Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies [Abstract]

Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]

Share Based Compensation

Share based compensation cost is measured at the grant date, based on the fair value of the award, and is recognized as expense over the employees' requisite service period.

Income Tax, Policy [Policy Text Block]

Income Taxes

The Company has elected to be taxed as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the "Code"). As a result, the Company generally is not subject to federal income taxation at the corporate level to the extent it distributes annually at least 100% of its REIT taxable income, as defined in the Code, to its shareholders and satisfies certain other organizational and operational requirements. The Company has met these requirements and, accordingly, no provision has been made for federal income taxes in the accompanying consolidated financial statements. If the Company fails to qualify as a REIT in any taxable year, the Company will be subject to federal income tax on its taxable income at regular corporate rates (including any alternative minimum tax) and may not be able to qualify as a REIT for the four subsequent taxable years. Even as a REIT, the Company may be subject to certain state and local income and property taxes, and to federal income and excise taxes on undistributed taxable income.

Several of the Company's subsidiaries are taxable REIT subsidiaries (each a "TRS") and are subject to federal income taxes. In general, a TRS may perform additional services for tenants and generally may engage in real estate or non-real estate businesses that are not permitted REIT activities. The Company is also taxed in certain states, the United Kingdom, and Luxembourg. Accordingly, the Company has recognized federal, state and foreign income taxes in accordance with US GAAP, as applicable.

There are no uncertain tax positions or possibly significant unrecognized tax benefits that are reasonably expected to occur within the next 12 months. The Company's policy is to recognize interest accrued related to unrecognized benefits in interest expense and penalties in other expense. There were no interest or penalties deducted in any of the years ended December 31, 2011, 2010 and 2009 and no interest and penalties accrued at December 31, 2011 or December 31, 2010.

Certain of the Company's taxable REIT subsidiaries had net operating loss carryforwards available of approximately $19.3 million as of December 31, 2011. These carryforwards begin to expire in 2018. The Company has considered estimated future taxable income and has determined that a valuation allowance for the full carrying value of net operating loss carryforwards is appropriate.

The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, certain state and local jurisdictions, the United Kingdom and Luxembourg. With few exceptions, the Company is no longer subject to U.S. federal, state, and local, or United Kingdom and Luxembourg examinations by tax authorities for years before 2007.

The Federal tax cost basis of the real estate was $5.8 billion and $5.6 billion at December 31, 2011 and 2010, respectively.

Revenue Recognition, Policy [Policy Text Block]

Revenues

The Company earns rental income under operating leases with tenants. Rental income is recognized on a straight line basis over the applicable lease term. Operating expense reimbursements consisting of amounts due from tenants for real estate taxes, utilities and other recoverable costs are recognized as revenue in the period in which the corresponding expenses are incurred.

Termination fees (included in rental revenue) are fees that the Company has agreed to accept in consideration for permitting certain tenants to terminate their lease prior to the contractual expiration date. The Company recognizes termination fees in accordance with Securities and Exchange Commission Staff Accounting Bulletin 104, "Revenue Recognition," when the following conditions are met:

a. the termination agreement is executed,

b. the termination fee is determinable,

c. all landlord services pursuant to the terminated lease have been rendered, and

d. collectability of the termination fee is assured.

Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]

Goodwill

Goodwill represented the amounts paid in excess of the fair value of the net assets acquired in connection with the acquisition of Republic Property Trust in October 2007. Pursuant to ASC 350, "Intangible - Goodwill and Other" ("ASC 350"), goodwill is not amortized to expense but rather is analyzed for impairment. In conjunction with the purchase of Republic Property Trust, goodwill and other intangibles of $15.7 million were recorded. The goodwill was assigned to the Metro Washington, D.C. operation ("reporting unit") which is part of the Metro reportable segment. The Company assessed goodwill for impairment annually in November and in interim periods if certain events occurred indicating the carrying value may be impaired. The Company performed its analysis for potential impairment of goodwill in accordance with ASC 350 in November 2009, which requires that a two-step impairment test be performed on goodwill. In the first step, the fair value of the reporting unit is compared to its carrying value. The estimated fair value of the reporting unit is determined using a discounted cash flow model which considers a number of assumptions that are subject to economic and market uncertainties including, among others, demand for space, competition for tenants, changes in market rental rates, and operating costs. If the fair value exceeds its carrying value, goodwill is not impaired, and no further testing is required. If the carrying value of the reporting unit exceeds its fair value, then a second step must be performed in order to determine the implied fair value of the goodwill and compare it to the carrying value of the goodwill. If the carrying value of goodwill exceeds its implied fair value then an impairment loss is recorded equal to the difference. An impairment loss of $15.7 million was recognized during the year ended December 31, 2009 and there is no longer any goodwill in the Company's consolidated balance sheets.

Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block]

Cash and Cash Equivalents

Highly liquid investments with a maturity of three months or less when purchased are classified as cash equivalents.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

The preparation of financial statements in conformity with U.S. generally accepted accounting principles ("US GAAP") requires management to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Consolidation, Policy [Policy Text Block]

Principles of Consolidation

The consolidated financial statements of the Company include the Trust, the Operating Partnership, wholly owned subsidiaries and those subsidiaries in which the Company owns a majority voting interest with the ability to control operations of the subsidiaries and where no approval, veto or other important rights have been granted to the noncontrolling shareholders. All significant intercompany transactions and accounts have been eliminated.

