31 (dollars in thousands): 2015 2014 Mortgage loans, effective interest rates ranging from 4.22% to 6.01%, maturing at various dates through September 2030 (1)(2) $ 312,216 $ 308,637 Unsecured term loan, effective interest rates ranging from LIBOR plus 1.45% to LIBOR plus 1.80%, with staggered maturity dates ranging from December 2020 to December 2022 (1) 300,000 300,000 Unsecured revolving credit facility, effective interest rate of LIBOR plus 1.50%, maturing December 2019 (1) 120,000 205,000 $ 732,216 $ 813,637 (1) At December 31, 2015 , LIBOR was 0.43% . All references to LIBOR in the consolidated financial statements refer to one-month LIBOR. (2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9 , Dispositions , for further discussion.
Summary of Company's Mortgage Debt	The following table provides a summary of our mortgage debt at December 31, 2015 and 2014 (dollars in thousands): Encumbered Property Contractual Interest Rate Effective Interest Rate Maturity Date December 31, 2015 December 31, 2014 Jackson National Life Loan (1) 5.19 % 5.19 % August 2015 $ — $ 64,943 440 First Street, NW Construction Loan (2) LIBOR + 2.50% LIBOR + 2.50% May 2016 32,216 32,216 Storey Park Land Loan (2) LIBOR + 2.50% LIBOR + 2.50% October 2016 22,000 22,000 Gateway Centre Manassas Building I (3) 7.35 % 5.88 % November 2016 — 432 Hillside I and II 5.75 % 4.62 % December 2016 12,540 12,949 Redland Corporate Center Buildings II & III 4.20 % 4.64 % November 2017 64,543 65,816 Northern Virginia Construction Loan (2) LIBOR + 1.85% LIBOR + 1.85% September 2019 9,176 — 840 First Street, NE 5.72 % 6.01 % July 2020 35,888 36,539 Battlefield Corporate Center 4.26 % 4.40 % November 2020 3,526 3,692 1211 Connecticut Avenue, NW 4.22 % 4.47 % July 2022 29,110 29,691 1401 K Street, NW 4.80 % 4.93 % June 2023 36,224 36,861 11 Dupont Circle, NW 4.05 % 4.22 % September 2030 66,780 — 4.58 % (4) 312,003 305,139 Unamortized fair value adjustments (172 ) (370 ) Principal balance 311,831 304,769 Debt Classified within Liabilities Held-for-Sale Gateway Centre Manassas Building I (3) 7.35 % 5.88 % November 2016 213 — Richmond Portfolio (5) Hanover Business Center Building D 8.88 % 6.63 % August 2015 — 104 Chesterfield Business Center Buildings C,D,G and H 8.50 % 6.63 % September 2015 — 302 Hanover Business Center Building C 7.88 % 6.63 % December 2017 — 505 Chesterfield Business Center Buildings A,B,E and F 7.45 % 6.63 % June 2021 — 1,674 Airpark Business Center 7.45 % 6.63 % June 2021 — 913 213 3,498 Total unamortized fair value adjustments (1 ) (73 ) Principal balance 212 3,425 Total principal balance $ 312,043 $ 308,194 (1) On July 21, 2015, we prepaid, without penalty, the $64.2 million outstanding balance on our Jackson National Life Loan, which was scheduled to mature in August 2015 and was secured by the following properties: Plaza 500, Van Buren Office Park, Greenbrier Technology Center II, Norfolk Business Center, Snowden Center and Rumsey Center, which was subsequently sold on July 28, 2015. (2) At December 31, 2015 , LIBOR was 0.43% . (3) Gateway Centre Manassas is included in the NOVA Non-Core Portfolio, which was classified as held-for-sale at December 31, 2015. The mortgage loan that encumbers Gateway Centre Manassas was classified within “ Liabilities held-for-sale ” on our December 31, 2015 consolidated balance sheet. (4) Weighted average interest rate on total mortgage debt. (5) The mortgage loans that encumbered properties within the Richmond Portfolio and related unamortized fair value adjustments were classified within “Liabilities held-for-sale” on our December 31, 2014 consolidated balance sheet and were repaid upon the sale of the Richmond Portfolio in March 2015.
Originated or Assumed Mortgages	We have originated or assumed the following mortgage loans since January 1, 2014 (dollars in thousands): Month Year Property Effective Interest Rate Principal Amount September 2015 Northern Virginia Construction Loan LIBOR + 1.85% (1) $ 9,176 August 2015 11 Dupont Circle, NW 4.22% 66,780 October 2014 Storey Park Land Loan LIBOR + 2.50% (1) 22,000 (2) April 2014 1401 K Street, NW 4.93% 37,269 (1) At December 31, 2015, LIBOR was 0.43% . (2) We have a 97% ownership interest in the property through a consolidated joint venture. The loan balance in the chart above reflects the entire loan balance, which is reflected in our consolidated balance sheets.
Repayment of Mortgages	We have repaid the following mortgage loans since January 1, 2014 (dollars in thousands): Month Year Property Effective Interest Rate Principal Balance Repaid July 2015 Jackson National Life Loan 5.19 % $ 64,230 March 2015 Hanover Business Center Building D 6.63 % 65 March 2015 Chesterfield Business Center Buildings C,D,G and H 6.63 % 202 March 2015 Hanover Business Center Building C 6.63 % 460 March 2015 Chesterfield Business Center Buildings A,B,E and F 6.63 % 1,584 March 2015 Airpark Business Center 6.63 % 864 October 2014 Storey Park Land Loan 5.80 % 22,000 May 2014 Annapolis Business Center 6.25 % 8,027
Unsecured Term Loan	The table below shows the outstanding balances and the interest rates of the three tranches of the $300.0 million unsecured term loan at December 31, 2015 (dollars in thousands): Maturity Date Amount Interest Rate (1) Tranche A December 2020 $ 100,000 LIBOR, plus 145 basis points Tranche B June 2021 100,000 LIBOR, plus 145 basis points Tranche C December 2022 100,000 LIBOR, plus 180 basis points $ 300,000 (1) At December 31, 2015 , LIBOR was 0.43% . The interest rate spread is subject to change based on our maximum total indebtedness ratio. For more information, see note 10 (e), Debt – Financial Covenants .
Aggregate Debt Maturities	(f) Aggregate Debt Maturities Our aggregate debt maturities as of December 31, 2015 , including amounts from properties that were classified as held-for-sale at December 31, 2015 , are as follows (dollars in thousands): 2016 $ 70,260 2017 65,456 2018 2,354 2019 131,648 2020 137,203 Thereafter 325,122 732,043 Unamortized fair value adjustments 173 Total contractual principal balance $ 732,216

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Swap Agreements	At December 31, 2015 , we fixed LIBOR at a weighted average interest rate of 1.5% on $300.0 million of our variable rate debt through eleven interest rate swap agreements that are summarized below (dollars in thousands): Maturity Date Notional Amount Interest Rate Contractual Component Fixed LIBOR Interest Rate July 2016 $ 35,000 LIBOR 1.754 % July 2016 25,000 LIBOR 1.763 % July 2017 30,000 LIBOR 2.093 % July 2017 30,000 LIBOR 2.093 % July 2017 25,000 LIBOR 1.129 % July 2017 12,500 LIBOR 1.129 % July 2017 50,000 LIBOR 0.955 % July 2018 12,500 LIBOR 1.383 % July 2018 30,000 LIBOR 1.660 % July 2018 25,000 LIBOR 1.394 % July 2018 25,000 LIBOR 1.135 % Total/Weighted Average $ 300,000 1.505 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
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 our consolidated assets and liabilities that are measured on a non-recurring and recurring basis as of December 31, 2015 and 2014 (amounts in thousands): Balance at December 31, 2015 Level 1 Level 2 Level 3 Non-recurring Measurements: Impaired real estate assets $ 104,625 $ — $ 90,625 $ 14,000 Recurring Measurements: Derivative instrument-swap liabilities 2,491 — 2,491 — Balance at December 31, 2014 Level 1 Level 2 Level 3 Recurring Measurements: Derivative instrument-swap assets $ 133 $ — $ 133 $ — Derivative instrument-swap liabilities 3,569 — 3,569 —
Fair Value of Debt Instruments	The carrying amount and estimated fair value of our notes receivable and debt instruments at December 31 are as follows (amounts in thousands): 2015 2014 Carrying Value Fair Value Carrying Value Fair Value Financial Assets: Notes receivable (1) $ 34,000 $ 34,000 $ 63,679 $ 63,720 Financial Liabilities: Mortgage debt (2) $ 312,216 $ 298,541 $ 308,637 $ 292,882 Unsecured term loan 300,000 300,000 300,000 300,000 Unsecured revolving credit facility 120,000 120,000 205,000 205,000 Total $ 732,216 $ 718,541 $ 813,637 $ 797,882 (1) The principal amount of our notes receivable was $34.0 million and $63.7 million at December 31, 2015 and 2014, respectively. On February 24, 2015, the owners of America’s Square, a 461,000 square foot office complex located in Washington, D.C., prepaid the $29.7 million outstanding balance of the $30.0 million mezzanine loan that we provided to them in April 2011. (2) Includes $0.2 million and $3.5 million of mortgage debt that were classified as held-for-sale and included within “Liabilities held-for-sale” on our consolidated balance sheets for December 31, 2015 and 2014, respectively. See note 9 , Dispositions for additional details.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Summary of Operating Leases Generating Future Minimum Rental Payments	Our rental properties are subject to non-cancelable operating leases generating future minimum contractual rent payments due from tenants, which as of December 31, 2015 are as follows (dollars in thousands): Future minimum contractual rent payments 2016 $ 129,004 2017 112,800 2018 100,533 2019 87,924 2020 72,606 Thereafter 206,499 $ 709,366
Schedule of Future Minimum Rental Payments	Future minimum rental payments under our corporate office leases as of December 31, 2015 are summarized as follows, net of sublease revenue (dollars in thousands): Future minimum rent payments 2016 $ 1,431 2017 1,469 2018 1,906 2019 1,995 2020 2,049 Thereafter 175 $ 9,025

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Characterization of Company's Dividends	The characterization of the dividends declared on our common and preferred shares for 2015 , 2014 and 2013 are as follows: Common Shares Preferred Shares 2015 2014 2013 2015 2014 2013 Ordinary income (1) 52.01 % 72.42 % 13.53 % 72.89 % 100.00 % 100.00 % Return of capital 28.64 % 27.58 % 86.47 % — — — Capital gains 19.35 % — — 27.11 % — — (1) The dividends classified above as ordinary income do not represent “qualified dividend income” and, therefore, are not eligible for reduced rates.

Noncontrolling Interests (Table

Noncontrolling Interests (Tables)	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Summary of Redeemable Noncontrolling Interests in Operating Partnership	The redeemable noncontrolling interests in the Operating Partnership for the three years ended December 31 are as follows (dollars in thousands): Redeemable noncontrolling interests Balance at December 31, 2013 $ 33,221 Net income 199 Changes in ownership, net 1,465 Distributions to owners (1,578 ) Other comprehensive income 25 Balance at December 31, 2014 33,332 Net loss (2,056 ) Changes in ownership, net (931 ) Distributions to owners (1,574 ) Other comprehensive income 42 Balance at December 31, 2015 $ 28,813

Benefit Plans (Tables)

Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation Plans Option Activity	A summary of our stock option activity for the three years ended December 31 is presented below: Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2012 1,384,006 $ 15.91 5.9 years $ 174,763 Granted 124,250 12.73 Exercised (14,733 ) 11.05 Expired (298,469 ) 15.00 Forfeited (105,762 ) 16.17 Outstanding at December 31, 2013 1,089,292 15.83 6.6 years $ 109,151 Granted 135,250 11.61 Exercised (17,171 ) 10.10 Expired (57,500 ) 19.08 Forfeited (98,512 ) 14.49 Outstanding at December 31, 2014 1,051,359 15.33 6.3 years $ 181,352 Granted 119,500 12.48 Exercised (2,750 ) 9.30 Expired (59,000 ) 22.44 Forfeited (145,971 ) 15.06 Outstanding at December 31, 2015 963,138 $ 14.59 6.1 years $ 59,002 Exercisable at December 31: 2015 805,259 $ 15.06 5.6 years $ 59,002 2014 552,620 16.49 5.1 years 102,039 2013 521,723 17.25 4.9 years 109,151 Options expected to vest, subsequent to December 31, 2015 142,530 $ 12.29 8.5 years $ —
Stock Options Information	The following table summarizes information about our stock options at December 31, 2015 : Options Outstanding Options Exercisable Year Issued Range of Exercise Prices Options Weighted Average Remaining Contractual Life Weighted Average Exercise Price Options Weighted Average Exercise Price 2006 $ 26.60 11,850 0.0 years $ 26.60 11,850 $ 26.60 2007 29.11 - 29.24 24,500 1.1 years 29.14 24,500 29.14 2008 17.29 26,250 2.0 years 17.29 26,250 17.29 2009 9.30 28,096 3.0 years 9.30 28,096 9.30 2010 12.57 33,830 4.0 years 12.57 33,830 12.57 2011 17.12 37,250 5.0 years 17.12 37,250 17.12 2012 13.54 - 15.00 553,001 6.0 years 14.86 549,937 14.87 2013 12.73 63,845 7.0 years 12.73 48,655 12.73 2014 11.61 87,266 8.0 years 11.61 44,891 11.61 2015 12.48 97,250 9.0 years 12.48 — — 963,138 6.1 years 14.60 805,259 15.06
Assumptions Used in Fair Value Determination of Stock Options Granted	The weighted average assumptions used in the fair value determination of stock options granted to employees for the years ended December 31 are summarized as follows: 2015 2014 2013 Risk-free interest rate 1.61 % 1.72 % 0.76 % Expected volatility 29.2 % 39.0 % 49.7 % Expected dividend yield 4.79 % 4.66 % 4.92 % Weighted average expected life of options 5.0 years 5.0 years 5.0 years
Summary of Company's Non-Vested Share Awards	A summary of our non-vested common share awards at December 31, 2015 is as follows: Non-vested Shares Weighted Average Grant Date Fair Value Non-vested at December 31, 2012 673,828 $ 12.83 Granted 313,086 12.14 Vested (297,778 ) 12.89 Expired (45,049 ) 11.42 Forfeited (6,425 ) 14.01 Non-vested at December 31, 2013 637,662 13.33 Granted 164,675 12.84 Vested (137,924 ) 14.21 Expired (29,514 ) 10.21 Forfeited (11,478 ) 13.04 Non-vested at December 31, 2014 623,421 13.16 Granted 152,598 11.79 Vested (401,888 ) 13.16 Expired (133,371 ) 12.61 Forfeited (48,378 ) 13.30 Non-vested at December 31, 2015 192,382 $ 12.42

