First Potomac Realty Trust (FPO) 10-K 24 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 22, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
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		58,698,267
Entity Public Float			$ 526,679,042

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Assets:
Rental property, net		$ 1,059,272	$ 1,130,266
Assets held-for-sale		13,176	90,674
Cash and cash equivalents		14,144	13,527
Escrows and reserves		1,419	2,514
Accounts and other receivables, net of allowance for doubtful accounts of $655 and $876, respectively		6,892	9,868
Accrued straight-line rents, net of allowance for doubtful accounts of $414 and $105, respectively		42,745	36,888
Notes receivable		0	34,000
Investment in affiliates		49,392	48,223
Deferred costs, net		42,712	36,537
Prepaid expenses and other assets		5,389	6,950
Intangible assets, net		25,106	32,959
Total assets	[1]	1,260,247	1,442,406	[2]
Liabilities:
Mortgage loans, net	[3]	296,212	307,769	[4]
Unsecured term loan, net		299,404	299,404
Unsecured revolving credit facility, net	[3]	141,555	116,865	[4]
Liabilities held-for-sale		0	1,513
Accounts payable and other liabilities		43,904	47,972
Accrued interest		1,537	1,603
Rents received in advance		6,234	6,003
Tenant security deposits		4,982	4,982
Deferred market rent, net		1,792	2,154
Total liabilities		795,620	788,265
Noncontrolling interests in the Operating Partnership		28,244	28,813
Equity:
Common shares, $0.001 par value per share, 150,000 shares authorized; 58,319 and 57,718 shares issued and outstanding, respectively		58	58
Additional paid-in capital		913,367	907,220
Noncontrolling interests in a consolidated partnership		0	800
Accumulated other comprehensive loss		(844)	(2,360)
Dividends in excess of accumulated earnings		(476,198)	(440,390)
Total equity		436,383	625,328
Total liabilities, noncontrolling interests and equity		1,260,247	1,442,406
Series A Preferred Shares [Member]
Equity:
Preferred Shares		$ 0	$ 160,000
[1]	(1) 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. Corporate assets not allocated to any of our reportable segments totaled $17,732, $41,357 and $81,130 at December 31, 2016, 2015 and 2014, respectively.
[2]	(4) Total assets at December 31, 2015 and 2014 have been restated to exclude a total of $7.9 million and $6.2 million, respectively of unamortized deferred financing costs that are now deducted from the respective debt liability in accordance with ASU 2015-03, which we adopted in the first quarter of 2016.
[3]	(1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively.
[4]	Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions, for further discussion.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts, accounts receivable and other	$ 655	$ 876
Allowance for doubtful accounts, Accrued straight-line rents	$ 414	$ 105
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	0	6,400
Series A Preferred Shares, shares outstanding	0	6,400
Common Stock, par value	$ 0.001	$ 0.001
Common Stock, shares authorized	150,000	150,000
Common Stock, shares issued	58,319	57,718
Common Stock, shares outstanding	58,319	57,718

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Rental	$ 129,225,000	$ 139,006,000	$ 128,226,000
Tenant reimbursements and other	31,109,000	33,840,000	33,426,000
Total revenues	160,334,000	172,846,000	161,652,000
Operating expenses:
Property operating	38,554,000	44,093,000	43,252,000
Real estate taxes and insurance	19,808,000	19,745,000	17,360,000
General and administrative	16,976,000	25,450,000	21,156,000
Acquisition costs	0	0	2,681,000
Depreciation and amortization	60,862,000	66,624,000	61,796,000
Impairment of rental property	2,772,000	60,826,000	3,956,000
Total operating expenses	138,972,000	216,738,000	150,201,000
Operating income (loss)	21,362,000	(43,892,000)	11,451,000
Other expenses (income):
Interest expense	26,370,000	26,797,000	24,696,000
Interest and other income	(2,348,000)	(6,794,000)	(6,799,000)
Equity in earnings of affiliates	(2,294,000)	(1,825,000)	(775,000)
Loss (gain) on sale of rental property	1,155,000	(29,477,000)	(21,230,000)
Loss on debt extinguishment / modification	48,000	1,824,000	0
Total other expenses (income)	22,931,000	(9,475,000)	(4,108,000)
(Loss) income from continuing operations	(1,569,000)	(34,417,000)	15,559,000
Discontinued operations:
(Loss) income from operations	0	(975,000)	146,000
Loss on debt extinguishment	0	(489,000)	0
Gain on sale of rental property	0	857,000	1,338,000
(Loss) income from discontinued operations	0	(607,000)	1,484,000
Net (loss) income	(1,569,000)	(35,024,000)	17,043,000
Less: Net loss (income) attributable to noncontrolling interests	502,000	2,058,000	(199,000)
Net (loss) income attributable to First Potomac Realty Trust	(1,067,000)	(32,966,000)	16,844,000
Less: Dividends on preferred shares	(3,053,000)	(12,400,000)	(12,400,000)
Payments of Stock Issuance Costs	(5,515,000)	0	0
Net (loss) income attributable to common shareholders	$ (9,635,000)	$ (45,366,000)	$ 4,444,000
Basic and diluted earnings per common share:
(Loss) income from continuing operations	$ (0.17)	$ (0.78)	$ 0.05
(Loss) income from discontinued operations	0	(0.01)	0.02
Net (loss) income	$ (0.17)	$ (0.79)	$ 0.07
Weighted Average Number of Shares Outstanding, Basic	57,581	57,982	58,150
Weighted average common shares outstanding – diluted	57,581	57,982	58,220

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net (loss) income	$ (1,569)	$ (35,024)	$ 17,043
Unrealized gain on derivative instruments	1,584	1,317	1,289
Unrealized loss on derivative instruments	0	(367)	(696)
Total comprehensive income (loss)	15	(34,074)	17,636
Net loss (income) attributable to noncontrolling interests	502	2,058	(199)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Noncontrolling Interest	(68)	(42)	(25)
Comprehensive income (loss) attributable to First Potomac Realty Trust	$ 449	$ (32,058)	$ 17,412

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) shares in Thousands, $ 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, 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
Dividends, Preferred Stock	(12,400)
Accrued common dividends	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)		0	(397)
Adjustment of common Operating Partnership units to fair value	1,424			1,424
Noncontrolling interest in consolidated joint ventures, at acquisition	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
Dividends, Preferred Stock	(12,400)
Shares issued in exchange for common Operating Partnership units	(117)						(117)
Restricted stock expense	3,447			3,442			5
Exercise of stock options	$ 26			$ 26
Repurchases of common shares	(10,180)		(1)	(10,179)
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)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	(1,643)				(74)
Net (loss) income	(1,569)						(1,569)
Net unrealized gain (loss) on derivative instruments	1,584					1,584
Net (income) loss attributable to noncontrolling interests	(434)					68	(502)
Dividends paid to common shareholders	(26,137)						26,137
Dividends on preferred shares	(3,053)						3,053
Dividends, Preferred Stock	(3,053)	(160,000)
Less: Issuance costs on redeemed preferred shares	(160,030)			5,485			(5,515)
Accrued common dividends	36						36
Restricted stock expense	1,964			1,964			0
Stock option and employee stock purchase plan expense	193			193
Issuance of common stock, net of net settlements	(97)			(97)
Adjustment of common Operating Partnership units to fair value	1,592			1,592
Net distributions from / contributions to noncontrolling interest in consolidated joint ventures	726				726
Ending balance at Dec. 31, 2016	$ 436,383	$ 0	$ 58	$ 913,367	$ 0	$ (844)	$ (476,198)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Adjustment Cost Basis	$ 6,100	$ 4,000
Cash flow from operating activities:
Net (loss) income	(1,569)	(35,024)	$ 17,043
Discontinued operations:
Gain on sale of rental property	0	(857)	(1,338)
Depreciation and amortization	0	1,222	3,665
Depreciation and amortization	61,896	67,729	62,843
Stock based compensation	2,314	4,865	3,731
Bad debt expense	830	580	1,110
Amortization of deferred market rent	301	138	(14)
Amortization of financing costs and discounts	1,588	1,482	1,445
Equity in earnings of affiliates	(2,294)	(1,825)	(775)
Distributions from investments in affiliates	1,424	1,490	1,356
Impairment of rental property	2,772	60,826	3,956
Loss (gain) on sale of rental property	1,155	(29,477)	(21,230)
Loss on debt extinguishment / modification	0	664	0
Changes in assets and liabilities:
Escrows and reserves	784	296	4,693
Accounts and other receivables	2,453	(7)	1,475
Accrued straight-line rents	(6,476)	(8,722)	(7,968)
Prepaid expenses and other assets	913	285	326
Tenant security deposits	(748)	(849)	677
Accounts payable and accrued expenses	9,524	7,921	1,227
Accrued interest	(68)	(115)	56
Rents received in advance	(307)	(1,767)	1,984
Deferred costs	(11,893)	(8,473)	(11,309)
Total adjustments	64,168	95,406	45,910
Net cash provided by operating activities	62,599	60,382	62,953
Cash flows from investing activities:
Investment in note receivable	0	0	(9,000)
Principal payments from note receivable	34,000	29,720	176
Proceeds from sale of rental property	143,159	129,247	97,701
Change in escrow and reserve accounts	312	176	0
Additions to rental property and furniture, fixtures and equipment	(45,068)	(52,955)	(39,338)
Additions to construction in progress	(11,863)	(20,895)	(11,451)
Acquisition of rental property and associated intangible assets	0	0	(150,731)
Investment in affiliates	(300)	(405)	(1,988)
Distributions from investments in affiliates	0	0	3,075
Net cash provided by (used in) investing activities	120,240	84,888	(111,556)
Cash flows from financing activities:
Financing costs	(319)	(4,476)	(870)
Issuance of debt	238,408	195,956	250,518
Repayments of debt	(227,044)	(277,108)	(147,577)
Contributions from consolidated joint venture partners	0	0	213
Distributions to consolidated joint venture partners	(726)	(96)	(96)
Dividends to common shareholders	(26,137)	(35,080)	(35,198)
Dividends to preferred shareholders	(4,603)	(12,400)	(12,400)
Distributions to noncontrolling interests	(1,166)	(1,574)	(1,578)
Repurchases of common shares	0	(10,180)	0
Redemption of preferred shares	(160,000)
Redemption of operating partnership units	(635)	(134)	0
Proceeds from stock option exercises	0	26	174
Net cash (used in) provided by financing activities	(182,222)	(145,066)	53,186
Net increase (decrease) in cash and cash equivalents	617	204	4,583
Cash and cash equivalents, beginning of year	13,527	13,323	8,740
Cash and cash equivalents, end of year	14,144	13,527	13,323
Cash paid for interest, net	24,550	25,129	23,083
Non-cash investing and financing activities:
Debt assumed in connection with the acquisition of rental property	0	0	37,269
Surrendered common shares to satisfy statutory minimum federal income tax obligations	137	1,781	487
Change in fair value of the outstanding common Operating Partnership units	1,592	(797)	1,424
Issuance of common Operating Partnership units in connection with the acquisition of rental property	0	0	40
Change in accruals:
Additions to rental property and furniture, fixtures and equipment	(3,561)	795	653
Additions to development and redevelopment	$ (5,576)	$ 4,408	$ (275)

Consolidated Statements of Cas8

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest Paid, Capitalized	$ 700	$ 1,900	$ 3,200
Surrendered common shares to satisfy statutory minimum federal income tax obligations	$ 137	$ 1,781	$ 487
Partners' Capital Account, Units, Acquisitions	0
Eight Four Zero First Street Ne [Member]
Partners' Capital Account, Units, Acquisitions		3,125
Operating Partnership Units Fair Valued		$ 40

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Description of Business	Description of Business First Potomac Realty Trust (the “Company”) is a leader in the ownership, management, redevelopment and development of office and business park properties in the greater Washington, D.C. region. The Company’s focus is owning and operating properties that it believes can benefit from its market knowledge and intensive operational skills with a focus on increasing 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 our Operating Partnership. We are the sole general partner of, and, as of December 31, 2016 , owned 95.8% 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, 2016 , we wholly owned properties totaling 6.7 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 0.6 million square feet of additional development. Our consolidated properties were 92.6% occupied by 384 tenants at December 31, 2016 . We do not include square footage of properties in development or redevelopment in our occupancy calculation. At December 31, 2016, none of our 6.7 million square feet owned through our properties was in development or redevelopment. We derive substantially all of our revenue from leases of space within our properties. As of December 31, 2016 , our largest tenant was the U.S. Government, which accounted for 16% of our total annualized cash basis rent, and the U.S. Government combined with government contractors accounted for 27% of our total annualized cash basis rent as of December 31, 2016 . We operate so as to qualify as a real estate investment trust (“REIT”) for federal income tax purposes. For the year ended December 31, 2016 , we had consolidated total revenues of $ 160.3 million and consolidated total assets of $1.3 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, 2016
Accounting Policies [Abstract]
Deferred Costs Policy [Text Block]	(f) Deferred Costs 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 $26.3 million and $22.0 million at December 31, 2016 and 2015 , respectively. The following table sets forth scheduled future amortization for deferred leasing costs at December 31, 2016 (amounts in thousands): Deferred Leasing (1) Deferred Lease Incentive (2) 2017 $ 5,464 $ 1,500 2018 4,915 1,473 2019 4,118 1,399 2020 3,363 1,327 2021 2,649 1,265 Thereafter 6,689 6,006 $ 27,198 $ 12,970 (1) Excludes the amortization of $1.8 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. (2) Excludes the amortization of $0.7 million of lease incentive 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 lease incentive costs will be amortized has yet to be determined.
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, which we consider to be a variable interest entity (“VIE”), 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, 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 2016 , 2015 and 2014 , we incurred charges of $0.8 million , $0.6 million and $1.1 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 , $0.1 million and $1.1 million for the years ended December 31, 2016 , 2015 and 2014 , 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 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 $26.3 million and $22.0 million at December 31, 2016 and 2015 , respectively. The following table sets forth scheduled future amortization for deferred leasing costs at December 31, 2016 (amounts in thousands): Deferred Leasing (1) Deferred Lease Incentive (2) 2017 $ 5,464 $ 1,500 2018 4,915 1,473 2019 4,118 1,399 2020 3,363 1,327 2021 2,649 1,265 Thereafter 6,689 6,006 $ 27,198 $ 12,970 (1) Excludes the amortization of $1.8 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. (2) Excludes the amortization of $0.7 million of lease incentive 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 lease incentive 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 binding contract pursuant to which the buyer has significant money at risk, or 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 the following properties are reflected within discontinued operations in our consolidated statements of operations for all periods presented: (i) all properties that were sold prior to the adoption of ASU 2014-08; (ii) 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; and (iii) 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”). 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 2016 , 2015 and 2014 . 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 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 depreciable life of the venture’s assets 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 account 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, 2016 , 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 2016 , 2015 and 2014 . (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 2016 , 2015 and 2014 . 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, 2016 , 2015 and 2014 , 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 record loans to owners of real estate properties, which can be collateralized by interest in the real estate property, as “Notes receivable” in our consolidated balance sheets. These 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. Any 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. During the second quarter of 2016, we received the full repayment of a mezzanine loan with an outstanding principal balance of $34.0 million . We did not have any notes receivable outstanding at December 31, 2016. Based on the review of the above criteria, we did not record an allowance for credit losses for our notes receivable during 2016, 2015 and 2014 . (p) Application of New Accounting Standards In January 2016, we adopted 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. The adoption of ASU 2015-01 did not have a material impact on our consolidated financial statements and related disclosures. In January 2016, we adopted ASU No. 2015-02, Amendments to the Consolidation Analysis (“ASU 2015-02”). This standard amends certain guidance applicable to the consolidation of various legal entities, including VIEs. In determining the method

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2016
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 and non-vested 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): 2016 2015 2014 Numerator for basic and diluted earnings per common share: (Loss) income from continuing operations $ (1,569 ) $ (34,417 ) $ 15,559 (Loss) income from discontinued operations — (607 ) 1,484 Net (loss) income (1,569 ) (35,024 ) 17,043 Less: Net loss (income) from continuing operations attributable to noncontrolling interests 502 2,032 (135 ) Less: Net loss (income) from discontinued operations attributable to noncontrolling interests — 26 (64 ) Net (loss) income attributable to First Potomac Realty Trust (1,067 ) (32,966 ) 16,844 Less: Dividends on preferred shares (3,053 ) (12,400 ) (12,400 ) Less: Issuance costs of redeemed preferred shares (1) (5,515 ) — — Net (loss) income attributable to common shareholders (9,635 ) (45,366 ) 4,444 Less: Allocation to participating securities (232 ) (241 ) (314 ) Net (loss) income attributable to common shareholders $ (9,867 ) $ (45,607 ) $ 4,130 Denominator for basic and diluted earnings per common share: Weighted average common shares outstanding – basic 57,581 57,982 58,150 Weighted average common shares outstanding – diluted 57,581 57,982 58,220 Basic and diluted earnings per common share: (Loss) income from continuing operations attributable to common shareholders $ (0.17 ) $ (0.78 ) $ 0.05 (Loss) income from discontinued operations attributable to common shareholders — (0.01 ) 0.02 Net (loss) income $ (0.17 ) $ (0.79 ) $ 0.07 (1) Represents the original issuance costs associated with the redemption of 6.4 million 7.750% Series A Cumulative Redeemable Perpetual Preferred Shares (the “7.750% Series A Preferred Shares”) during the year ended December 31, 2016. 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): 2016 2015 2014 Stock option awards 960 1,020 1,122 Non-vested share awards 669 310 398 1,629 1,330 1,520

Rental Property

Rental Property	12 Months Ended
	Dec. 31, 2016
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): 2016 (1) 2015 (2) Land and land improvements $ 282,923 $ 280,149 Buildings and improvements 824,867 793,184 Construction in progress 4,605 97,361 Tenant improvements 189,031 168,946 Furniture, fixtures and equipment 408 410 1,301,834 1,340,050 Less: accumulated depreciation (242,562 ) (209,784 ) $ 1,059,272 $ 1,130,266 (1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017. (2) 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 and was sold on March 25, 2016. 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. At December 31, 2016 , we owned developable land that can accommodate 0.6 million square feet of additional building space, of which 34 thousand 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 (the “NOVA build-to-suit”) in our Northern Virginia reporting segment, which was on vacant land that we had in our portfolio. We substantially completed construction of the new building in the first quarter of 2016, and we substantially completed construction of the tenant improvements during the third quarter of 2016. We commenced revenue recognition in August 2016, at which time the building was placed in-service. At December 31, 2016, our total investment in the newly constructed building, excluding tenant improvements and leasing commission costs, was $35.0 million , which related to the costs of construction of the building and included the original cost basis of the applicable portion of the vacant land of $5.2 million . On August 4, 2011, we formed a joint venture, in which we had 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 could accommodate up to 712,000 square feet. On July 25, 2016 , our consolidated joint venture sold Storey Park for a contractual purchase price of $54.5 million , which generated net proceeds of $52.7 million . In June 2016, we recorded a $2.8 million impairment charge based on the sales price, less estimated selling costs. On January 1, 2016, we ceased capitalizing expenses associated with the development project as we began marketing the property for sale. See note 9 , Dispositions , for more information. During 2016, other than the NOVA build-to-suit, we did no t place in-service any completed development or redevelopment space. At December 31, 2016, we did no t have any completed development or redevelopment space that had yet to be placed in-service.

Investment in Affiliates

Investment in Affiliates	12 Months Ended
	Dec. 31, 2016
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, the liabilities and the 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” on our consolidated balance sheets. Our investment in affiliates consisted of the following (dollars in thousands): Reporting Segment Ownership Interest Investment at December 31, 2016 Investment at December 31, 2015 Prosperity Metro Plaza Northern Virginia 51 % $ 26,414 $ 24,909 1750 H Street, NW Washington, D.C. 50 % 14,625 15,168 Aviation Business Park (1) Maryland 50 % 5,941 5,899 Rivers Park I and II (1)(2) Maryland 25 % 2,413 2,247 $ 49,392 $ 48,223 (1) In January 2017, the unconsolidated joint ventures that own these properties entered into a binding contract to sell Aviation Business Park and Rivers Park I and II, which are all located in our Maryland reporting segment. We anticipate completing the sale in March 2017; however, we can provide no assurances regarding the timing or pricing of such sale, or that such sale will ultimately occur. (2) Rivers Park I and Rivers Park II are owned through two separate unconsolidated joint ventures. The following table provides a summary of the mortgage debt held by our unconsolidated joint ventures (dollars in thousands): FPO Ownership Effective Interest Rate Maturity Date Principal Balance at December 31, 2016 (1) Principal Balance at December 31, 2015 (1) Rivers Park I and II (2) 25% LIBOR + 1.90% (3) September 2017 $ 28,000 $ 28,000 1750 H Street, NW (4) 50% 3.92% August 2024 32,000 32,000 Prosperity Metro Plaza (5) 51% 3.91% December 2029 50,000 50,000 Weighted Average/Total 3.60% $ 110,000 $ 110,000 (1) Reflects the entire balance of the debt secured by the properties, not our portion of the debt. (2) The loan is repayable in full, without penalty, at any time during the term of the loan. Of the outstanding principal balance, $2.8 million is recourse to us. 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. (3) At December 31, 2016, LIBOR was 0.77% . All references to LIBOR in the financial statements refer to one-month LIBOR. (4) The loan requires interest-only payments with a constant interest rate over the life of the loan. The loan is repayable in full, without penalty, on or after August 1, 2021. (5) The loan requires interest-only payments through December 2024, at which time the loan requires principal and interest payments through its maturity date. The loan in repayable in full without penalty on or after June 1, 2029. The net assets of our unconsolidated joint ventures consisted of the following at December 31 (dollars in thousands): 2016 2015 Assets: Rental property, net $ 189,245 $ 193,243 Cash and cash equivalents 9,887 5,992 Other assets 20,726 16,490 Total assets 219,858 215,725 Liabilities: Mortgage loans, net (1)(2) 109,372 109,273 Other liabilities 8,674 7,214 Total liabilities 118,046 116,487 Net assets $ 101,812 $ 99,238 (1) Of the total mortgage debt that encumbers our unconsolidated properties, $2.8 million is recourse to us. We believe the fair value of the potential liability to us under this guaranty is inconsequential as the likelihood of our need to perform under the debt agreement is remote. (2) In the first quarter of 2016, our unconsolidated joint ventures adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and which is applied on a retrospective basis. Mortgage loans, net at December 31, 2016 and 2015 included $ 0.6 million and $0.7 million , respectively, of unamortized deferred financing costs. Our share of earnings or losses related to our unconsolidated joint ventures is recorded in our consolidated statements of operations as “Equity in earnings 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 (dollars in thousands): 2016 2015 2014 Total revenues $ 24,704 $ 24,255 $ 23,285 Total operating expenses (7,770 ) (7,660 ) (7,408 ) Net operating income 16,934 16,595 15,877 Depreciation and amortization (8,044 ) (8,718 ) (9,893 ) Interest expense, net (3,995 ) (3,909 ) (3,890 ) Provision for income taxes — — (63 ) Contingent consideration charge — — 126 Net income $ 4,895 $ 3,968 $ 2,157 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 $ 0.6 million , $ 0.7 million , and $ 0.7 million in 2016, 2015 and 2014, 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, 2016
Receivables [Abstract]
Notes Receivable	Notes Receivable On June 2, 2016, the owners of 950 F Street, NW, a ten-story, 287,000 square-foot office/retail building located in Washington, D.C., prepaid a mezzanine loan that was secured by a portion of the owners’ interest in the property and had an outstanding balance of $34.0 million . The mezzanine loan, which had a fixed interest rate of 9.75% was scheduled to mature on April 1, 2017 and had been prepayable since December 21, 2015. In addition to the prepayment of the loan's entire principal balance, we received interest through June 24, 2016 and an exit fee upon the loan's prepayment. We recognized $0.2 million of accelerated income in the second quarter of 2016 related to the payment of the exit fee, which is reflected in “Interest and other income” in our consolidated statement of operations for the year ended December 31, 2016. We used the proceeds from the prepayment of the note receivable to redeem the remaining 0.6 million 7.750% Series A Preferred Shares outstanding and to pay down a portion of our unsecured revolving credit facility. On February 24, 2015, the owners of America’s 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 . The loan had a fixed-interest rate of 9.0% and was scheduled to mature on May 1, 2016 . With the prepayment of the loan, we received a yield maintenance payment of $2.4 million , which is reflected within “Interest and other income” on our consolidated statement of operations for the year ended December 31, 2015. We recorded interest income related to our notes receivable of $ 1.6 million , $3.7 million and $6.1 million during 2016, 2015, and 2014, respectively, which is included within “Interest and other income” in our consolidated statements of operations.