Re

Comparability of Prior Year Financial Data, Policy [Policy Text Block]

Reclassifications

Certain amounts from prior years have been reclassified to conform to current-year presentation

Property, Plant and Equipment, Policy [Policy Text Block]

Real Estate and Depreciation

The properties are recorded at cost and are depreciated using the straight line method over their estimated useful lives. The estimated useful lives are as follows:

Building and improvements	40 years (blended)
Capital improvements	15 - 20 years
Equipment	5 - 10 years
Tenant improvements	Term of the related lease

Expenditures directly related to the acquisition or improvement of real estate, including interest and other costs capitalized during development, are included in net real estate and are stated at cost. The capitalized costs include pre-construction costs essential to the development of the property, development and construction costs, interest costs, real estate taxes, development-related salaries and other costs incurred during the period of development. In accordance with Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") 805, "Business Combinations" ("ASC 805"), effective January 1, 2009, certain acquisition-related costs are expensed as incurred. Expenditures for maintenance and repairs are charged to operations as incurred.

In accordance with ASC 805, the Company allocates the purchase price of real estate acquired to land, building and improvements and intangibles based on the relative fair value of each component. Lease values for acquired properties are recorded based on the present value (using a discount rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to each in-place lease and (ii) management's estimate of fair market lease rates for each corresponding in-place lease. Origination values are also assigned to in-place leases, and, where appropriate, value is assigned to customer relationships.

The Company considers any renewal options in determining the lease term in accordance with the definition included in ASC 840, "Leases." To the extent a lease includes a tenant option to renew or extend the duration of the lease at a fixed or determinable rental rate, the Company evaluates whether or not that option represents a bargain renewal option by analyzing if there is reasonable assurance at the acquisition date that the tenant will exercise the option because the rental rate is sufficiently lower than the expected rental rate for equivalent property under similar terms and conditions at the exercise date.

The Company depreciates the amounts allocated to building and improvements over 40 years and the amounts allocated to intangibles relating to in-place leases, which are included in deferred financing and leasing costs and other liabilities in the accompanying consolidated balance sheets, over the remaining term of the related leases. This calculation includes both the remaining noncancelable period and any bargain renewal option periods.

Once a property is designated as held for sale, no further depreciation expense is recorded. Operations for properties identified as held for sale and/or sold where no continuing involvement exists are presented in discontinued operations for all periods presented.

The Company evaluates its real estate investments upon occurrence of a significant adverse change in its operations to assess whether any impairment indicators are present that affect the recovery of the recorded value. If indicators of impairment are identified, the Company estimates the future undiscounted cash flows from the use and eventual disposition of the property and compares this amount to the carrying value of the property. If any real estate investment is considered impaired, a loss is recognized to reduce the carrying value of the property to its estimated fair value.

Equity Method Investments, Policy [Policy Text Block]

Investments in Unconsolidated Joint Ventures

The Company accounts for its investments in unconsolidated joint ventures using the equity method of accounting as the Company exercises significant influence, but does not control these entities. Under the equity method of accounting, the net equity investment of the Company is reflected in the accompanying consolidated balance sheets and the Company's share of net income from the joint ventures is included in the accompanying consolidated statements of operations.

On a periodic basis, management assesses whether there are any indicators that the value of the Company's investments in unconsolidated joint ventures may be impaired. An investment is impaired only if management's estimate of the value of the investment is less than the carrying value of the investment, and such decline in value is deemed to be other-than-temporary. To the extent impairment has occurred, the loss is measured as the excess of the carrying amount of the investment over the estimated fair value of the investment. The estimated fair value of the investments is determined using a discounted cash flow model which is a Level III valuation under ASC 820, "Fair Value Measurement." The Company considers a number of assumptions that are subject to economic and market uncertainties including, among others, demand for space, competition for tenants, changes in market rental rates, operating costs, capitalization rates, holding periods and discount rates. As these factors are difficult to predict and are subject to future events that may alter management's assumptions, the values estimated by management in its impairment analyses may not be realized.

During the year ended December 31, 2009, the Company recognized impairment charges related to the decline in the fair values below the carrying values of certain of the Company's investments in unconsolidated joint ventures. The Company considered the decline in fair value below the carrying value of $78.8 million to be other-than-temporary. The investment in unconsolidated joint ventures was impaired for the following reportable segments as of December 31, 2009 (in thousands):

Reportable Segment	Impairment Amount
Central	$	6,963
Metro	64,060
United Kingdom	7,779
Total	$	78,802

No impairment losses on unconsolidated joint ventures were recognized during the years ended December 31, 2011 or 2010.

Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]

Restricted Cash

Restricted cash includes tenant security deposits and escrow funds that the Company maintains pursuant to certain mortgage loans. Restricted cash also includes the undistributed proceeds from the sale of residential land in Kent County, United Kingdom.

Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy

Accounts Receivable/Deferred Rent Receivable

The Company's accounts receivable are comprised of rents and charges for property operating costs due from tenants. The Company's deferred rent receivable represents the cumulative difference between rent revenue recognized on a straight line basis and contractual payments due under the terms of tenant leases. The Company periodically performs a detailed review of amounts due from tenants to determine if accounts receivable and deferred rent receivable balances are collectible. Based on this review, accounts receivable and deferred rent receivable are reduced by an allowance for doubtful accounts. The Company considers tenant credit quality and payment history and general economic conditions in determining the allowance for doubtful accounts. If the accounts receivable balance or the deferred rent receivable balance is subsequently deemed uncollectible, the receivable and allowance for doubtful account balance are written off.

Deferred Charges, Policy [Policy Text Block]

Deferred Financing and Leasing Costs

Costs incurred in connection with financing or leasing are capitalized and amortized on a straight line basis over the term of the related loan or lease. Deferred financing cost amortization is reported as interest expense. Intangible assets related to acquired in-place leases are amortized over the terms of the related leases.