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Summary of Segment Information	The results of continuing operations for our four reporting segments for the three years ended December 31 are as follows (dollars in thousands): 2015 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (1) 6 34 40 19 99 Square feet (1) 918,375 1,885,630 2,661,448 2,023,639 7,489,092 Total revenues $ 44,553 $ 44,226 $ 55,230 $ 28,837 $ 172,846 Property operating expense (11,363 ) (11,457 ) (13,540 ) (7,733 ) (44,093 ) Real estate taxes and insurance (8,238 ) (3,540 ) (5,540 ) (2,427 ) (19,745 ) Total property operating income $ 24,952 $ 29,229 $ 36,150 $ 18,677 109,008 Depreciation and amortization expense (66,624 ) General and administrative (25,450 ) Impairment of rental property (60,826 ) Other income 9,475 Loss from discontinued operations (607 ) Net income $ (35,024 ) Total assets (2)(3) $ 521,107 $ 341,898 $ 374,811 $ 167,467 $ 1,450,371 Capital expenditures (4) $ 12,930 $ 9,003 $ 43,125 $ 7,961 $ 73,850 2014 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (1) 6 38 49 38 131 Square feet (1) 917,008 1,999,332 3,021,509 2,852,298 8,790,147 Total revenues $ 33,959 $ 45,767 $ 53,645 $ 28,281 $ 161,652 Property operating expense (9,683 ) (11,482 ) (13,352 ) (8,735 ) (43,252 ) Real estate taxes and insurance (5,583 ) (3,907 ) (5,592 ) (2,278 ) (17,360 ) Total property operating income $ 18,693 $ 30,378 $ 34,701 $ 17,268 101,040 Depreciation and amortization expense (61,796 ) General and administrative (21,156 ) Acquisition costs (2,681 ) Impairment of rental property (3,956 ) Other income 4,108 Income from discontinued operations 1,484 Net income $ 17,043 Total assets (2)(3) $ 505,842 $ 360,470 $ 439,833 $ 228,306 $ 1,618,460 Capital expenditures (4) $ 23,422 $ 10,185 $ 7,816 $ 8,436 $ 50,789 2013 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (1)(5) 4 53 51 38 146 Square feet (1)(5) 522,605 2,638,988 3,086,057 2,852,471 9,100,121 Total revenues $ 28,208 $ 41,735 $ 51,787 $ 27,085 $ 148,815 Property operating expense (6,693 ) (10,579 ) (12,601 ) (8,407 ) (38,280 ) Real estate taxes and insurance (4,792 ) (3,436 ) (5,679 ) (2,167 ) (16,074 ) Total property operating income $ 16,723 $ 27,720 $ 33,507 $ 16,511 94,461 Depreciation and amortization expense (54,567 ) General and administrative (21,979 ) Acquisition costs (602 ) Contingent consideration related to acquisition of property 213 Other expenses (28,287 ) Income from discontinued operations 21,742 Net income $ 10,981 Total assets (2)(3) $ 344,739 $ 430,498 $ 423,839 $ 230,175 $ 1,502,460 Capital expenditures (4) $ 26,910 $ 16,216 $ 13,685 $ 10,106 $ 68,002 (1) Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013. (2) Total assets include our investment in properties that are owned through joint ventures that are not consolidated within our consolidated financial statements. For more information on our unconsolidated investments, including locations within our reportable segments, see note 5 , Investment in Affiliates . (3) Corporate assets not allocated to any of our reportable segments totaled $45,088 , $84,009 and $73,209 at December 31, 2015 , 2014 and 2013 , respectively. (4) Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $831 , $930 and $1,085 at December 31, 2015 , 2014 and 2013 , respectively. (5) Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

Quarterly Financial Informati44

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Information	Quarterly Financial Information (unaudited) 2015 (1) First Second Third Fourth (amounts in thousands, except per share amounts) Quarter Quarter Quarter Quarter Revenues $ 43,849 $ 43,039 $ 42,854 $ 43,104 Operating expenses 40,016 37,268 37,079 102,375 Operating income (loss) 3,833 5,771 5,775 (59,271 ) Income (loss) from continuing operations 1,099 476 3,997 (39,990 ) (Loss) income from discontinued operations (607 ) — — — Less: Net loss (income) attributable to noncontrolling interests 112 114 (38 ) 1,870 Net (loss) income attributable to First Potomac Realty Trust 604 590 3,959 (38,120 ) Less: Dividends on preferred shares (3,100 ) (3,100 ) (3,100 ) (3,100 ) Net (loss) income attributable to common shareholders $ (2,496 ) $ (2,510 ) $ 859 $ (41,220 ) Basic and diluted earnings per common share: (Loss) income from continuing operations $ (0.03 ) $ (0.04 ) $ 0.01 $ (0.72 ) (Loss) income from discontinued operations (0.01 ) — — — Net (loss) income $ (0.04 ) $ (0.04 ) $ 0.01 $ (0.72 ) 2014 (1) First Second Third Fourth (amounts in thousands, except per share amounts) Quarter Quarter Quarter Quarter Revenues $ 39,363 $ 39,307 $ 40,055 $ 42,928 Operating expenses 35,744 39,579 36,283 38,595 Operating income (loss) 3,619 (272 ) 3,772 4,333 (Loss) income from continuing operations (586 ) 16,796 (248 ) (402 ) (Loss) income from discontinued operations (857 ) 1,538 297 505 Less: Net loss (income) attributable to noncontrolling interests 195 (652 ) 131 128 Net (loss) income attributable to First Potomac Realty Trust (1,248 ) 17,682 180 231 Less: Dividends on preferred shares (3,100 ) (3,100 ) (3,100 ) (3,100 ) Net (loss) income attributable to common shareholders $ (4,348 ) $ 14,582 $ (2,920 ) $ (2,869 ) Basic and diluted earnings per common share: (Loss) income from continuing operations $ (0.07 ) $ 0.22 $ (0.05 ) $ (0.06 ) (Loss) income from discontinued operations (0.01 ) 0.03 — 0.01 Net (loss) income $ (0.08 ) $ 0.25 $ (0.05 ) $ (0.05 ) (1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2014USD ($)ft²

Sep. 30, 2014USD ($)

[3]

Jun. 30, 2014USD ($)

[3]

Mar. 31, 2014USD ($)

[3]

Dec. 31, 2013USD ($)

[3]

Sep. 30, 2013USD ($)

[3]

Jun. 30, 2013USD ($)

[3]

Mar. 31, 2013USD ($)

[3]

Dec. 31, 2015USD ($)ft²segmentjoint_venturepersonRate

Dec. 31, 2014USD ($)ft²

Dec. 31, 2013USD ($)

Dec. 31, 2012USD ($)ft²

Real Estate Properties [Line Items]

Operating Partnership in preferred

100.00%

Interest in Operating Partnership

95.70%

Square Feet

[1]

8,790,147

7,489,092

8,790,147

9,100,121

[2]

Unconsolidated joint ventures | joint_venture

5

Square footage of land for additional development

1,300,000

Occupancy rate in the Company's consolidated properties

90.30%

Number Of Tenants In Companys Consolidated Rental Properties | person

454

Square footage in development or redevelopment not included on occupancy calculation

200,000

Annualized Cash Basis Rent Percent for Government Tenant | Rate

12.00%

Percentage of outstanding account receivables accounted by government

24.00%

Revenues | $

$ 43,104

[3]

$ 42,854

$ 43,039

$ 43,849

$ 42,928

$ 40,055

$ 39,307

$ 39,363

$ 172,846

$ 161,652

$ 148,815

Consolidated Total assets | $

[4],[5]

$ 1,618,460

$ 1,450,371

$ 1,618,460

$ 1,502,460

Number of separate reporting segments of properties | segment

4

Wholly-owned Properties [Member]

Real Estate Properties [Line Items]

Square Feet

7,500,000

Unconsolidated Properties [Member]

Real Estate Properties [Line Items]

Square Feet

900,000

[1]

Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.

[2]

Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

[3]

(1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.

[4]

Corporate assets not allocated to any of our reportable segments totaled $45,088, $84,009 and $73,209 at December 31, 2015, 2014 and 2013, respectively.

[5]

Total assets include our investment in properties that are owned through joint ventures that are not consolidated within our consolidated financial statements. For more information on our unconsolidated investments, including locations within our reportable segments, see note 5, Investment in Affiliates.

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Bad Debt Expense		$ 600,000			$ 1,100,000	$ 800,000
Termination Fee Revenue		100,000			1,100,000	1,000,000
Age of highly liquid investments considered as cash equivalents	90 days or less
Accumulated amortization of financing costs related to long-term debt	$ 30,100,000	30,100,000	$ 30,100,000	$ 30,100,000	24,800,000
Required distribution percentage of ordinary annual taxable income to shareholders to maintain Company status as a REIT			90.00%
Required distribution percentage of REIT taxable income of the Company to shareholders to avoid federal income tax and non-deductible exercise tax			100.00%	100.00%
Percentage of likelihood that the Company may recognize tax benefit from uncertain tax position when it is more-likely-than-not that the position will be sustained, based on technical merits			50.00%
Uncertain tax positions		0			0	0
Allowance for credit losses for its notes receivable		$ 0			$ 0	$ 0

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Scheduled Future Amortization for Deferred Financing and Leasing Costs (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	$ 7,954	[1]
Future Amortization Expense for Deferred Leasing Cost	27,181	[1],[2]
Lease Incentive	6,318
Excluded leasing costs amortization for tenants not yet placed in-service	3,100
2016 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	1,935	[1]
Future Amortization Expense for Deferred Leasing Cost	2,979	[1],[2]
Lease Incentive	645
2017 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	1,557	[1]
Future Amortization Expense for Deferred Leasing Cost	5,033	[1],[2]
Lease Incentive	868
2018 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	1,347	[1]
Future Amortization Expense for Deferred Leasing Cost	4,482	[1],[2]
Lease Incentive	834
2019 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	1,313	[1]
Future Amortization Expense for Deferred Leasing Cost	3,673	[1],[2]
Lease Incentive	761
2020 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	379	[1]
Future Amortization Expense for Deferred Leasing Cost	2,986	[1],[2]
Lease Incentive	691
Thereafter [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost	1,423	[1]
Future Amortization Expense for Deferred Leasing Cost	8,028	[1],[2]
Lease Incentive	$ 2,519
[1]	(1) Includes amounts from properties that were classified as held-for-sale at December 31, 2015.
[2]	(2) Excludes the amortization of $3.1 million of leasing costs that have yet to be placed in-service as the associated tenants have not moved into their related spaces and, therefore, the period over which the leasing costs will be amortized has yet to be determined.

Summary of Significant Accoun48

Summary of Significant Accounting Policies - Estimated Useful Lives of Company's Assets, by Class (Detail)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Tenant improvements, Useful life	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]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	5 years
Minimum [Member] | Building and 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]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	39 years
Maximum [Member] | Building and 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 Accoun49

Summary of Significant Accounting Policies - Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Indefinite-lived Intangible Assets [Line Items]
Goodwill, Fair Value Disclosure	$ 2,100,000
Goodwill, Impairment Loss	0	$ 0	$ 0
Uncertain tax positions	0	0	0
Allowance for credit losses for its notes receivable	$ 0	$ 0	$ 0
Eight Four Zero First Street [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Goodwill				$ 4,800,000

Earnings Per Common Share - Com

Earnings Per Common Share - Computation of Company's Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2014	[1]	Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2013	[1]	Sep. 30, 2013	[1]	Jun. 30, 2013	[1]	Mar. 31, 2013	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator for basic and diluted earnings per common share:
(Loss) income from continuing operations	$ (39,990)		$ 3,997		$ 476		$ 1,099		$ (402)		$ (248)		$ 16,796		$ (586)		$ (34,417)	$ 15,559	$ (10,761)
(Loss) income from discontinued operations	0		0		0		(607)		505		297		1,538		(857)		(607)	1,484	21,742
Net (loss) income																	(35,024)	17,043	10,981
Less: Net loss (income) from continuing operations attributable to noncontrolling interests																	2,032	(135)	1,047
Less: Net loss (income) from discontinued operations attributable to noncontrolling interests																	26	(64)	(954)
Net (loss) income attributable to First Potomac Realty Trust	(38,120)		3,959		590		604		231		180		17,682		(1,248)		(32,966)	16,844	11,074
Less: Dividends on preferred shares	(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(12,400)	(12,400)	(12,400)
Net (loss) income attributable to common shareholders																	(45,366)	4,444	(1,326)
Less: Allocation to participating securities																	(241)	(314)	(388)
Net (loss) income attributable to common shareholders	$ (41,220)		$ 859		$ (2,510)		$ (2,496)		$ (2,869)		$ (2,920)		$ 14,582		$ (4,348)		$ (45,607)	$ 4,130	$ (1,714)
Denominator for basic and diluted earnings per common share:
Weighted average common shares outstanding – basic																	57,982	58,150	55,034
Weighted average common shares outstanding – diluted																	57,982	58,220	55,034
Basic and diluted earnings per common share:
(Loss) income from continuing operations	$ (0.72)		$ 0.01		$ (0.04)		$ (0.03)		$ (0.06)		$ (0.05)		$ 0.22		$ (0.07)		$ (0.78)	$ 0.05	$ (0.41)
(Loss) income from discontinued operations	0		0		0		(0.01)		0.01		0		0.03		(0.01)		(0.01)	0.02	0.38
Net (loss) income	$ (0.72)		$ 0.01		$ (0.04)		$ (0.04)		$ (0.05)		$ (0.05)		$ 0.25		$ (0.08)		$ (0.79)	$ 0.07	$ (0.03)
[1]	(1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.

Earnings Per Common Share - Ant

Earnings Per Common Share - Anti-Dilutive Shares Not Included in Calculation of Diluted Earnings Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, Amount	1,330	1,520	1,840
Stock option awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, Amount	1,020	1,122	1,369
Non-vested share awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, Amount	310	398	471

Rental Property - Summary of Re

Rental Property - Summary of Rental Property (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Land and land improvements	$ 280,149	[1]	$ 325,214	[2]
Buildings and improvements	793,184	[1]	949,683	[2]
Construction in progress	97,361	[1]	69,181	[2]
Tenant improvements	168,946	[1]	159,867	[2]
Furniture, fixtures and equipment	410	[1]	427	[2]
Rental property, gross	1,340,050	[1]	1,504,372	[2]
Less: accumulated depreciation	(209,784)	[1]	(215,499)	[2]
Rental property, net	1,130,266	[1]	1,288,873	[2]
Southern Virginia [Member]
Property, Plant and Equipment [Line Items]
Rental property, net			$ 57,700
NOVA Non Core Portfolio
Property, Plant and Equipment [Line Items]
Rental property, net	$ 90,600
[1]	1) Excludes rental property totaling $90.6 million at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9(a), Dispositions), which was classified as held-for-sale at December 31, 2015.
[2]	(2) Excludes rental property totaling $57.7 million at December 31, 2014 related to the sale of the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015.

Rental Property - Additional In

Rental Property - Additional Information (Detail) $ in Thousands		Aug. 04, 2013aft²	Dec. 31, 2015USD ($)ft²		Dec. 31, 2014USD ($)ft²		Oct. 15, 2013ft²	Dec. 31, 2012ft²	[2]	Aug. 04, 2011Rate
Segment Reporting Information [Line Items]
Area of land available for development in additional building space			1,300,000
Square Feet	[1]		7,489,092		8,790,147			9,100,121
Original cost basis of the property | $			$ 793,184	[3]	$ 949,683	[4]
Lease expiration date			Jan. 31, 2021
Anticipated completion of redevelopment							139,000
Projected incremental investment in redevelopment project | $			$ 55,500
Leased Percentage			71.70%
Occupancy Percentage			56.90%
Completed and placed in-service redevelopment efforts			0
Development Efforts Yet To Be Placed In Service			0
Greyhound Property [Member]
Segment Reporting Information [Line Items]
Percentage Of Interest In Joint Venture Owned By Entity | Rate										97.00%
440 First Street, NW [Member]
Segment Reporting Information [Line Items]
Original cost basis of the property | $			$ 23,600
Washington, D.C Reporting Segment [Member]
Segment Reporting Information [Line Items]
Area of land available for development in additional building space			700,000
Projected incremental investment in development project | $			$ 58,000
Original cost basis of the property | $			$ 43,300
Lease expiration date		Aug. 31, 2013
Development of area for operations by joint venture | a		1.6
Redevelopment efforts yet to be placed-in service			0
Washington, D.C Reporting Segment [Member] | Greyhound Property [Member]
Segment Reporting Information [Line Items]
Percentage Of Interest In Joint Venture Owned By Entity										97.00%
Maryland Reporting Segment [Member]
Segment Reporting Information [Line Items]
Area of land available for development in additional building space			100,000
Northern Virginia Reporting Segment [Member]
Segment Reporting Information [Line Items]
Area of land available for development in additional building space			400,000
Square Feet			167,000
Projected incremental investment in development project | $			$ 29,500
Original cost basis of the property | $			$ 5,200
Southern Virginia [Member]
Segment Reporting Information [Line Items]
Area of land available for development in additional building space			100,000
Minimum [Member]
Segment Reporting Information [Line Items]
Estimated useful lives of the assets			5 years
Maximum [Member]
Segment Reporting Information [Line Items]
Estimated useful lives of the assets			39 years
Maximum [Member] | Washington, D.C Reporting Segment [Member] | Greyhound Property [Member]
Segment Reporting Information [Line Items]
Area of land available for development in additional building space		712,000
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.
[3]	1) Excludes rental property totaling $90.6 million at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9(a), Dispositions), which was classified as held-for-sale at December 31, 2015.
[4]	(2) Excludes rental property totaling $57.7 million at December 31, 2014 related to the sale of the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015.