Intangible Assets and Deferred

Intangible Assets and Deferred Market Rent Liabilities	12 Months Ended
	Dec. 31, 2016
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): 2016 2015 Gross Intangibles Accumulated Amortization Net Intangibles Gross Intangibles Accumulated Amortization Net Intangibles In-place leases $ 38,804 $ (25,423 ) $ 13,381 $ 45,901 $ (26,961 ) $ 18,940 Customer relationships 663 (663 ) — 663 (601 ) 62 Leasing commissions 9,499 (5,882 ) 3,617 10,612 (5,485 ) 5,127 Legal leasing fees 299 (193 ) 106 344 (177 ) 167 Deferred market rent assets 2,880 (1,808 ) 1,072 3,558 (1,825 ) 1,733 Goodwill 6,930 — 6,930 6,930 — 6,930 $ 59,075 $ (33,969 ) $ 25,106 $ 68,008 $ (35,049 ) $ 32,959 Deferred market rent liability $ 4,173 $ (2,381 ) $ 1,792 $ 4,869 $ (2,715 ) $ 2,154 We recognized $ 7.0 million , $10.6 million , and $10.3 million of amortization expense on intangible assets for the years ended December 31, 2016, 2015 and 2014, respectively. Through the net amortization of deferred market rent assets and deferred market rent liabilities, we recognized a $0.3 million reduction of rental revenue in 2016, a $0.1 million reduction of rental revenue in 2015 and an additional $14 thousand of revenue in 2014. 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 $ 3.0 million , $0.5 million and $1.1 million during 2016, 2015 and 2014, respectively. The projected net amortization of intangible assets and deferred market liabilities as of December 31, 2016 are as follows (amounts in thousands): 2017 $ 4,114 2018 2,646 2019 2,361 2020 2,147 2021 1,463 Thereafter 3,653 $ 16,384

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
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 2016, 2015 or 2014. At both December 31, 2016 and 2015, we had recorded an estimated receivable of $1.2 million 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, 2016 and 2015, 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 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, 2016
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 2016, 2015 and 2014. (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 One Fair Oaks (1) Northern Virginia 1/9/2017 Office 214,214 $ 13,255 Storey Park (2) Washington, D.C. 7/25/2016 Land — 52,659 NOVA Non-Core Portfolio (3) Northern Virginia 3/25/2016 Various 945,745 90,501 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) One Fair Oaks was classified as held-for-sale at December 31, 2016. (2) This development site could have supported up to 712,000 rentable square feet. (3) 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”). At December 31, 2016, One Fair Oaks met our held-for-sale criteria and, therefore, the assets of the building were classified within “Assets held-for-sale” on our consolidated balance sheet. The assets classified within held-for-sale as of December 31, 2016 primarily consisted of $17.6 million in building and building improvements, $1.6 million of land and $6.0 million of accumulated depreciation. No material liabilities were classified as held-for-sale at December 31, 2016. On July 25, 2016 , we sold Storey Park, a development site located in our Washington, D.C reporting segment that was 97% owned by us through a consolidated joint venture, for net proceeds of $ 52.7 million . We used the proceeds from the sale to prepay, without penalty, the $ 22.0 million loan encumbering the Storey Park land (the “Storey Park Land Loan”), to make a distribution to our 3% joint venture partner for their allocable share of the joint venture’s net assets and to pay down a portion of the outstanding balance of our unsecured revolving credit facility. 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 included one mortgage that was defeased in March 2016, were classified within “Liabilities held-for-sale” on 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. On February 17, 2017, we sold Plaza 500, a 503,000 square-foot office building located in Northern Virginia, for net proceeds of $72.5 million . The sale of Plaza 500 represented the divestiture of our last industrial property. We used the proceeds from the sale to pay down a portion of the outstanding balance under our unsecured revolving credit facility. Plaza 500 did not meet the criteria to be classified as held-for-sale at December 31, 2016. In addition, in January 2017, the unconsolidated joint ventures that own Aviation Business Park and Rivers Park I and II entered into a binding contract to sell Aviation Business Park and Rivers Park I and II, which are all located in Maryland. We anticipate completing the sale in March 2017; however, we can provide no assurances regarding the timing or pricing of such sale, or that such sale will ultimately occur. 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): 2016 2015 2014 Revenues $ 11,156 $ 29,773 $ 31,027 Property operating expenses (4,307 ) (10,353 ) (11,055 ) Depreciation and amortization (1,070 ) (10,310 ) (11,289 ) Interest expense, net of interest income (436 ) (465 ) (843 ) Loss on debt extinguishment (48 ) — — Impairment of rental property (2,772 ) (60,826 ) — Income (loss) from operations of disposed property 2,523 (52,181 ) 7,840 (Loss) gain on sale of rental property (1,155 ) 29,477 21,230 Net income (loss) from continuing operations $ 1,368 $ (22,704 ) $ 29,070 (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 (1) Consists of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land. 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. The following table summarizes the results of operations of properties included in discontinued operations for the years ended December 31 (dollars in thousands): 2016 2015 2014 Revenues $ — $ 877 $ 7,688 Property operating expenses — (638 ) (3,612 ) Depreciation and amortization — (1,222 ) (3,662 ) Net interest income (expense) — 8 (268 ) (Loss) income from operations of disposed property — (975 ) 146 Loss on debt extinguishment — (489 ) — Gain on sale of rental property — 857 1,338 Net (loss) income from discontinued operations $ — $ (607 ) $ 1,484

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt	Debt Our borrowings consisted of the following at December 31 (dollars in thousands): 2016 (1) 2015 (1)(2) Mortgage loans, net effective interest rates ranging from 4.22% to 6.01%, maturing at various dates through September 2030 (3)(4) $ 296,212 $ 307,769 Unsecured term loan, net 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 (3) 299,404 299,404 Unsecured revolving credit facility, net effective interest rate of LIBOR plus 1.50%, maturing December 2019 (3) 141,555 116,865 $ 737,171 $ 724,038 (1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $ 6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively. (2) Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions , for further discussion. (3) At December 31, 2016 , LIBOR was 0.77% . All references to LIBOR in the consolidated financial statements refer to one-month LIBOR. (4) At December 31, 2016 and 2015, the mortgage loans balance includes two construction loans. At December 31, 2015, the mortgage loans balance includes two construction loans and the Storey Park Land Loan, which was repaid in July 2016. (a) Mortgage Loans The following table provides a summary of our mortgage debt, which includes two construction loans and, for the year ended December 31, 2015, the Storey Park Land Loan (dollars in thousands): Encumbered Property Contractual Interest Rate Effective Interest Rate Maturity Date December 31, 2016 December 31, 2015 Storey Park Land Loan (1)(2) LIBOR + 2.50% LIBOR + 2.50% October 2016 $ — $ 22,000 Hillside I and II (3) 5.75 % 4.62 % December 2016 — 12,368 440 First Street, NW Construction Loan (1)(4) LIBOR + 2.50% LIBOR + 2.50% May 2017 32,216 32,216 Redland II & III 4.20 % 4.64 % November 2017 63,214 64,543 Northern Virginia Construction Loan (1)(5) LIBOR + 1.85% LIBOR + 1.85% September 2019 34,584 9,176 840 First Street, NE 5.72 % 6.01 % July 2020 35,201 35,888 Battlefield Corporate Center 4.26 % 4.40 % November 2020 3,353 3,526 1211 Connecticut Avenue, NW 4.22 % 4.47 % July 2022 28,503 29,110 1401 K Street, NW 4.80 % 4.93 % June 2023 35,556 36,224 11 Dupont Circle, NW 4.05 % 4.22 % September 2030 66,780 66,780 Principal balance 4.41 % (6) 299,407 311,831 Unamortized fair value adjustments — 172 Unamortized deferred financing costs (7) (3,195 ) (4,234 ) Total balance, net $ 296,212 $ 307,769 Debt Classified within Liabilities Held-for-Sale Gateway Centre Manassas Building I (8) 7.35 % 5.88 % November 2016 $ — $ 212 Unamortized fair value adjustments — 1 Total balance, net $ — $ 213 (1) At December 31, 2016 , LIBOR was 0.77% . (2) The Storey Park Land Loan encumbered the Storey Park land and was entered into by our 97% owned consolidated joint venture that owned Storey Park. On July 25, 2016 , our consolidated joint venture sold Storey Park and the Storey Park Land Loan was concurrently repaid with proceeds from the sale. (3) On October 6, 2016 , we used available cash to prepay, without penalty, the Hillside I and II loan. (4) This construction loan (the “440 First Street, NW Construction Loan”) is collateralized by 440 First Street, NW. In May 2016, we extended the maturity date by one year to May 30, 2017 . We can repay all or a portion of the construction loan, without penalty, at any time during the term of the loan. At December 31, 2016, per the terms of the loan agreement, 50% of the outstanding principal balance and all of the outstanding accrued interest were recourse to us. (5) This construction loan has a borrowing capacity of up to $43.7 million and is collateralized by the NOVA build-to-suit (the “Northern Virginia Construction Loan”), which was placed in-service in August 2016. We can repay all or a portion of the Northern Virginia Construction loan, without penalty, at any time during the term of the loan. (6) Represents the weighted average interest rate on total mortgage debt. (7) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. (8) The mortgage loan that encumbered Gateway Centre Manassas, which was included in the NOVA Non-Core Portfolio and sold on March 25, 2016, was classified within “Liabilities held-for-sale” on our December 31, 2015 consolidated balance sheet. In February 2016, we used $ 0.2 million in available cash to defease the outstanding balance of the mortgage loan. Northern Virginia Construction Loan On September 1, 2015, we entered into the Northern Virginia Construction Loan, which is collateralized by the NOVA build-to-suit (which was placed in-service in August 2016). The loan has a borrowing capacity of up to $ 43.7 million , of which we borrowed $ 34.6 million and $ 9.2 million at December 31, 2016 and 2015, respectively. 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. With the exception of the 440 First Street, NW Construction Loan, our mortgage debt is recourse solely to specific assets. We had 8 and 11 consolidated properties that secured mortgage debt at December 31, 2016 and 2015, respectively. We have originated the following mortgage and construction loans since January 1, 2015 (dollars in thousands): Month Year Property Effective Interest Rate Principal Balance at December 31, 2016 September 2015 Northern Virginia Construction Loan LIBOR + 1.85% (1) $ 34,584 (2) August 2015 11 Dupont Circle, NW 4.22% 66,780 (1) At December 31, 2016, LIBOR was 0.77% . (2) The loan has a borrowing capacity of up to $43.7 million , of which we borrowed $25.4 million and $9.2 million during 2016 and 2015, respectively. We have repaid the following mortgage and land loans since January 1, 2015 (dollars in thousands): Month Year Property Effective Interest Rate Principal Balance Repaid October 2016 Hillside I and II 4.62 % $ 12,199 August 2016 Storey Park Land Loan LIBOR + 2.50% (1) 22,000 February 2016 Gateway Centre Manassas 5.88 % 174 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 (1) At December 31, 2016, LIBOR was 0.77% . (b) Unsecured Term Loan and 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 term loan’s three $ 100 million tranches to December 2020 , June 2021 and December 2022 from October 2018 , October 2019 and October 2020, respectively and 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 term loan and 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, the Company incurred $1.8 million of debt modification charges related to amending and restating the unsecured revolving credit facility and 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, 2016 and 2015 (dollars in thousands): Maturity Date Interest Rate (1) December 31, 2016 December 31, 2015 Tranche A December 2020 LIBOR + 1.45% $ 100,000 $ 100,000 Tranche B June 2021 LIBOR + 1.45% 100,000 100,000 Tranche C December 2022 LIBOR + 1.80% 100,000 100,000 Total 300,000 300,000 Unamortized deferred financing costs (2) (596 ) (596 ) Total, net $ 299,404 $ 299,404 (1) At December 31, 2016 , LIBOR was 0.77% . 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 . (2) In the first quarter of 2016, we adopted ASU-2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The weighted average borrowings outstanding under the unsecured revolving credit facility were $154.9 million with a weighted average interest rate of 1.9% during 2016 compared with $ 165.5 million and 1.9% , respectively, during 2015 . Our maximum outstanding borrowings were $204.0 million and $218.0 million during 2016 and 2015 , respectively. At December 31, 2016 , outstanding borrowings under the unsecured revolving credit facility were $144.0 million with a weighted average interest rate of 2.2% . Our outstanding borrowings under the unsecured revolving credit facility do not include $ 2.4 million of unamortized deferred financing costs that are deducted from the facility’s balance in the December 31, 2016 consolidated balance sheet in accordance with ASU 2015-03, which we adopted in the first quarter of 2016. At December 31, 2016 , LIBOR was 0.77% and the applicable spread on our unsecured revolving credit facility was 150 basis points. The available capacity under the unsecured revolving credit facility was $150.9 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, 2016 , we were in compliance with all the financial covenants of the unsecured revolving credit facility. (d) Interest Rate Swap Agreements At December 31, 2016 , we fixed LIBOR, at a weighted average interest rate of 1.4% , on $ 240.0 million of our variable rate debt through nine interest rate swap agreements. In July 2016, two swaps that together fixed LIBOR at a weighted average interest rate of 1.8% on $60.0 million of variable rate debt expired. See note 11 , Derivative Instruments , for more information about our interest rate swap agreements. (e) Financial Covenants The credit agreement governing our unsecured revolving credit facility and unsecured term loan contains various restrictive covenants, including with respect to liens, indebtedness, investments, distributions, mergers and asset sales. 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 under the agreement to be immediately due and payable 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, 2016 , we were in compliance with the covenants of our amended, restated and consolidated unsecured revolving credit facility and unsecured term loan, the 440 First Street, NW Construction Loan and the Northern Virginia Construction 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, 2016 , the applicable interest rate spreads on the unsecured revolving credit facility and the unsecured term loan will remain unchanged. (f) Aggregate Debt Maturities Our aggregate debt maturities as of December 31, 2016 , are as follows (dollars in thousands): Debt Maturities 2017 $ 97,672 2018 2,354 2019 181,055 2020 137,203 2021 101,598 Thereafter 223,525 Total contractual principal balance $ 743,407 Financing costs related to long-term debt are deferred and amortized over the remaining life of the debt using the effective interest method. These costs are presented as a direct deduction from the carrying value of the respective debt liability (dollars in thousands). Deferred Financing Costs 2017 $ 1,540 2018 1,399 2019 1,365 2020 400 2021 400 Thereafter 1,132 Total deferred financing costs $ 6,236

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2016
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 2016 , 2015 and 2014 . 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, 2016 , we fixed LIBOR at a weighted average interest rate of 1.4% on $240.0 million of our variable rate debt through nine interest rate swap agreements that are summarized below (dollars in thousands): Maturity Date Notional Amount Interest Rate Contractual Component Fixed LIBOR Interest Rate 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 $ 240,000 1.442 % In July 2016, two swap agreements that together fixed LIBOR at a weighted average interest rate of 1.8% on $60.0 million of variable rate debt expired. Amounts reported in “Accumulated other comprehensive loss” on our consolidated balance sheet at December 31, 2016 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 $ 2.8 million , $4.0 million and $4.1 million in 2016 , 2015 and 2014 , respectively. At December 31, 2016 , we estimated that $0.9 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, 2016
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, 2016 and 2015 (dollars in thousands): Balance at December 31, 2016 Level 1 Level 2 Level 3 Recurring Measurements: Derivative instrument-swap liabilities $ 906 $ — $ 906 $ — 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 — 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, 2016 and 2015. 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, 2016 and 2015. 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 March 2016, we sold 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 for the fourth quarter of 2015, and we recorded an additional loss on the sale of $1.2 million in the first quarter of 2016. See note 9 , Dispositions for more information. CACI International, which fully leased One Fair Oaks in our Northern Virginia reporting segment, had a lease that terminated on December 31, 2016. In connection with our fourth quarter reporting for 2015, we evaluated the potential loss of cash flow at One Fair Oaks and the anticipated challenges of re-leasing the property, and as a result, we 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. On January 9, 2017 , we sold One Fair Oaks for net proceeds of $13.3 million . See note 9 , Dispositions for more information. We incurred impairment charges of $ 2.8 million , $60.8 million and $4.0 million during 2016, 2015 and 2014, respectively. The total impairment charges incurred during 2016 related to our sale of Storey Park in July 2016 and during 2015 related to the aforementioned NOVA Non-Core Portfolio and One Fair Oaks, which are all 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. See note 9 , Dispositions , for more information. Interest Rate Derivatives At December 31, 2016 , we had hedged $240.0 million of our variable rate debt through nine 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): 2016 2015 Carrying Value (1) Fair Value Carrying Value (1) Fair Value Financial Assets: Notes receivable (2) $ — $ — $ 34,000 $ 34,000 Financial Liabilities: Mortgage debt (3) $ 299,407 $ 300,927 $ 312,216 $ 298,541 Unsecured term loan 300,000 300,000 300,000 300,000 Unsecured revolving credit facility 144,000 144,000 120,000 120,000 Total $ 743,407 $ 744,927 $ 732,216 $ 718,541 (1) In the first quarter of 2016, we adopted 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 respective debt liability and which is applied on a retrospective basis. The debt balances exclude a combined total of $ 6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively. (2) The note receivable was prepaid on June 2, 2016 . See note 5 , Notes Receivable , for more information regarding the prepayment of the note receivable. (3) Includes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9 , Dispositions for more information.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
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, 2016 are as follows (dollars in thousands): Future minimum contractual rent payments 2017 $ 114,009 2018 106,865 2019 96,101 2020 82,139 2021 66,787 Thereafter 195,825 $ 661,726 Our consolidated properties were 92.6% occupied by 384 tenants at December 31, 2016 . We do not include square footage of properties in development or redevelopment in our occupancy calculation. At December 31, 2016, none of our 6.7 million square feet owned through our properties was in development or redevelopment. 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 . Subsequent to commencement of the sublease, we entered into two amendments to the sublease, which expanded the subleased premise by 4,000 square feet with the last sublease amendment commencing in December 2015. The subtenant’s lease will expire in January 2018 . Rent expense incurred under the terms of the corporate office leases, net of subleased revenue, was $1.5 million , $1.6 million and $1.8 million for the years ended December 31, 2016, 2015 and 2014. Future minimum rental payments under our corporate office leases as of December 31, 2016 are summarized as follows, net of sublease revenue (dollars in thousands): Future minimum rent payments 2017 $ 1,469 2018 1,906 2019 1,995 2020 2,049 2021 175 $ 7,594 (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, 2016 , we had contractual construction in progress obligations, which included amounts accrued at December 31, 2016 , of $3.1 million . The amount of contractual construction in progress obligations are primarily related to development activities at 540 Gaither Road at Redland in our Maryland reporting segment. As of December 31, 2016 , we had contractual rental property and furniture, fixtures and equipment obligations of $5.5 million outstanding, which included amounts accrued at December 31, 2016 . The amount of contractual rental property and furniture, fixtures and equipment obligations at December 31, 2016 are related to tenant improvement and capital improvement costs for various properties across our reporting segments, including significant tenant improvements at Atlantic Corporate Park and capital improvements at 11 Dupont Circle, NW. 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, 2016 , we remained liable to those local municipalities for $2.3 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, 2016
Equity [Abstract]
Equity	14 ) Equity In December 2015, our Board of Trustees authorized the redemption of some or all of our 6.4 million outstanding 7.750% Series A Preferred Shares. On January 19, 2016 and April 27, 2016 , we used proceeds from dispositions to redeem 2.2 million shares and 3.6 million shares, respectively, of our 7.750% Series A Preferred Shares at a redemption price of $25.00 per share, plus accrued dividends up to the applicable dates of redemption. On July 6, 2016 , we used proceeds from the repayment of the 950 F Street, NW mezzanine loan to redeem the remaining 0.6 million outstanding shares of our 7.750% Series A Preferred Shares at a redemption price of $25.00 per share, plus accrued dividends up to the date of redemption. The 7.750% Series A Preferred Shares (NYSE: FPO-PA) were delisted from trading on the New York Stock Exchange (the “NYSE”) upon redemption of the remaining 0.6 million outstanding shares on July 6, 2016. In July 2015, our Board of Trustees authorized a share repurchase program that allowed 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 were not obligated to acquire any particular amount of common shares and the share repurchase program was subject to suspension 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 proceeds from dispositions. During the year ended December 31, 2016, we did not repurchase any common shares under the share repurchase program. We are no longer authorized to repurchase common shares under the previously authorized share repurchase program, which expired at the end of July 2016. We declared and paid total dividends of $0.45 per common share to common shareholders during 2016 and $0.60 per common share to common shareholders during both 2015 and 2014 . During 2016, we declared and paid accrued dividends at a rate of 7.750% on the $25 face value per share of our 7.750% Series A Preferred Shares. The 7.750% Series A Preferred Shares were redeemed during 2016 with the last redemption occurring on July 6, 2016, at which time our 7.750% Series A Preferred Shares were delisted from the NYSE. All 7.7 50% Series A Preferred Shares redeemed during 2016 received a payment of dividends accrued up to, but not including, their applicable date of redemption. We declared and pai d dividends of $1.9375 per share on our Series A Preferred Shares during both 2015 and 2014. On January 24, 2017 , we declared a dividend of $0.10 per common share, equating to an annualized dividend of $0.40 per common share. The dividend was paid on February 15, 2017 to common shareholders of record as of February 8, 2017 . Dividends on all non-vested share awards are recorded as a reduction of shareholders’ equity. For each dividend paid by us on our common shares and, when applicable, preferred shares, the Operating Partnership distributes an equivalent distribution on our common and preferred Operating Partnership units, respectively. Our unsecured revolving credit facility and unsecured term loan, the 440 First Street, NW Construction Loan and the Northern Virginia Construction 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. 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 2016 , 2015 and 2014 are as follows: Common Shares Preferred Shares 2016 2015 2014 2016 2015 2014 Ordinary income (1) — % 52.01 % 72.42 % — % 72.89 % 100.00 % Return of capital 100.00 % 28.64 % 27.58 % 100.00 % — % — % 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, 2016
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, 2016, 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 $27.9 million . At December 31, 2016 and 2015, we recorded adjustments of $ 6.1 million and $4.0 million , respectively, to present certain common Operating Partnership units at the greater of their carrying value or redemption value. We owned 95.8% of the outstanding common Operating Partnership units at December 31, 2016 and 95.7% of the outstanding common Operating Partnership units at December 31, 2015 and 2014 . At December 31, 2016, 2,545,602 of the total common Operating Partnership units, or 4.2% , were not owned by us. During 2016 and 2015, 73,467 and 11,508 common Operating Partnership units, respectively were redeemed with available cash. There were no common Operating Partnership units redeemed for cash in 2014. No common Operating Partnership units were redeemed for common shares in 2016, 2015 or 2014. 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, 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 Net loss (428 ) Changes in ownership, net 957 Distributions to owners (1,166 ) Other comprehensive income 68 Balance at December 31, 2016 $ 28,244 (b) Noncontrolling Interests in a Consolidated Partnership 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” on our consolidated statements of operations. On August 4, 2011, we formed a joint venture, in which we had a 97% interest, with an affiliate of Perseus Realty, LLC to acquire Storey Park in our Washington, D.C. reporting segment, which was placed into development in August 2013. Storey Park was sold July 25, 2016 , at which time all assets and liabilities owned by the joint venture were either sold or settled at the time of disposition and the remaining proceeds from the sale were distributed to the joint venture partners in accordance with the terms of the joint venture agreement. See note 9 , Dispositions , for more information.

