Summary of Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2015

Earnings Per Share, Basic and Diluted [Line Items]

Earnings Per Share, Policy [Policy Text Block]

Earnings Per Share of the REIT

Basic earnings per share is calculated by dividing the income available to common shareholders for the period by the weighted average number of common shares outstanding during the period using the two class method. Diluted earnings per share is calculated by dividing the net income available to common shareholders for the period by the weighted average number of common and dilutive securities outstanding during the period.

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.

Principles of 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. The Company consolidates joint ventures that are considered to be variable interest entities (“VIEs”) where we are the primary beneficiary. The Company (i) evaluates the sufficiency of the total equity investment at risk, (ii) reviews the voting rights and decision-making authority of the equity investment holders as a group and whether there are any guaranteed returns, protection against losses, or capping of residual returns within the group and (iii) establishes whether activities within the venture are on behalf of an investor with disproportionately few voting rights in making this VIE determination. To the extent that the Company (i) is the sole entity that has the power to direct the activities of the VIE and (ii) has the obligation or rights to absorb the VIE's losses or receive its benefits, then the Company would be the primary beneficiary and would consolidate the VIE.

All significant intercompany transactions and accounts have been eliminated.

Reclassifications, Policy [Policy Text Block]

Reclassifications

Certain amounts from prior years have been reclassified to conform to current-year presentation including reclassifying the accompanying consolidated balance sheets for assets held for sale.

As disclosed in Note 12, Shareholders' Equity - Trust - Share Repurchase, the Company repurchased common shares pursuant to a share repurchase program authorized by the Company's Board of Trustees. These repurchased shares along with those repurchased in prior periods are subject to state corporate laws that establish the legal status of redeemed shares and prevent them from being reported as treasury shares within the consolidated financial statements. The Trust previously misclassified the repurchased shares as common shares in treasury. The share repurchases should have been classified as reductions of common shares of beneficial interest and additional paid-in capital. The accompanying consolidated balance sheet and statement of equity of the Trust has been restated to correct the misclassification as follows (in thousands except share amounts):

	December 31,						January 1,
	2014			2013			2013
Common shares of beneficial interest (as previously reported)	$	150		$	148		$	119
Impact of reclassification	(1		)	(1		)	(1		)
Common shares of beneficial interest (as adjusted and currently reported)	$	149		$	147		$	118
Additional paid-in capital (as previously reported)	$	3,740,594		$	3,669,618		$	2,687,701
Impact of reclassification	(51,950		)	(51,950		)	(51,950		)
Additional paid-in capital (as adjusted and currently reported)	$	3,688,644		$	3,617,668		$	2,635,751
Common shares in treasury, at cost (as previously reported)	$	(51,951	)	$	(51,951	)	$	(51,951	)
Impact of reclassification	51,951			51,951			51,951
Common shares in treasury, at cost (as adjusted and currently reported)	$	—		$	—		$	—
Number of common shares (as previously reported)	149,807,179			147,846,801			119,720,776
Impact of reclassification	(1,249,909		)	(1,249,909		)	(1,249,909		)
Number of common shares (as adjusted and currently reported)	148,557,270			146,596,892			118,470,867

The reclassification has no impact on the previously reported consolidated statements of comprehensive income, nor does it have any effect on the previously reported consolidated statements of cash flows or shareholders' equity in total.  In addition, the reclassification has no impact on the previously reported consolidated financial statements of the Operating Partnership.

Real Estate and Depreciation, 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 the 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. The total of capitalized compensation costs directly related to the development of property for the years ended December 31, 2015, 2014 and 2013 was $5.5 million, $5.1 million and $3.3 million, respectively. Construction related payables at December 31, 2015 and 2014 were $42.9 million and $41.5 million, respectively.

The Company allocates the purchase price of real estate acquired to land, building and improvements and intangibles at the 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 ("Market Value Intangible"). Origination values are also assigned to in-place leases, and, where appropriate, value is assigned to customer relationships ("Origination Value Intangible").

Acquisition-related costs for properties with in-place leases are expensed as incurred. Expenditures for maintenance and repairs are charged to operations as incurred.

The Company depreciates the amounts allocated to building and improvements over 40 years and amortizes 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. Market Value Intangible amortization is recorded as rental revenue. Origination Value Intangible amortization is recorded as depreciation and amortization. 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.