Investment in Affiliates - Comp

Investment in Affiliates - Components of Investments in Affiliates (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Jul. 10, 2014
Schedule of Equity Method Investments [Line Items]
Company Investment		$ 48,223	$ 47,482
Debt		110,000	110,000
Recourse Debt	[1]	$ 2,800	$ 2,800
Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment		Northern Virginia	Northern Virginia
Ownership Interest		51.00%	51.00%
Company Investment		$ 24,909	$ 24,651
Debt		50,000	50,000
Recourse Debt		$ 0	$ 0
1750 H Street, NW [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment		Washington, D.C.	Washington, D.C.
Ownership Interest		50.00%	50.00%	50.00%
Company Investment		$ 15,168	$ 14,834
Debt		32,000	32,000
Recourse Debt		$ 0	$ 0
Aviation Business Park [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment		Maryland	Maryland
Ownership Interest		50.00%	50.00%
Company Investment		$ 5,899	$ 5,748
Debt		0	0
Recourse Debt		$ 0	$ 0
Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment	[2]	Maryland	Maryland
Ownership Interest	[2]	25.00%	25.00%
Company Investment	[2]	$ 2,247	$ 2,249
Debt	[2]	28,000	28,000
Recourse Debt	[1],[2]	$ 2,800	$ 2,800
[1]	(1) We believe the fair value of the potential liability to us related to the recourse debt is inconsequential as the likelihood of our need to perform under the debt agreement is remote.
[2]	(2) Rivers Park I and Rivers Park II are owned through two separate joint ventures.

Investment in Affiliates - Addi

Investment in Affiliates - Additional Information (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2015USD ($)ft²Rate	Dec. 31, 2014USD ($)ft²	Dec. 31, 2013USD ($)	Nov. 12, 2014USD ($)ft²Rate	Sep. 26, 2014USD ($)ft²Rate	Jul. 10, 2014USD ($)ft²Rate	Mar. 26, 2014Rate	Dec. 31, 2012ft²	[2]
Schedule of Equity Method Investments [Line Items]
Long-term Debt		$ 732,216	$ 813,637
Square Feet | ft²	[1]	7,489,092	8,790,147						9,100,121
Fees from joint ventures		$ 700	$ 700	$ 600
Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest | Rate					51.00%
Square Feet | ft²					327,000
Contractual interest rate | Rate					3.91%
Interest only payment date		Dec. 31, 2024
Maturity date of senior notes		Dec. 1, 2029
Joint venture loan prepayment date		Jun. 1, 2029
Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest | Rate						25.00%
Square Feet | ft²						308,000
Maturity date of senior notes		Sep. 26, 2017
Reduction in variable rate | Rate		0.60%
Percentage of outstanding principal | Rate						10.00%		25.00%
Repayment of Long Term Debt [Member] | Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt					$ 48,300
New Loan [Member] | Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt					$ 50,000
Amendment or Modification [Member] | Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt						$ 28,000
1750 H Street, NW [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest		50.00%	50.00%				50.00%
Investment in Affiliates Joint Venture Repaid Mortgage							$ 27,900
Square Feet | ft²							113,000
Investment in Affiliates Joint Venture Financing							$ 32,000
Contractual interest rate | Rate							3.92%
Maturity date of senior notes		Aug. 1, 2024
Joint venture loan prepayment date		Aug. 1, 2021
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

Investment in Affiliates - Net

Investment in Affiliates - Net Assets of Company's Unconsolidated Joint Ventures (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets:
Rental property, net		$ 1,130,266	$ 1,288,873
Cash and cash equivalents		13,527	13,323	$ 8,740	$ 9,374
Total assets	[1],[2]	1,450,371	1,618,460		$ 1,502,460
Liabilities:
Total liabilities		796,230	874,223
Unconsolidated Joint Ventures [Member]
Assets:
Rental property, net		193,243	193,533
Cash and cash equivalents		5,992	4,567
Other assets		17,218	16,748
Total assets		216,453	214,848
Liabilities:
Mortgage loans		110,000	110,000
Other liabilities		7,215	7,256
Total liabilities		117,215	117,256
Net assets		$ 99,238	$ 97,592
[1]	Corporate assets not allocated to any of our reportable segments totaled $45,088, $84,009 and $73,209 at December 31, 2015, 2014 and 2013, respectively.
[2]	Total assets include our investment in properties that are owned through joint ventures that are not consolidated within our consolidated financial statements. For more information on our unconsolidated investments, including locations within our reportable segments, see note 5, Investment in Affiliates.

Investment in Affiliates - Resu

Investment in Affiliates - Results of Operations of Company's Unconsolidated Joint Ventures (Detail) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2014	[1]	Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2013	[1]	Sep. 30, 2013	[1]	Jun. 30, 2013	[1]	Mar. 31, 2013	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 43,104		$ 42,854		$ 43,039		$ 43,849		$ 42,928		$ 40,055		$ 39,307		$ 39,363		$ 172,846	$ 161,652	$ 148,815
Total operating expenses	(102,375)		(37,079)		(37,268)		(40,016)		(38,595)		(36,283)		(39,579)		(35,744)		(216,738)	(150,201)	(131,289)
Operating (loss) income	$ (59,271)		$ 5,775		$ 5,771		$ 3,833		$ 4,333		$ 3,772		$ (272)		$ 3,619		(43,892)	11,451	17,526
Depreciation and amortization																	(66,624)	(61,796)	(54,567)
Interest expense, net																	(26,797)	(24,696)	(32,803)
Provision for income taxes																	0	0	0
Net income																	1,825	775	(47)
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenues																	24,255	23,285	24,017
Total operating expenses																	(7,660)	(7,408)	(7,753)
Operating (loss) income																	16,595	15,877	16,264
Depreciation and amortization																	(8,718)	(9,893)	(11,551)
Interest expense, net																	(3,909)	(3,890)	(4,222)
Provision for income taxes																	0	(63)	(83)
Contingent consideration charge																	0	126	0
Net income																	$ 3,968	$ 2,157	$ 408
[1]	(1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.

Notes Receivable - Summary of N

Notes Receivable - Summary of Notes Receivable (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Receivables with Imputed Interest [Line Items]
Face Amount		$ 63,720
Unamortized Origination Fees		(41)
Balance		63,679
Nine Hundered And Fifty Street Nw [Member] | Notes Receivables Issued on December 2010 [Member]
Receivables with Imputed Interest [Line Items]
Face Amount	$ 34,000	34,000
Unamortized Origination Fees	0	0
Balance	$ 34,000	$ 34,000
Interest Rate	9.75%	9.75%
America Square [Member] | Notes Receivables Issued on April 2011 [Member]
Receivables with Imputed Interest [Line Items]
Face Amount		$ 29,720
Unamortized Origination Fees		(41)
Balance		$ 29,679
Interest Rate		9.00%

Notes Receivable - Additional I

Notes Receivable - Additional Information (Detail) $ in Millions		Feb. 24, 2015USD ($)	Jan. 10, 2014USD ($)	Apr. 01, 2011	Dec. 31, 2015USD ($)ft²	Dec. 31, 2014USD ($)ft²	Dec. 31, 2013USD ($)	Dec. 31, 2012ft²		Jan. 27, 2015ft²	Apr. 30, 2011USD ($)
Receivables with Imputed Interest [Line Items]
Square Feet | ft²	[1]				7,489,092	8,790,147		9,100,121	[2]
Notes Receivables Issued on April 2011 [Member]
Receivables with Imputed Interest [Line Items]
Notes Receivables Issued Date						Apr. 1, 2011
Notes Receivables Issued on December 2010 [Member]
Receivables with Imputed Interest [Line Items]
Square Feet | ft²					287,000
Mezzanine loan provided to owners			$ 34		$ 25
Notes Receivables Issued Date					Dec. 1, 2010
Maturity date of loan								Apr. 1, 2017
Unsecured revolving credit facility			$ 9
Interest income					$ 3.7	$ 6.1	$ 5.9
Notes Receivables Issued on December 2010 [Member] | Maximum [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan			12.50%
Notes Receivables Issued on December 2010 [Member] | Minimum [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan			9.75%
Nine Hundered And Fifty Street Nw [Member]
Receivables with Imputed Interest [Line Items]
Write Off Unamortized Loan Origination Fees						$ 0.1
Nine Hundered And Fifty Street Nw [Member] | Notes Receivables Issued on December 2010 [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan					9.75%	9.75%
America Square [Member]
Receivables with Imputed Interest [Line Items]
Square Feet | ft²										461,000
Mezzanine loan provided to owners		$ 29.7									$ 30
Maturity date of loan					May 1, 2016
Prepayment Fee Income		2.4
America Square [Member] | Maximum [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan				9.00%
America Square [Member] | Notes Receivables Issued on April 2011 [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan						9.00%
Loans Receivable Payment Receipt [Member] | America Square [Member]
Receivables with Imputed Interest [Line Items]
Mezzanine loan provided to owners		$ 30
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

Intangible Assets - Intangible

Intangible Assets - Intangible Assets and Deferred Market Rent Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Intangible Assets By Major Class [Line Items]
Deferred market rent liability, Net Intangibles	$ 2,154	$ 2,827
All Properties, Including Held for Sale [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	68,008	74,712
Accumulated Amortization	(35,049)	(28,796)
Net Intangibles	32,959	45,916
Goodwill	6,930	6,930
Deferred market rent liability, Gross Intangible	4,869	5,193
Deferred market rent liability, Accumulated Amortization	(2,715)	(2,348)
Deferred market rent liability, Net Intangibles	2,154	2,845
All Properties, Including Held for Sale [Member] | In-place Leases [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	45,901	51,258
Accumulated Amortization	(26,961)	(22,443)
Net Intangibles	18,940	28,815
All Properties, Including Held for Sale [Member] | Customer Relationships [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	663	906
Accumulated Amortization	(601)	(654)
Net Intangibles	62	252
All Properties, Including Held for Sale [Member] | Leasing Commissions [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	10,612	11,335
Accumulated Amortization	(5,485)	(4,272)
Net Intangibles	5,127	7,063
All Properties, Including Held for Sale [Member] | Legal Fees [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	344	377
Accumulated Amortization	(177)	(118)
Net Intangibles	167	259
All Properties, Including Held for Sale [Member] | Deferred Market Rent Assets [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	3,558	3,906
Accumulated Amortization	(1,825)	(1,309)
Net Intangibles	$ 1,733	$ 2,597

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 10,600	$ 10,300	$ 8,300
Additional rental revenue	14
Reduction in rental revenue	100		100
Losses due to termination of tenant leases and defaults	$ 500	$ 1,100	$ 1,000

Intangible Assets - Projected N

Intangible Assets - Projected Net Amortization of Intangible Assets and Deferred Market Liabilities Including Amounts from Properties Classified as Held-For-Sale (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,016	$ 7,318
2,017	4,203
2,018	2,700
2,019	2,388
2,020	2,146
Thereafter	5,120
Total	$ 23,875

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Real Estate Acquired Through Foreclosure Under Forward Purchase Agreements [Line Items]
Franchise taxes effective rate	0.00%	9.975%
Provision for income taxes		$ 0	$ 0	$ 0
Deferred tax assets		0	0
Deferred tax liabilities		0	0
Accounts and Other Receivables [Member]
Real Estate Acquired Through Foreclosure Under Forward Purchase Agreements [Line Items]
Tax refund receivable		$ 1,200,000	$ 1,200,000

Dispositions - Summary of Compl

Dispositions - Summary of Completed Property Dispositions within Continuing Operations(Detail) $ in Thousands		Dec. 31, 2015USD ($)ft²	Dec. 23, 2015USD ($)ft²	Dec. 17, 2015USD ($)ft²	Jul. 28, 2015USD ($)ft²	Oct. 16, 2014USD ($)ft²	Jun. 26, 2014USD ($)ft²	Dec. 31, 2015ft²	Dec. 31, 2014ft²	Dec. 31, 2012ft²	[2]
Schedule Of Discontinued Operations [Line Items]
Square Feet	[1]	7,489,092						7,489,092	8,790,147	9,100,121
Northern Virginia Reporting Segment [Member]
Schedule Of Discontinued Operations [Line Items]
Square Feet		167,000						167,000
NOVA Non Core Portfolio | Northern Virginia [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment								Northern Virginia
Property Type								Various
Square Feet		945,745						945,745
Net Sale Proceeds | $		$ 90,600
Cedar Hill I and III [Member] | Northern Virginia [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment								Northern Virginia
Disposition Date								Dec. 23, 2015
Property Type								Office
Square Feet			102,632
Net Sale Proceeds | $			$ 25,939
Newington Business Park Center [Member] | Northern Virginia [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment								Northern Virginia
Disposition Date								Dec. 17, 2015
Property Type								Industrial
Square Feet				255,600
Net Sale Proceeds | $				$ 31,409
Rumsey Center [Member] | Maryland [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment								Maryland
Disposition Date								Jul. 28, 2015
Property Type								Business Park
Square Feet					135,015
Net Sale Proceeds | $					$ 14,956
Owings Mills Business Park [Domain] | Maryland [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment								Maryland
Disposition Date								Oct. 16, 2014
Property Type								Business Park
Square Feet						180,475
Net Sale Proceeds | $						$ 12,417
Corporate Campus at Ashburn Center [Member] | Northern Virginia Reporting Segment [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment								Northern Virginia
Disposition Date								Jun. 26, 2014
Property Type								Business Park
Square Feet							194,184
Net Sale Proceeds | $							$ 39,910
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

Dispositions - Disposed or Held

Dispositions - Disposed or Held-for-Sale Properties within Continuing Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 877	$ 7,688	$ 31,654
Property operating expenses	(638)	(3,612)	(10,564)
Depreciation and amortization	(1,222)	(3,662)	(8,937)
Interest expense, net of interest income		(268)	(1,268)
Impairment of rental property	0	0	(4,092)
(Loss) income from operations of disposed property	(975)	146	6,793
Loss on debt extinguishment	(489)	0	(4,414)
Continuing Operations [Member] | Corporate Campus at Ashburn Center and Owings Mills Business Park [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	21,826	26,037	29,016
Property operating expenses	(7,745)	(9,664)	(10,249)
Depreciation and amortization	(7,037)	(9,114)	(9,697)
Interest expense, net of interest income	(465)	(842)	(1,258)
Impairment of rental property	(26,929)	(3,956)	0
(Loss) income from operations of disposed property	(20,350)	2,461	7,812
Gain on sale of rental property	29,477	21,230	0
Net income from continuing operations	$ 9,127	$ 23,691	$ 7,812

Dispositions - Additional Infor

Dispositions - Additional Information (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2015USD ($)ft²propertybuilding		Dec. 31, 2014USD ($)ft²building		Dec. 31, 2013USD ($)	Oct. 16, 2014USD ($)	Dec. 31, 2012ft²building	[2]
Schedule Of Discontinued Operations [Line Items]
Number Of Buildings | building	[1]	99		131				146
Square Feet | ft²	[1]	7,489,092		8,790,147				9,100,121
Impairment of real estate assets		$ 60,800		$ 4,000		$ 4,100
Land and land improvements		280,149	[3]	325,214	[4]
Buildings and improvements		793,184	[3]	949,683	[4]
Tenant improvements		168,946	[3]	159,867	[4]
Construction in progress		97,361	[3]	69,181	[4]
Real Estate Investment Property, Accumulated Depreciation		209,784	[3]	215,499	[4]
Mortgage Loans Payable		$ 312,216	[5],[6]	308,637	[5],[6]		$ 22,000
Northern Virginia Development Project [Member]
Schedule Of Discontinued Operations [Line Items]
Number Of Buildings | property		8
NOVA Non Core Portfolio
Schedule Of Discontinued Operations [Line Items]
Impairment of real estate assets		$ 26,900
Land and land improvements		25,200
Buildings and improvements		88,000
Tenant improvements		14,400
Real Estate Investment Property, Accumulated Depreciation		37,000
Mortgage Loans Payable		$ 200
Richmond [Member]
Schedule Of Discontinued Operations [Line Items]
Disposition Date		Mar. 19, 2015
Number Of Buildings | building		19
Square Feet | ft²		827,900
Land and land improvements				7,700
Buildings and improvements				62,000
Tenant improvements				8,500
Construction in progress				100
Real Estate Investment Property, Accumulated Depreciation				20,600
Other assets				2,000
Mortgage Loans Payable				3,498
Other liabilities				$ 1,100
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.
[3]	1) Excludes rental property totaling $90.6 million at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9(a), Dispositions), which was classified as held-for-sale at December 31, 2015.
[4]	(2) Excludes rental property totaling $57.7 million at December 31, 2014 related to the sale of the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015.
[5]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[6]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.