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Benefit Plans	Benefit Plans (a) Share-Based Payments We have 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, 2013 and 2016. In 2016 and 2011, we received shareholder approval to authorize an additional 4.1 million and 4.5 million shares, respectively, 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, 2016 , we had 11.5 million share equity awards authorized under the 2009 Plan and, of those awards, 4.8 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, 2016 , 2.4 million stock options have been awarded of which 0.9 million stock options remained outstanding. During the first quarter of 2016, we issued 95,000 stock options to our non-officer employees. The stock options have a ten -year contractual life and vest 25% on the first anniversary of the date of grant and 6.25% in each subsequent calendar quarter. We recognized compensation expense associated with stock option awards in the amount of $0.2 million , $1.2 million and $0.5 million for the years ended December 31, 2016, 2015 and 2014, respectively. 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, 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 Granted 95,000 11.03 Expired (11,850 ) 26.60 Forfeited (140,851 ) 12.87 Outstanding at December 31, 2016 905,437 $ 14.34 4.7 years $ 35,700 Exercisable at December 31: 2016 773,067 $ 14.81 4.1 years $ 35,700 2015 805,259 15.06 5.6 years 59,002 2014 552,620 16.49 5.1 years 102,039 Options expected to vest, subsequent to December 31, 2016 110,528 $ 11.64 8.3 years $ — The following table summarizes information about our stock options at December 31, 2016 : 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 2007 $ 29.11 - 29.24 21,500 0.0 years $ 29.14 21,500 $ 29.14 2008 17.29 22,250 1.0 year 17.29 22,250 17.29 2009 9.30 21,377 2.0 years 9.30 21,377 9.30 2010 12.57 25,892 3.0 years 12.57 25,892 12.57 2011 17.12 27,500 4.0 years 17.12 27,500 17.12 2012 13.54 - 15.00 537,750 3.9 years 14.90 537,750 14.87 2013 12.73 43,686 6.0 years 12.73 40,975 12.73 2014 11.61 61,936 7.0 years 11.61 42,743 11.61 2015 12.48 75,046 8.0 years 12.48 33,080 12.48 2016 11.03 68,500 9.0 years 11.03 — 11.03 905,437 4.7 years 14.34 773,067 14.81 As of December 31, 2016 , we had $0.2 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: 2016 2015 2014 Risk-free interest rate 1.73 % 1.61 % 1.72 % Expected volatility 27.0 % 29.2 % 39.0 % Expected dividend yield 3.63 % 4.79 % 4.66 % 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 2016, 2015 and 2014 was $1.87 , $1.96 and $2.67 , respectively. Option Exercises No options were exercised during 2016. We received $26 thousand and $174 thousand from the exercise of stock options during 2015 and 2014, 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 and $43 thousand during 2015 and 2014, respectively. 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 January 2016, we granted a total of 290,000 non-vested common shares to our executive officers. The awards have a five-year term and vest in one-quarter increments on the second through fifth anniversaries of the grant date. In February 2016, we granted a total of 103,429 non-vested common shares to our officers, which will vest ratably on an annual basis over a three-year period from the grant date. In July 2016, we granted a total of 181,357 non-vested performance-based common shares to our officers. The number of shares that will be earned will be determined at the end of 2018, based upon the achievement of specified market performance goals measured over the performance period from February 22, 2016 (the date we announced our 2016 Strategic Plan) through December 31, 2018. Of the shares earned, 50% will vest on February 1, 2019 and the remaining earned shares will vest on February 1, 2020. Any shares that are not earned will be forfeited. 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. 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 2016, we granted 36,828 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 2017 annual meetings of our shareholders, subject to continued service by the trustee until that date. In October 2016, our Board of Trustees appointed a new non-employee trustee. We granted 3,508 non-vested common shares to the new trustee, which will vest on the earlier of May 24, 2017 or the date of our 2017 annual meetings of our shareholders, subject to continued service by the trustee until that date. We recognized $0.3 million of compensation expense associated with trustee restricted share awards for the year ended December 31, 2016, and $0.4 million for both years ended December 31, 2015 and 2014. We recognized a total $2.1 million , $3.6 million and $3.2 million of compensation expense associated with all of our non-vested common share awards in 2016, 2015 and 2014, respectively. Compensation expense associated with our non-vested common shares for 2015 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. 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. A summary of our non-vested common share awards at December 31, 2016 is as follows: Non-vested Shares Weighted Average Grant Date Fair Value 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 Granted 615,122 9.40 Vested (91,007 ) 12.14 Expired (1,630 ) 12.21 Forfeited (3,493 ) 9.54 Non-vested at December 31, 2016 711,374 $ 9.85 As of December 31, 2016 , we had $4.9 million of unrecognized compensation cost related to non-vested common shares. We anticipate this cost will be recognized over a weighted average period of 3.2 years . We value our non-vested time-based awards issued in 2016, 2015 and 2014 at the grant date fair value, which is the market price of our common shares. For the non-vested performance-based common share awards granted in July 2016, 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 years, which ranged from 0.48% to 0.96% , respectively. The volatility used for our common share price in the Monte Carlo Simulation varied between 24.10% and 26.20% . 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 2016, 2015 and 2014 were $ 9.40 , $11.79 and $12.84 , respectively. The total fair value of shares vested were $1.1 million , $5.3 million and $2.0 million during 2016, 2015 and 2014, 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, 2016, 2015 and 2014, 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 $0.5 million for the year ended December 31, 2016 and $0.6 million for both of the years ended December 31, 2015 and 2014. The employer match payable to the 401(k) plan was fully funded as of December 31, 2016. (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 7,585 , 5,843 and 8,950 under the Plan during the years ended December 31, 2016, 2015 and 2014, respectively, which resulted in compensation expense totaling $10 thousand , $11 thousand and $20 thousand , respectively.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2016
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 reporting in their operating results other than the impact of straight-line revenue and the amortization deferred market rents, deferred lease incentives and deferred tenant improvement reimbursements. 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): 2016 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings 6 34 15 19 74 Square feet 918,266 1,886,183 1,885,958 2,023,858 6,714,265 Total revenues $ 45,062 $ 44,710 $ 40,658 $ 29,904 $ 160,334 Property operating expense (11,538 ) (9,794 ) (9,716 ) (7,506 ) (38,554 ) Real estate taxes and insurance (9,375 ) (3,881 ) (4,075 ) (2,477 ) (19,808 ) Total property operating income $ 24,149 $ 31,035 $ 26,867 $ 19,921 101,972 Depreciation and amortization expense (60,862 ) General and administrative (16,976 ) Impairment of rental property (2,772 ) Other expense (22,931 ) Net loss $ (1,569 ) Total assets (1) $ 445,528 $ 332,655 $ 302,769 $ 161,563 $ 1,260,247 Capital expenditures (2) $ 13,971 $ 5,308 $ 33,847 $ 3,269 $ 56,931 2015 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (3) 6 34 40 19 99 Square feet (3) 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 loss $ (35,024 ) Total assets (1)(4) $ 517,928 $ 341,375 $ 374,299 $ 167,447 $ 1,442,406 Capital expenditures (2) $ 12,930 $ 9,003 $ 43,125 $ 7,961 $ 73,850 2014 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (3) 6 38 49 38 131 Square feet (3) 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 (1)(4) $ 503,530 $ 359,603 $ 439,803 $ 228,234 $ 1,612,300 Capital expenditures (2) $ 23,422 $ 10,185 $ 7,816 $ 8,436 $ 50,789 (1) 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 . Corporate assets not allocated to any of our reportable segments totaled $ 17,732 , $ 41,357 and $ 81,130 at December 31, 2016 , 2015 and 2014 , respectively. (2) Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $536 , $831 and $ 930 at December 31, 2016 , 2015 and 2014 , respectively. (3) Excludes Storey Park, our 97% owned consolidated joint venture within our Washington, DC reporting segment, which was in development during 2014 and 2015 and was sold in July 2016. (4) Total assets at December 31, 2015 and 2014 have been restated to exclude a total of $ 7.9 million and $ 6.2 million , respectively of unamortized deferred financing costs that are now deducted from the respective debt liability in accordance with ASU 2015-03, which we adopted in the first quarter of 2016.

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (unaudited)	Quarterly Financial Information (unaudited) 2016 (1) First Second Third Fourth (amounts in thousands, except per share amounts) Quarter Quarter Quarter Quarter Revenues $ 42,697 $ 38,493 $ 40,172 $ 38,972 Operating expenses 36,337 35,681 32,295 34,658 Operating income 6,360 2,812 7,877 4,314 (Loss) income from continuing operations (101 ) (1,992 ) 2,242 (1,717 ) Less: Net loss (income) attributable to noncontrolling interests 147 390 (107 ) 71 Net income (loss) attributable to First Potomac Realty Trust 46 (1,602 ) 2,135 (1,646 ) Less: Dividends on preferred shares (2,248 ) (794 ) (11 ) — Less: Issuance costs on redeemed preferred shares (1,904 ) (3,095 ) (517 ) — Net (loss) income attributable to common shareholders $ (4,106 ) $ (5,491 ) $ 1,607 $ (1,646 ) Basic and diluted earnings per common share: Net (loss) income $ (0.07 ) $ (0.10 ) $ 0.03 $ (0.03 ) 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 from discontinued operations (607 ) — — — Less: Net loss (income) attributable to noncontrolling interests 112 114 (38 ) 1,870 Net income (loss) 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 from discontinued operations (0.01 ) — — — Net (loss) income $ (0.04 ) $ (0.04 ) $ 0.01 $ (0.72 ) (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 2016 or 2015. 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, 2016
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, 2016 (Amounts in thousands) Property Location (1) Date Acquired Property Type (2) Encumbrances at December 31, 2016 (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 II & III Rockville Nov 2010 Office 63,214 TenThreeTwenty Columbia Feb 2011 Office — Hillside I and II Columbia Nov 2011 Office — 540 Gaither Road (Redland I) Rockville Oct 2013 Office — Total Maryland 63,214 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 28,503 840 First Street, NE NoMA Mar 2011 Office 35,201 1401 K Street, NW East End Apr 2014 Office 35,556 11 Dupont Circle, NW CBD Sep 2014 Office 66,780 Total Washington, D.C. 198,256 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 — 1775 Wiehle Avenue Reston Jun 2014 Office — Northern Virginia build-to-suit Northern Virginia 34,584 Total Northern Virginia 34,584 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 3,353 Greenbrier Towers Chesapeake Jul 2011 Office — Total Southern Virginia 3,353 Land held for future development — Other — Total Consolidated Portfolio $ 299,407 Initial Costs Gross Amount at End of Year Land Building and Improvements Since Acquisition Land Building and Improvements Total Accumulated Depreciation $ 3,404 $ 12,824 $ 5,159 $ 3,404 $ 17,983 $ 21,387 $ 7,878 9,220 32,056 3,138 9,220 35,194 44,414 11,175 18,302 20,562 9,049 18,302 29,611 47,913 8,741 5,673 17,168 12,946 5,672 30,115 35,787 10,750 2,398 7,659 6,763 2,398 14,422 16,820 6,275 6,101 12,602 681 6,102 13,282 19,384 3,267 7,097 14,211 3,144 7,097 17,355 24,452 3,539 17,272 63,480 15,134 17,271 78,615 95,886 19,109 2,041 5,327 14,403 2,041 19,730 21,771 4,626 3,302 10,926 3,618 3,301 14,545 17,846 1,759 6,458 19,831 616 6,753 20,152 26,905 3,346 81,268 216,646 74,651 81,561 291,004 372,565 80,465 25,806 33,883 628 25,995 34,322 60,317 7,048 — 15,300 51,633 9,122 57,811 66,933 7,279 27,077 17,520 11,937 27,077 29,457 56,534 4,790 16,846 60,905 9,879 16,846 70,784 87,630 12,618 29,506 23,269 12,809 29,506 36,078 65,584 2,875 15,744 64,832 5,788 15,744 70,620 86,364 5,147 114,979 215,709 92,674 124,290 299,072 423,362 39,757 6,265 35,433 7,548 6,265 42,981 49,246 20,515 3,940 12,547 4,417 3,940 16,964 20,904 6,037 14,656 10,750 23,482 20,010 28,878 48,888 10,410 1,614 3,611 2,871 1,646 6,450 8,096 2,133 — 13,653 24,608 4,181 34,080 38,261 9,639 5,895 11,655 22,080 5,895 33,735 39,630 7,057 3,542 30,575 211 3,541 30,786 34,328 3,370 5,241 — 49,343 — 54,584 54,584 — 41,153 118,224 134,560 45,478 248,458 293,937 59,161 5,160 23,660 14,124 5,160 37,784 42,944 17,333 1,365 5,119 1,347 1,365 6,466 7,831 2,921 1,323 4,967 1,411 1,324 6,377 7,701 2,936 1,036 6,254 1,503 1,036 7,757 8,793 2,606 1,221 8,693 4,387 1,221 13,080 14,301 5,459 4,447 24,739 4,582 4,815 28,953 33,768 8,871 2,657 11,597 2,875 2,646 14,483 17,129 4,990 1,292 3,899 756 1,292 4,655 5,947 1,703 1,320 2,293 610 1,320 2,904 4,223 1,060 4,164 18,984 6,113 4,164 25,097 29,261 7,338 2,024 7,960 2,381 2,024 10,341 12,365 3,465 1,860 6,071 804 1,881 6,854 8,735 1,414 2,997 9,173 6,406 2,997 15,579 18,576 3,024 30,866 133,409 47,299 31,245 180,330 211,574 63,120 343 — 6 349 — 349 — — — 47 — 47 47 59 $ 268,609 $ 683,988 $ 349,237 $ 282,923 $ 1,018,911 $ 1,301,834 $ 242,562 (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. 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 $1,435 million and $1,547 million at December 31, 2016 and 2015, respectively. (a) Reconciliation of Rental Property (1) The following table reconciles the rental property investments for the years ended December 31 (amounts in thousands): 2016 2015 2014 Beginning balance $ 1,340,050 $ 1,504,372 $ 1,330,180 Acquisitions of rental property (2) — — 170,823 Capital expenditures (3) 56,030 73,125 49,860 Impairments — (51,521 ) (3,956 ) Dispositions of rental property (55,625 ) (59,652 ) (30,916 ) Assets held-for-sale (19,407 ) (127,907 ) (643 ) Other (4) (19,214 ) 1,633 (10,976 ) Ending balance $ 1,301,834 $ 1,340,050 $ 1,504,372 (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): 2016 2015 2014 Beginning balance $ 209,784 $ 215,499 $ 185,725 Depreciation of rental property 44,952 49,772 47,625 Assets held-for-sale 31,034 (16,400 ) (1,631 ) Dispositions of rental property (37,001 ) (35,964 ) (5,712 ) Other (4) (6,207 ) (3,123 ) (10,508 ) Ending balance $ 242,562 $ 209,784 $ 215,499 (1) Excludes rental property and applicable accumulated depreciation at December 31, 2016 related to the One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017. Also excludes the rental property and applicable accumulated depreciation at December 31, 2015 related to the NOVA Non-Core Portfolio, which was classified as held-for-sale at December 31, 2015 and was sold on March 24, 2016. (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, 2016
Accounting Policies [Abstract]
Principles of Consolidation	(a) Principles of Consolidation Our consolidated financial statements include our accounts and the accounts of our Operating Partnership, which we consider to be a variable interest entity (“VIE”), 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, 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 2016 , 2015 and 2014 , we incurred charges of $0.8 million , $0.6 million and $1.1 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 , $0.1 million and $1.1 million for the years ended December 31, 2016 , 2015 and 2014 , 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 Policy [Text Block]	(f) Deferred Costs 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 $26.3 million and $22.0 million at December 31, 2016 and 2015 , respectively. The following table sets forth scheduled future amortization for deferred leasing costs at December 31, 2016 (amounts in thousands): Deferred Leasing (1) Deferred Lease Incentive (2) 2017 $ 5,464 $ 1,500 2018 4,915 1,473 2019 4,118 1,399 2020 3,363 1,327 2021 2,649 1,265 Thereafter 6,689 6,006 $ 27,198 $ 12,970 (1) Excludes the amortization of $1.8 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. (2) Excludes the amortization of $0.7 million of lease incentive 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 lease incentive 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 binding contract pursuant to which the buyer has significant money at risk, or 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 the following properties are reflected within discontinued operations in our consolidated statements of operations for all periods presented: (i) all properties that were sold prior to the adoption of ASU 2014-08; (ii) 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; and (iii) 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”). 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 2016 , 2015 and 2014 . 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 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 depreciable life of the venture’s assets 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 account 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, 2016 , 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 2016 , 2015 and 2014 .
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 2016 , 2015 and 2014 . 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, 2016 , 2015 and 2014 , 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 record loans to owners of real estate properties, which can be collateralized by interest in the real estate property, as “Notes receivable” in our consolidated balance sheets. These 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. Any 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. During the second quarter of 2016, we received the full repayment of a mezzanine loan with an outstanding principal balance of $34.0 million . We did not have any notes receivable outstanding at December 31, 2016. Based on the review of the above criteria, we did not record an allowance for credit losses for our notes receivable during 2016, 2015 and 2014 .
Application of New Accounting Standards	(p) Application of New Accounting Standards In January 2016, we adopted 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. The adoption of ASU 2015-01 did not have a material impact on our consolidated financial statements and related disclosures. In January 2016, we adopted ASU No. 2015-02, Amendments to the Consolidation Analysis (“ASU 2015-02”). This standard amends certain guidance applicable to the consolidation of various legal entities, including VIEs. In determining the method of accounting for partially owned joint ventures, we evaluate the characteristics of associated entities and determine whether an entity is a VIE and, if so, determine which party is the primary beneficiary by analyzing whether we have both the power to direct the entity's significant economic activities and the obligation to absorb potentially significant losses or receive potentially significant benefits. Significant judgments and assumptions inherent in this analysis include the nature of the entity's operations, the entity's financing and capital structure, and contractual relationship and terms, including consideration of governance and decision making rights. We consolidate a VIE when we have determined that we are the primary beneficiary. We evaluated the application of ASU 2015-02 and concluded that no change was required to our accounting for any of our interests in less-than-wholly owned joint ventures. We continued to consolidate our joint venture in Storey Park, which was sold on July 25, 2016, as described in note 15 (b), Noncontrolling Interests in a Consolidated Partnership , as it continued to meet the definition and certain criteria as a VIE in which we were considered to be the primary beneficiary. Under ASU 2015-02, our Operating Partnership now meets the definition of a VIE, we are the primary beneficiary, and, accordingly, we continue to consolidate the Operating Partnership. Our sole significant asset is our investment in the Operating Partnership and, consequently, substantially all of our assets and liabilities represent assets and liabilities of the Operating Partnership. All of our debt is an obligation of the Operating Partnership and may only be settled with the assets of the Operating Partnership. In January 2016, we adopted 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 applied on a retrospective basis, which resulted in the reclassification of our debt issuance costs from previously presented balances. The guidance did not have a material impact on our consolidated financial statements and related disclosures. In January 2016, we adopted 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. The adoption of ASU 2015-16 did not have a material impact on our consolidated financial statements and related disclosures. 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 begun to evaluate each of the revenue streams under the new model and the pattern of recognition is not expected to change significantly. 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 became 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 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. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (“ASU 2016-02”), which requires a lessee to record on the balance sheet a right-of-use asset with a corresponding lease liability created by lease terms of more than 12 months. Additional qualitative and quantitative disclosures will also be required. The guidance will become effective for periods beginning after December 15, 2018 and will be applied using a modified retrospective transition method. We are currently evaluating the impact that ASU 2016-02 will have on our consolidated financial statements and related disclosures. In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”) , which is intended to simplify several aspects of the accounting for employee share-based payment transactions, including income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. The guidance became effective for periods beginning after December 15, 2016 and early adoption is permitted. ASU 2016-09 permits the use of the cumulative-effect and prospective methods. The guidance is not expected to have a material impact on our consolidated financial statements and related disclosures. In August 2016, the FASB issued Accounting Standards Update No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) . The guidance addresses eight classification issues related to the statement of cash flows, including debt prepayment or debt extinguishment costs and distributions received from equity-method investees. The guidance will become effective for periods beginning after December 15, 2017 and early adoption is permitted. ASU 2016-15 requires the use of a retrospective transition method to each period presented. If such retrospective transition is impracticable for certain issues, the adoption of ASU 2016-15 for the applicable issues may be applied prospectively as of the earliest date practicable. The guidance is not expected to have a material impact on our consolidated financial statements or related disclosures. In October 2016, the FASB issued Accounting Standards Update No. 2016-17, Consolidation (Topic 810): Interests Held through Related Parties That Are under Common Control (“ASU 2016-17”), which requires a single decision maker or service provider, in evaluating whether it is the primary beneficiary, to consider on a proportionate basis indirect interests held through related parties under common control. ASU 2016-17 was effective for periods beginning after December 15, 2016. ASU 2016-17 requires the use of a retrospective transition method beginning with the earliest annual period in which ASU 2015-02 was adopted. The adoption of ASU 2016-17 will not have a material impact on our consolidated financial statements or related disclosures. In November 2016, the FASB issued Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASU 2016-18”), which requires companies to include cash and cash equivalents that have restrictions on withdrawal or use in total cash and cash equivalents on the statement of cash flows. ASU 2016-18 is effective for periods beginning after December 15, 2017 and early adoption is permitted. The guidance is not expected to have a material impact on our consolidated financial statements and related disclosures. (q) Reclassifications Certain prior year asset and debt balances have been reclassified to conform to the current year presentation as a result of adopting ASU 2015-03 in January 2016, which requires debt issuance costs to be presented in the balance sheet as a direct deduction from the carrying value of the debt liability and which is applied on a retrospective basis. See note 2(p), Summary of Significant Accounting Policies - Application of New Accounting Standards for more information.
Reclassifications Policy [Text Block]	(q) Reclassifications Certain prior year asset and debt balances have been reclassified to conform to the current year presentation as a result of adopting ASU 2015-03 in January 2016, which requires debt issuance costs to be presented in the balance sheet as a direct deduction from the carrying value of the debt liability and which is applied on a retrospective basis. See note 2(p), Summary of Significant Accounting Policies - Application of New Accounting Standards for more information.