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.

Investments in Unconsolidated Joint Ventures, 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 comprehensive income.

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 other-than-temporarily-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 3 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.

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.

Restricted Cash, 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.

Accounts Receivable Deferred Rent Receivable, 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.

Revenues, 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 non-cancelable 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.

The Company considers any renewal options in determining the lease term. 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 lease inception 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.

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 during the period that landlord services are rendered in accordance with Securities and Exchange Commission Staff Accounting Bulletin 104, "Revenue Recognition," after the following conditions are met:

a. the termination agreement is executed,

b. the termination fee is determinable, and

c. collectability of the termination fee is assured.

Deferred Financing and Leasing Costs, Policy [Policy Text Block]

Deferred Financing and Leasing Costs

Costs incurred in connection with the financing of the credit facility or leasing are capitalized and amortized on a straight line basis over the term of the related loan or lease. Costs incurred in connection with the financing of mortgage loans or unsecured notes are reported as a deduction from the face amount of that liability and amortized on a straight line basis over the term of the related loan. Deferred financing cost amortization is reported as interest expense. Certain employees of the Company are compensated for leasing services related to the Company's properties. The compensation directly related to these leasing services is capitalized and amortized as a deferred leasing cost over the term of the related lease.

Fair Value of Financial Instruments, Policy [Policy Text Block]

Fair Value of Financial Instruments

The following disclosure of estimated fair value was determined by management using available market information and appropriate valuation methodologies. However, considerable judgment is necessary to interpret market data and develop estimated fair value. Accordingly, the following estimates are not necessarily indicative of the amounts the Company could have realized on disposition of the financial instruments at December 31, 2015 and December 31, 2014. The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts.

The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments. The carrying value of the outstanding amounts under the Company's credit facility is also a reasonable estimate of fair value because interest rates float at a rate based on LIBOR.

The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented. See Note 21 - Derivative Instruments.

The Company used a discounted cash flow model to determine the estimated fair value of its debt as of December 31, 2015 and December 31, 2014. This is a Level 3 fair value calculation. The inputs used in preparing the discounted cash flow model include actual maturity dates and scheduled cash flows as well as estimates for market value discount rates. The Company updates the discounted cash flow model on a quarterly basis to reflect any changes in the Company's debt holdings and changes to discount rate assumptions.

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 still 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 and state income taxes separate from the Company. 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 itself is also subject to tax in certain states and the United Kingdom. Accordingly, the Company recognizes 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, 2015, 2014 and 2013 and no interest and penalties accrued at December 31, 2015 or December 31, 2014 which related to any uncertain tax positions or significant unrecognized tax benefits.

Certain of the Company's taxable REIT subsidiaries had net operating loss carryforwards available of approximately $29.1 million as of December 31, 2015. These carryforwards begin to expire in 2018. The Company has considered 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 (in prior years) Luxembourg. With few exceptions, the Company and its subsidiaries are no longer subject to examination by taxing authorities in these jurisdictions for years prior to 2009.

The Federal tax cost basis of the wholly owned real estate was $7.6 billion and $7.5 billion at December 31, 2015 and 2014, respectively.

Share-based Compensation, 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.

Derivatives, Policy [Policy Text Block]

Derivative Financial Instruments

We borrow funds at a combination of fixed and variable rates. Borrowings under our revolving credit facility and certain bank mortgage loans bear interest at variable rates. Our long-term debt typically bears interest at fixed rates. Our interest rate risk management objectives are to limit generally the impact of interest rate changes on earnings and cash flows and to lower our overall borrowing costs. To achieve these objectives, from time to time, we enter into interest rate hedge contracts such as collars, swaps, caps and treasury lock agreements in order to mitigate our interest rate risk with respect to various debt instruments. We generally do not hold or issue these derivative contracts for trading or speculative purposes. The interest rate on all of our variable rate debt is generally adjusted at one or three month intervals, subject to settlements under interest rate hedge contracts.

Interest rate swaps involve the receipt of variable-rate amounts from a counterparty in exchange for making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive loss (for the Trust) and general partner's equity and limited partners' equity - common units (for the Operating Partnership) and is subsequently reclassified into interest expense in the period that the hedged forecasted transaction affects earnings.