Dispositions - Summary of Com67

Dispositions - Summary of Completed and Anticipated Property Dispositions within Discontinued Operations (Detail) $ in Thousands		Jun. 18, 2013property	May. 07, 2013ft²	Jun. 30, 2013property	Dec. 31, 2015USD ($)ft²building	Dec. 31, 2014USD ($)ft²building	Dec. 31, 2013USD ($)	Dec. 31, 2012ft²building	[2]
Schedule Of Discontinued Operations [Line Items]
Number Of Buildings | building	[1]				99	131		146
Square Feet	[1]				7,489,092	8,790,147		9,100,121
Net Sale Proceeds | $					$ 129,247	$ 97,701	$ 263,469
Number of industrial properties company sold | property				24
Number Of Remaining Industrial Properties Sold | property		23
Richmond [Member]
Schedule Of Discontinued Operations [Line Items]
Number Of Buildings | building					19
Reporting Segment					Southern Virginia
Disposition Date					Mar. 19, 2015
Property Type					Business Park
Square Feet					827,900
Net Sale Proceeds | $					$ 53,768
Patrick Center [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Maryland
Disposition Date					Apr. 16, 2014
Property Type					Office
Square Feet					66,269
Net Sale Proceeds | $					$ 10,888
West Park [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Maryland
Disposition Date					Apr. 2, 2014
Property Type					Office
Square Feet					28,333
Net Sale Proceeds | $					$ 2,871
Girard Business Center and Gateway Center [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Maryland
Disposition Date					Jan. 29, 2014
Property Type					Business Park and Office
Square Feet					341,973
Net Sale Proceeds | $					$ 31,616
Worman's Mill Court [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Maryland
Disposition Date					Nov. 19, 2013
Property Type					Office
Square Feet					40,099
Net Sale Proceeds | $					$ 3,362
Triangle Business Center [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Maryland
Disposition Date					Sep. 27, 2013
Property Type					Business Park
Square Feet					74,429
Net Sale Proceeds | $					$ 2,732
4200 Tech Court [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Northern Virginia
Disposition Date					Aug. 15, 2013
Property Type					Office
Square Feet					33,875
Net Sale Proceeds | $					$ 3,210
Industrial Portfolio [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Various
Property Type					Industrial
Square Feet					4,280,985
Net Sale Proceeds | $					$ 176,569
4212 Tech Court [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment					Northern Virginia
Disposition Date					Jun. 5, 2013
Property Type					Office
Square Feet					32,055
Net Sale Proceeds | $					$ 2,469
Haymarket [Member] | Virginia [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting segment included in company's industrial properties			236,000
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.

Dispositions - Net Income from

Dispositions - Net Income from Discontinued Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Discontinued Operations and Disposal Groups [Abstract]
Revenues	$ 877	$ 7,688	$ 31,654
Property operating expenses	(638)	(3,612)	(10,564)
Depreciation and amortization	(1,222)	(3,662)	(8,937)
Disposal Group, Including Discontinued Operation, Interest Income	8
Interest expense, net of interest income		(268)	(1,268)
Impairment of rental property	0	0	(4,092)
(Loss) income from operations of disposed property	(975)	146	6,793
Loss on debt extinguishment	(489)	0	(4,414)
Gain on sale of real estate property	857	1,338	19,363
Net income from discontinued operations	$ (607)	$ 1,484	$ 21,742

Debt - Schedule of Borrowings (

Debt - Schedule of Borrowings (Detail) - USD ($) $ in Thousands		Dec. 31, 2015		Dec. 31, 2014		Oct. 16, 2014
Debt Instrument [Line Items]
Mortgage Loans Payable		$ 312,216	[1],[2]	$ 308,637	[1],[2]	$ 22,000
Unsecured revolving credit facility, effective interest rate of LIBOR plus 1.50%, maturing October 2017	[2]	120,000		205,000
Long-term Debt		$ 732,216		813,637
Effective interest rate on the notes		0.43%
Unsecured Term Loan, Effective Interest Rates Ranging from LIBOR Plus 1.45% to LIBOR Plus 1.90%, with Staggered Maturity Dates ranging from October 2018 to October 2020 [Member]
Debt Instrument [Line Items]
Unsecured term loan, effective interest rates ranging from LIBOR plus 1.45% to LIBOR plus 1.90%, with staggered maturity dates ranging from October 2018 to October 2020		$ 300,000		300,000
NOVA Non Core Portfolio
Debt Instrument [Line Items]
Mortgage Loans Payable		$ 200
Richmond [Member]
Debt Instrument [Line Items]
Mortgage Loans Payable				$ 3,498
[1]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.

Debt - Schedule of Borrowings 2

Debt - Schedule of Borrowings 2 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Oct. 16, 2014
Debt Instrument [Line Items]
Effective interest rate on the notes	0.43%
Effective interest rate on secured term loan	1.50%
Mortgage Loans Payable	$ 312,216	[1],[2]	$ 308,637	[1],[2]	$ 22,000
Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage rate range, minimum	4.22%
Debt instrument, interest rate, effective percentage rate range, maximum	6.01%
Debt instrument maturity date	September 2,030
Unsecured Term Loan, Effective Interest Rates Ranging from LIBOR Plus 1.45% to LIBOR Plus 1.90%, with Staggered Maturity Dates ranging from October 2018 to October 2020 [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate, minimum	1.45%
Debt instrument basis spread on variable rate, maximum	1.80%
Debt instrument maturity date	December 2020 to October 2022
Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Effective interest rate on the notes	1.50%
Debt instrument maturity date	December 2,019
NOVA Non Core Portfolio
Debt Instrument [Line Items]
Mortgage Loans Payable	$ 200
Richmond [Member]
Debt Instrument [Line Items]
Mortgage Loans Payable			$ 3,498
[1]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.

Debt - Summary of Company's Mor

Debt - Summary of Company's Mortgage Debt (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Jul. 21, 2015	Dec. 31, 2014		Oct. 16, 2014
Debt Instrument [Line Items]
Effective interest rate on the notes		0.43%
Total Mortgage Debt		$ 312,216	[1],[2]		$ 308,637	[1],[2]	$ 22,000
Debt, Weighted Average Interest Rate		4.58%
Unamortized fair value adjustments		$ (173)
Total contractual principal balance		732,216			813,637
Mortgage Loans [Member]
Debt Instrument [Line Items]
Total contractual principal balance		$ 312,043			308,194
Jackson National Life Loan [Member]
Debt Instrument [Line Items]
Contractual interest rate	[3]	5.19%
Effective interest rate on the notes	[3]	5.19%
Debt instrument maturity date	[3]	August 2,015
Total Mortgage Debt		$ 0	[3]	$ 64,200	64,943	[3]
440 First Street, NW Construction Loan [Member]
Debt Instrument [Line Items]
Contractual interest rate		2.50%
Contractual Interest Rate terms	[4]	LIBOR + 2.50%
Effective interest rate on the notes		2.93%
Debt instrument maturity date	[4]	May 2,016
Total Mortgage Debt	[4]	$ 32,216			32,216
Storey Park [Member]
Debt Instrument [Line Items]
Contractual interest rate		2.50%
Contractual Interest Rate terms	[4]	LIBOR + 2.50%
Effective interest rate on the notes		2.93%
Debt instrument maturity date	[4]	October 2,016
Total Mortgage Debt	[4]	$ 22,000			22,000
Gateway Centre Manassas Building I [Member]
Debt Instrument [Line Items]
Contractual interest rate	[5]	7.35%
Effective interest rate on the notes	[5]	5.88%
Debt instrument maturity date	[5]	November 2016
Total Mortgage Debt	[5]	$ 0			432
Hillside I and II [Member]
Debt Instrument [Line Items]
Contractual interest rate		5.75%
Effective interest rate on the notes		4.62%
Debt instrument maturity date		December 2016
Total Mortgage Debt		$ 12,540			12,949
Redland Corporate Center Buildings II & III [Member]
Debt Instrument [Line Items]
Contractual interest rate		4.20%
Effective interest rate on the notes		4.64%
Debt instrument maturity date		November 2,017
Total Mortgage Debt		$ 64,543			65,816
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Contractual Interest Rate terms	[4]	LIBOR + 1.85%
Debt instrument maturity date	[4]	September 1, 2019
Total Mortgage Debt	[4]	$ 9,176			0
840 First Street, NE / 500 First Street, NW [Member]
Debt Instrument [Line Items]
Contractual interest rate		5.72%
Effective interest rate on the notes		6.01%
Debt instrument maturity date		July 2,020
Total Mortgage Debt		$ 35,888			36,539
Battlefield Corporate Center [Member]
Debt Instrument [Line Items]
Contractual interest rate		4.26%
Effective interest rate on the notes		4.40%
Debt instrument maturity date		November 2,020
Total Mortgage Debt		$ 3,526			3,692
1211 Connecticut Avenue, NW [Member]
Debt Instrument [Line Items]
Contractual interest rate		4.22%
Effective interest rate on the notes		4.47%
Debt instrument maturity date		July 2,022
Total Mortgage Debt		$ 29,110			29,691
1401 K Street, NW [Member]
Debt Instrument [Line Items]
Contractual interest rate		4.80%
Effective interest rate on the notes		4.93%
Debt instrument maturity date		June 2,023
Total Mortgage Debt		$ 36,224			36,861
Eleven Dupont Circle [Member]
Debt Instrument [Line Items]
Contractual interest rate		4.05%
Effective interest rate on the notes		4.22%
Debt instrument maturity date		September 2,030
Total Mortgage Debt		$ 66,780			0
Continuing Operations Properties [Member]
Debt Instrument [Line Items]
Total Mortgage Debt	[6]	312,003			305,139
Unamortized fair value adjustments		(172)			(370)
Continuing Operations Properties [Member] | Mortgage Loans [Member]
Debt Instrument [Line Items]
Total contractual principal balance		$ 311,831			304,769
NOVA Non Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate	[5]	7.35%
Effective interest rate on the notes	[5]	5.88%
Debt instrument maturity date	[5]	November 2016
Total Mortgage Debt	[5]	$ 213			0
Hanover Business Center [Member]
Debt Instrument [Line Items]
Contractual interest rate	[7]	8.88%
Effective interest rate on the notes	[7]	6.63%
Debt instrument maturity date	[7]	August 2,015
Total Mortgage Debt	[7]	$ 0			104
Chesterfield Business Center [Member]
Debt Instrument [Line Items]
Contractual interest rate	[7]	8.50%
Effective interest rate on the notes	[7]	6.63%
Debt instrument maturity date	[7]	September 2,015
Total Mortgage Debt	[7]	$ 0			302
Hanonver Business Building C [Member]
Debt Instrument [Line Items]
Contractual interest rate	[7]	7.88%
Effective interest rate on the notes	[7]	6.63%
Debt instrument maturity date	[7]	December 2,017
Total Mortgage Debt	[7]	$ 0			505
Chesterfield Business Center Bldg ABEF [Member]
Debt Instrument [Line Items]
Contractual interest rate	[7]	7.45%
Effective interest rate on the notes	[7]	6.63%
Debt instrument maturity date	[7]	June 2,021
Total Mortgage Debt	[7]	$ 0			1,674
Airpark Business Center [Member]
Debt Instrument [Line Items]
Contractual interest rate	[7]	7.45%
Effective interest rate on the notes	[7]	6.63%
Debt instrument maturity date	[7]	June 2,021
Total Mortgage Debt	[7]	$ 0			913
Richmond [Member]
Debt Instrument [Line Items]
Total Mortgage Debt	[7]	213			3,498
Unamortized fair value adjustments	[7]	1			73
Total contractual principal balance	[7]	$ 212			$ 3,425
[1]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.
[3]	(1) At December 31, 2015, LIBOR was 0.43%.
[4]	(2) At December 31, 2015, LIBOR was 0.43%.
[5]	(3) Gateway Centre Manassas is included in the NOVA Non-Core Portfolio, which was classified as held-for-sale at December 31, 2015. The mortgage loan that encumbers Gateway Centre Manassas was classified within “Liabilities held-for-sale” on our December 31, 2015 consolidated balance sheet.
[6]	(4) Weighted average interest rate on total mortgage debt.
[7]	(5) The mortgage loans that encumbered properties within the Richmond Portfolio and related unamortized fair value adjustments were classified within “Liabilities held-for-sale” on our December 31, 2014 consolidated balance sheet and were repaid upon the sale of the Richmond Portfolio in March 2015.

Debt - Summary of Company's M72

Debt - Summary of Company's Mortgage Debt 2 (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015		Dec. 31, 2014	[1],[2]	Oct. 16, 2014
Debt Disclosure [Abstract]
Effective interest rate on the notes		0.43%
Amount borrowed	$ 21,700
Mortgage Loans Payable		$ 312,216	[1],[2]	$ 308,637		$ 22,000
Debt Instrument, Basis Spread on Variable Rate		1.50%
[1]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.

Debt - Additional Information (

Debt - Additional Information (Detail) $ in Thousands		Oct. 16, 2014USD ($)Rate	May. 31, 2016	Sep. 30, 2013USD ($)	Dec. 31, 2015USD ($)ft²property		Dec. 31, 2014USD ($)property		Sep. 30, 2014Rate	Jun. 05, 2013USD ($)	Aug. 04, 2011Rate
Debt Instrument [Line Items]
Mortgage Loans Payable		$ 22,000			$ 312,216	[1],[2]	$ 308,637	[1],[2]
Debt Instrument, Basis Spread on Variable Rate					1.50%
Long-term Debt					$ 732,216		$ 813,637
Borrowing capacity of a construction loan					$ 43,700
Amount borrowed				$ 21,700
Number of consolidated properties that secured mortgage debt | property					11		18
Greyhound Property [Member]
Debt Instrument [Line Items]
Percentage Of Interest In Joint Venture Owned By Entity | Rate											97.00%
Mortgage Loans on Real Estate		$ 22,000
Contractual interest rate | Rate									5.00%
Debt Instrument, Basis Spread on Variable Rate | Rate		2.50%
Maturity date of senior notes					Oct. 16, 2016
Long-term Debt		$ 6,000
440 First Street, NW [Member]
Debt Instrument [Line Items]
Borrowing capacity of a construction loan										$ 43,500
Maturity Period					1 year
Percentage of outstanding principal					50.00%
Subsequent Event [Member] | 440 First Street, NW [Member]
Debt Instrument [Line Items]
Maturity date of senior notes			May 30, 2016
Northern Virginia Reporting Segment [Member]
Debt Instrument [Line Items]
Area of land placed under development | ft²					167,000
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Mortgage Loans Payable	[3]				$ 9,176		$ 0
Debt Instrument, Basis Spread on Variable Rate					1.85%
Amount borrowed					$ 9,200
Debt instrument maturity date	[3]				September 1, 2019
440 First Street, NW Construction Loan [Member]
Debt Instrument [Line Items]
Contractual interest rate					2.50%
Mortgage Loans Payable	[3]				$ 32,216		$ 32,216
Debt Instrument, Basis Spread on Variable Rate					2.50%
Amount borrowed					$ 10,500
Debt instrument maturity date	[3]				May 2,016
[1]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.
[3]	(2) At December 31, 2015, LIBOR was 0.43%.