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Scheduled Future Amortization for Deferred Financing and Leasing Costs	The following table sets forth scheduled future amortization for deferred leasing costs at December 31, 2016 (amounts in thousands): Deferred Leasing (1) Deferred Lease Incentive (2) 2017 $ 5,464 $ 1,500 2018 4,915 1,473 2019 4,118 1,399 2020 3,363 1,327 2021 2,649 1,265 Thereafter 6,689 6,006 $ 27,198 $ 12,970 (1) Excludes the amortization of $1.8 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. (2) Excludes the amortization of $0.7 million of lease incentive 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 lease incentive 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, 2016
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): 2016 2015 2014 Numerator for basic and diluted earnings per common share: (Loss) income from continuing operations $ (1,569 ) $ (34,417 ) $ 15,559 (Loss) income from discontinued operations — (607 ) 1,484 Net (loss) income (1,569 ) (35,024 ) 17,043 Less: Net loss (income) from continuing operations attributable to noncontrolling interests 502 2,032 (135 ) Less: Net loss (income) from discontinued operations attributable to noncontrolling interests — 26 (64 ) Net (loss) income attributable to First Potomac Realty Trust (1,067 ) (32,966 ) 16,844 Less: Dividends on preferred shares (3,053 ) (12,400 ) (12,400 ) Less: Issuance costs of redeemed preferred shares (1) (5,515 ) — — Net (loss) income attributable to common shareholders (9,635 ) (45,366 ) 4,444 Less: Allocation to participating securities (232 ) (241 ) (314 ) Net (loss) income attributable to common shareholders $ (9,867 ) $ (45,607 ) $ 4,130 Denominator for basic and diluted earnings per common share: Weighted average common shares outstanding – basic 57,581 57,982 58,150 Weighted average common shares outstanding – diluted 57,581 57,982 58,220 Basic and diluted earnings per common share: (Loss) income from continuing operations attributable to common shareholders $ (0.17 ) $ (0.78 ) $ 0.05 (Loss) income from discontinued operations attributable to common shareholders — (0.01 ) 0.02 Net (loss) income $ (0.17 ) $ (0.79 ) $ 0.07
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): 2016 2015 2014 Stock option awards 960 1,020 1,122 Non-vested share awards 669 310 398 1,629 1,330 1,520

Rental Property (Tables)

Rental Property (Tables)	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Summary of Rental Property	Rental property consists of the following at December 31 (dollars in thousands): 2016 (1) 2015 (2) Land and land improvements $ 282,923 $ 280,149 Buildings and improvements 824,867 793,184 Construction in progress 4,605 97,361 Tenant improvements 189,031 168,946 Furniture, fixtures and equipment 408 410 1,301,834 1,340,050 Less: accumulated depreciation (242,562 ) (209,784 ) $ 1,059,272 $ 1,130,266 (1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017. (2) 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 and was sold on March 25, 2016.

Investment in Affiliates (Table

Investment in Affiliates (Tables)	12 Months Ended
	Dec. 31, 2016
Equity Method Investments and Joint Ventures [Abstract]
Components of Investments in Affiliates	Our investment in affiliates consisted of the following (dollars in thousands): Reporting Segment Ownership Interest Investment at December 31, 2016 Investment at December 31, 2015 Prosperity Metro Plaza Northern Virginia 51 % $ 26,414 $ 24,909 1750 H Street, NW Washington, D.C. 50 % 14,625 15,168 Aviation Business Park (1) Maryland 50 % 5,941 5,899 Rivers Park I and II (1)(2) Maryland 25 % 2,413 2,247 $ 49,392 $ 48,223 (1) In January 2017, the unconsolidated joint ventures that own these properties entered into a binding contract to sell Aviation Business Park and Rivers Park I and II, which are all located in our Maryland reporting segment. We anticipate completing the sale in March 2017; however, we can provide no assurances regarding the timing or pricing of such sale, or that such sale will ultimately occur. (2) Rivers Park I and Rivers Park II are owned through two separate unconsolidated joint ventures.
mortgage debt of joint ventures [Table Text Block]	The following table provides a summary of the mortgage debt held by our unconsolidated joint ventures (dollars in thousands): FPO Ownership Effective Interest Rate Maturity Date Principal Balance at December 31, 2016 (1) Principal Balance at December 31, 2015 (1) Rivers Park I and II (2) 25% LIBOR + 1.90% (3) September 2017 $ 28,000 $ 28,000 1750 H Street, NW (4) 50% 3.92% August 2024 32,000 32,000 Prosperity Metro Plaza (5) 51% 3.91% December 2029 50,000 50,000 Weighted Average/Total 3.60% $ 110,000 $ 110,000 (1) Reflects the entire balance of the debt secured by the properties, not our portion of the debt. (2) The loan is repayable in full, without penalty, at any time during the term of the loan. Of the outstanding principal balance, $2.8 million is recourse to us. 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. (3) At December 31, 2016, LIBOR was 0.77% . All references to LIBOR in the financial statements refer to one-month LIBOR. (4) The loan requires interest-only payments with a constant interest rate over the life of the loan. The loan is repayable in full, without penalty, on or after August 1, 2021. (5) The loan requires interest-only payments through December 2024, at which time the loan requires principal and interest payments through its maturity date. The loan in repayable in full without penalty on or after June 1, 2029.
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): 2016 2015 Assets: Rental property, net $ 189,245 $ 193,243 Cash and cash equivalents 9,887 5,992 Other assets 20,726 16,490 Total assets 219,858 215,725 Liabilities: Mortgage loans, net (1)(2) 109,372 109,273 Other liabilities 8,674 7,214 Total liabilities 118,046 116,487 Net assets $ 101,812 $ 99,238
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 (dollars in thousands): 2016 2015 2014 Total revenues $ 24,704 $ 24,255 $ 23,285 Total operating expenses (7,770 ) (7,660 ) (7,408 ) Net operating income 16,934 16,595 15,877 Depreciation and amortization (8,044 ) (8,718 ) (9,893 ) Interest expense, net (3,995 ) (3,909 ) (3,890 ) Provision for income taxes — — (63 ) Contingent consideration charge — — 126 Net income $ 4,895 $ 3,968 $ 2,157

Intangible Assets and Deferre33

Intangible Assets and Deferred Market Rent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
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): 2016 2015 Gross Intangibles Accumulated Amortization Net Intangibles Gross Intangibles Accumulated Amortization Net Intangibles In-place leases $ 38,804 $ (25,423 ) $ 13,381 $ 45,901 $ (26,961 ) $ 18,940 Customer relationships 663 (663 ) — 663 (601 ) 62 Leasing commissions 9,499 (5,882 ) 3,617 10,612 (5,485 ) 5,127 Legal leasing fees 299 (193 ) 106 344 (177 ) 167 Deferred market rent assets 2,880 (1,808 ) 1,072 3,558 (1,825 ) 1,733 Goodwill 6,930 — 6,930 6,930 — 6,930 $ 59,075 $ (33,969 ) $ 25,106 $ 68,008 $ (35,049 ) $ 32,959 Deferred market rent liability $ 4,173 $ (2,381 ) $ 1,792 $ 4,869 $ (2,715 ) $ 2,154
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, 2016 are as follows (amounts in thousands): 2017 $ 4,114 2018 2,646 2019 2,361 2020 2,147 2021 1,463 Thereafter 3,653 $ 16,384

Dispositions (Tables)

Dispositions (Tables)	12 Months Ended
	Dec. 31, 2016
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): 2016 2015 2014 Revenues $ 11,156 $ 29,773 $ 31,027 Property operating expenses (4,307 ) (10,353 ) (11,055 ) Depreciation and amortization (1,070 ) (10,310 ) (11,289 ) Interest expense, net of interest income (436 ) (465 ) (843 ) Loss on debt extinguishment (48 ) — — Impairment of rental property (2,772 ) (60,826 ) — Income (loss) from operations of disposed property 2,523 (52,181 ) 7,840 (Loss) gain on sale of rental property (1,155 ) 29,477 21,230 Net income (loss) from continuing operations $ 1,368 $ (22,704 ) $ 29,070
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 One Fair Oaks (1) Northern Virginia 1/9/2017 Office 214,214 $ 13,255 Storey Park (2) Washington, D.C. 7/25/2016 Land — 52,659 NOVA Non-Core Portfolio (3) Northern Virginia 3/25/2016 Various 945,745 90,501 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 (1) Consists of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land.
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): 2016 2015 2014 Revenues $ — $ 877 $ 7,688 Property operating expenses — (638 ) (3,612 ) Depreciation and amortization — (1,222 ) (3,662 ) Net interest income (expense) — 8 (268 ) (Loss) income from operations of disposed property — (975 ) 146 Loss on debt extinguishment — (489 ) — Gain on sale of rental property — 857 1,338 Net (loss) income from discontinued operations $ — $ (607 ) $ 1,484

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Borrowings	Our borrowings consisted of the following at December 31 (dollars in thousands): 2016 (1) 2015 (1)(2) Mortgage loans, net effective interest rates ranging from 4.22% to 6.01%, maturing at various dates through September 2030 (3)(4) $ 296,212 $ 307,769 Unsecured term loan, net 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 (3) 299,404 299,404 Unsecured revolving credit facility, net effective interest rate of LIBOR plus 1.50%, maturing December 2019 (3) 141,555 116,865 $ 737,171 $ 724,038 (1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $ 6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively. (2) Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions , for further discussion. (3) At December 31, 2016 , LIBOR was 0.77% . All references to LIBOR in the consolidated financial statements refer to one-month LIBOR. (4) At December 31, 2016 and 2015, the mortgage loans balance includes two construction loans. At December 31, 2015, the mortgage loans balance includes two construction loans and the Storey Park Land Loan, which was repaid in July 2016.
Summary of Company's Mortgage Debt	The following table provides a summary of our mortgage debt, which includes two construction loans and, for the year ended December 31, 2015, the Storey Park Land Loan (dollars in thousands): Encumbered Property Contractual Interest Rate Effective Interest Rate Maturity Date December 31, 2016 December 31, 2015 Storey Park Land Loan (1)(2) LIBOR + 2.50% LIBOR + 2.50% October 2016 $ — $ 22,000 Hillside I and II (3) 5.75 % 4.62 % December 2016 — 12,368 440 First Street, NW Construction Loan (1)(4) LIBOR + 2.50% LIBOR + 2.50% May 2017 32,216 32,216 Redland II & III 4.20 % 4.64 % November 2017 63,214 64,543 Northern Virginia Construction Loan (1)(5) LIBOR + 1.85% LIBOR + 1.85% September 2019 34,584 9,176 840 First Street, NE 5.72 % 6.01 % July 2020 35,201 35,888 Battlefield Corporate Center 4.26 % 4.40 % November 2020 3,353 3,526 1211 Connecticut Avenue, NW 4.22 % 4.47 % July 2022 28,503 29,110 1401 K Street, NW 4.80 % 4.93 % June 2023 35,556 36,224 11 Dupont Circle, NW 4.05 % 4.22 % September 2030 66,780 66,780 Principal balance 4.41 % (6) 299,407 311,831 Unamortized fair value adjustments — 172 Unamortized deferred financing costs (7) (3,195 ) (4,234 ) Total balance, net $ 296,212 $ 307,769 Debt Classified within Liabilities Held-for-Sale Gateway Centre Manassas Building I (8) 7.35 % 5.88 % November 2016 $ — $ 212 Unamortized fair value adjustments — 1 Total balance, net $ — $ 213 (1) At December 31, 2016 , LIBOR was 0.77% . (2) The Storey Park Land Loan encumbered the Storey Park land and was entered into by our 97% owned consolidated joint venture that owned Storey Park. On July 25, 2016 , our consolidated joint venture sold Storey Park and the Storey Park Land Loan was concurrently repaid with proceeds from the sale. (3) On October 6, 2016 , we used available cash to prepay, without penalty, the Hillside I and II loan. (4) This construction loan (the “440 First Street, NW Construction Loan”) is collateralized by 440 First Street, NW. In May 2016, we extended the maturity date by one year to May 30, 2017 . We can repay all or a portion of the construction loan, without penalty, at any time during the term of the loan. At December 31, 2016, per the terms of the loan agreement, 50% of the outstanding principal balance and all of the outstanding accrued interest were recourse to us. (5) This construction loan has a borrowing capacity of up to $43.7 million and is collateralized by the NOVA build-to-suit (the “Northern Virginia Construction Loan”), which was placed in-service in August 2016. We can repay all or a portion of the Northern Virginia Construction loan, without penalty, at any time during the term of the loan. (6) Represents the weighted average interest rate on total mortgage debt. (7) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. (8) The mortgage loan that encumbered Gateway Centre Manassas, which was included in the NOVA Non-Core Portfolio and sold on March 25, 2016, was classified within “Liabilities held-for-sale” on our December 31, 2015 consolidated balance sheet. In February 2016, we used $ 0.2 million in available cash to defease the outstanding balance of the mortgage loan.
Originated or Assumed Mortgages	We have originated the following mortgage and construction loans since January 1, 2015 (dollars in thousands): Month Year Property Effective Interest Rate Principal Balance at December 31, 2016 September 2015 Northern Virginia Construction Loan LIBOR + 1.85% (1) $ 34,584 (2) August 2015 11 Dupont Circle, NW 4.22% 66,780 (1) At December 31, 2016, LIBOR was 0.77% . (2) The loan has a borrowing capacity of up to $43.7 million , of which we borrowed $25.4 million and $9.2 million during 2016 and 2015, respectively.
Repayment of Mortgages	We have repaid the following mortgage and land loans since January 1, 2015 (dollars in thousands): Month Year Property Effective Interest Rate Principal Balance Repaid October 2016 Hillside I and II 4.62 % $ 12,199 August 2016 Storey Park Land Loan LIBOR + 2.50% (1) 22,000 February 2016 Gateway Centre Manassas 5.88 % 174 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 (1) At December 31, 2016, LIBOR was 0.77% .
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, 2016 and 2015 (dollars in thousands): Maturity Date Interest Rate (1) December 31, 2016 December 31, 2015 Tranche A December 2020 LIBOR + 1.45% $ 100,000 $ 100,000 Tranche B June 2021 LIBOR + 1.45% 100,000 100,000 Tranche C December 2022 LIBOR + 1.80% 100,000 100,000 Total 300,000 300,000 Unamortized deferred financing costs (2) (596 ) (596 ) Total, net $ 299,404 $ 299,404 (1) At December 31, 2016 , LIBOR was 0.77% . 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, 2016 , are as follows (dollars in thousands): Debt Maturities 2017 $ 97,672 2018 2,354 2019 181,055 2020 137,203 2021 101,598 Thereafter 223,525 Total contractual principal balance $ 743,407 Financing costs related to long-term debt are deferred and amortized over the remaining life of the debt using the effective interest method. These costs are presented as a direct deduction from the carrying value of the respective debt liability (dollars in thousands). Deferred Financing Costs 2017 $ 1,540 2018 1,399 2019 1,365 2020 400 2021 400 Thereafter 1,132 Total deferred financing costs $ 6,236

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Swap Agreements	At December 31, 2016 , we fixed LIBOR at a weighted average interest rate of 1.4% on $240.0 million of our variable rate debt through nine interest rate swap agreements that are summarized below (dollars in thousands): Maturity Date Notional Amount Interest Rate Contractual Component Fixed LIBOR Interest Rate 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 $ 240,000 1.442 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 and 2015 (dollars in thousands): Balance at December 31, 2016 Level 1 Level 2 Level 3 Recurring Measurements: Derivative instrument-swap liabilities $ 906 $ — $ 906 $ — 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 —
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): 2016 2015 Carrying Value (1) Fair Value Carrying Value (1) Fair Value Financial Assets: Notes receivable (2) $ — $ — $ 34,000 $ 34,000 Financial Liabilities: Mortgage debt (3) $ 299,407 $ 300,927 $ 312,216 $ 298,541 Unsecured term loan 300,000 300,000 300,000 300,000 Unsecured revolving credit facility 144,000 144,000 120,000 120,000 Total $ 743,407 $ 744,927 $ 732,216 $ 718,541 (1) In the first quarter of 2016, we adopted 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 respective debt liability and which is applied on a retrospective basis. The debt balances exclude a combined total of $ 6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively. (2) The note receivable was prepaid on June 2, 2016 . See note 5 , Notes Receivable , for more information regarding the prepayment of the note receivable. (3) Includes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9 , Dispositions for more information.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 are as follows (dollars in thousands): Future minimum contractual rent payments 2017 $ 114,009 2018 106,865 2019 96,101 2020 82,139 2021 66,787 Thereafter 195,825 $ 661,726
Schedule of Future Minimum Rental Payments	Future minimum rental payments under our corporate office leases as of December 31, 2016 are summarized as follows, net of sublease revenue (dollars in thousands): Future minimum rent payments 2017 $ 1,469 2018 1,906 2019 1,995 2020 2,049 2021 175 $ 7,594

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Characterization of Company's Dividends	The characterization of the dividends declared on our common and preferred shares for 2016 , 2015 and 2014 are as follows: Common Shares Preferred Shares 2016 2015 2014 2016 2015 2014 Ordinary income (1) — % 52.01 % 72.42 % — % 72.89 % 100.00 % Return of capital 100.00 % 28.64 % 27.58 % 100.00 % — % — % 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, 2016
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, 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 Net loss (428 ) Changes in ownership, net 957 Distributions to owners (1,166 ) Other comprehensive income 68 Balance at December 31, 2016 $ 28,244

Benefit Plans (Tables)

Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
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, 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 Granted 95,000 11.03 Expired (11,850 ) 26.60 Forfeited (140,851 ) 12.87 Outstanding at December 31, 2016 905,437 $ 14.34 4.7 years $ 35,700 Exercisable at December 31: 2016 773,067 $ 14.81 4.1 years $ 35,700 2015 805,259 15.06 5.6 years 59,002 2014 552,620 16.49 5.1 years 102,039 Options expected to vest, subsequent to December 31, 2016 110,528 $ 11.64 8.3 years $ —
Stock Options Information	The following table summarizes information about our stock options at December 31, 2016 : 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 2007 $ 29.11 - 29.24 21,500 0.0 years $ 29.14 21,500 $ 29.14 2008 17.29 22,250 1.0 year 17.29 22,250 17.29 2009 9.30 21,377 2.0 years 9.30 21,377 9.30 2010 12.57 25,892 3.0 years 12.57 25,892 12.57 2011 17.12 27,500 4.0 years 17.12 27,500 17.12 2012 13.54 - 15.00 537,750 3.9 years 14.90 537,750 14.87 2013 12.73 43,686 6.0 years 12.73 40,975 12.73 2014 11.61 61,936 7.0 years 11.61 42,743 11.61 2015 12.48 75,046 8.0 years 12.48 33,080 12.48 2016 11.03 68,500 9.0 years 11.03 — 11.03 905,437 4.7 years 14.34 773,067 14.81
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: 2016 2015 2014 Risk-free interest rate 1.73 % 1.61 % 1.72 % Expected volatility 27.0 % 29.2 % 39.0 % Expected dividend yield 3.63 % 4.79 % 4.66 % 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, 2016 is as follows: Non-vested Shares Weighted Average Grant Date Fair Value 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 Granted 615,122 9.40 Vested (91,007 ) 12.14 Expired (1,630 ) 12.21 Forfeited (3,493 ) 9.54 Non-vested at December 31, 2016 711,374 $ 9.85

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
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): 2016 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings 6 34 15 19 74 Square feet 918,266 1,886,183 1,885,958 2,023,858 6,714,265 Total revenues $ 45,062 $ 44,710 $ 40,658 $ 29,904 $ 160,334 Property operating expense (11,538 ) (9,794 ) (9,716 ) (7,506 ) (38,554 ) Real estate taxes and insurance (9,375 ) (3,881 ) (4,075 ) (2,477 ) (19,808 ) Total property operating income $ 24,149 $ 31,035 $ 26,867 $ 19,921 101,972 Depreciation and amortization expense (60,862 ) General and administrative (16,976 ) Impairment of rental property (2,772 ) Other expense (22,931 ) Net loss $ (1,569 ) Total assets (1) $ 445,528 $ 332,655 $ 302,769 $ 161,563 $ 1,260,247 Capital expenditures (2) $ 13,971 $ 5,308 $ 33,847 $ 3,269 $ 56,931 2015 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (3) 6 34 40 19 99 Square feet (3) 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 loss $ (35,024 ) Total assets (1)(4) $ 517,928 $ 341,375 $ 374,299 $ 167,447 $ 1,442,406 Capital expenditures (2) $ 12,930 $ 9,003 $ 43,125 $ 7,961 $ 73,850 2014 Washington, D.C. Maryland Northern Virginia Southern Virginia Consolidated Number of buildings (3) 6 38 49 38 131 Square feet (3) 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 (1)(4) $ 503,530 $ 359,603 $ 439,803 $ 228,234 $ 1,612,300 Capital expenditures (2) $ 23,422 $ 10,185 $ 7,816 $ 8,436 $ 50,789 (1) 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 . Corporate assets not allocated to any of our reportable segments totaled $ 17,732 , $ 41,357 and $ 81,130 at December 31, 2016 , 2015 and 2014 , respectively. (2) Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $536 , $831 and $ 930 at December 31, 2016 , 2015 and 2014 , respectively. (3) Excludes Storey Park, our 97% owned consolidated joint venture within our Washington, DC reporting segment, which was in development during 2014 and 2015 and was sold in July 2016. (4) Total assets at December 31, 2015 and 2014 have been restated to exclude a total of $ 7.9 million and $ 6.2 million , respectively of unamortized deferred financing costs that are now deducted from the respective debt liability in accordance with ASU 2015-03, which we adopted in the first quarter of 2016.