Foreign Currency Transactions and Translations Policy [Policy Text Block]

Foreign Currency

The functional currency of the Company's United Kingdom operations is pounds sterling. The Company translates the financial statements for the United Kingdom operations into US dollars. For the Trust, gains and losses resulting from this translation are included in accumulated other comprehensive loss as a separate component of shareholders' equity and a proportionate amount of gain or loss is allocated to noncontrolling interest - operating partnership - common units. For the Operating Partnership, gains and losses resulting from this translation are included in general partner's equity and limited partners' equity - common units. Upon sale or upon complete or substantially complete liquidation of the Company's foreign investment, the gain or loss on the sale will include the cumulative translation adjustments that have been previously recorded in accumulated other comprehensive loss and noncontrolling interest - operating partnership - common units (for the Trust) and in general partner's equity and limited partners' equity - common units (for the Operating Partnership).

Comprehensive Income, Policy [Policy Text Block]

Comprehensive Income

Comprehensive income, as reflected on the consolidated statements of comprehensive income, is defined as all changes in equity during each period except for those resulting from investments by or distributions to shareholders. Accumulated other comprehensive loss, as reflected on the Company's consolidated balance sheets and consolidated statements of equity, reflects the effective portion of the cumulative changes in the fair value of derivatives in qualifying cash flow hedge relationships as well as gains and losses resulting from foreign currency translation.

Real Estate Held for Development and Sale, Policy [Policy Text Block]

Sales of Real Estate

The Company accounts for the sale of real estate assets and any related gain recognition in accordance with the accounting guidance applicable to sales of real estate, which establishes standards for recognition of profit on all real estate sales transactions, other than retail land sales. The Company recognizes the sale, and associated gain or loss from the disposition, provided that the earnings process is complete and the Company is not obligated to perform significant activities after the sale.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently Issued Accounting Standards

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which supersedes nearly all existing revenue recognition guidance. The standard clarifies the required factors that an entity must consider when recognizing revenue. The standard also requires additional disclosures concerning contracts with customers, judgments concerning revenue recognition, and assets recognized for the costs to obtain or fulfill a contract. ASU 2014-09 is effective for the Company beginning January 1, 2018. The Company is evaluating the impact ASU 2014-09 will have on its financial position and results of operations.

In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs ("ASU 2015-03"). The standard requires the costs for issuing debt to appear on a balance sheet as a direct deduction from the debt's value. In August 2015, the FASB issued ASU 2015-15, Interest - Imputation of Interest (Subtopic 835-30): Presentation and Subsequent Measurements of Debt Issuance Costs Associated with Line-of-Credit Arrangements. The standard allows companies to elect to continue to classify costs related to a credit facility as an asset, and the Company has elected to do so. ASU 2015-03 is effective for the Company beginning January 1, 2016 and the standard allows for early adoption. The Company has adopted ASU 2015-03 as of  December 31, 2015 and the standard has been applied retrospectively. See "Change in Accounting Principle" above.

In February 2015, the FASB issued ASU 2015-02, Amendments to the Consolidation Analysis (Topic 810) ("ASU 2015-02"). The standard requires that all entities re-evaluate and revise consolidation documentation for limited partnerships and similar legal entities. It makes changes to both the variable interest model and voting model. ASU 2015-02 is effective for the Company beginning January 1, 2016. The standard allows for either a full retrospective or a modified retrospective approach to adoption. The Company does not believe that ASU 2015-02 will have a material impact on its financial position and results of operations.

In February 2016, the FASB issued ASU 2016-02, ‘‘Leases’’ ("ASU 2016-02"). ASU 2016-02 amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. ASU 2016-02 is effective for the Company beginning January 1, 2019. Early adoption of ASU 2016-02 is permitted. The standard requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. The Company is evaluating the impact ASU 2016-02 will have on its financial position and results of operations.

Liberty Property Limited Partnership [Member]

Earnings Per Share, Basic and Diluted [Line Items]

Earnings Per Share, Policy [Policy Text Block]

Earnings Per Unit of the Operating Partnership

Basic earnings per unit is calculated by dividing the income available to common unitholders for the period by the weighted average number of common units outstanding during the period using the two class method. Diluted earnings per unit is calculated by dividing the income available to common unitholders for the period by the weighted average number of common and dilutive securities outstanding during the period.