Debt - Originated or Assumed Mo

Debt - Originated or Assumed Mortgages (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Effective interest rate on the notes	0.43%
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Month	September
Year	2,015
Contractual Interest Rate terms	LIBOR + 1.85%	[1]
Principal Amount	$ 9,176
Eleven Dupont Circle [Member]
Debt Instrument [Line Items]
Month	August
Year	2,015
Effective interest rate on the notes	4.22%
Principal Amount	$ 66,780
Storey Park [Member]
Debt Instrument [Line Items]
Month	October
Year	2,014
Contractual Interest Rate terms	LIBOR + 2.50%	[1]
Effective interest rate on the notes	5.80%
Principal Amount	$ 22,000	[2]
1401 K Street, NW [Member]
Debt Instrument [Line Items]
Month	April
Year	2,014
Effective interest rate on the notes	4.93%
Principal Amount	$ 37,269
[1]	(1) At December 31, 2015, LIBOR was 0.43%.
[2]	(2) We have a 97% ownership interest in the property through a consolidated joint venture. The loan balance in the chart above reflects the entire loan balance, which is reflected in our consolidated balance sheets.

Debt - Originated or Assumed 75

Debt - Originated or Assumed Mortgages 2 (Detail)	Dec. 31, 2015	Aug. 04, 2011Rate
Debt Instrument [Line Items]
Effective interest rate on the notes	0.43%
Storey Park [Member]
Debt Instrument [Line Items]
Effective interest rate on the notes	2.93%
Percentage Of Interest In Joint Venture Owned By Entity		97.00%

Debt - Repayment of Mortgages (

Debt - Repayment of Mortgages (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Effective interest rate on the notes	0.43%
Jackson National Life Loan [Member]
Debt Instrument [Line Items]
Month	July
Year	2,015
Effective interest rate on the notes	5.19%
Principal Balance Repaid	$ 64,230
Hanover Business Center [Member]
Debt Instrument [Line Items]
Month	March
Year	2,015
Effective interest rate on the notes	6.63%
Principal Balance Repaid	$ 65
Chesterfield Business Center [Member]
Debt Instrument [Line Items]
Month	March
Year	2,015
Effective interest rate on the notes	6.63%
Principal Balance Repaid	$ 202
Hanonver Business Building C [Member]
Debt Instrument [Line Items]
Month	March
Year	2,015
Effective interest rate on the notes	6.63%
Principal Balance Repaid	$ 460
Chesterfield Business Center Bldg ABEF [Member]
Debt Instrument [Line Items]
Month	March
Year	2,015
Effective interest rate on the notes	6.63%
Principal Balance Repaid	$ 1,584
Airpark Business Center [Member]
Debt Instrument [Line Items]
Month	March
Year	2,015
Effective interest rate on the notes	6.63%
Principal Balance Repaid	$ 864
Storey Park [Member]
Debt Instrument [Line Items]
Month	October
Year	2,014
Effective interest rate on the notes	5.80%
Principal Balance Repaid	$ 22,000
Annapolis Business Center [Member]
Debt Instrument [Line Items]
Month	May
Year	2,014
Effective interest rate on the notes	6.25%
Principal Balance Repaid	$ 8,027

Debt - Unsecured Term Loan (Det

Debt - Unsecured Term Loan (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Amount		$ 300,000	$ 300,000
Debt Instrument, Basis Spread on Variable Rate		1.50%
Tranche A [Member]
Debt Instrument [Line Items]
Maturity Date		December 2,020
Amount		$ 100,000
Interest Rate	[1]	LIBOR, plus 145 basis points
Debt Instrument, Basis Spread on Variable Rate		1.45%
Tranche B [Member]
Debt Instrument [Line Items]
Maturity Date		June 2,021
Amount		$ 100,000
Interest Rate	[1]	LIBOR, plus 145 basis points
Debt Instrument, Basis Spread on Variable Rate		1.45%
Tranche C [Member]
Debt Instrument [Line Items]
Maturity Date		December 2,022
Amount		$ 100,000
Interest Rate	[1]	LIBOR, plus 180 basis points
Debt Instrument, Basis Spread on Variable Rate		1.80%
Term Loan [Member]
Debt Instrument [Line Items]
Amount		$ 300,000
[1]	(1) At December 31, 2015, LIBOR was 0.43%. The interest rate spread is subject to change based on our maximum total indebtedness ratio. For more information, see note 10(e), Debt – Financial Covenants.

Debt - Interest Rate Swap Agree

Debt - Interest Rate Swap Agreements (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2015USD ($)derivative	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jan. 31, 2014USD ($)
Debt Instrument [Line Items]
Gains (Losses) on Extinguishment of Debt		$ (1,824)	$ 0	$ (1,810)
Weighted average borrowings outstanding on unsecured revolving credit facility		$ 165,500	$ 136,100
Weighted average interest rate		1.90%	1.70%
Maximum outstanding borrowings		$ 218,000	$ 216,000
Debt instrument variable rate basis		0.43%
Unsecured revolving credit facility	[1]	$ 120,000	$ 205,000
Debt Instrument, Basis Spread on Variable Rate		1.50%
Weighted average interest rate		1.80%
Available capacity on the unsecured revolving credit facility		$ 114,000
Number of interest rate swap agreements | derivative		11
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Fixed effective interest rate		1.505%
Amount on variable rate debt		$ 300,000			$ 50,000
Minimum [Member]
Debt Instrument [Line Items]
Annual commitment fee		0.15%
Maximum [Member]
Debt Instrument [Line Items]
Annual commitment fee		0.25%
Term Loan [Member]
Debt Instrument [Line Items]
Gains (Losses) on Extinguishment of Debt		$ 1,700
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Gains (Losses) on Extinguishment of Debt		$ 100
Tranche A [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.45%
Debt Instrument, Interest Rate, Increase (Decrease)		0.15%
Tranche C [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.80%
Debt Instrument, Interest Rate, Increase (Decrease)		0.20%
[1]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.

Debt - Aggregate Debt Maturitie

Debt - Aggregate Debt Maturities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
2,016	$ 70,260
2,017	65,456
2,018	2,354
2,019	131,648
2,020	137,203
Thereafter	325,122
Long term debt before unamortized discount	732,043
Unamortized fair value adjustments	173
Total contractual principal balance	$ 732,216	$ 813,637

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)derivative	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jan. 31, 2014USD ($)
Derivatives, Fair Value [Line Items]
Number of interest rate swap agreements | derivative	11
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Fixed effective interest rate	1.505%
Weighted average rate amount on variable rate debt	$ 300,000			$ 50,000
Interest Rate Swap [Member] | Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive loss reclassified as an increase in interest expense	4,000	$ 4,100	$ 4,600
Estimated accumulated other comprehensive loss reclassified as an increase in interest expense over the following twelve months	$ 2,400

Derivative Instruments - Summar

Derivative Instruments - Summary of Interest Rate Swap Agreements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Jan. 31, 2014
Interest Rate Swap One [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2016
Notional Amount	$ 35,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.754%
Interest Rate Swap Two [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2016
Notional Amount	$ 25,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.763%
Interest Rate Swap Three [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2017
Notional Amount	$ 30,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	2.093%
Interest Rate Swap Four [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2017
Notional Amount	$ 30,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	2.093%
Interest Rate Swap Six [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2017
Notional Amount	$ 25,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.129%
Interest Rate Swap Seven[Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2017
Notional Amount	$ 12,500
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.129%
Interest Rate Swap Eight [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2018
Notional Amount	$ 12,500
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.383%
Interest Rate Swap Five [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2018
Notional Amount	$ 30,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.66%
Interest Rate Swap Six [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2018
Notional Amount	$ 25,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.394%
Interest Rate Swap Eleven [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2018
Notional Amount	$ 25,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	1.135%
Interest Rate Swap Nine [Member]
Derivatives, Fair Value [Line Items]
Maturity Date	Jul. 31, 2017
Notional Amount	$ 50,000
Interest Rate Contractual Component	LIBOR
Fixed LIBOR Interest Rate	0.955%
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 300,000	$ 50,000
Fixed LIBOR Interest Rate	1.505%

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Measurements, Non-recurring [Member]
Non-recurring Measurements:
Impaired real estate assets	$ 104,625
Fair Value Measurements, Recurring [Member]
Recurring Measurements:
Derivative instrument-swap assets		$ 133
Derivative instrument-swap liabilities	2,491	3,569
Fair Value, Inputs, Level 1 [Member] | Fair Value Measurements, Non-recurring [Member]
Non-recurring Measurements:
Impaired real estate assets	0
Fair Value, Inputs, Level 1 [Member] | Fair Value Measurements, Recurring [Member]
Recurring Measurements:
Derivative instrument-swap assets		0
Derivative instrument-swap liabilities	0	0
Level 2 [Member] | Fair Value Measurements, Non-recurring [Member]
Non-recurring Measurements:
Impaired real estate assets	90,625
Level 2 [Member] | Fair Value Measurements, Recurring [Member]
Recurring Measurements:
Derivative instrument-swap assets		133
Derivative instrument-swap liabilities	2,491	3,569
Level 3 [Member] | Fair Value Measurements, Non-recurring [Member]
Non-recurring Measurements:
Impaired real estate assets	14,000
Level 3 [Member] | Fair Value Measurements, Recurring [Member]
Recurring Measurements:
Derivative instrument-swap assets		0
Derivative instrument-swap liabilities	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)Ratederivative		Dec. 31, 2014USD ($)		Dec. 31, 2013USD ($)	Feb. 24, 2015USD ($)	Oct. 16, 2014USD ($)	Apr. 30, 2011USD ($)
Derivatives, Fair Value [Line Items]
Impairment of real estate assets	$ 60,800		$ 4,000		$ 4,100
Number of interest rate swap agreements | derivative	11
Mortgage Loans Payable	$ 312,216	[1],[2]	308,637	[1],[2]			$ 22,000
Owings Mills Business Park [Member]
Derivatives, Fair Value [Line Items]
Impairment of real estate assets			4,000
America Square [Member]
Derivatives, Fair Value [Line Items]
Mezzanine loan provided to owners						$ 29,700		$ 30,000
NOVA Non Core Portfolio
Derivatives, Fair Value [Line Items]
Impairment of real estate assets	26,900
Mortgage Loans Payable	200
One Fair Oaks [Member]
Derivatives, Fair Value [Line Items]
Impairment of real estate assets	33,900
Richmond [Member]
Derivatives, Fair Value [Line Items]
Mortgage Loans Payable			$ 3,498
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Variable rate debt hedged	$ 300,000
Minimum number of daily snapshot used for valuation of interest rate swap agreements | Rate	7,500
[1]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.

Fair Value Measurements - Fai84

Fair Value Measurements - Fair Value of Debt Instruments (Detail) $ in Thousands		Dec. 31, 2015USD ($)ft²		Feb. 24, 2015USD ($)	Jan. 27, 2015ft²	Dec. 31, 2014USD ($)ft²		Oct. 16, 2014USD ($)	Dec. 31, 2012ft²	[2]	Apr. 30, 2011USD ($)
Financial Assets:
Carrying value of notes receivable		$ 34,000				$ 63,679
Financial Liabilities:
Square Feet | ft²	[1]	7,489,092				8,790,147			9,100,121
Mortgage Loans Payable		$ 312,216	[3],[4]			$ 308,637	[3],[4]	$ 22,000
Mezzanine Properties [Member]
Financial Assets:
Fair value of notes receivable		34,000				63,700
America Square [Member]
Financial Liabilities:
Square Feet | ft²					461,000
Mezzanine loan provided to owners				$ 29,700							$ 30,000
NOVA Non Core Portfolio
Financial Liabilities:
Mortgage Loans Payable		$ 200
Richmond [Member]
Financial Liabilities:
Square Feet | ft²		827,900
Mortgage Loans Payable						3,498
Reported Value Measurement [Member]
Financial Assets:
Carrying value of notes receivable	[5]	$ 34,000				63,679
Financial Liabilities:
Carrying value of the debt instruments		732,216				813,637
Reported Value Measurement [Member] | Mortgage Debt [Member]
Financial Liabilities:
Carrying value of the debt instruments	[6]	312,216				308,637
Reported Value Measurement [Member] | Unsecured Debt [Member]
Financial Liabilities:
Carrying value of the debt instruments		300,000				300,000
Reported Value Measurement [Member] | Unsecured Revolving Credit Facility [Member]
Financial Liabilities:
Carrying value of the debt instruments		120,000				205,000
Estimate of Fair Value Measurement [Member]
Financial Assets:
Fair value of notes receivable	[5]	34,000				63,720
Financial Liabilities:
Fair value of the debt instruments		718,541				797,882
Estimate of Fair Value Measurement [Member] | Mortgage Debt [Member]
Financial Liabilities:
Fair value of the debt instruments	[6]	298,541				292,882
Estimate of Fair Value Measurement [Member] | Unsecured Debt [Member]
Financial Liabilities:
Fair value of the debt instruments		300,000				300,000
Estimate of Fair Value Measurement [Member] | Unsecured Revolving Credit Facility [Member]
Financial Liabilities:
Fair value of the debt instruments		$ 120,000				$ 205,000
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.
[3]	(1) At December 31, 2015, LIBOR was 0.43%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[4]	(2) Includes mortgage debt of $0.2 million and $3.5 million at December 31, 2015 and December 31, 2014, respectively, that was classified within “Liabilities held-for-sale” on our consolidated balance sheets for the periods presented. See note 9, Dispositions, for further discussion.
[5]	The principal amount of our notes receivable was $34.0 million and $63.7 million at December 31, 2015 and 2014, respectively. On February 24, 2015, the owners of America’s Square, a 461,000 square foot office complex located in Washington, D.C., prepaid the $29.7 million outstanding balance of the $30.0 million mezzanine loan that we provided to them in April 2011.
[6]	(2) Includes $0.2 million and $3.5 million of mortgage debt that were classified as held-for-sale and included within “Liabilities held-for-sale” on our consolidated balance sheets for December 31, 2015 and 2014, respectively. See note 9, Dispositions for additional details.