Quarterly Financial Informati43

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Information	Quarterly Financial Information (unaudited) 2016 (1) First Second Third Fourth (amounts in thousands, except per share amounts) Quarter Quarter Quarter Quarter Revenues $ 42,697 $ 38,493 $ 40,172 $ 38,972 Operating expenses 36,337 35,681 32,295 34,658 Operating income 6,360 2,812 7,877 4,314 (Loss) income from continuing operations (101 ) (1,992 ) 2,242 (1,717 ) Less: Net loss (income) attributable to noncontrolling interests 147 390 (107 ) 71 Net income (loss) attributable to First Potomac Realty Trust 46 (1,602 ) 2,135 (1,646 ) Less: Dividends on preferred shares (2,248 ) (794 ) (11 ) — Less: Issuance costs on redeemed preferred shares (1,904 ) (3,095 ) (517 ) — Net (loss) income attributable to common shareholders $ (4,106 ) $ (5,491 ) $ 1,607 $ (1,646 ) Basic and diluted earnings per common share: Net (loss) income $ (0.07 ) $ (0.10 ) $ 0.03 $ (0.03 ) 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 from discontinued operations (607 ) — — — Less: Net loss (income) attributable to noncontrolling interests 112 114 (38 ) 1,870 Net income (loss) 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 from discontinued operations (0.01 ) — — — Net (loss) income $ (0.04 ) $ (0.04 ) $ 0.01 $ (0.72 ) (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, 2016USD ($)ft²personRate	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)ft²		Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)ft²segmentjoint_venturepersonRate	Dec. 31, 2015USD ($)ft²		Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)ft²
Real Estate Properties [Line Items]
Interest in Operating Partnership		95.80%									95.80%
Square Feet		6,714,265				7,489,092					6,714,265	7,489,092			8,790,147
Unconsolidated joint ventures | joint_venture											5
Square Footage Of Land For Additional Development		600,000									600,000
Occupancy rate in the Company's consolidated properties		92.60%									92.60%
Number Of Tenants In Companys Consolidated Rental Properties | person		384									384
Annualized Cash Basis Rent Percent for Government Tenant | Rate		16.00%									16.00%
Percentage of outstanding account receivables accounted by government		27.00%									27.00%
Revenues | $		$ 38,972	$ 40,172	$ 38,493	$ 42,697	$ 43,104		$ 42,854	$ 43,039	$ 43,849	$ 160,334	$ 172,846		$ 161,652
Consolidated Total assets | $	[1]	$ 1,260,247				$ 1,442,406	[2]				$ 1,260,247	$ 1,442,406	[2]		$ 1,612,300	[2]
Number of separate reporting segments of properties | segment											4
Wholly-owned Properties [Member]
Real Estate Properties [Line Items]
Square Feet		6,700,000									6,700,000
Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Square Feet		900,000									900,000
[1]	(1) 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. Corporate assets not allocated to any of our reportable segments totaled $17,732, $41,357 and $81,130 at December 31, 2016, 2015 and 2014, respectively.
[2]	(4) Total assets at December 31, 2015 and 2014 have been restated to exclude a total of $7.9 million and $6.2 million, respectively of unamortized deferred financing costs that are now deducted from the respective debt liability in accordance with ASU 2015-03, which we adopted in the first quarter of 2016.

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Principal payments from note receivable				$ 34,000,000		$ 29,720,000	$ 176,000
Amortization of Lease Incentives				700,000
Amortization of Deferred Leasing Fees				1,800,000
Bad Debt Expense				800,000		600,000	1,100,000
Termination Fee Revenue				100,000		100,000	1,100,000
Age of highly liquid investments considered as cash equivalents		90 days or less
Accumulated amortization of financing costs related to long-term debt		$ (26,300,000)	$ (26,300,000)	(26,300,000)	$ (26,300,000)	(22,000,000)
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
Nine Hundered And Fifty Street Nw [Member]
Loans and Leases Receivable Disclosure [Line Items]
Principal payments from note receivable	$ 34,000,000			$ 34,000,000

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Scheduled Future Amortization for Deferred Financing and Leasing Costs (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		$ 6,236	$ 8,000
Future Amortization Expense for Deferred Leasing Cost	[1]	27,198
Deferred Leasing And Financing Costs	[2]	12,970
Two Thousand And Sixteen [Member]
Amortization Expense [Line Items]
Deferred Leasing And Financing Costs	[2]	1,500
Two Thousand Seventeen [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,540
Future Amortization Expense for Deferred Leasing Cost	[1]	5,464
Deferred Leasing And Financing Costs	[2]	1,473
Two Thousand And Eighteen [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,399
Future Amortization Expense for Deferred Leasing Cost	[1]	4,915
Deferred Leasing And Financing Costs	[2]	1,399
Two Thousand And Twenty (2020) [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		400
Future Amortization Expense for Deferred Leasing Cost	[1]	3,363
Two Thousand And Nineteen [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,365
Future Amortization Expense for Deferred Leasing Cost	[1]	4,118
Deferred Leasing And Financing Costs	[2]	1,327
2021 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		400
Future Amortization Expense for Deferred Leasing Cost	[1]	2,649
Deferred Leasing And Financing Costs	[2]	1,265
Thereafter [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,132
Future Amortization Expense for Deferred Leasing Cost	[1]	6,689
Deferred Leasing And Financing Costs	[2]	$ 6,006
[1]	(1) Excludes the amortization of $1.8 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.
[2]	(2) Excludes the amortization of $0.7 million of lease incentive 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 lease incentive costs will be amortized has yet to be determined.

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Estimated Useful Lives of Company's Assets, by Class (Detail)	12 Months Ended
	Dec. 31, 2016
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 Accoun48

Summary of Significant Accounting Policies - Intangible Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator for basic and diluted earnings per common share:
(Loss) income from continuing operations	$ (1,717,000)	$ 2,242,000	$ (1,992,000)	$ (101,000)	$ (39,990,000)	$ 3,997,000	$ 476,000	$ 1,099,000	$ (1,569,000)	$ (34,417,000)	$ 15,559,000
(Loss) income from discontinued operations					0	0	0	(607,000)	0	(607,000)	1,484,000
Net (loss) income									(1,569,000)	(35,024,000)	17,043,000
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest									(502,000)	(2,032,000)	135,000
Less: Net loss (income) from discontinued operations attributable to noncontrolling interests									0	26,000	(64,000)
Net (loss) income attributable to First Potomac Realty Trust	(1,646,000)	2,135,000	(1,602,000)	46,000	(38,120,000)	3,959,000	590,000	604,000	(1,067,000)	(32,966,000)	16,844,000
Less: Dividends on preferred shares	0	(11,000)	(794,000)	(2,248,000)	(3,100,000)	(3,100,000)	(3,100,000)	(3,100,000)	(3,053,000)	(12,400,000)	(12,400,000)
Other Preferred Stock Dividends and Adjustments									(5,515,000)	0	0
Net (loss) income attributable to common shareholders									(9,635,000)	(45,366,000)	4,444,000
Less: Allocation to participating securities									(232,000)	(241,000)	(314,000)
Net (loss) income attributable to common shareholders	$ (1,646,000)	$ 1,607,000	$ (5,491,000)	$ (4,106,000)	$ (41,220,000)	$ 859,000	$ (2,510,000)	$ (2,496,000)	$ (9,867,000)	$ (45,607,000)	$ 4,130,000
Denominator for basic and diluted earnings per common share:
Weighted average common shares outstanding – basic									57,581	57,982	58,150
Weighted average common shares outstanding – diluted									57,581	57,982	58,220
Basic and diluted earnings per common share:
(Loss) income from continuing operations					$ (0.72)	$ 0.01	$ (0.04)	$ (0.03)	$ (0.17)	$ (0.78)	$ 0.05
(Loss) income from discontinued operations					0	0	0	(0.01)	0	(0.01)	0.02
Net (loss) income	$ (0.03)	$ 0.03	$ (0.10)	$ (0.07)	$ (0.72)	$ 0.01	$ (0.04)	$ (0.04)	$ (0.17)	$ (0.79)	$ 0.07
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Shares		600	3,600	2,200					6,400
Dividends in Excess of Accumulated Earnings [Member]
Numerator for basic and diluted earnings per common share:
Net (loss) income									$ (1,569,000)	$ (35,024,000)	$ 17,043,000

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, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share, Amount	1,629	1,330	1,520
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	960	1,020	1,122
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	669	310	398

Rental Property - Summary of Re

Rental Property - Summary of Rental Property (Detail) - USD ($) $ in Thousands	Dec. 31, 2016		Dec. 31, 2015	[2]
Property, Plant and Equipment [Line Items]
Land and land improvements	$ 282,923	[1]	$ 280,149
Buildings and improvements	824,867	[1]	793,184
Construction in progress	4,605	[1]	97,361
Tenant improvements	189,031	[1]	168,946
Furniture, fixtures and equipment	408	[1]	410
Rental property, gross	1,301,834	[1]	1,340,050
Less: accumulated depreciation	(242,562)	[1]	(209,784)
Rental property, net	1,059,272	[1]	$ 1,130,266
NOVA Non Core Portfolio
Property, Plant and Equipment [Line Items]
Rental property, net	90,600
FairOaks [Member]
Property, Plant and Equipment [Line Items]
Rental property, net	$ 13,200
[1]	1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017.
[2]	(2) 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 and was sold on March 25, 2016.

Rental Property - Additional In

Rental Property - Additional Information (Detail) $ in Thousands

Jul. 25, 2016USD ($)

Aug. 31, 2013ft²

Aug. 04, 2013a

Sep. 30, 2016USD ($)

Dec. 31, 2016USD ($)ft²

Dec. 31, 2015USD ($)ft²

Dec. 31, 2014USD ($)

Jun. 30, 2016ft²

Dec. 31, 2013ft²

Aug. 04, 2011

Segment Reporting Information [Line Items]

Real Estate Investment Property, Net | $

$ 1,059,272

[1]

$ 1,130,266

[2]

Square Footage Of Land For Additional Development

600,000

Square Feet

6,714,265

7,489,092

8,790,147

Original cost basis of the property | $

$ 824,867

[1]

$ 793,184

[2]

Ownership Interest

97.00%

Lease expiration date

Jan. 31, 2021

Completed and placed in-service redevelopment efforts

0

Development Efforts Yet To Be Placed In Service

0

Impairment of Real Estate | $

$ 2,772

$ 60,826

$ 3,956

Storey Park [Member]

Segment Reporting Information [Line Items]

Square Feet

0

[3]

712,000

Ownership Interest

97.00%

Disposition Date

Jul. 25, 2016

Jul. 25, 2016

[3]

Contractual purchase price | $

$ 54,500

Net Sale Proceeds | $

$ 52,700

$ 52,659

[3]

Impairment of Real Estate | $

$ 2,800

Washington, D.C Reporting Segment [Member]

Segment Reporting Information [Line Items]

Area of land available for development in additional building space

0

Development of area for operations by joint venture | a

1.6

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 | $

$ 35,000

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

FairOaks [Member]

Segment Reporting Information [Line Items]

Real Estate Investment Property, Net | $

$ 13,200

[1]

1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017.

[2]

(2) 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 and was sold on March 25, 2016.

[3]

(2) This development site could have supported up to 712,000 rentable square feet.

Investment in Affiliates - Comp

Investment in Affiliates - Components of Investments in Affiliates (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Aug. 04, 2011
Schedule of Equity Method Investments [Line Items]
Ownership Interest				97.00%
Investment at December 31, 2016		$ 49,392	$ 48,223
Investment at December 31, 2015		$ 48,223
Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment		Northern Virginia
Ownership Interest	[1]	51.00%
Investment at December 31, 2016		$ 26,414
Investment at December 31, 2015		$ 24,909
1750 H Street, NW [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment		Washington, D.C.
Ownership Interest	[2]	50.00%
Investment at December 31, 2016		$ 14,625
Investment at December 31, 2015		$ 15,168
Aviation Business Park [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment	[3]	Maryland
Ownership Interest	[3]	50.00%
Investment at December 31, 2016	[3]	$ 5,941
Investment at December 31, 2015	[3]	$ 5,899
Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Reporting Segment	[3],[4]	Maryland
Ownership Interest	[3],[4],[5]	25.00%
Investment at December 31, 2016	[3],[4]	$ 2,413
Investment at December 31, 2015	[3],[4]	$ 2,247
[1]	(5) The loan requires interest-only payments through December 2024, at which time the loan requires principal and interest payments through its maturity date. The loan in repayable in full without penalty on or after June 1, 2029.
[2]	(4) The loan requires interest-only payments with a constant interest rate over the life of the loan. The loan is repayable in full, without penalty, on or after August 1, 2021.
[3]	(1) In January 2017, the unconsolidated joint ventures that own these properties entered into a binding contract to sell Aviation Business Park and Rivers Park I and II, which are all located in our Maryland reporting segment. We anticipate completing the sale in March 2017; however, we can provide no assurances regarding the timing or pricing of such sale, or that such sale will ultimately occur.
[4]	(2) Rivers Park I and Rivers Park II are owned through two separate unconsolidated joint ventures.
[5]	(2) The loan is repayable in full, without penalty, at any time during the term of the loan. Of the outstanding principal balance, $2.8 million is recourse to us. 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.

Investment in Affiliates - Addi

Investment in Affiliates - Additional Information (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2016USD ($)ft²Rate	Dec. 31, 2015USD ($)ft²		Dec. 31, 2014USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2013ft²	Aug. 04, 2011
Schedule of Equity Method Investments [Line Items]
Ownership Interest								97.00%
Long-term Debt	[1]	$ 737,171	$ 724,038	[2]
Square Feet | ft²		6,714,265	7,489,092				8,790,147
Fees from joint ventures		$ 600	$ 700		$ 700
Debt Issuance Costs, Line of Credit Arrangements, Net		$ 2,400	7,900		$ 6,200
Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Reduction in variable rate | Rate		0.60%
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Debt Issuance Costs, Line of Credit Arrangements, Net		$ 600	700
Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	[3],[4],[5]	25.00%
1750 H Street, NW [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	[6]	50.00%
Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	[7]	51.00%
Mortgage Debt [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt	[8]	$ 110,000	110,000
Effective interest rate on the notes		3.60%
Mortgage Debt [Member] | Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 2,800
Mortgage and Other Indebtedness	[5],[8]	28,000	28,000
Mortgage Debt [Member] | 1750 H Street, NW [Member]
Schedule of Equity Method Investments [Line Items]
Mortgage and Other Indebtedness	[6],[8]	$ 32,000	32,000
Effective interest rate on the notes	[6]	3.92%
Mortgage Debt [Member] | Prosperity Metro Plaza [Member]
Schedule of Equity Method Investments [Line Items]
Mortgage and Other Indebtedness	[7],[8]	$ 50,000	$ 50,000
Effective interest rate on the notes	[7]	3.91%
London Interbank Offered Rate (LIBOR) [Member]
Schedule of Equity Method Investments [Line Items]
Effective interest rate on the notes		0.77%
Unconsolidated Entities [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt						$ 2,800
[1]	(1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively.
[2]	Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions, for further discussion.
[3]	(1) In January 2017, the unconsolidated joint ventures that own these properties entered into a binding contract to sell Aviation Business Park and Rivers Park I and II, which are all located in our Maryland reporting segment. We anticipate completing the sale in March 2017; however, we can provide no assurances regarding the timing or pricing of such sale, or that such sale will ultimately occur.
[4]	(2) Rivers Park I and Rivers Park II are owned through two separate unconsolidated joint ventures.
[5]	(2) The loan is repayable in full, without penalty, at any time during the term of the loan. Of the outstanding principal balance, $2.8 million is recourse to us. 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.
[6]	(4) The loan requires interest-only payments with a constant interest rate over the life of the loan. The loan is repayable in full, without penalty, on or after August 1, 2021.
[7]	(5) The loan requires interest-only payments through December 2024, at which time the loan requires principal and interest payments through its maturity date. The loan in repayable in full without penalty on or after June 1, 2029.
[8]	(1) Reflects the entire balance of the debt secured by the properties, not our portion of the debt.

Investment in Affiliates - Net

Investment in Affiliates - Net Assets of Company's Unconsolidated Joint Ventures (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Assets:
Rental property, net		$ 1,059,272	$ 1,130,266
Cash and cash equivalents		14,144	13,527		$ 13,323	$ 8,740
Total assets	[1]	1,260,247	1,442,406	[2]		$ 1,612,300	[2]
Liabilities:
Total liabilities		795,620	788,265
Unconsolidated Joint Ventures [Member]
Assets:
Rental property, net		189,245	193,243
Cash and cash equivalents		9,887	5,992
Other assets		20,726	16,490
Total assets		219,858	215,725
Liabilities:
Mortgage loans	[3],[4]	109,372	109,273
Other liabilities		8,674	7,214
Total liabilities		118,046	116,487
Net assets		$ 101,812	$ 99,238
[1]	(1) 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. Corporate assets not allocated to any of our reportable segments totaled $17,732, $41,357 and $81,130 at December 31, 2016, 2015 and 2014, respectively.
[2]	(4) Total assets at December 31, 2015 and 2014 have been restated to exclude a total of $7.9 million and $6.2 million, respectively of unamortized deferred financing costs that are now deducted from the respective debt liability in accordance with ASU 2015-03, which we adopted in the first quarter of 2016.
[3]	(1) Of the total mortgage debt that encumbers our unconsolidated properties, $2.8 million is recourse to us. We believe the fair value of the potential liability to us under this guaranty is inconsequential as the likelihood of our need to perform under the debt agreement is remote.
[4]	(2) In the first quarter of 2016, our unconsolidated joint ventures adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and which is applied on a retrospective basis. Mortgage loans, net at December 31, 2016 and 2015 included $0.6 million and $0.7 million, respectively, of unamortized deferred financing costs.

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Total revenues		$ 38,972	$ 40,172	$ 38,493	$ 42,697	$ 43,104	$ 42,854	$ 43,039	$ 43,849	$ 160,334	$ 172,846	$ 161,652
Total operating expenses		(34,658)	(32,295)	(35,681)	(36,337)	(102,375)	(37,079)	(37,268)	(40,016)	(138,972)	(216,738)	(150,201)
Operating (loss) income		$ 4,314	$ 7,877	$ 2,812	$ 6,360	$ (59,271)	$ 5,775	$ 5,771	$ 3,833	21,362	(43,892)	11,451
Depreciation and amortization										(60,862)	(66,624)	(61,796)
Interest expense, net										(26,370)	(26,797)	(24,696)
Provision for income taxes										0	0	0
Net income										2,294	1,825	775
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenues										24,704	24,255	23,285
Total operating expenses										(7,770)	(7,660)	(7,408)
Operating (loss) income										16,934	16,595	15,877
Depreciation and amortization										(8,044)	(8,718)	(9,893)
Interest expense, net										(3,995)	(3,909)	(3,890)
Provision for income taxes										0	0	(63)
Contingent consideration charge										0	0	126
Net income										$ 4,895	$ 3,968	$ 2,157
Mortgage Debt [Member] | London Interbank Offered Rate (LIBOR) [Member] | Rivers Park I and II [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Description of Variable Rate Basis	[1]									LIBOR
Derivative, Basis Spread on Variable Rate	[1]	1.90%								1.90%
[1]	(3) At December 31, 2016, LIBOR was 0.77%. All references to LIBOR in the financial statements refer to one-month LIBOR.