Commitments and Contingencies -

Commitments and Contingencies - Summary of Operating Leases Generating Future Minimum Rental Payments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
Future minimum rents, 2016	$ 129,004
Future minimum rents, 2017	112,800
Future minimum rents, 2018	100,533
Future minimum rents, 2019	87,924
Future minimum rents, 2020	72,606
Future minimum rents, Thereafter	206,499
Future minimum rents, Total	$ 709,366

Commitments and Contingencies86

Commitments and Contingencies - Additional Information (Detail) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 30, 2015ft²	Dec. 31, 2013ft²	Dec. 31, 2012ft²tenant	Dec. 31, 2015USD ($)ft²person	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Operating Leases [Abstract]
Occupancy rate in the Company's consolidated properties				90.30%
Number of tenants in the company's consolidated rental properties | person				454
Square Footage In Development Or Redevelopment | ft²				200,000
Lease expiration date				Jan. 31, 2021
Area Of Sublease Space | ft²			5,000
Number Of Tenants Related To Subleasing Of Former Corporate Office Space | tenant			1
Lease agreement commence date		Jan. 1, 2013
Additional Area Of Sublease Space | ft²	1,321	2,700
Subtenant expansion occupancy date				Mar. 7, 2014
Subtenant second expansion occupancy date				Dec. 21, 2015
Subtenant Lease Expiration Date				Jan. 31, 2018
Subtenant Termination Option Date				Jan. 21, 2016
Corporate Office Leases Rent Expense				$ 1.6	$ 1.8	$ 1.8
Longterm Purchase Commitment Time Period Milestones				5 years
Contingent Consideration [Abstract]
Amount Accrued Outstanding Related To Redevelopment Activities				$ 13.7
Debt Instrument Collateralized Debt Obligations Amount				27.8
Contingent Liability Upon Default On Development Projects				$ 2.6

Commitments and Contingencies87

Commitments and Contingencies - Schedule of Future Minimum Rental Payments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 1,431
2,017	1,469
2,018	1,906
2,019	1,995
2,020	2,049
Thereafter	175
Future minimum rent	$ 9,025

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 16, 2016	Feb. 09, 2016	Jan. 26, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 19, 2016
Class of Stock [Line Items]
Series A Preferred Shares, shares outstanding				6,400,000	6,400,000
Preferred Stock, Redemption Date				Jan. 19, 2016
Percent of Preferred Stock, Shares Outstanding				34.00%
Preferred Stock, Redemption Price Per Share				$ 25
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				5,000,000
Repurchases of common shares				924,198
Stock Repurchased and Retired During Period, Weighted Average Share Price				$ 10.99
Stock Repurchased and Retired During Period, Value				$ 10,180
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased				4,100,000
Dividends paid on Common Share				$ 0.60	$ 0.60	$ 600
Subsequent Event [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Redeemed							2,200,000
Dividends Payable, Date Declared			Jan. 26, 2016
Dividend record date		Feb. 9, 2016
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Dividends paid on Series A Preferred Shares				$ 1.93750	$ 1,937.5000	$ 1.93750
Series A Preferred Shares [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Common share dividend per share declared			$ 0.15
Common share dividend per share annualized			0.60
Dividends declared on Series A Preferred Shares			$ 0.484375
Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Dividend Paid Date	Feb. 16, 2016

Equity - Characterization of Co

Equity - Characterization of Company's Dividends (Detail)		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Common Shares, Ordinary income	[1]	52.01%	72.42%	13.53%
Common Shares, Return of capital		28.64%	27.58%	86.47%
Common Shares, Capital gains		19.35%	0.00%	0.00%
Preferred Shares, Ordinary income	[1]	72.89%	100.00%	100.00%
Preferred Shares, Return of capital		0.00%	0.00%	0.00%
Preferred Shares, Capital gains		27.11%	0.00%	0.00%
[1]	The dividends classified above as ordinary income do not represent “qualified dividend income” and, therefore, are not eligible for reduced rates.

Noncontrolling Interests - Addi

Noncontrolling Interests - Additional Information (Detail) $ in Thousands	Oct. 16, 2014USD ($)Rate	Aug. 04, 2013aft²	Mar. 31, 2014shares	Dec. 31, 2015USD ($)ft²Rateshares		Dec. 31, 2014USD ($)shares		Dec. 31, 2013shares	Sep. 30, 2014Rate	Oct. 17, 2012USD ($)	Aug. 04, 2011Rate
Business Acquisition [Line Items]
Cost to acquire all of the outstanding common Operating Partnership units not owned by the Company				$ 29,900
Fair value adjustment, cost basis				$ 4,000		$ 4,700
Percentage of outstanding Operating Partnership units				95.70%		95.70%		95.70%
Outstanding Operating Partnership units not owned by the Company | shares				2,619,069
Operating Partnership units not owned by Company | Rate				4.30%
Common operating partnership units redeemed for cash | shares				11,508		0		6,718
Operating Partnership units redeemed for common shares | shares				0		0		0
Number Of Common Operating Partnership Units Issued For Additional Space Purchased | shares			3,125
Lease Expiration Date				Jan. 31, 2021
Area Of Land Available For Development In Additional Building Space | ft²				1,300,000
Buildings and improvements				$ 793,184	[1]	$ 949,683	[2]
Debt Instrument, Basis Spread on Variable Rate				1.50%
Storey Park [Member]
Business Acquisition [Line Items]
Mortgage Loans on Real Estate										$ 22,000
Washington D C Reporting Segment [Member]
Business Acquisition [Line Items]
Lease Expiration Date		Aug. 31, 2013
Development Of Area For Operations By Joint Venture | a		1.6
Area Of Land Available For Development In Additional Building Space | ft²				700,000
Real Estate Investment Investment In Development Project				$ 58,000
Buildings and improvements				$ 43,300
Washington D C Reporting Segment [Member] | Greyhound Property [Member]
Business Acquisition [Line Items]
Percentage Of Interest In Joint Venture Owned By Entity											97.00%
Greyhound Property [Member]
Business Acquisition [Line Items]
Percentage Of Interest In Joint Venture Owned By Entity | Rate											97.00%
Mortgage Loans on Real Estate	$ 22,000
Contractual interest rate | Rate									5.00%
Debt Instrument, Basis Spread on Variable Rate | Rate	2.50%
Maximum [Member] | Washington D C Reporting Segment [Member] | Greyhound Property [Member]
Business Acquisition [Line Items]
Area Of Land Available For Development In Additional Building Space | ft²		712,000
[1]	1) Excludes rental property totaling $90.6 million at December 31, 2015 related to the NOVA Non-Core Portfolio (defined in note 9(a), Dispositions), which was classified as held-for-sale at December 31, 2015.
[2]	(2) Excludes rental property totaling $57.7 million at December 31, 2014 related to the sale of the Richmond Portfolio, which was classified as held-for-sale at December 31, 2014 and was sold on March 19, 2015.

Noncontrolling Interests - Summ

Noncontrolling Interests - Summary of Redeemable Noncontrolling Interests in Operating Partnership (Detail) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013	[1]	Jun. 30, 2013	[1]	Mar. 31, 2013	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Noncontrolling Interest [Line Items]
Net loss	$ (41,220)	[1]	$ 859		$ (2,510)		$ (2,496)	[1]	$ (2,869)	[1]	$ (2,920)		$ 14,582		$ (4,348)		$ (45,607)	$ 4,130	$ (1,714)
Distributions to owners																	(35,080)	(35,198)	(32,917)
Redeemable Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Beginning balance							$ 33,221										33,332	33,221
Net loss																	(2,056)	199
Changes in ownership, net																	(931)	1,465
Distributions to owners																	(1,574)	(1,578)
Other comprehensive income																	42	25
Ending balance	$ 33,332								$ 33,221								$ 28,813	$ 33,332	$ 33,221
[1]	(1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.

Benefit Plans - Additional Info

Benefit Plans - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2013shares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013USD ($)$ / sharesshares	Dec. 31, 2012USD ($)shares	Mar. 31, 2013shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares for issuance					4,500,000
Reduction in awards available for issuance on the issue of every stock options granted			1
Reduction in awards available for issuance			3.44
Equity awards authorized under 2009 Plan		7,400,000
Common equity awards remained available for issuance by the Company		2,800,000
Stock options awarded		2,300,000
Stock options outstanding		1,000,000
Percentage of options to be vested on the first anniversary of the grant date		25.00%
Percentage of options to be vested after the date of grant in each subsequent quarter		6.25%
Term of stock granted		10 years
Stock Option Expense | $		$ 1,200	$ 500	$ 500
Unrecognized compensation cost related to non-vested shares | $		$ 300
Weighted-average period for recognition of non-vested shares		1 year 8 months
Weighted average grant date fair value of the stock options issued | $ / shares		$ 1.96	$ 2.67	$ 3.61
Amount received from the exercise of stock options | $		$ 26	$ 174	$ 163
Total intrinsic value of options exercised | $		$ 7	$ 43	43
Number of common shares issued to independent non-employee trustees		57,718,000	58,704,000
Total fair value of vested shares | $		$ 5,300	$ 2,000		$ 3,800
Eligibility for contribution by employees			After 60 days of consecutive service
Company matching employee contribution percentage		6.00%	6.00%
Year of consecutive service		60 days
Vesting of employer contributions occurrence percentage		4 years
Company's contribution | $		$ 600	$ 600	$ 600
Stock issued during period, shares		200,000
Maximum offering periods		5 years
Offering period of Plan		Not exceed five years
Percentage of fair value of common shares on the offering date for the calculation of purchase price		85.00%
Percentage of fair value of common shares on the purchase date for the calculation of purchase price		85.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Zero coupon risk-free rate time frame		3 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Zero coupon risk-free rate time frame		3 years
Non-Officer Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options awarded						119,500
Stock option awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Option Shares, Accelerated Vesting, Number		300,000
Weighted-average period for recognition of non-vested shares		2 years 2 months
Stock option awards | Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Compensation Expense, Accelerated Vesting | $		$ 800
Restricted Share Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Option Shares, Accelerated Vesting, Number		229,171
Stock Compensation Expense, Accelerated Vesting | $		$ 1,200
Unrecognized compensation cost related to non-vested shares | $		$ 1,400
Non-vested share awards issued	121,380
Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares issued under the plan		5,843	8,950	11,007
Compensation expense associated with restricted share based awards | $		$ 11	$ 20	$ 26
Non-Vested Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested share awards issued		152,598	164,675	313,086
Compensation expense associated with restricted share based awards | $		$ 3,300	$ 2,800	$ 3,500
Weighted average grant date fair value of shares issued | $ / shares		$ 11.79	$ 12.84	$ 12.14
Non-Vested Share Awards [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		0.11%
Expected volatility		24.31%
Non-Vested Share Awards [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		0.40%
Expected volatility		29.11%
Independent Trustees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares issued to independent non-employee trustees		31,218
Trustee Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with restricted share based awards | $		$ 400	$ 400	$ 400
Employee Severance [Member] | Non-Vested Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with restricted share based awards | $		$ 1,200		$ 1,200

Benefit Plans - Compensation Pl

Benefit Plans - Compensation Plans Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Option, Beginning Balance	1,051,359	1,089,292	1,384,006
Option, Granted	119,500	135,250	124,250
Option, Exercised	(2,750)	(17,171)	(14,733)
Option, Expired	(59,000)	(57,500)	(298,469)
Option, Forfeited	(145,971)	(98,512)	(105,762)
Option, Ending Balance	963,138	1,051,359	1,089,292	1,384,006
Option, Exercisable	805,259	552,620		521,723
Options expected to vest, subsequent to December 31, 2015	142,530
Weighted Average Exercise Price, Beginning Balance	$ 15.33	$ 15.83	$ 15.91
Weighted Average Exercise Price, Granted	12.48	11.61	12.73
Weighted Average Exercise Price, Exercised	9.30	10.10	11.05
Weighted Average Exercise Price, Expired	22.44	19.08	15
Weighted Average Exercise Price, Forfeited	15.06	14.49	16.17
Weighted Average Exercise Price, Ending Balance	14.59	15.33	$ 15.83	$ 15.91
Weighted Average Exercise Price, Exercisable	15.06	$ 16.49		$ 17.25
Weighted Average Exercise Price, Options expected to vest, subsequent to December 31, 2013	$ 12.29
Weighted Average Remaining Contractual Term	6 years 1 month	6 years 3 months	6 years 7 months 6 days	5 years 11 months
Weighted Average Remaining Contractual Term, Exercisable	5 years 7 months	5 years 1 month 24 days
Weighted Average Remaining Contractual Term, Exercisable	8 years 6 months		4 years 10 months 24 days
Aggregate Intrinsic Value, Beginning Balance	$ 181,352	$ 109,151	$ 174,763
Aggregate Intrinsic Value, Ending Balance	59,002	181,352	$ 109,151	$ 174,763
Aggregate Intrinsic Value, Exercisable	59,002	$ 102,039		$ 109,151
Aggregate Intrinsic Value, Options expected to vest, subsequent to December 31, 2015	$ 0

Benefit Plans - Stock Option In

Benefit Plans - Stock Option Information (Detail)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option Outstanding - Options | shares	963,138
Options Outstanding - Weighted Average Remaining Contractual Life	6 years 1 month
Options Outstanding - Weighted Average Exercise Price	$ 14.60
Options Exercisable - Options | shares	805,259
Options Exercisable - Weighted Average Exercise Price	$ 15.06
2006 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 26.60
Option Outstanding - Options | shares	11,850
Options Outstanding - Weighted Average Remaining Contractual Life	1 day
Options Outstanding - Weighted Average Exercise Price	$ 26.60
Options Exercisable - Options | shares	11,850
Options Exercisable - Weighted Average Exercise Price	$ 26.60
2007 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range	29.11
Exercise Price Upper Range	$ 29.24
Option Outstanding - Options | shares	24,500
Options Outstanding - Weighted Average Remaining Contractual Life	1 year 1 month
Options Outstanding - Weighted Average Exercise Price	$ 29.14
Options Exercisable - Options | shares	24,500
Options Exercisable - Weighted Average Exercise Price	$ 29.14
2008 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 17.29
Option Outstanding - Options | shares	26,250
Options Outstanding - Weighted Average Remaining Contractual Life	2 years
Options Outstanding - Weighted Average Exercise Price	$ 17.29
Options Exercisable - Options | shares	26,250
Options Exercisable - Weighted Average Exercise Price	$ 17.29
2009 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 9.30
Option Outstanding - Options | shares	28,096
Options Outstanding - Weighted Average Remaining Contractual Life	3 years
Options Outstanding - Weighted Average Exercise Price	$ 9.30
Options Exercisable - Options | shares	28,096
Options Exercisable - Weighted Average Exercise Price	$ 9.30
2010 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 12.57
Option Outstanding - Options | shares	33,830
Options Outstanding - Weighted Average Remaining Contractual Life	4 years
Options Outstanding - Weighted Average Exercise Price	$ 12.57
Options Exercisable - Options | shares	33,830
Options Exercisable - Weighted Average Exercise Price	$ 12.57
2011 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 17.12
Option Outstanding - Options | shares	37,250
Options Outstanding - Weighted Average Remaining Contractual Life	5 years
Options Outstanding - Weighted Average Exercise Price	$ 17.12
Options Exercisable - Options | shares	37,250
Options Exercisable - Weighted Average Exercise Price	$ 17.12
2012 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Lower Range	13.54
Exercise Price Upper Range	$ 15
Option Outstanding - Options | shares	553,001
Options Outstanding - Weighted Average Remaining Contractual Life	6 years
Options Outstanding - Weighted Average Exercise Price	$ 14.86
Options Exercisable - Options | shares	549,937
Options Exercisable - Weighted Average Exercise Price	$ 14.87
2013 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 12.73
Option Outstanding - Options | shares	63,845
Options Outstanding - Weighted Average Remaining Contractual Life	7 years 6 days
Options Outstanding - Weighted Average Exercise Price	$ 12.73
Options Exercisable - Options | shares	48,655
Options Exercisable - Weighted Average Exercise Price	$ 12.73
2014 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 11.61
Option Outstanding - Options | shares	87,266
Options Outstanding - Weighted Average Remaining Contractual Life	8 years
Options Outstanding - Weighted Average Exercise Price	$ 11.61
Options Exercisable - Options | shares	44,891
Options Exercisable - Weighted Average Exercise Price	$ 11.61
2015 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 12.48
Option Outstanding - Options | shares	97,250
Options Outstanding - Weighted Average Remaining Contractual Life	9 years
Options Outstanding - Weighted Average Exercise Price	$ 12.48
Options Exercisable - Options | shares	0
Options Exercisable - Weighted Average Exercise Price	$ 0

Benefit Plans - Assumptions Use

Benefit Plans - Assumptions Used in Fair Value Determination of Stock Option Granted (Detail) - Stock option awards	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.61%	1.72%	0.76%
Expected volatility	29.20%	39.00%	49.70%
Expected dividend yield	4.79%	4.66%	4.92%
Weighted average expected life of options	5 years	5 years	5 years

Benefit Plans - Summary of Comp

Benefit Plans - Summary of Company's Non-vested Share Awards (Detail) - Non-Vested Share Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Shares, Beginning Balance	623,421	637,662	673,828
Non-vested Shares, Granted	152,598	164,675	313,086
Non-vested Shares, Vested	(401,888)	(137,924)	(297,778)
Non-vested Shares, Expired	(133,371)	(29,514)	(45,049)
Non-vested Shares, Forfeited	(48,378)	(11,478)	(6,425)
Non-vested Shares, Ending Balance	192,382	623,421	637,662
Weighted Average Grant Date Fair Value, Beginning Balance	$ 13.16	$ 13.33	$ 12.83
Weighted Average Grant Date Fair Value, Granted	11.79	12.84	12.14
Weighted Average Grant Date Fair Value, Vested	13.16	14.21	12.89
Weighted Average Grant Date Fair Value, Expired	12.61	10.21	11.42
Weighted Average Grant Date Fair Value, Forfeited	13.30	13.04	14.01
Weighted Average Grant Date Fair Value, Ending Balance	$ 12.42	$ 13.16	$ 13.33

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)segment	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Segment Reporting [Abstract]
Number of distinct operating segments | segment	4
Corporate Assets Not Allocated To Any Reportable Segments	$ 45,088	$ 84,009,000	$ 73,209,000
Capital Expenditure For Corporate Assets Not Allocated To Any Reportable Segments	$ 831,000	$ 930,000	$ 1,085,000

Segment Information - Summary o

Segment Information - Summary of Segment Information (Detail) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2014USD ($)ft²building		Sep. 30, 2014USD ($)	[3]	Jun. 30, 2014USD ($)	[3]	Mar. 31, 2014USD ($)	[3]	Dec. 31, 2013USD ($)	[3]	Sep. 30, 2013USD ($)	[3]	Jun. 30, 2013USD ($)	[3]	Mar. 31, 2013USD ($)	[3]	Dec. 31, 2015USD ($)ft²building	Dec. 31, 2014USD ($)ft²building	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)ft²building
Segment Reporting Information [Line Items]
Number Of Buildings | building	[1]	131																99	131		146	[2]
Square Feet | ft²	[1]	8,790,147																7,489,092	8,790,147		9,100,121	[2]
Total revenues		$ 43,104	[3]	$ 42,854		$ 43,039		$ 43,849		$ 42,928		$ 40,055		$ 39,307		$ 39,363		$ 172,846	$ 161,652	$ 148,815
Property operating expense																		(44,093)	(43,252)	(38,280)
Real estate taxes and insurance																		(19,745)	(17,360)	(16,074)
Total property operating income																		109,008	101,040	94,461
Depreciation and amortization expense																		(66,624)	(61,796)	(54,567)
General and administrative																		(25,450)	(21,156)	(21,979)
Acquisition costs																		0	(2,681)	(602)
Impairment of real estate assets																		(60,826)	(3,956)	0
Contingent consideration related to acquisition of property																		0	0	213
Other Nonoperating Income (Expense)																		9,475	4,108	(28,287)
(Loss) income from discontinued operations		0	[3]	$ 0		$ 0		$ (607)		$ 505		$ 297		$ 1,538		$ (857)		(607)	1,484	21,742
Net (loss) income																		(35,024)	17,043	10,981
Total assets	[4],[5]	$ 1,618,460																1,450,371	1,618,460		$ 1,502,460
Capital expenditures	[6]																	$ 73,850	$ 50,789	68,002
Washington, D.C. [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building	[1]	6																6	6		4	[2]
Square Feet | ft²	[1]	917,008																918,375	917,008		522,605	[2]
Total revenues																		$ 44,553	$ 33,959	28,208
Property operating expense																		(11,363)	(9,683)	(6,693)
Real estate taxes and insurance																		(8,238)	(5,583)	(4,792)
Total property operating income																		24,952	18,693	16,723
Total assets	[4],[5]	$ 505,842																521,107	505,842		$ 344,739
Capital expenditures	[6]																	$ 12,930	$ 23,422	26,910
Maryland [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building	[1]	38																34	38		53	[2]
Square Feet | ft²	[1]	1,999,332																1,885,630	1,999,332		2,638,988	[2]
Total revenues																		$ 44,226	$ 45,767	41,735
Property operating expense																		(11,457)	(11,482)	(10,579)
Real estate taxes and insurance																		(3,540)	(3,907)	(3,436)
Total property operating income																		29,229	30,378	27,720
Total assets	[4],[5]	$ 360,470																341,898	360,470		$ 430,498
Capital expenditures	[6]																	$ 9,003	$ 10,185	16,216
Northern Virginia Reporting Segment [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building	[1]	49																40	49		51	[2]
Square Feet | ft²	[1]	3,021,509																2,661,448	3,021,509		3,086,057	[2]
Total revenues																		$ 55,230	$ 53,645	51,787
Property operating expense																		(13,540)	(13,352)	(12,601)
Real estate taxes and insurance																		(5,540)	(5,592)	(5,679)
Total property operating income																		36,150	34,701	33,507
Total assets	[4],[5]	$ 439,833																374,811	439,833		$ 423,839
Capital expenditures	[6]																	$ 43,125	$ 7,816	13,685
Southern Virginia [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building	[1]	38																19	38		38	[2]
Square Feet | ft²	[1]	2,852,298																2,023,639	2,852,298		2,852,471	[2]
Total revenues																		$ 28,837	$ 28,281	27,085
Property operating expense																		(7,733)	(8,735)	(8,407)
Real estate taxes and insurance																		(2,427)	(2,278)	(2,167)
Total property operating income																		18,677	17,268	16,511
Total assets	[4],[5]	$ 228,306																167,467	228,306		$ 230,175
Capital expenditures	[6]																	$ 7,961	$ 8,436	$ 10,106
[1]	Excludes Storey Park from our Washington, D.C. reporting segment, which was placed in development in the third quarter of 2013.
[2]	Includes occupied space at 440 First Street, NW in our Washington, D.C. reporting segment, which was substantially completed in the third quarter of 2013. In 2014, the property was placed in service.
[3]	(1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.
[4]	Corporate assets not allocated to any of our reportable segments totaled $45,088, $84,009 and $73,209 at December 31, 2015, 2014 and 2013, respectively.
[5]	Total assets include our investment in properties that are owned through joint ventures that are not consolidated within our consolidated financial statements. For more information on our unconsolidated investments, including locations within our reportable segments, see note 5, Investment in Affiliates.
[6]	Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $831, $930 and $1,085 at December 31, 2015, 2014 and 2013, respectively.

Quarterly Financial Informati99

Quarterly Financial Information - Summary of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2014	[1]	Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2013	[1]	Sep. 30, 2013	[1]	Jun. 30, 2013	[1]	Mar. 31, 2013	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 43,104		$ 42,854		$ 43,039		$ 43,849		$ 42,928		$ 40,055		$ 39,307		$ 39,363		$ 172,846	$ 161,652	$ 148,815
Operating expenses	102,375		37,079		37,268		40,016		38,595		36,283		39,579		35,744		216,738	150,201	131,289
Operating (loss) income	(59,271)		5,775		5,771		3,833		4,333		3,772		(272)		3,619		(43,892)	11,451	17,526
Income (loss) from continuing operations	(39,990)		3,997		476		1,099		(402)		(248)		16,796		(586)		(34,417)	15,559	(10,761)
(Loss) income from discontinued operations	0		0		0		(607)		505		297		1,538		(857)		(607)	1,484	21,742
Less: Net loss (income) attributable to noncontrolling interests	1,870		(38)		114		112		128		131		(652)		195		2,058	(199)	93
Net (loss) income attributable to First Potomac Realty Trust	(38,120)		3,959		590		604		231		180		17,682		(1,248)		(32,966)	16,844	11,074
Less: Dividends on preferred shares	(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(3,100)		(12,400)	(12,400)	(12,400)
Net (loss) income attributable to common shareholders	$ (41,220)		$ 859		$ (2,510)		$ (2,496)		$ (2,869)		$ (2,920)		$ 14,582		$ (4,348)		$ (45,607)	$ 4,130	$ (1,714)
Basic and diluted earnings per common share:
(Loss) income from continuing operations	$ (0.72)		$ 0.01		$ (0.04)		$ (0.03)		$ (0.06)		$ (0.05)		$ 0.22		$ (0.07)		$ (0.78)	$ 0.05	$ (0.41)
(Loss) income from discontinued operations	0		0		0		(0.01)		0.01		0		0.03		(0.01)		(0.01)	0.02	0.38
Net (loss) income	$ (0.72)		$ 0.01		$ (0.04)		$ (0.04)		$ (0.05)		$ (0.05)		$ 0.25		$ (0.08)		$ (0.79)	$ 0.07	$ (0.03)
[1]	(1) These figures are rounded to the nearest thousand, which may impact cross-footing in reconciling to full year totals.

Quarterly Financial Informat100

Quarterly Financial Information - Additional Information (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Common shares sold	0	0