Notes Receivable (Detail)

Notes Receivable (Detail) shares in Thousands, $ in Thousands	Apr. 01, 2011	Jun. 30, 2016USD ($)	Jun. 30, 2015	Dec. 31, 2016USD ($)ft²shares	Dec. 31, 2015USD ($)ft²shares	Dec. 31, 2014USD ($)	Jul. 06, 2016shares	Feb. 24, 2015USD ($)	Dec. 31, 2013ft²	Apr. 30, 2011ft²
Receivables with Imputed Interest [Line Items]
Square Feet | ft²				6,714,265	7,489,092				8,790,147
Principal payments from note receivable				$ 34,000	$ 29,720	$ 176
Series A Preferred Shares, shares outstanding | shares				0	6,400
Notes Receivables Issued on December 2010 [Member]
Receivables with Imputed Interest [Line Items]
Interest income				$ 1,600	$ 3,700	$ 6,100
Nine Hundered And Fifty Street Nw [Member]
Receivables with Imputed Interest [Line Items]
Square Feet | ft²				287,000
Principal payments from note receivable		$ 34,000		$ 34,000
Recognition of Deferred Revenue		$ 200
Nine Hundered And Fifty Street Nw [Member] | Minimum [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan				9.75%
America Square [Member]
Receivables with Imputed Interest [Line Items]
Square Feet | ft²										461,000
Mezzanine loan provided to owners								$ 29,700
Prepayment Fee Income				$ 2,400
Maturity date of loan			May 1, 2016	Apr. 1, 2017
America Square [Member] | Maximum [Member]
Receivables with Imputed Interest [Line Items]
Fixed interest rate on loan	9.00%
Series A Preferred Shares [Member]
Receivables with Imputed Interest [Line Items]
Series A Preferred Shares, shares outstanding | shares					6,400		600

Intangible Assets - Intangible

Intangible Assets - Intangible Assets and Deferred Market Rent Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets By Major Class [Line Items]
Deferred market rent liability, Net Intangibles	$ 1,792	$ 2,154
All Properties, Including Held for Sale [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	59,075	68,008
Accumulated Amortization	(33,969)	(35,049)
Net Intangibles	25,106	32,959
Goodwill	6,930	6,930
Deferred market rent liability, Gross Intangible	4,173	4,869
Deferred market rent liability, Accumulated Amortization	(2,381)	(2,715)
Deferred market rent liability, Net Intangibles	1,792	2,154
All Properties, Including Held for Sale [Member] | In-place Leases [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	38,804	45,901
Accumulated Amortization	(25,423)	(26,961)
Net Intangibles	13,381	18,940
All Properties, Including Held for Sale [Member] | Customer Relationships [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	663	663
Accumulated Amortization	(663)	(601)
Net Intangibles	0	62
All Properties, Including Held for Sale [Member] | Leasing Commissions [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	9,499	10,612
Accumulated Amortization	(5,882)	(5,485)
Net Intangibles	3,617	5,127
All Properties, Including Held for Sale [Member] | Legal Fees [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	299	344
Accumulated Amortization	(193)	(177)
Net Intangibles	106	167
All Properties, Including Held for Sale [Member] | Deferred Market Rent Assets [Member]
Intangible Assets By Major Class [Line Items]
Gross Intangibles	2,880	3,558
Accumulated Amortization	(1,808)	(1,825)
Net Intangibles	$ 1,072	$ 1,733

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 7	$ 10.6	$ 10.3
Reduction in rental revenue	0.3	0.1	0
Losses due to termination of tenant leases and defaults	$ 3	$ 0.5	$ 1.1

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, 2016USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,016	$ 4,114
2,017	2,646
2,018	2,361
2,019	2,147
2,020	1,463
Thereafter	3,653
Total	$ 16,384

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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

Dispositions - Summary of Compl

Dispositions - Summary of Completed Property Dispositions within Continuing Operations(Detail) $ in Thousands

Jul. 25, 2016

Dec. 31, 2015USD ($)ft²

Dec. 23, 2015USD ($)ft²

Dec. 17, 2015USD ($)ft²

Jul. 28, 2015USD ($)ft²

Sep. 30, 2016USD ($)

Dec. 31, 2016USD ($)ft²

Jun. 30, 2016ft²

Dec. 31, 2013ft²

Schedule Of Discontinued Operations [Line Items]

Land and land improvements | $

$ 280,149

[1]

$ 282,923

[2]

Square Feet | ft²

7,489,092

6,714,265

8,790,147

Northern Virginia Reporting Segment [Member]

Schedule Of Discontinued Operations [Line Items]

Square Feet | ft²

167,000

NOVA Non Core Portfolio | Northern Virginia [Member]

Schedule Of Discontinued Operations [Line Items]

Reporting Segment

[3]

Northern Virginia

Disposition Date

[3]

Mar. 25, 2016

Property Type

[3]

Various

Square Feet | ft²

[3]

945,745

Net Sale Proceeds | $

[3]

$ 90,501

Storey Park [Member]

Schedule Of Discontinued Operations [Line Items]

Reporting Segment

[4]

Washington, D.C.

Disposition Date

Jul. 25, 2016

Jul. 25, 2016

[4]

Property Type

[4]

Land

Square Feet | ft²

0

[4]

712,000

Net Sale Proceeds | $

$ 52,700

$ 52,659

[4]

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 | ft²

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 | ft²

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 | ft²

135,015

Net Sale Proceeds | $

$ 14,956

Owings Mills Business Park [Domain] | Maryland [Member]

Schedule Of Discontinued Operations [Line Items]

Disposition Date

Oct. 16, 2014

Property Type

Business Park

Square Feet | ft²

180,475

Net Sale Proceeds | $

$ 12,417

Corporate Campus at Ashburn Center [Member] | Northern Virginia [Member]

Schedule Of Discontinued Operations [Line Items]

Disposition Date

Jun. 26, 2014

Property Type

Business Park

Square Feet | ft²

194,184

Net Sale Proceeds | $

$ 39,910

FairOaks [Member]

Schedule Of Discontinued Operations [Line Items]

Land and land improvements | $

$ 1,600

FairOaks [Member] | Northern Virginia [Member]

Schedule Of Discontinued Operations [Line Items]

Reporting Segment

[5]

Northern Virginia

Disposition Date

[5]

Jan. 9, 2017

Property Type

[5]

Office

Square Feet | ft²

[5]

214,214

Net Sale Proceeds | $

[5]

$ 13,255

[1]

(2) 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 and was sold on March 25, 2016.

[2]

1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017.

[3]

(3) 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”).

[4]

(2) This development site could have supported up to 712,000 rentable square feet.

[5]

(1) One Fair Oaks was classified as held-for-sale at December 31, 2016.

Dispositions - Disposed or Held

Dispositions - Disposed or Held-for-Sale Properties within Continuing Operations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)ft²		Dec. 31, 2015USD ($)ft²		Dec. 31, 2014USD ($)	Jun. 30, 2016ft²	Dec. 31, 2013ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Land and land improvements	$ 282,923	[1]	$ 280,149	[2]
Square Feet | ft²	6,714,265		7,489,092				8,790,147
Revenues	$ 0		$ 877		$ 7,688
Property operating expenses	0		(638)		(3,612)
Depreciation and amortization	0		(1,222)		(3,662)
Interest expense, net of interest income			(8)		(268)
Loss on debt extinguishment / modification	48		1,824		0
Income (loss) from operations of disposed property	0		(975)		146
Loss on debt extinguishment	$ 0		(489)		0
Storey Park [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²	0	[3]				712,000
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	$ 11,156		29,773		31,027
Property operating expenses	(4,307)		(10,353)		(11,055)
Depreciation and amortization	(1,070)		(10,310)		(11,289)
Interest expense, net of interest income	(436)		(465)		(843)
Impairment of rental property	(2,772)		(60,826)		0
Income (loss) from operations of disposed property	2,523		(52,181)		7,840
(Loss) gain on sale of rental property	(1,155)		29,477		21,230
Net income (loss) from continuing operations	1,368		(22,704)		29,070
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member] | Continuing Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on debt extinguishment / modification	$ 48		$ 0		$ 0
[1]	1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017.
[2]	(2) 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 and was sold on March 25, 2016.
[3]	(2) This development site could have supported up to 712,000 rentable square feet.

Dispositions - Additional Infor

Dispositions - Additional Information (Detail) $ in Thousands

Feb. 17, 2017USD ($)ft²

Jul. 25, 2016

Sep. 30, 2016USD ($)

Dec. 31, 2015USD ($)ft²building

Dec. 31, 2016USD ($)ft²building

Dec. 31, 2015USD ($)ft²building

Dec. 31, 2014USD ($)

Jun. 30, 2016ft²

Dec. 31, 2013ft²building

Aug. 04, 2011

Schedule Of Discontinued Operations [Line Items]

Number Of Buildings | building

99

74

99

131

Square Feet | ft²

7,489,092

6,714,265

7,489,092

8,790,147

Impairment of real estate assets

$ 2,800

$ 60,800

$ 4,000

Land and land improvements

$ 280,149

[1]

282,923

[2]

280,149

[1]

Buildings and improvements

793,184

[1]

824,867

[2]

793,184

[1]

Tenant improvements

168,946

[1]

189,031

[2]

168,946

[1]

Construction in progress

97,361

[1]

4,605

[2]

97,361

[1]

Real Estate Investment Property, Accumulated Depreciation

209,784

[1]

242,562

[2]

209,784

[1]

Ownership Interest

97.00%

NOVA Non Core Portfolio

Schedule Of Discontinued Operations [Line Items]

Impairment of real estate assets

26,900

Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment

37,000

37,000

Buildings and improvements

88,000

88,000

Tenant improvements

14,400

14,400

Mortgage Loans Payable

$ 200

Land and Land Improvements

$ 25,200

$ 25,200

Richmond [Member]

Schedule Of Discontinued Operations [Line Items]

Disposition Date

Mar. 19, 2015

[3]

Mar. 19, 2015

Number Of Buildings | building

19

19

Square Feet | ft²

827,900

827,900

[3]

827,900

FairOaks [Member]

Schedule Of Discontinued Operations [Line Items]

Land and land improvements

$ 1,600

Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment

6,000

Buildings and improvements

$ 17,600

Storey Park [Member]

Schedule Of Discontinued Operations [Line Items]

Disposition Date

Jul. 25, 2016

Jul. 25, 2016

[4]

Square Feet | ft²

0

[4]

712,000

Mortgage Loans Payable

$ 22,000

Ownership Interest

97.00%

Net Sale Proceeds

$ 52,700

$ 52,659

[4]

Noncontrolling Interest, Description

0.03

Subsequent Event [Member] | Plaza Five Hundred [Member]

Schedule Of Discontinued Operations [Line Items]

Square Feet | ft²

503,000

Net Sale Proceeds

$ 72,500

[1]

(2) 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 and was sold on March 25, 2016.

[2]

1) Excludes rental property totaling $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017.

[3]

(1) Consists of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land.

[4]

(2) This development site could have supported up to 712,000 rentable square feet.

Dispositions - Summary of Com65

Dispositions - Summary of Completed and Anticipated Property Dispositions within Discontinued Operations (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2016USD ($)ft²building		Dec. 31, 2015USD ($)ft²building	Dec. 31, 2014USD ($)	Dec. 31, 2013ft²building
Schedule Of Discontinued Operations [Line Items]
Number Of Buildings | building		74		99		131
Square Feet | ft²		6,714,265		7,489,092		8,790,147
Net Sale Proceeds | $		$ 143,159		$ 129,247	$ 97,701
Richmond [Member]
Schedule Of Discontinued Operations [Line Items]
Number Of Buildings | building				19
Reporting Segment	[1]	Southern Virginia
Disposition Date		Mar. 19, 2015	[1]	Mar. 19, 2015
Property Type	[1]	Business Park
Square Feet | ft²		827,900	[1]	827,900
Net Sale Proceeds | $	[1]	$ 53,768
Patrick Center [Member]
Schedule Of Discontinued Operations [Line Items]
Reporting Segment		Maryland
Disposition Date		Apr. 16, 2014
Property Type		Office
Square Feet | ft²		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 | ft²		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 | ft²		341,973
Net Sale Proceeds | $		$ 31,616
[1]	(1) Consists of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land.

Dispositions - Net Income from

Dispositions - Net Income from Discontinued Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Revenues	$ 0	$ 877	$ 7,688
Property operating expenses	0	(638)	(3,612)
Depreciation and amortization	0	(1,222)	(3,662)
Disposal Group, Including Discontinued Operation, Interest Income	0
Interest expense, net of interest income		(8)	(268)
Income (loss) from operations of disposed property	0	(975)	146
Loss on debt extinguishment	0	(489)	0
Gain on sale of real estate property	0	857	1,338
Net income from discontinued operations	$ 0	$ (607)	$ 1,484

Debt - Schedule of Borrowings (

Debt - Schedule of Borrowings (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Future Amortization Expense for Deferred Financing Cost		$ 6,236	$ 8,000
Mortgage loans, net	[1]	296,212	307,769	[2]
Unsecured term loan, net		299,404	299,404
Unsecured revolving credit facility, net	[1]	141,555	116,865	[2]
Total contractual principal balance	[1]	737,171	724,038	[2]
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, net	[1]	$ 299,404	299,404	[2]
NOVA Non Core Portfolio
Debt Instrument [Line Items]
Mortgage and Other Indebtedness			$ 200
[1]	(1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively.
[2]	Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions, for further discussion.

Debt - Schedule of Borrowings 2

Debt - Schedule of Borrowings 2 (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Effective interest rate on secured term loan	1.50%
Mortgage Loans [Member]
Debt Instrument [Line Items]
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%	[1]
Debt instrument basis spread on variable rate, maximum	1.80%	[1]
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%	[1]
Debt instrument maturity date	December 2,019
NOVA Non Core Portfolio
Debt Instrument [Line Items]
Mortgage Loans Payable	$ 0.2
Minimum [Member] | Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Basis for Effective Rate	0.0422	[1],[2]
Maximum [Member] | Mortgage Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Basis for Effective Rate	0.0601	[1],[2]
[1]	(3) At December 31, 2016, LIBOR was 0.77%. All references to LIBOR in the consolidated financial statements refer to one-month LIBOR.
[2]	(4) At December 31, 2016 and 2015, the mortgage loans balance includes two construction loans. At December 31, 2015, the mortgage loans balance includes two construction loans and the Storey Park Land Loan, which was repaid in July 2016.

Debt - Summary of Company's Mor

Debt - Summary of Company's Mortgage Debt (Detail) - USD ($) $ in Thousands		Oct. 06, 2016	Dec. 31, 2016	Dec. 31, 2015		Mar. 31, 2016	Aug. 04, 2011
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	[1]		4.41%
Unamortized fair value adjustments			$ 0
Total contractual principal balance	[2]		$ 737,171	$ 724,038	[3]
Ownership Interest							97.00%
Hillside Prepayment		Oct. 6, 2016
Storey Park [Member]
Debt Instrument [Line Items]
Contractual interest rate			2.50%
Debt Instrument, Interest Rate Terms	[4],[5]		LIBOR + 2.50%
Effective interest rate on the notes			2.93%
Debt instrument maturity date	[6]		October 2,016
Total Mortgage Debt	[6]		$ 0	22,000
Ownership Interest			97.00%
440 First Street, NW Construction Loan [Member]
Debt Instrument [Line Items]
Contractual interest rate			2.50%
Debt Instrument, Interest Rate Terms	[5]		LIBOR + 2.50%
Effective interest rate on the notes			2.93%
Debt instrument maturity date	[7]		May 30, 2017
Total Mortgage Debt	[7]		$ 32,216	32,216
Hillside I and II [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date	[8]		December 2016
Total Mortgage Debt	[8]		$ 0	12,368
Redland Corporate Center Buildings II & III [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date			November 2,017
Total Mortgage Debt			$ 63,214	64,543
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Contractual interest rate			1.85%
Debt Instrument, Interest Rate Terms	[5]		LIBOR + 1.85%
Debt instrument maturity date	[9]		September 1, 2019
Total Mortgage Debt	[9]		$ 34,584
Amount Borrowed YTD			$ (25,400)	9,176	[9]
Eight Hundred Forty First Street [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date			July 2,020
Total Mortgage Debt			$ 35,201	35,888
Battlefield Corporate Center [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date			November 2,020
Total Mortgage Debt			$ 3,353	3,526
One thousand two hundred eleven Connecticut Avenue NW. [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date			July 2,022
Total Mortgage Debt			$ 28,503	29,110
1401 K Street, NW [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date			June 2,023
Total Mortgage Debt			$ 35,556	36,224
Eleven Dupont Circle [Member]
Debt Instrument [Line Items]
Contractual interest rate			0.00%
Effective interest rate on the notes			0.00%
Debt instrument maturity date			September 2,030
Total Mortgage Debt			$ 66,780	66,780
Continuing Operations Properties [Member]
Debt Instrument [Line Items]
Total Mortgage Debt			299,407	311,831
Unamortized fair value adjustments				(172)
Continuing Operations Properties [Member] | Mortgage Loans [Member]
Debt Instrument [Line Items]
Total contractual principal balance			$ 296,212	307,769
NOVA Non Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate			7.35%
Effective interest rate on the notes			5.88%
Debt instrument maturity date	[10]		November 2016
Total Mortgage Debt	[10]		$ 0	212
Richmond [Member]
Debt Instrument [Line Items]
Unamortized fair value adjustments			0	(1)
Total contractual principal balance			0	213
Gateway Centre Building One Debt [Member]
Debt Instrument [Line Items]
Mortgage and Other Indebtedness						$ 200
Continuing Operations [Member]
Debt Instrument [Line Items]
Unamortized fair value adjustments	[11]		3,195	$ 4,234
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Debt Instrument Maximum Borrowing Capacity			$ 43,700
[1]	(6) Represents the weighted average interest rate on total mortgage debt.
[2]	(1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively.
[3]	Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions, for further discussion.
[4]	(1) At December 31, 2016, LIBOR was 0.77% .
[5]	(1) At December 31, 2016, LIBOR was 0.77%.
[6]	The Storey Park Land Loan encumbered the Storey Park land and was entered into by our 97% owned consolidated joint venture that owned Storey Park. On July 25, 2016, our consolidated joint venture sold Storey Park and the Storey Park Land Loan was concurrently repaid with proceeds from the sale.
[7]	(4) This construction loan (the “440 First Street, NW Construction Loan”) is collateralized by 440 First Street, NW. In May 2016, we extended the maturity date by one year to May 30, 2017. We can repay all or a portion of the construction loan, without penalty, at any time during the term of the loan.
[8]	On October 6, 2016, we used available cash to prepay, without penalty, the Hillside I and II loan.
[9]	(5) This construction loan has a borrowing capacity of up to $43.7 million and is collateralized by the NOVA build-to-suit (the “Northern Virginia Construction Loan”), which was placed in-service in August 2016. We can repay all or a portion of the Northern Virginia Construction loan, without penalty, at any time during the term of the loan.
[10]	(8) The mortgage loan that encumbered Gateway Centre Manassas, which was included in the NOVA Non-Core Portfolio and sold on March 25, 2016, was classified within “Liabilities held-for-sale” on our December 31, 2015 consolidated balance sheet. In February 2016, we used $0.2 million in available cash to defease the outstanding balance of the mortgage loan.
[11]	(7) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis.

Debt - Summary of Company's M70

Debt - Summary of Company's Mortgage Debt 2 (Detail)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt Instrument, Basis Spread on Variable Rate	1.50%

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Long-term Debt	[1]	$ 737,171	$ 724,038	[2]
Line of Credit Facility, Interest Rate at Period End		2.20%
Debt Issuance Costs, Line of Credit Arrangements, Net		$ 2,400	7,900		$ 6,200
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Debt Instrument Maximum Borrowing Capacity		$ 43,700
Tranche A [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	[3]	100
Debt Instrument, Basis Spread on Variable Rate		1.45%
Debt instrument maturity date		December 2,020
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Contractual interest rate		1.85%
Mortgage Loans Payable	[4]	$ 34,584
Debt instrument maturity date	[4]	September 1, 2019
440 First Street, NW Construction Loan [Member]
Debt Instrument [Line Items]
Contractual interest rate		2.50%
Mortgage Loans Payable	[5]	$ 32,216	32,216
Debt instrument maturity date	[5]	May 30, 2017
Storey Park [Member]
Debt Instrument [Line Items]
Contractual interest rate		2.50%
Mortgage Loans Payable	[6]	$ 0	22,000
Debt instrument maturity date	[6]	October 2,016
Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Average Outstanding Amount		$ 154,900	$ 165,500
Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit		$ 144,000
Debt instrument maturity date		December 2,019
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Expired Swap Percentage		1.80%
Expired Swap		$ 60,000
[1]	(1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively.
[2]	Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions, for further discussion.
[3]	(1) At December 31, 2016, LIBOR was 0.77%. 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.
[4]	(5) This construction loan has a borrowing capacity of up to $43.7 million and is collateralized by the NOVA build-to-suit (the “Northern Virginia Construction Loan”), which was placed in-service in August 2016. We can repay all or a portion of the Northern Virginia Construction loan, without penalty, at any time during the term of the loan.
[5]	(4) This construction loan (the “440 First Street, NW Construction Loan”) is collateralized by 440 First Street, NW. In May 2016, we extended the maturity date by one year to May 30, 2017. We can repay all or a portion of the construction loan, without penalty, at any time during the term of the loan.
[6]	The Storey Park Land Loan encumbered the Storey Park land and was entered into by our 97% owned consolidated joint venture that owned Storey Park. On July 25, 2016, our consolidated joint venture sold Storey Park and the Storey Park Land Loan was concurrently repaid with proceeds from the sale.

Debt - Originated or Assumed Mo

Debt - Originated or Assumed Mortgages (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	[3]
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Month		September
Year		2,015
Debt Instrument, Interest Rate Terms	[1]	LIBOR + 1.85%
Principal Amount	[2]	$ 34,584
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
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Mortgage Loans Payable	[3]	$ 34,584
Debt Instrument, Interest Rate Terms	[4]	LIBOR + 1.85%
Amount Borrowed YTD		$ 25,400	$ (9,176)
[1]	(1) At December 31, 2016, LIBOR was 0.77% .
[2]	(2) The loan has a borrowing capacity of up to $43.7 million, of which we borrowed $25.4 million and $9.2 million during 2016 and 2015, respectively.
[3]	(5) This construction loan has a borrowing capacity of up to $43.7 million and is collateralized by the NOVA build-to-suit (the “Northern Virginia Construction Loan”), which was placed in-service in August 2016. We can repay all or a portion of the Northern Virginia Construction loan, without penalty, at any time during the term of the loan.
[4]	(1) At December 31, 2016, LIBOR was 0.77%.

Debt - Originated or Assumed 73

Debt - Originated or Assumed Mortgages 2 (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Northern Virginia Development Project [Member]
Debt Instrument [Line Items]
Mortgage Loans Payable	[1]	$ 34,584
Storey Park [Member]
Debt Instrument [Line Items]
Mortgage Loans Payable	[2]	$ 0	$ 22,000
Effective interest rate on the notes		2.93%
[1]	(5) This construction loan has a borrowing capacity of up to $43.7 million and is collateralized by the NOVA build-to-suit (the “Northern Virginia Construction Loan”), which was placed in-service in August 2016. We can repay all or a portion of the Northern Virginia Construction loan, without penalty, at any time during the term of the loan.
[2]	The Storey Park Land Loan encumbered the Storey Park land and was entered into by our 97% owned consolidated joint venture that owned Storey Park. On July 25, 2016, our consolidated joint venture sold Storey Park and the Storey Park Land Loan was concurrently repaid with proceeds from the sale.

Debt - Repayment of Mortgages (

Debt - Repayment of Mortgages (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Hillside I and II [Member]
Debt Instrument [Line Items]
Month	October
Year	2,016
Effective interest rate on the notes	4.62%
Principal Balance Repaid	$ 12,199
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	August
Year	2,016
Principal Balance Repaid	$ 22,000
Gateway Centre Manassas Building I [Member]
Debt Instrument [Line Items]
Month	February
Year	2,016
Effective interest rate on the notes	5.88%
Principal Balance Repaid	$ 174
Storey Park [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR + 2.50%	[1],[2]
Effective interest rate on the notes	2.93%
[1]	(1) At December 31, 2016, LIBOR was 0.77% .
[2]	(1) At December 31, 2016, LIBOR was 0.77%.