Schedule III - Real Estate a101

Schedule III - Real Estate and Accumulated Depreciation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 312,003
Initial Costs, Land	317,969
Initial Costs, Building and Improvements	731,358
Gross Amount at End of Year, Since Acquisition	290,723
Gross Amount at End of Year, Land	280,149
Gross Amount at End of Year, Building and Improvements	1,059,901
Gross Amount at End of Year, Total	1,340,050
Gross Amount at End of Year, Accumulated Depreciation	209,784
Real Estate, Beginning balance	1,504,372	$ 1,330,180	$ 1,605,722
Real Estate, Acquisitions of rental property	0	170,823	26,289
Real Estate, Capital expenditures	73,125	49,860	66,808
Real Estate, Impairments	(51,521)	(3,956)	(4,069)
Real Estate, Dispositions of rental property	(59,652)	(30,916)	(290,777)
Real Estate, Asset held-for-sale	(127,907)	(643)	(55,767)
Real Estate, Other	1,633	(10,976)	(18,026)
Real Estate, Ending balance	1,340,050	1,504,372	1,330,180
Accumulated Depreciation, Beginning balance	215,499	185,725	215,154
Accumulated Depreciation, Depreciation of rental property	(49,772)	(47,625)	(48,638)
Accumulated Depreciation, Assets held-for-sale	(16,400)	(1,631)	(13,470)
Accumulated Depreciation, Dispositions of rental property	(35,964)	(5,712)	(54,377)
Accumulated Depreciation, Other	(3,123)	(10,508)	(10,220)
Accumulated Depreciation, Ending balance	$ 209,784	$ 215,499	$ 185,725
Snowden Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Columbia
Date Acquired	Oct. 31, 2002
Property Type	BP
Initial Costs, Land	$ 3,404
Initial Costs, Building and Improvements	12,824
Gross Amount at End of Year, Since Acquisition	4,569
Gross Amount at End of Year, Land	3,404
Gross Amount at End of Year, Building and Improvements	17,393
Gross Amount at End of Year, Total	20,797
Gross Amount at End of Year, Accumulated Depreciation	$ 7,016
Metro Park North [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Rockville
Date Acquired	Dec. 31, 2004
Property Type	Office
Initial Costs, Land	$ 9,220
Initial Costs, Building and Improvements	32,056
Gross Amount at End of Year, Since Acquisition	3,065
Gross Amount at End of Year, Land	9,220
Gross Amount at End of Year, Building and Improvements	35,121
Gross Amount at End of Year, Total	44,341
Gross Amount at End of Year, Accumulated Depreciation	$ 9,942
Gateway 270 West [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Clarksburg
Date Acquired	Jul. 31, 2006
Property Type	BP
Initial Costs, Land	$ 18,302
Initial Costs, Building and Improvements	20,562
Gross Amount at End of Year, Since Acquisition	8,432
Gross Amount at End of Year, Land	18,302
Gross Amount at End of Year, Building and Improvements	28,994
Gross Amount at End of Year, Total	47,296
Gross Amount at End of Year, Accumulated Depreciation	$ 7,176
Indian Creek Court [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Beltsville
Date Acquired	Aug. 31, 2006
Property Type	BP
Initial Costs, Land	$ 5,673
Initial Costs, Building and Improvements	17,168
Gross Amount at End of Year, Since Acquisition	12,937
Gross Amount at End of Year, Land	5,673
Gross Amount at End of Year, Building and Improvements	30,105
Gross Amount at End of Year, Total	35,778
Gross Amount at End of Year, Accumulated Depreciation	$ 9,189
Ammendale Commerce Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Beltsville
Date Acquired	Mar. 31, 2007
Property Type	BP
Initial Costs, Land	$ 2,398
Initial Costs, Building and Improvements	7,659
Gross Amount at End of Year, Since Acquisition	5,890
Gross Amount at End of Year, Land	2,398
Gross Amount at End of Year, Building and Improvements	13,549
Gross Amount at End of Year, Total	15,947
Gross Amount at End of Year, Accumulated Depreciation	$ 5,988
Annapolis Business Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Annapolis
Date Acquired	Jun. 30, 2007
Property Type	Office
Initial Costs, Land	$ 6,101
Initial Costs, Building and Improvements	12,602
Gross Amount at End of Year, Since Acquisition	556
Gross Amount at End of Year, Land	6,101
Gross Amount at End of Year, Building and Improvements	13,158
Gross Amount at End of Year, Total	19,259
Gross Amount at End of Year, Accumulated Depreciation	$ 2,860
Cloverleaf Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Germantown
Date Acquired	Oct. 31, 2009
Property Type	Office
Initial Costs, Land	$ 7,097
Initial Costs, Building and Improvements	14,211
Gross Amount at End of Year, Since Acquisition	1,028
Gross Amount at End of Year, Land	7,097
Gross Amount at End of Year, Building and Improvements	15,239
Gross Amount at End of Year, Total	22,336
Gross Amount at End of Year, Accumulated Depreciation	$ 2,857
Redland Corporate Center Buildings II & III [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Rockville
Date Acquired	Nov. 30, 2010
Property Type	Office
Encumbrances	$ 64,543
Initial Costs, Land	17,272
Initial Costs, Building and Improvements	63,480
Gross Amount at End of Year, Since Acquisition	14,606
Gross Amount at End of Year, Land	17,720
Gross Amount at End of Year, Building and Improvements	77,638
Gross Amount at End of Year, Total	95,358
Gross Amount at End of Year, Accumulated Depreciation	$ 15,561
Ten Three Twenty [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Columbia
Date Acquired	Feb. 28, 2011
Property Type	Office
Initial Costs, Land	$ 2,041
Initial Costs, Building and Improvements	5,327
Gross Amount at End of Year, Since Acquisition	13,640
Gross Amount at End of Year, Land	2,041
Gross Amount at End of Year, Building and Improvements	18,967
Gross Amount at End of Year, Total	21,008
Gross Amount at End of Year, Accumulated Depreciation	$ 3,310
Hillside First And Second [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Columbia
Date Acquired	Nov. 30, 2011
Property Type	Office
Encumbrances	$ 12,540
Initial Costs, Land	3,302
Initial Costs, Building and Improvements	10,926
Gross Amount at End of Year, Since Acquisition	3,552
Gross Amount at End of Year, Land	3,302
Gross Amount at End of Year, Building and Improvements	14,478
Gross Amount at End of Year, Total	17,780
Gross Amount at End of Year, Accumulated Depreciation	$ 1,222
Five Hundred Forty Gaither Road Redland First [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Rockville
Date Acquired	Oct. 31, 2013
Property Type	Office
Initial Costs, Land	$ 6,458
Initial Costs, Building and Improvements	19,831
Gross Amount at End of Year, Since Acquisition	256
Gross Amount at End of Year, Land	6,539
Gross Amount at End of Year, Building and Improvements	20,006
Gross Amount at End of Year, Total	26,545
Gross Amount at End of Year, Accumulated Depreciation	2,294
Maryland [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	77,083
Initial Costs, Land	81,268
Initial Costs, Building and Improvements	216,646
Gross Amount at End of Year, Since Acquisition	68,531
Gross Amount at End of Year, Land	81,797
Gross Amount at End of Year, Building and Improvements	284,648
Gross Amount at End of Year, Total	366,445
Gross Amount at End of Year, Accumulated Depreciation	$ 67,415
500 First Street, NW [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Capitol Hill
Date Acquired	Jun. 30, 2010
Property Type	Office
Initial Costs, Land	$ 25,806
Initial Costs, Building and Improvements	33,883
Gross Amount at End of Year, Since Acquisition	542
Gross Amount at End of Year, Land	25,827
Gross Amount at End of Year, Building and Improvements	34,404
Gross Amount at End of Year, Total	60,231
Gross Amount at End of Year, Accumulated Depreciation	$ 6,034
440 First Street, NW [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Capitol Hill
Date Acquired	Dec. 31, 2010
Property Type	Office
Encumbrances	$ 32,216
Initial Costs, Land	0
Initial Costs, Building and Improvements	15,300
Gross Amount at End of Year, Since Acquisition	49,133
Gross Amount at End of Year, Land	9,121
Gross Amount at End of Year, Building and Improvements	55,312
Gross Amount at End of Year, Total	64,433
Gross Amount at End of Year, Accumulated Depreciation	$ 3,853
1211 Connecticut Ave, NW [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	CBD
Date Acquired	Dec. 31, 2010
Property Type	Office
Encumbrances	$ 29,110
Initial Costs, Land	27,077
Initial Costs, Building and Improvements	17,520
Gross Amount at End of Year, Since Acquisition	11,227
Gross Amount at End of Year, Land	27,077
Gross Amount at End of Year, Building and Improvements	28,747
Gross Amount at End of Year, Total	55,824
Gross Amount at End of Year, Accumulated Depreciation	$ 3,456
840 First Street, NE [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	NoMA
Date Acquired	Mar. 31, 2011
Property Type	Office
Encumbrances	$ 35,888
Initial Costs, Land	16,846
Initial Costs, Building and Improvements	60,905
Gross Amount at End of Year, Since Acquisition	11,273
Gross Amount at End of Year, Land	16,846
Gross Amount at End of Year, Building and Improvements	72,178
Gross Amount at End of Year, Total	89,024
Gross Amount at End of Year, Accumulated Depreciation	$ 10,267
Storey Park [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	NoMA
Date Acquired	Aug. 31, 2011
Property Type	Office
Encumbrances	$ 22,000
Initial Costs, Land	43,672
Initial Costs, Building and Improvements	4,194
Gross Amount at End of Year, Since Acquisition	10,135
Gross Amount at End of Year, Land	0
Gross Amount at End of Year, Building and Improvements	58,001
Gross Amount at End of Year, Total	58,001
Gross Amount at End of Year, Accumulated Depreciation	$ 0
1401 K Street, NW [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	East End
Date Acquired	Apr. 8, 2014
Property Type	Office
Encumbrances	$ 36,224
Initial Costs, Land	29,506
Initial Costs, Building and Improvements	23,269
Gross Amount at End of Year, Since Acquisition	4,775
Gross Amount at End of Year, Land	29,506
Gross Amount at End of Year, Building and Improvements	28,044
Gross Amount at End of Year, Total	57,550
Gross Amount at End of Year, Accumulated Depreciation	$ 1,921
11 DuPont Circle, NW [Domain]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	CBD
Date Acquired	Sep. 24, 2014
Property Type	Office
Encumbrances	$ 66,780
Initial Costs, Land	15,744
Initial Costs, Building and Improvements	64,832
Gross Amount at End of Year, Since Acquisition	5,343
Gross Amount at End of Year, Land	15,744
Gross Amount at End of Year, Building and Improvements	70,175
Gross Amount at End of Year, Total	85,919
Gross Amount at End of Year, Accumulated Depreciation	2,947
Washington, D.C. [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	222,218
Initial Costs, Land	158,651
Initial Costs, Building and Improvements	219,903
Gross Amount at End of Year, Since Acquisition	92,428
Gross Amount at End of Year, Land	124,121
Gross Amount at End of Year, Building and Improvements	346,861
Gross Amount at End of Year, Total	470,982
Gross Amount at End of Year, Accumulated Depreciation	$ 28,478
Plaza 500 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Alexandria
Date Acquired	Dec. 31, 1997
Property Type	I
Initial Costs, Land	$ 6,265
Initial Costs, Building and Improvements	35,433
Gross Amount at End of Year, Since Acquisition	6,790
Gross Amount at End of Year, Land	6,268
Gross Amount at End of Year, Building and Improvements	42,220
Gross Amount at End of Year, Total	48,488
Gross Amount at End of Year, Accumulated Depreciation	$ 19,056
403/405 Glenn Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Sterling
Date Acquired	Oct. 31, 2005
Property Type	BP
Initial Costs, Land	$ 3,940
Initial Costs, Building and Improvements	12,547
Gross Amount at End of Year, Since Acquisition	4,367
Gross Amount at End of Year, Land	3,940
Gross Amount at End of Year, Building and Improvements	16,914
Gross Amount at End of Year, Total	20,854
Gross Amount at End of Year, Accumulated Depreciation	$ 5,375
Sterling Park Business Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Sterling
Date Acquired	Feb. 28, 2006
Property Type	BP
Initial Costs, Land	$ 14,656
Initial Costs, Building and Improvements	10,750
Gross Amount at End of Year, Since Acquisition	18,931
Gross Amount at End of Year, Land	15,559
Gross Amount at End of Year, Building and Improvements	28,778
Gross Amount at End of Year, Total	44,337
Gross Amount at End of Year, Accumulated Depreciation	$ 8,220
Davis Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Sterling
Date Acquired	Aug. 31, 2006
Property Type	BP
Initial Costs, Land	$ 1,614
Initial Costs, Building and Improvements	3,611
Gross Amount at End of Year, Since Acquisition	3,462
Gross Amount at End of Year, Land	1,646
Gross Amount at End of Year, Building and Improvements	7,041
Gross Amount at End of Year, Total	8,687
Gross Amount at End of Year, Accumulated Depreciation	$ 2,081
Three Flint Hill [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Oakton
Date Acquired	Apr. 30, 2010
Property Type	Office
Initial Costs, Land	$ 0
Initial Costs, Building and Improvements	13,653
Gross Amount at End of Year, Since Acquisition	24,779
Gross Amount at End of Year, Land	4,181
Gross Amount at End of Year, Building and Improvements	34,251
Gross Amount at End of Year, Total	38,432
Gross Amount at End of Year, Accumulated Depreciation	$ 7,517
Atlantic Corporate Park [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Sterling
Date Acquired	Nov. 30, 2010
Property Type	Office
Initial Costs, Land	$ 5,895
Initial Costs, Building and Improvements	11,655
Gross Amount at End of Year, Since Acquisition	18,319
Gross Amount at End of Year, Land	5,895
Gross Amount at End of Year, Building and Improvements	29,974
Gross Amount at End of Year, Total	35,869
Gross Amount at End of Year, Accumulated Depreciation	$ 5,093
One Fair Oaks [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Fairfax
Date Acquired	Apr. 30, 2011
Property Type	Office
Initial Costs, Land	$ 5,688
Initial Costs, Building and Improvements	43,176
Gross Amount at End of Year, Since Acquisition	(25,909)
Gross Amount at End of Year, Land	1,607
Gross Amount at End of Year, Building and Improvements	21,348
Gross Amount at End of Year, Total	22,955
Gross Amount at End of Year, Accumulated Depreciation	$ 9,248
1775 Wiehle Avenue [Domain]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Reston
Date Acquired	Jun. 25, 2014
Property Type	Office
Initial Costs, Land	$ 3,542
Initial Costs, Building and Improvements	30,575
Gross Amount at End of Year, Since Acquisition	48
Gross Amount at End of Year, Land	3,541
Gross Amount at End of Year, Building and Improvements	30,624
Gross Amount at End of Year, Total	34,165
Gross Amount at End of Year, Accumulated Depreciation	$ 2,062
Northern Virginia Development Project [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Northern Virginia
Encumbrances	$ 9,176
Initial Costs, Land	5,241
Initial Costs, Building and Improvements	0
Gross Amount at End of Year, Since Acquisition	33,930
Gross Amount at End of Year, Land	0
Gross Amount at End of Year, Building and Improvements	39,171
Gross Amount at End of Year, Total	39,171
Gross Amount at End of Year, Accumulated Depreciation	0
Northern Virginia [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	9,176
Initial Costs, Land	46,841
Initial Costs, Building and Improvements	161,400
Gross Amount at End of Year, Since Acquisition	84,717
Gross Amount at End of Year, Land	42,637
Gross Amount at End of Year, Building and Improvements	250,321
Gross Amount at End of Year, Total	292,958
Gross Amount at End of Year, Accumulated Depreciation	$ 58,652
Crossways Commerce Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Dec. 31, 1999
Property Type	BP
Initial Costs, Land	$ 5,160
Initial Costs, Building and Improvements	23,660
Gross Amount at End of Year, Since Acquisition	13,801
Gross Amount at End of Year, Land	5,160
Gross Amount at End of Year, Building and Improvements	37,461
Gross Amount at End of Year, Total	42,621
Gross Amount at End of Year, Accumulated Depreciation	$ 15,652
Greenbrier Technology Center II [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Oct. 31, 2002
Property Type	BP
Initial Costs, Land	$ 1,365
Initial Costs, Building and Improvements	5,119
Gross Amount at End of Year, Since Acquisition	1,325
Gross Amount at End of Year, Land	1,365
Gross Amount at End of Year, Building and Improvements	6,444
Gross Amount at End of Year, Total	7,809
Gross Amount at End of Year, Accumulated Depreciation	$ 2,522
Norfolk Business Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Norfolk
Date Acquired	Oct. 31, 2002
Property Type	BP
Initial Costs, Land	$ 1,323
Initial Costs, Building and Improvements	4,967
Gross Amount at End of Year, Since Acquisition	1,270
Gross Amount at End of Year, Land	1,324
Gross Amount at End of Year, Building and Improvements	6,236
Gross Amount at End of Year, Total	7,560
Gross Amount at End of Year, Accumulated Depreciation	$ 2,487
Crossways II [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Oct. 31, 2004
Property Type	BP
Initial Costs, Land	$ 1,036
Initial Costs, Building and Improvements	6,254
Gross Amount at End of Year, Since Acquisition	1,843
Gross Amount at End of Year, Land	1,036
Gross Amount at End of Year, Building and Improvements	8,097
Gross Amount at End of Year, Total	9,133
Gross Amount at End of Year, Accumulated Depreciation	$ 2,493
Norfolk Commerce Park II [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Norfolk
Date Acquired	Oct. 31, 2004
Property Type	BP
Initial Costs, Land	$ 1,221
Initial Costs, Building and Improvements	8,693
Gross Amount at End of Year, Since Acquisition	4,379
Gross Amount at End of Year, Land	1,221
Gross Amount at End of Year, Building and Improvements	13,072
Gross Amount at End of Year, Total	14,293
Gross Amount at End of Year, Accumulated Depreciation	$ 4,793
1434 Crossways Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Aug. 31, 2005
Property Type	BP
Initial Costs, Land	$ 4,447
Initial Costs, Building and Improvements	24,739
Gross Amount at End of Year, Since Acquisition	4,198
Gross Amount at End of Year, Land	4,815
Gross Amount at End of Year, Building and Improvements	28,569
Gross Amount at End of Year, Total	33,384
Gross Amount at End of Year, Accumulated Depreciation	$ 7,691
Crossways I [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Feb. 28, 2006
Property Type	BP
Initial Costs, Land	$ 2,657
Initial Costs, Building and Improvements	11,597
Gross Amount at End of Year, Since Acquisition	2,892
Gross Amount at End of Year, Land	2,646
Gross Amount at End of Year, Building and Improvements	14,500
Gross Amount at End of Year, Total	17,146
Gross Amount at End of Year, Accumulated Depreciation	$ 4,301
Crossways Commerce Center IV [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	May 31, 2006
Property Type	BP
Initial Costs, Land	$ 1,292
Initial Costs, Building and Improvements	3,899
Gross Amount at End of Year, Since Acquisition	700
Gross Amount at End of Year, Land	1,292
Gross Amount at End of Year, Building and Improvements	4,599
Gross Amount at End of Year, Total	5,891
Gross Amount at End of Year, Accumulated Depreciation	$ 1,561
Gateway II [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Norfolk
Date Acquired	Nov. 30, 2006
Property Type	BP
Initial Costs, Land	$ 1,320
Initial Costs, Building and Improvements	2,293
Gross Amount at End of Year, Since Acquisition	617
Gross Amount at End of Year, Land	1,320
Gross Amount at End of Year, Building and Improvements	2,910
Gross Amount at End of Year, Total	4,230
Gross Amount at End of Year, Accumulated Depreciation	$ 947
Greenbrier Circle Corporate Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Jan. 31, 2007
Property Type	BP
Initial Costs, Land	$ 4,164
Initial Costs, Building and Improvements	18,984
Gross Amount at End of Year, Since Acquisition	5,817
Gross Amount at End of Year, Land	4,164
Gross Amount at End of Year, Building and Improvements	24,801
Gross Amount at End of Year, Total	28,965
Gross Amount at End of Year, Accumulated Depreciation	$ 6,210
Greenbrier Technology Center I [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Jan. 31, 2007
Property Type	BP
Initial Costs, Land	$ 2,024
Initial Costs, Building and Improvements	7,960
Gross Amount at End of Year, Since Acquisition	2,386
Gross Amount at End of Year, Land	2,024
Gross Amount at End of Year, Building and Improvements	10,346
Gross Amount at End of Year, Total	12,370
Gross Amount at End of Year, Accumulated Depreciation	$ 3,044
Battlefield Corporate Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Oct. 31, 2010
Property Type	BP
Encumbrances	$ 3,526
Initial Costs, Land	1,860
Initial Costs, Building and Improvements	6,071
Gross Amount at End of Year, Since Acquisition	798
Gross Amount at End of Year, Land	1,881
Gross Amount at End of Year, Building and Improvements	6,848
Gross Amount at End of Year, Total	8,729
Gross Amount at End of Year, Accumulated Depreciation	$ 1,170
Greenbrier Towers [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location	Chesapeake
Date Acquired	Jul. 31, 2011
Property Type	Office
Initial Costs, Land	$ 2,997
Initial Costs, Building and Improvements	9,173
Gross Amount at End of Year, Since Acquisition	4,948
Gross Amount at End of Year, Land	2,997
Gross Amount at End of Year, Building and Improvements	14,121
Gross Amount at End of Year, Total	17,118
Gross Amount at End of Year, Accumulated Depreciation	2,292
Southern Virginia [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	3,526
Initial Costs, Land	30,866
Initial Costs, Building and Improvements	133,409
Gross Amount at End of Year, Since Acquisition	44,974
Gross Amount at End of Year, Land	31,245
Gross Amount at End of Year, Building and Improvements	178,004
Gross Amount at End of Year, Total	209,249
Gross Amount at End of Year, Accumulated Depreciation	55,163
Land Held for Future Development [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Initial Costs, Land	343
Initial Costs, Building and Improvements	0
Gross Amount at End of Year, Since Acquisition	6
Gross Amount at End of Year, Land	349
Gross Amount at End of Year, Building and Improvements	0
Gross Amount at End of Year, Total	349
Gross Amount at End of Year, Accumulated Depreciation	0
Other [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Initial Costs, Land	0
Initial Costs, Building and Improvements	0
Gross Amount at End of Year, Since Acquisition	67
Gross Amount at End of Year, Land	0
Gross Amount at End of Year, Building and Improvements	67
Gross Amount at End of Year, Total	67
Gross Amount at End of Year, Accumulated Depreciation	$ 76

Schedule III - Additional Infor

Schedule III - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Tax basis of real estate assets	$ 1,547	$ 1,576
Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Estimated lives of Company's assets	5 years
Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Estimated lives of Company's assets	39 years