Debt - Unsecured Term Loan (Det

Debt - Unsecured Term Loan (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Unsecured term loan, net		$ 299,404	$ 299,404
Debt Instrument, Basis Spread on Variable Rate		1.50%
Loss on debt extinguishment / modification		$ 48	1,824	$ 0
Deferred Costs, Noncurrent		$ (42,712)	(36,537)
Tranche A [Member]
Debt Instrument [Line Items]
Maturity Date		December 2,020
Debt Instrument, Basis Spread on Variable Rate		1.45%
Tranche B [Member]
Debt Instrument [Line Items]
Maturity Date		June 2,021
Debt Instrument, Basis Spread on Variable Rate		1.45%
Tranche C [Member]
Debt Instrument [Line Items]
Maturity Date		December 2,022
Debt Instrument, Basis Spread on Variable Rate		1.80%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Carrying value of the debt instruments		$ 300,000	300,000
Deferred Costs, Noncurrent	[1]	$ (596)	(596)
Unsecured Debt [Member] | Tranche A [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	[2]	LIBOR + 1.45%
Carrying value of the debt instruments		$ 100,000	100,000
Unsecured Debt [Member] | Tranche B [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	[2]	LIBOR + 1.45%
Carrying value of the debt instruments		$ 100,000	100,000
Unsecured Debt [Member] | Tranche C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	[2]	LIBOR + 1.80%
Carrying value of the debt instruments		$ 100,000	100,000
Term Loan [Member]
Debt Instrument [Line Items]
Unsecured term loan, net		$ 300,000
Loss on debt extinguishment / modification			$ (1,800)
[1]	(2) In the first quarter of 2016, we adopted ASU-2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis.
[2]	(1) At December 31, 2016, LIBOR was 0.77%. 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, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016derivative	Dec. 31, 2016Integer	Sep. 30, 2016USD ($)
Debt Instrument [Line Items]
Loss on debt extinguishment / modification	$ 48	$ 1,824	$ 0
Weighted average interest rate	1.90%	1.90%
Maximum outstanding borrowings	$ 204,000	$ 218,000
Debt Instrument, Basis Spread on Variable Rate	1.50%
Line of Credit Facility, Interest Rate at Period End	2.20%
Available capacity on the unsecured revolving credit facility				$ 150,900
Number of interest rate swap agreements					9	9
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Fixed effective interest rate	1.442%						1.40%
Amount on variable rate debt				240,000			$ 0
Expired Swap				$ 60,000
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]
Loss on debt extinguishment / modification		$ (1,800)
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%

Debt - Aggregate Debt Maturitie

Debt - Aggregate Debt Maturities (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015	[2]
Debt Disclosure [Abstract]
2,016		$ 97,672
2,017		2,354
2,018		181,055
2,019		137,203
2,020		101,598
Thereafter		223,525
Long term debt before unamortized discount		743,407
Unamortized fair value adjustments		0
Total contractual principal balance	[1]	$ 737,171	$ 724,038
[1]	(1) In the first quarter of 2016, we adopted ASU 2015-03, which requires debt issuance costs to be presented on the balance sheet as a direct deduction from the carrying value of the respective debt liability and is applied on a retrospective basis. The balances include a total of $6.2 million and $8.0 million of unamortized deferred financing costs at December 31, 2016 and 2015, respectively.
[2]	Excludes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions, for further discussion.

Debt Future Deferred Financing

Debt Future Deferred Financing Expense (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		$ 6,236	$ 8,000
Deferred Leasing And Financing Costs	[1]	12,970
Two Thousand And Sixteen [Member]
Amortization Expense [Line Items]
Deferred Leasing And Financing Costs	[1]	1,500
Two Thousand Seventeen [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,540
Deferred Leasing And Financing Costs	[1]	1,473
Two Thousand And Eighteen [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,399
Deferred Leasing And Financing Costs	[1]	1,399
Two Thousand And Nineteen [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,365
Deferred Leasing And Financing Costs	[1]	1,327
2021 [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		400
Deferred Leasing And Financing Costs	[1]	1,265
Thereafter [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		1,132
Deferred Leasing And Financing Costs	[1]	6,006
Two Thousand And Twenty (2020) [Member]
Amortization Expense [Line Items]
Future Amortization Expense for Deferred Financing Cost		$ 400
[1]	(2) Excludes the amortization of $0.7 million of lease incentive 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 lease incentive costs will be amortized has yet to be determined.

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016derivative	Dec. 31, 2016Integer	Sep. 30, 2016USD ($)
Derivatives, Fair Value [Line Items]
Number of interest rate swap agreements					9	9
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Fixed effective interest rate	1.442%						1.40%
Weighted average rate amount on variable rate debt				$ 240,000			$ 0
Expired Swap Percentage	1.80%
Expired Swap				$ 60,000
Interest Rate Swap [Member] | Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive loss reclassified as an increase in interest expense	$ 2,800	$ 4,000	$ 4,100
Estimated accumulated other comprehensive loss reclassified as an increase in interest expense over the following twelve months	$ 900

Derivative Instruments - Summar

Derivative Instruments - Summary of Interest Rate Swap Agreements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016
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	$ 240,000	$ 0
Fixed LIBOR Interest Rate	1.442%	1.40%

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Assets and Liabilities (Detail) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Recurring Measurements:
Derivative instrument-swap liabilities	$ 906	$ 2,491
Fair Value, Inputs, Level 1 [Member]
Recurring Measurements:
Derivative instrument-swap assets		0
Derivative instrument-swap liabilities	0	0
Level 2 [Member]
Recurring Measurements:
Derivative instrument-swap assets		90,625
Derivative instrument-swap liabilities	906	2,491
Level 3 [Member]
Recurring Measurements:
Derivative instrument-swap assets		14,000
Derivative instrument-swap liabilities	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) $ in Thousands		Dec. 31, 2015USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2016USD ($)Rate		Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2016derivative	Dec. 31, 2016Integer	Feb. 24, 2015USD ($)
Derivatives, Fair Value [Line Items]
Future Amortization Expense for Deferred Financing Cost		$ 8,000		$ 8,000	$ 6,236		$ 8,000
Impairment of real estate assets					2,800		60,800	$ 4,000
Number of interest rate swap agreements									9	9
Loss (gain) on sale of rental property			$ 1,200		1,155		(29,477)	(21,230)
Impairment of Real Estate					2,772		$ 60,826	$ 3,956
America Square [Member]
Derivatives, Fair Value [Line Items]
Mezzanine loan provided to owners											$ 29,700
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				33,900
Richmond [Member]
Derivatives, Fair Value [Line Items]
Disposition Date					Mar. 19, 2015	[1]	Mar. 19, 2015
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Variable rate debt hedged					$ 240,000
Minimum number of daily snapshot used for valuation of interest rate swap agreements | Rate					7,500
Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Assets, Fair Value Disclosure, Nonrecurring		104,625		104,625			$ 104,625
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative instrument-swap assets		90,625		90,625			90,625
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative instrument-swap assets		14,000		14,000			14,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives, Fair Value [Line Items]
Derivative instrument-swap assets		0		$ 0			$ 0
Northern Virginia [Member] | NOVA Non Core Portfolio
Derivatives, Fair Value [Line Items]
Disposition Date	[2]				Mar. 25, 2016
Net Sale Proceeds	[2]	$ 90,501
Northern Virginia [Member] | FairOaks [Member]
Derivatives, Fair Value [Line Items]
Disposition Date	[3]				Jan. 9, 2017
Net Sale Proceeds	[3]				$ 13,255
[1]	(1) Consists of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land.
[2]	(3) 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”).
[3]	(1) One Fair Oaks was classified as held-for-sale at December 31, 2016.

Fair Value Measurements - Fai83

Fair Value Measurements - Fair Value of Debt Instruments (Detail) $ in Thousands		Dec. 31, 2016USD ($)ft²		Dec. 31, 2015USD ($)ft²		Feb. 24, 2015USD ($)	Dec. 31, 2013ft²	Apr. 30, 2011ft²
Financial Assets:
Carrying value of notes receivable		$ 0		$ 34,000
Financial Liabilities:
Square Feet | ft²		6,714,265		7,489,092			8,790,147
America Square [Member]
Financial Liabilities:
Square Feet | ft²								461,000
Mezzanine loan provided to owners						$ 29,700
NOVA Non Core Portfolio
Financial Liabilities:
Mortgage Loans Payable		$ 200
Richmond [Member]
Financial Liabilities:
Square Feet | ft²		827,900	[1]	827,900
Reported Value Measurement [Member]
Financial Assets:
Carrying value of notes receivable		$ 0		$ 34,000	[2]
Financial Liabilities:
Carrying value of the debt instruments		743,407		732,216
Reported Value Measurement [Member] | Mortgage Debt [Member]
Financial Liabilities:
Carrying value of the debt instruments	[3]	299,407		312,216
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		144,000		120,000
Estimate of Fair Value Measurement [Member]
Financial Assets:
Fair value of notes receivable		0		34,000	[2]
Financial Liabilities:
Fair value of the debt instruments		744,927		718,541
Estimate of Fair Value Measurement [Member] | Mortgage Debt [Member]
Financial Liabilities:
Fair value of the debt instruments		300,927		298,541
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		$ 144,000		$ 120,000
[1]	(1) Consists of Chesterfield Business Center, Hanover Business Center, Park Central, Virginia Technology Center and a three-acre parcel of undeveloped land.
[2]	(2) The note receivable was prepaid on June 2, 2016. See note 5, Notes Receivable, for more information regarding the prepayment of the note receivable.
[3]	(3) Includes $0.2 million of mortgage debt that was classified within “Liabilities held-for-sale” on our consolidated balance sheet at December 31, 2015. See note 9, Dispositions for more information.

Commitments and Contingencies -

Commitments and Contingencies - Summary of Operating Leases Generating Future Minimum Rental Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
Future minimum rents, 2016	$ 114,009
Future minimum rents, 2017	106,865
Future minimum rents, 2018	96,101
Future minimum rents, 2019	82,139
Future minimum rents, 2020	66,787
Future minimum rents, Thereafter	195,825
Future minimum rents, Total	$ 661,726

Commitments and Contingencies85

Commitments and Contingencies - Additional Information (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013ft²tenant	Dec. 31, 2016USD ($)person	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Operating Leases [Abstract]
Occupancy rate in the Company's consolidated properties			92.60%
Number of tenants in the company's consolidated rental properties | person			384
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
Subtenant Lease Expiration Date			Jan. 31, 2018
Corporate Office Leases Rent Expense			$ 1.5	$ 1.6	$ 1.8
Longterm Purchase Commitment Time Period Milestones			5 years
Contingent Consideration [Abstract]
Amount Accrued Outstanding Related To Redevelopment Activities			$ 3.1
Debt Instrument Collateralized Debt Obligations Amount			5.5
Contingent Liability Upon Default On Development Projects			$ 2.3

Commitments and Contingencies86

Commitments and Contingencies - Schedule of Future Minimum Rental Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 1,469
2,017	1,906
2,018	1,995
2,019	2,049
2,020	175
Future minimum rent	$ 7,594

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions

Feb. 15, 2017

Feb. 08, 2017

Jan. 24, 2017

Jul. 06, 2016

Jan. 19, 2016

Apr. 27, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Jul. 31, 2015

Class of Stock [Line Items]

Series A Preferred Shares, shares outstanding

0

6,400,000

Repurchases of common shares

10,180,000

Dividends paid on Common Share

$ 0.45

$ 0.60

$ 600

Subsequent Event [Member]

Class of Stock [Line Items]

Dividend Declaration Date

Jan. 24, 2017

Series A Preferred Shares [Member]

Class of Stock [Line Items]

Series A Preferred Shares, shares outstanding

600,000

6,400,000

Preferred Stock, Redemption Date

Jul. 6, 2016

Jan. 19, 2016

Apr. 27, 2016

Stock Redeemed or Called During Period, Shares

600,000

3,600,000

2,200,000

6,400,000

Preferred Stock, Redemption Price Per Share

$ 25

$ 25

Dividends paid on Series A Preferred Shares

$ 1.93750

$ 1,937.5000

$ 1.93750

Common Stock [Member]

Class of Stock [Line Items]

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

$ 0

Common Stock [Member] | Subsequent Event [Member]

Class of Stock [Line Items]

Common share dividend per share declared

$ 0.10

Common share dividend per share annualized

$ 0.40

Dividend Paid Date

Feb. 15, 2017

Dividend Record Date

Feb. 8, 2017

Equity - Characterization of Co

Equity - Characterization of Company's Dividends (Detail)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Common Shares, Ordinary income	[1]	0.00%	52.01%	72.42%
Common Shares, Return of capital		100.00%	28.64%	27.58%
Common Shares, Capital gains		0.00%	19.35%	0.00%
Preferred Shares, Ordinary income	[1]	0.00%	72.89%	100.00%
Preferred Shares, Return of capital		100.00%	0.00%	0.00%
Preferred Shares, Capital gains		0.00%	27.11%	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	Jul. 25, 2016	Aug. 31, 2013ft²	Aug. 04, 2013a	Mar. 31, 2015shares	Dec. 31, 2016USD ($)ft²Rateshares		Dec. 31, 2015USD ($)shares		Dec. 31, 2014shares	Sep. 30, 2016	Aug. 04, 2011
Business Acquisition [Line Items]
Cost to acquire all of the outstanding common Operating Partnership units not owned by the Company | $					$ 27,900
Fair Value Adjustment Cost Basis | $					$ 6,100		$ 4,000
Percentage of outstanding Operating Partnership units					95.80%		95.70%		95.70%
Outstanding Operating Partnership units not owned by the Company					2,545,602
Operating Partnership units not owned by Company | Rate					4.20%
Common operating partnership units redeemed for cash					73,467		11,508
Operating Partnership units redeemed for common shares							0		0
Number Of Common Operating Partnership Units Issued For Additional Space Purchased				3,125
Ownership Interest											97.00%
Lease Expiration Date					Jan. 31, 2021
Buildings and improvements | $					$ 824,867	[1]	$ 793,184	[2]
Debt Instrument, Basis Spread on Variable Rate					1.50%
Washington D C Reporting Segment [Member]
Business Acquisition [Line Items]
Development Of Area For Operations By Joint Venture | a			1.6
Area Of Land Available For Development In Additional Building Space | ft²					0
Storey Park [Member]
Business Acquisition [Line Items]
Ownership Interest										97.00%
Disposition Date	Jul. 25, 2016				Jul. 25, 2016	[3]
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 $13.2 million at December 31, 2016 related to One Fair Oaks, which was classified as held-for-sale at December 31, 2016 and was sold on January 9, 2017.
[2]	(2) 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 and was sold on March 25, 2016.
[3]	(2) This development site could have supported up to 712,000 rentable square feet.

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Net loss	$ (1,646)	$ 1,607	$ (5,491)	$ (4,106)	$ (41,220)	$ 859	$ (2,510)	$ (2,496)	$ (9,867)	$ (45,607)	$ 4,130
Distributions to owners									(26,137)	(35,080)	(35,198)
Redeemable Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Beginning balance				$ 28,813				$ 33,332	28,813	33,332
Net loss									(428)	(2,056)
Changes in ownership, net									957	(931)
Distributions to owners									(1,166)	(1,574)
Other comprehensive income									68	42
Ending balance	$ 28,244				$ 28,813				$ 28,244	$ 28,813	$ 33,332

Benefit Plans - Additional Info

Benefit Plans - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended	12 Months Ended
	Jul. 31, 2016shares	Feb. 28, 2016shares	Jan. 31, 2016shares	Nov. 30, 2015shares	Dec. 31, 2016USD ($)shares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2011shares	Jun. 30, 2016shares	Dec. 31, 2013USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares for issuance						4,100,000			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					11,500,000	11,500,000
Common equity awards remained available for issuance by the Company					4,800,000	4,800,000
Stock options awarded					2,400,000	2,400,000
Stock options outstanding					900,000	900,000
Percentage of options to be vested on the first anniversary of the grant date					25.00%	25.00%
Percentage of options to be vested after the date of grant in each subsequent quarter					6.25%	6.25%
Stock Option Expense | $						$ 200	$ 1,200	$ 500
Unrecognized compensation cost related to non-vested shares | $					$ 200	$ 200
Weighted-average period for recognition of non-vested shares						3 years 2 months
Weighted average grant date fair value of the stock options issued | $ / shares						$ 1.87	$ 1.96	$ 2.67
Amount received from the exercise of stock options | $							$ 26	$ 174
Total intrinsic value of options exercised | $							$ 7	43
Number of common shares issued to independent non-employee trustees					58,319,000	58,319,000	57,718,000
Total fair value of vested shares | $					$ 1,100	$ 1,100	$ 5,300				$ 2,000
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 | $						$ 500	$ 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%
Risk-free interest rate						1.73%	1.61%	1.72%
Expected volatility						27.00%	29.20%	39.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate					25.00%	0.48%
Expected volatility						24.10%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate					300.00%	0.96%
Expected volatility						26.20%
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 Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested share awards issued	181,357	103,429	290,000	229,171
Restricted Share Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested shares | $					$ 4,900	$ 4,900
Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares issued under the plan						7,585	5,843	8,950
Compensation expense associated with restricted share based awards | $						$ 10	$ 11	$ 20
Non-Vested Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested share awards issued						615,122	152,598	164,675
Compensation expense associated with restricted share based awards | $						$ 2,100	$ 3,600	$ 3,200
Weighted average grant date fair value of shares issued | $ / shares						$ 9.40	$ 11.79	$ 12.84
Independent Trustees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares issued to independent non-employee trustees					3,508	3,508				36,828
Trustee Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with restricted share based awards | $						$ 300	$ 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, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Option, Beginning Balance	963,138	1,051,359	1,089,292
Option, Granted	95,000	119,500	135,250
Option, Exercised		(2,750)	(17,171)
Option, Expired	(11,850)	(59,000)	(57,500)
Option, Forfeited	(140,851)	(145,971)	(98,512)
Option, Ending Balance	905,437	963,138	1,051,359	1,089,292
Option, Exercisable	773,067	805,259		552,620
Options expected to vest, subsequent to December 31, 2015	110,528
Weighted Average Exercise Price, Beginning Balance	$ 14.59	$ 15.33	$ 15.83
Weighted Average Exercise Price, Granted	11.03	12.48	11.61
Weighted Average Exercise Price, Exercised		9.30	10.10
Weighted Average Exercise Price, Expired	26.60	22.44	19.08
Weighted Average Exercise Price, Forfeited	12.87	15.06	14.49
Weighted Average Exercise Price, Ending Balance	14.34	14.59	$ 15.33	$ 15.83
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	14.81	$ 15.06		$ 16.49
Weighted Average Exercise Price, Options expected to vest, subsequent to December 31, 2013	$ 11.64
Weighted Average Remaining Contractual Term	4 years 8 months	6 years 1 month	6 years 3 months	6 years 7 months 6 days
Weighted Average Remaining Contractual Term, Exercisable	4 years 1 month	5 years 7 months
Weighted Average Remaining Contractual Term, Exercisable	8 years 3 months 24 days		5 years 1 month 24 days
Aggregate Intrinsic Value, Beginning Balance	$ 59,002	$ 181,352	$ 109,151
Aggregate Intrinsic Value, Ending Balance	35,700	59,002	$ 181,352	$ 109,151
Aggregate Intrinsic Value, Exercisable	35,700	$ 59,002		$ 102,039
Aggregate Intrinsic Value, Options expected to vest, subsequent to December 31, 2015	$ 0

Benefit Plans - Stock Option In

Benefit Plans - Stock Option Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option Outstanding - Options	905,437
Options Outstanding - Weighted Average Remaining Contractual Life	4 years 8 months
Options Outstanding - Weighted Average Exercise Price	$ 14.34
Options Exercisable - Options	773,067
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 14.81	$ 15.06	$ 16.49
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	21,500
Options Outstanding - Weighted Average Remaining Contractual Life	0 years
Options Outstanding - Weighted Average Exercise Price	$ 29.14
Options Exercisable - Options	21,500
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	22,250
Options Outstanding - Weighted Average Remaining Contractual Life	1 year
Options Outstanding - Weighted Average Exercise Price	$ 17.29
Options Exercisable - Options	22,250
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	21,377
Options Outstanding - Weighted Average Remaining Contractual Life	2 years
Options Outstanding - Weighted Average Exercise Price	$ 9.30
Options Exercisable - Options	21,377
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	25,892
Options Outstanding - Weighted Average Remaining Contractual Life	3 years
Options Outstanding - Weighted Average Exercise Price	$ 12.57
Options Exercisable - Options	25,892
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	27,500
Options Outstanding - Weighted Average Remaining Contractual Life	4 years
Options Outstanding - Weighted Average Exercise Price	$ 17.12
Options Exercisable - Options	27,500
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	537,750
Options Outstanding - Weighted Average Remaining Contractual Life	3 years 11 months
Options Outstanding - Weighted Average Exercise Price	$ 14.90
Options Exercisable - Options	537,750
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	43,686
Options Outstanding - Weighted Average Remaining Contractual Life	6 years
Options Outstanding - Weighted Average Exercise Price	$ 12.73
Options Exercisable - Options	40,975
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	61,936
Options Outstanding - Weighted Average Remaining Contractual Life	7 years
Options Outstanding - Weighted Average Exercise Price	$ 11.61
Options Exercisable - Options	42,743
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	75,046
Options Outstanding - Weighted Average Remaining Contractual Life	8 years
Options Outstanding - Weighted Average Exercise Price	$ 12.48
Options Exercisable - Options	33,080
Options Exercisable - Weighted Average Exercise Price	$ 12.48
Two Thousand And Sixteen [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Upper Range	$ 11.03
Option Outstanding - Options	68,500
Options Outstanding - Weighted Average Remaining Contractual Life	9 years
Options Outstanding - Weighted Average Exercise Price	$ 11.03
Options Exercisable - Options	0
Options Exercisable - Weighted Average Exercise Price	$ 11.03

Benefit Plans - Assumptions Use

Benefit Plans - Assumptions Used in Fair Value Determination of Stock Option Granted (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	1.73%	1.61%	1.72%
Expected volatility	27.00%	29.20%	39.00%
Expected dividend yield	3.63%	4.79%	4.66%
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, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Shares, Beginning Balance	192,382	623,421	637,662
Non-vested Shares, Granted	615,122	152,598	164,675
Non-vested Shares, Vested	(91,007)	(401,888)	(137,924)
Non-vested Shares, Expired	(1,630)	(133,371)	(29,514)
Non-vested Shares, Forfeited	(3,493)	(48,378)	(11,478)
Non-vested Shares, Ending Balance	711,374	192,382	623,421
Weighted Average Grant Date Fair Value, Beginning Balance	$ 12.42	$ 13.16	$ 13.33
Weighted Average Grant Date Fair Value, Granted	9.40	11.79	12.84
Weighted Average Grant Date Fair Value, Vested	12.14	13.16	14.21
Weighted Average Grant Date Fair Value, Expired	12.21	12.61	10.21
Weighted Average Grant Date Fair Value, Forfeited	9.54	13.30	13.04
Weighted Average Grant Date Fair Value, Ending Balance	$ 9.85	$ 12.42	$ 13.16

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)segment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Segment Reporting [Abstract]
Number of distinct operating segments | segment	4
Corporate Assets Not Allocated To Any Reportable Segments	$ 17,732	$ 41,357	$ 81,130
Capital Expenditure For Corporate Assets Not Allocated To Any Reportable Segments	$ 536	$ 831	$ 930

Segment Information - Summary o

Segment Information - Summary of Segment Information (Detail)		3 Months Ended										12 Months Ended
		Dec. 31, 2016USD ($)ft²building		Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)ft²	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)ft²building		Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2016USD ($)ft²building		Dec. 31, 2015USD ($)ft²building		Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)ft²building		Aug. 04, 2011
Segment Reporting Information [Line Items]
Corporate Assets Not Allocated To Any Reportable Segments		$ 17,732,000					$ 41,357,000					$ 17,732,000		$ 41,357,000		$ 81,130,000
Number Of Buildings | building		74					99					74		99			131
Square Feet | ft²		6,714,265					7,489,092					6,714,265		7,489,092			8,790,147
Total revenues		$ 38,972,000		$ 40,172,000	$ 38,493,000	$ 42,697,000	$ 43,104,000		$ 42,854,000	$ 43,039,000	$ 43,849,000	$ 160,334,000		$ 172,846,000		161,652,000
Property operating expense												(38,554,000)		(44,093,000)		(43,252,000)
Real estate taxes and insurance												(19,808,000)		(19,745,000)		(17,360,000)
Total property operating income												101,972,000		109,008,000		101,040,000
Depreciation and amortization expense												(60,862,000)		(66,624,000)		(61,796,000)
General and administrative												(16,976,000)		(25,450,000)		(21,156,000)
Acquisition costs												0		0		(2,681,000)
Impairment of real estate assets												(2,772,000)		(60,826,000)		(3,956,000)
Other Nonoperating Income (Expense)												(22,931,000)		9,475,000		4,108,000
(Loss) income from discontinued operations							0		$ 0	$ 0	$ (607,000)	0		(607,000)		1,484,000
Net (loss) income												(1,569,000)		(35,024,000)		17,043,000
Total assets	[1]	1,260,247,000					1,442,406,000	[2]				1,260,247,000		1,442,406,000	[2]		$ 1,612,300,000	[2]
Capital expenditures	[3]											56,931,000		73,850,000		50,789,000
Capital Expenditure For Corporate Assets Not Allocated To Any Reportable Segments												536,000		831,000		930,000
Ownership Interest																			97.00%
Debt Issuance Costs, Line of Credit Arrangements, Net		$ 2,400,000					$ 7,900,000					$ 2,400,000		$ 7,900,000		6,200,000
Washington, D.C. [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building		6					6	[4]				6		6	[4]		6	[4]
Square Feet | ft²		918,266					918,375	[4]				918,266		918,375	[4]		917,008	[4]
Total revenues												$ 45,062,000		$ 44,553,000		33,959,000
Property operating expense												(11,538,000)		(11,363,000)		(9,683,000)
Real estate taxes and insurance												(9,375,000)		(8,238,000)		(5,583,000)
Total property operating income												24,149,000		24,952,000		18,693,000
Total assets	[1]	$ 445,528					$ 517,928,000	[2]				445,528		517,928,000	[2]		$ 503,530,000	[2]
Capital expenditures												$ 13,971,000		$ 12,930,000		23,422,000
Maryland [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building		34					34					34		34			38
Square Feet | ft²		1,886,183					1,885,630					1,886,183		1,885,630			1,999,332
Total revenues												$ 44,710,000		$ 44,226,000		45,767,000
Property operating expense												(9,794,000)		(11,457,000)		(11,482,000)
Real estate taxes and insurance												(3,881,000)		(3,540,000)		(3,907,000)
Total property operating income												31,035,000		29,229,000		30,378,000
Total assets	[1]	$ 332,655					$ 341,375,000	[2]				332,655		341,375,000	[2]		$ 359,603,000	[2]
Capital expenditures												$ 5,308,000		$ 9,003,000		10,185,000
Northern Virginia Reporting Segment [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building		15					40					15		40			49
Square Feet | ft²		1,885,958					2,661,448					1,885,958		2,661,448			3,021,509
Total revenues												$ 40,658,000		$ 55,230,000		53,645,000
Property operating expense												(9,716,000)		(13,540,000)		(13,352,000)
Real estate taxes and insurance												(4,075,000)		(5,540,000)		(5,592,000)
Total property operating income												26,867,000		36,150,000		34,701,000
Total assets	[1]	$ 302,769					$ 374,299,000	[2]				302,769		374,299,000	[2]		$ 439,803,000	[2]
Capital expenditures												$ 33,847,000		$ 43,125,000		7,816,000
Southern Virginia [Member]
Segment Reporting Information [Line Items]
Number Of Buildings | building		19					19					19		19			38
Square Feet | ft²		2,023,858					2,023,639					2,023,858		2,023,639			2,852,298
Total revenues												$ 29,904,000		$ 28,837,000		28,281,000
Property operating expense												(7,506,000)		(7,733,000)		(8,735,000)
Real estate taxes and insurance												(2,477,000)		(2,427,000)		(2,278,000)
Total property operating income												19,921,000		18,677,000		17,268,000
Total assets	[1]	$ 161,563					$ 167,447,000	[2]				161,563		167,447,000	[2]		$ 228,234,000	[2]
Capital expenditures												$ 3,269,000		$ 7,961,000		$ 8,436,000
Storey Park [Member]
Segment Reporting Information [Line Items]
Square Feet | ft²		0	[5]		712,000							0	[5]
Impairment of real estate assets				$ (2,800,000)
Ownership Interest				97.00%
[1]	(1) 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. Corporate assets not allocated to any of our reportable segments totaled $17,732, $41,357 and $81,130 at December 31, 2016, 2015 and 2014, respectively.
[2]	(4) Total assets at December 31, 2015 and 2014 have been restated to exclude a total of $7.9 million and $6.2 million, respectively of unamortized deferred financing costs that are now deducted from the respective debt liability in accordance with ASU 2015-03, which we adopted in the first quarter of 2016.
[3]	(2) Capital expenditures for corporate assets not allocated to any of our reportable segments totaled $536, $831 and $930 at December 31, 2016, 2015 and 2014, respectively.
[4]	(3) Excludes Storey Park, our 97% owned consolidated joint venture within our Washington, DC reporting segment, which was in development during 2014 and 2015 and was sold in July 2016.
[5]	(2) This development site could have supported up to 712,000 rentable square feet.

Quarterly Financial Informati98

Quarterly Financial Information - Summary of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 38,972	$ 40,172	$ 38,493	$ 42,697	$ 43,104	$ 42,854	$ 43,039	$ 43,849	$ 160,334	$ 172,846	$ 161,652
Operating expenses	34,658	32,295	35,681	36,337	102,375	37,079	37,268	40,016	138,972	216,738	150,201
Operating income (loss)	4,314	7,877	2,812	6,360	(59,271)	5,775	5,771	3,833	21,362	(43,892)	11,451
(Loss) income from continuing operations	(1,717)	2,242	(1,992)	(101)	(39,990)	3,997	476	1,099	(1,569)	(34,417)	15,559
Loss from discontinued operations					0	0	0	(607)	0	(607)	1,484
Less: Net loss (income) attributable to noncontrolling interests	71	(107)	390	147	1,870	(38)	114	112	502	2,058	(199)
Net (loss) income attributable to First Potomac Realty Trust	(1,646)	2,135	(1,602)	46	(38,120)	3,959	590	604	(1,067)	(32,966)	16,844
Less: Dividends on preferred shares	0	(11)	(794)	(2,248)	(3,100)	(3,100)	(3,100)	(3,100)	(3,053)	(12,400)	(12,400)
Less: Issuance costs on redeemed preferred shares	0	(517)	(3,095)	(1,904)					(160,030)
Net (loss) income attributable to common shareholders	$ (1,646)	$ 1,607	$ (5,491)	$ (4,106)	$ (41,220)	$ 859	$ (2,510)	$ (2,496)	$ (9,867)	$ (45,607)	$ 4,130
Basic and diluted earnings per common share:
(Loss) income from continuing operations					$ (0.72)	$ 0.01	$ (0.04)	$ (0.03)	$ (0.17)	$ (0.78)	$ 0.05
Loss from discontinued operations					0	0	0	(0.01)	0	(0.01)	0.02
Net (loss) income	$ (0.03)	$ 0.03	$ (0.10)	$ (0.07)	$ (0.72)	$ 0.01	$ (0.04)	$ (0.04)	$ (0.17)	$ (0.79)	$ 0.07

Quarterly Financial Informati99

Quarterly Financial Information - Additional Information (Detail) - shares	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Common shares sold	0	0

Schedule III - Real Estate a100

Schedule III - Real Estate and Accumulated Depreciation (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 299,407
Initial Costs, Land		268,609
Initial Costs, Building and Improvements		683,988
Gross Amount at End of Year, Since Acquisition		349,237
Gross Amount at End of Year, Land		282,923
Gross Amount at End of Year, Building and Improvements		1,018,911
Gross Amount at End of Year, Total		1,301,834
Gross Amount at End of Year, Accumulated Depreciation		242,562
Real Estate, Beginning balance		1,340,050	$ 1,504,372	$ 1,330,180
Real Estate, Acquisitions of rental property		0	0	170,823
Real Estate, Capital expenditures		56,030	73,125	49,860
Real Estate, Impairments		0	(51,521)	(3,956)
Real Estate, Dispositions of rental property		(55,625)	(59,652)	(30,916)
Real Estate, Asset held-for-sale		(19,407)	(127,907)	(643)
Real Estate, Other		(19,214)	1,633	(10,976)
Real Estate, Ending balance		1,301,834	1,340,050	1,504,372
Accumulated Depreciation, Beginning balance		209,784	215,499	185,725
Accumulated Depreciation, Depreciation of rental property		(44,952)	(49,772)	(47,625)
Accumulated Depreciation, Assets held-for-sale		(31,034)	(16,400)	(1,631)
Accumulated Depreciation, Dispositions of rental property		(37,001)	(35,964)	(5,712)
Accumulated Depreciation, Other		(6,207)	(3,123)	(10,508)
Accumulated Depreciation, Ending balance		$ 242,562	$ 209,784	$ 215,499
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		5,159
Gross Amount at End of Year, Land		3,404
Gross Amount at End of Year, Building and Improvements		17,983
Gross Amount at End of Year, Total		21,387
Gross Amount at End of Year, Accumulated Depreciation		$ 7,878
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		3,138
Gross Amount at End of Year, Land		9,220
Gross Amount at End of Year, Building and Improvements		35,194
Gross Amount at End of Year, Total		44,414
Gross Amount at End of Year, Accumulated Depreciation		$ 11,175
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		9,049
Gross Amount at End of Year, Land		18,302
Gross Amount at End of Year, Building and Improvements		29,611
Gross Amount at End of Year, Total		47,913
Gross Amount at End of Year, Accumulated Depreciation		$ 8,741
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		12,946
Gross Amount at End of Year, Land		5,672
Gross Amount at End of Year, Building and Improvements		30,115
Gross Amount at End of Year, Total		35,787
Gross Amount at End of Year, Accumulated Depreciation		$ 10,750
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		6,763
Gross Amount at End of Year, Land		2,398
Gross Amount at End of Year, Building and Improvements		14,422
Gross Amount at End of Year, Total		16,820
Gross Amount at End of Year, Accumulated Depreciation		$ 6,275
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		681
Gross Amount at End of Year, Land		6,102
Gross Amount at End of Year, Building and Improvements		13,282
Gross Amount at End of Year, Total		19,384
Gross Amount at End of Year, Accumulated Depreciation		$ 3,267
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		3,144
Gross Amount at End of Year, Land		7,097
Gross Amount at End of Year, Building and Improvements		17,355
Gross Amount at End of Year, Total		24,452
Gross Amount at End of Year, Accumulated Depreciation		$ 3,539
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		$ 63,214
Initial Costs, Land		17,272
Initial Costs, Building and Improvements		63,480
Gross Amount at End of Year, Since Acquisition		15,134
Gross Amount at End of Year, Land		17,271
Gross Amount at End of Year, Building and Improvements		78,615
Gross Amount at End of Year, Total		95,886
Gross Amount at End of Year, Accumulated Depreciation		$ 19,109
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		14,403
Gross Amount at End of Year, Land		2,041
Gross Amount at End of Year, Building and Improvements		19,730
Gross Amount at End of Year, Total		21,771
Gross Amount at End of Year, Accumulated Depreciation		$ 4,626
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		$ 0
Initial Costs, Land		3,302
Initial Costs, Building and Improvements		10,926
Gross Amount at End of Year, Since Acquisition		3,618
Gross Amount at End of Year, Land		3,301
Gross Amount at End of Year, Building and Improvements		14,545
Gross Amount at End of Year, Total		17,846
Gross Amount at End of Year, Accumulated Depreciation		$ 1,759
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		616
Gross Amount at End of Year, Land		6,753
Gross Amount at End of Year, Building and Improvements		20,152
Gross Amount at End of Year, Total		26,905
Gross Amount at End of Year, Accumulated Depreciation		3,346
Maryland [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		63,214
Initial Costs, Land		81,268
Initial Costs, Building and Improvements		216,646
Gross Amount at End of Year, Since Acquisition		74,651
Gross Amount at End of Year, Land		81,561
Gross Amount at End of Year, Building and Improvements		291,004
Gross Amount at End of Year, Total		372,565
Gross Amount at End of Year, Accumulated Depreciation		$ 80,465
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		628
Gross Amount at End of Year, Land		25,995
Gross Amount at End of Year, Building and Improvements		34,322
Gross Amount at End of Year, Total		60,317
Gross Amount at End of Year, Accumulated Depreciation		$ 7,048
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		51,633
Gross Amount at End of Year, Land		9,122
Gross Amount at End of Year, Building and Improvements		57,811
Gross Amount at End of Year, Total		66,933
Gross Amount at End of Year, Accumulated Depreciation		$ 7,279
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		$ 28,503
Initial Costs, Land		27,077
Initial Costs, Building and Improvements		17,520
Gross Amount at End of Year, Since Acquisition		11,937
Gross Amount at End of Year, Land		27,077
Gross Amount at End of Year, Building and Improvements		29,457
Gross Amount at End of Year, Total		56,534
Gross Amount at End of Year, Accumulated Depreciation		$ 4,790
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		$ 35,201
Initial Costs, Land		16,846
Initial Costs, Building and Improvements		60,905
Gross Amount at End of Year, Since Acquisition		9,879
Gross Amount at End of Year, Land		16,846
Gross Amount at End of Year, Building and Improvements		70,784
Gross Amount at End of Year, Total		87,630
Gross Amount at End of Year, Accumulated Depreciation		$ 12,618
Storey Park [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Property Type	[1]	Land
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		$ 35,556
Initial Costs, Land		29,506
Initial Costs, Building and Improvements		23,269
Gross Amount at End of Year, Since Acquisition		12,809
Gross Amount at End of Year, Land		29,506
Gross Amount at End of Year, Building and Improvements		36,078
Gross Amount at End of Year, Total		65,584
Gross Amount at End of Year, Accumulated Depreciation		$ 2,875
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		5,788
Gross Amount at End of Year, Land		15,744
Gross Amount at End of Year, Building and Improvements		70,620
Gross Amount at End of Year, Total		86,364
Gross Amount at End of Year, Accumulated Depreciation		5,147
Washington, D.C. [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		198,256
Initial Costs, Land		114,979
Initial Costs, Building and Improvements		215,709
Gross Amount at End of Year, Since Acquisition		92,674
Gross Amount at End of Year, Land		124,290
Gross Amount at End of Year, Building and Improvements		299,072
Gross Amount at End of Year, Total		423,362
Gross Amount at End of Year, Accumulated Depreciation		$ 39,757
Plaza Five Hundred [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		7,548
Gross Amount at End of Year, Land		6,265
Gross Amount at End of Year, Building and Improvements		42,981
Gross Amount at End of Year, Total		49,246
Gross Amount at End of Year, Accumulated Depreciation		$ 20,515
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		4,417
Gross Amount at End of Year, Land		3,940
Gross Amount at End of Year, Building and Improvements		16,964
Gross Amount at End of Year, Total		20,904
Gross Amount at End of Year, Accumulated Depreciation		$ 6,037
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		23,482
Gross Amount at End of Year, Land		20,010
Gross Amount at End of Year, Building and Improvements		28,878
Gross Amount at End of Year, Total		48,888
Gross Amount at End of Year, Accumulated Depreciation		$ 10,410
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		2,871
Gross Amount at End of Year, Land		1,646
Gross Amount at End of Year, Building and Improvements		6,450
Gross Amount at End of Year, Total		8,096
Gross Amount at End of Year, Accumulated Depreciation		$ 2,133
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		24,608
Gross Amount at End of Year, Land		4,181
Gross Amount at End of Year, Building and Improvements		34,080
Gross Amount at End of Year, Total		38,261
Gross Amount at End of Year, Accumulated Depreciation		$ 9,639
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		22,080
Gross Amount at End of Year, Land		5,895
Gross Amount at End of Year, Building and Improvements		33,735
Gross Amount at End of Year, Total		39,630
Gross Amount at End of Year, Accumulated Depreciation		$ 7,057
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		211
Gross Amount at End of Year, Land		3,541
Gross Amount at End of Year, Building and Improvements		30,786
Gross Amount at End of Year, Total		34,328
Gross Amount at End of Year, Accumulated Depreciation		$ 3,370
Northern Virginia Development Project [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Location		Northern Virginia
Encumbrances		$ 34,584
Initial Costs, Land		5,241
Initial Costs, Building and Improvements		0
Gross Amount at End of Year, Since Acquisition		49,343
Gross Amount at End of Year, Land		0
Gross Amount at End of Year, Building and Improvements		54,584
Gross Amount at End of Year, Total		54,584
Gross Amount at End of Year, Accumulated Depreciation		0
Northern Virginia [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		34,584
Initial Costs, Land		41,153
Initial Costs, Building and Improvements		118,224
Gross Amount at End of Year, Since Acquisition		134,560
Gross Amount at End of Year, Land		45,478
Gross Amount at End of Year, Building and Improvements		248,458
Gross Amount at End of Year, Total		293,937
Gross Amount at End of Year, Accumulated Depreciation		$ 59,161
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		14,124
Gross Amount at End of Year, Land		5,160
Gross Amount at End of Year, Building and Improvements		37,784
Gross Amount at End of Year, Total		42,944
Gross Amount at End of Year, Accumulated Depreciation		$ 17,333
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		1,347
Gross Amount at End of Year, Land		1,365
Gross Amount at End of Year, Building and Improvements		6,466
Gross Amount at End of Year, Total		7,831
Gross Amount at End of Year, Accumulated Depreciation		$ 2,921
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		1,411
Gross Amount at End of Year, Land		1,324
Gross Amount at End of Year, Building and Improvements		6,377
Gross Amount at End of Year, Total		7,701
Gross Amount at End of Year, Accumulated Depreciation		$ 2,936
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		1,503
Gross Amount at End of Year, Land		1,036
Gross Amount at End of Year, Building and Improvements		7,757
Gross Amount at End of Year, Total		8,793
Gross Amount at End of Year, Accumulated Depreciation		$ 2,606
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		4,387
Gross Amount at End of Year, Land		1,221
Gross Amount at End of Year, Building and Improvements		13,080
Gross Amount at End of Year, Total		14,301
Gross Amount at End of Year, Accumulated Depreciation		$ 5,459
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		4,582
Gross Amount at End of Year, Land		4,815
Gross Amount at End of Year, Building and Improvements		28,953
Gross Amount at End of Year, Total		33,768
Gross Amount at End of Year, Accumulated Depreciation		$ 8,871
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		2,875
Gross Amount at End of Year, Land		2,646
Gross Amount at End of Year, Building and Improvements		14,483
Gross Amount at End of Year, Total		17,129
Gross Amount at End of Year, Accumulated Depreciation		$ 4,990
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		756
Gross Amount at End of Year, Land		1,292
Gross Amount at End of Year, Building and Improvements		4,655
Gross Amount at End of Year, Total		5,947
Gross Amount at End of Year, Accumulated Depreciation		$ 1,703
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		610
Gross Amount at End of Year, Land		1,320
Gross Amount at End of Year, Building and Improvements		2,904
Gross Amount at End of Year, Total		4,223
Gross Amount at End of Year, Accumulated Depreciation		$ 1,060
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		6,113
Gross Amount at End of Year, Land		4,164
Gross Amount at End of Year, Building and Improvements		25,097
Gross Amount at End of Year, Total		29,261
Gross Amount at End of Year, Accumulated Depreciation		$ 7,338
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		2,381
Gross Amount at End of Year, Land		2,024
Gross Amount at End of Year, Building and Improvements		10,341
Gross Amount at End of Year, Total		12,365
Gross Amount at End of Year, Accumulated Depreciation		$ 3,465
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		$ 3,353
Initial Costs, Land		1,860
Initial Costs, Building and Improvements		6,071
Gross Amount at End of Year, Since Acquisition		804
Gross Amount at End of Year, Land		1,881
Gross Amount at End of Year, Building and Improvements		6,854
Gross Amount at End of Year, Total		8,735
Gross Amount at End of Year, Accumulated Depreciation		$ 1,414
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		6,406
Gross Amount at End of Year, Land		2,997
Gross Amount at End of Year, Building and Improvements		15,579
Gross Amount at End of Year, Total		18,576
Gross Amount at End of Year, Accumulated Depreciation		3,024
Southern Virginia [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		3,353
Initial Costs, Land		30,866
Initial Costs, Building and Improvements		133,409
Gross Amount at End of Year, Since Acquisition		47,299
Gross Amount at End of Year, Land		31,245
Gross Amount at End of Year, Building and Improvements		180,330
Gross Amount at End of Year, Total		211,574
Gross Amount at End of Year, Accumulated Depreciation		63,120
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		47
Gross Amount at End of Year, Land		0
Gross Amount at End of Year, Building and Improvements		47
Gross Amount at End of Year, Total		47
Gross Amount at End of Year, Accumulated Depreciation		$ 59
[1]	(2) This development site could have supported up to 712,000 rentable square feet.

Schedule III - Additional Infor

Schedule III - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Tax basis of real estate assets	$ 1,435	$ 1,547
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