Fair Value Disclosures [Abstract] Summary Of Carrying Amount And Fair Value Of Financial Instruments Schedule of Carrying Amount and Fair Value of Financial Instruments [Table Text Block] Schedule of Carrying Amount and Fair Value of Financial Instruments [Table Text Block] Fair Value, Liabilities Measured on Recurring Basis Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] Components Of Rental Income and Expense [Abstract] Components Of Rental Income And Expense [Abstract] Schedule of Minimum Rents [Table] Schedule of Minimum Rents [Table] Schedule of Minimum Rents [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Below Market Leases [Member] Below Market Leases [Member] Below Market Leases [Member] Above Market Leases [Member] Above Market Leases [Member] Above Market Leases [Member] Minimum Rent [Line Items] Minimum Rent [Line Items] Minimum Rent [Line Items] Straight-line rents Straight Line Rent This element represents the adjustment made to recognize base rents on a straight line basis from when the tenant controls the space through the term of the related lease, net of valuation adjustments. Net amortization of above and below market leases Finite Lived Intangible Asset Liabilities Amortization Expense Net amortization of acquired above and below market leases. Amortization of Acquired Intangible Assets Amortization of Acquired Intangible Assets Amortization Of Acquired Below Market Leases Amortization Of Acquired Below Market Leases This element represents the amortization of acquired below market lease liabilities over the related lease term. The amortization is reflected as additional rental income from below market leases. Stockholders' Equity Note [Abstract] Stockholders' Equity [Table] Stockholders' Equity [Table] Stockholders' Equity [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] 5.417% Series 1 Cumulative Convertible Preferred [Member] 5.417% Series 1 Cumulative Convertible Preferred [Member] Five point Four One Seven Percentage Series One Cumulative Convertible Preferred Stock [Member] Common Stock [Member] Common Stock [Member] Statement, Equity Components [Axis] Equity Component [Domain] Subsidiary, Sale of Stock [Axis] Subsidiary, Sale of Stock [Axis] Sale of Stock, Name of Transaction [Domain] Sale of Stock, Name of Transaction [Domain] At The Market Equity Program [Member] At The Market Equity Program [Member] At The Market Equity Program [Member] Statement [Line Items] Statement [Line Items] Preferred Stock, Dividends, Per Share, Cash Paid Preferred Stock, Dividends, Per Share, Cash Paid Preferred Stock, Dividends Per Share, Declared Preferred Stock, Dividends Per Share, Declared Common Stock, Dividends, Per Share, Declared Common Stock, Dividends, Per Share, Declared Common Stock, Dividends, Per Share, Cash Paid Common Stock, Dividends, Per Share, Cash Paid Preferred Shares, percentage Preferred Stock, Dividend Rate, Percentage Convertible Preferred Stock, Converstion Price Per Share Convertible Preferred Stock, Conversion Price Per Share Convertible Preferred Stock, Conversion Price Per Share Aggregate offering price of common share Aggregate Offering Price Of Common Share Maximum aggregate offering price of common shares. Shares issued under equity program Stock Issued During Period, Shares, New Issues Weighted average price per common share Weighted Average Price Per Common Share Weighted average price per common share Net cash proceeds of common stock Proceeds from Issuance of Common Stock Commissions related to sales of common shares Payments of Stock Issuance Costs Common Stock Issued, Per Share Common Stock Issued, Per Share Common Stock Issued, Per Share Preferred Stock, Shares Outstanding Preferred Stock, Conversion Basis Earnings Per Share [Abstract] EARNINGS PER SHARE Earnings Per Share [Text Block] Accounting Policies [Abstract] Total interest costs incurred Interest Costs Incurred Interest capitalized Interest Costs, Capitalized During Period Interest expense Interest Expense Cash paid for interest, net of amounts capitalized Interest Paid, Net Cash paid for income taxes Income Taxes Paid, Net Loans Assumed Loans Assumed Components of Rental Income [Table] Components of Rental Income [Table] Components of Rental Income [Table] Products and Services [Axis] Products and Services [Domain] Commercial Real Estate [Member] Residential Real Estate [Member] Minimum rents Operating Leases, Income Statement, Minimum Lease Revenue Cost reimbursement Tenant Reimbursements Percentage rent Operating Leases, Income Statement, Percentage Revenue Other Other Rental Income This element represents other rental revenue earned during the period. Total rental income Rental income The total amount of rental revenue recognized for the period from real estate operations, including minimum rent, straight-line rent, percentage rent and tenant reimbursements. Nature Of Operations [Abstract] Nature Of Operations [Abstract] Number of Real Estate Properties Minimum Percentage Of Taxable Income Distributed To Shareholders Minimum Percentage Of Taxable Income Distributed To Shareholders Minimum percentage of taxable income distributed to shareholders. Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investment, Equity Method Investee, Name [Axis] Schedule of Equity Method Investment, Equity Method Investee, Name [Axis] Equity Method Investee, Name [Domain] Equity Method Investee, Name [Domain] Federal / Lion Venture LP [Member] Federal / Lion Venture LP [Member] Federal / Lion Venture LP [Member] Real Estate Partnerships Operating Results [Line Items] Real Estate Partnerships Operating Results [Line Items] Real Estate Partnerships Operating Results [Line Items] Revenue Revenues Other operating expenses Other Expenses Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Interest expense Total expenses Total Expenses Total expenses including operating expenses, interest expense, depreciation and amortization, and other expenses. NET INCOME Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Our share of net income from real estate partnership Income (Loss) from Equity Method Investments Real estate, net Real Estate Investment Property, Net Cash Cash and Cash Equivalents, at Carrying Value Other assets Other Assets TOTAL ASSETS Assets Mortgages payable Secured Debt Other liabilities Other Liabilities Partners' capital Partners' Capital TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY Liabilities and Equity Our share of unconsolidated debt Share Of Unconsolidated Debt Share Of Unconsolidated Debt Our investment in real estate partnership Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Related Party Transactions, by Related Party [Axis] Related Party [Domain] Chief Executive Officer [Member] Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Award Type and Plan Name [Axis] Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Award Type and Plan Name [Axis] Share-based Compensation Arrangements by Share-based Payment Award, Award Type and Plan Name [Domain] Share-based Compensation Arrangements by Share-based Payment Award, Award Type and Plan Name [Domain] Restricted Stock [Member] Stock Options [Member] Stock Options [Member] Performance Incentive Plan 2010 [Member] Performance Incentive Plan 2010 [Member] Long Term Incentive Plan 2001 [Member] Long Term Incentive Plan 2001 [Member] Long Term Incentive Plan 1993 [Member] Long Term Incentive Plan 1993 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Stock Award [Member] Stock Award [Member] Stock Award [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number Of Share Based Compensation Plans Number Of Share Based Compensation Plans Number Of Share Based Compensation Plans with outstanding grants Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Contractual term (in years) Share Based Compensation Arrangement By Share Based Payment Award Contractual Period Contractual period as to when the equity-based award expires as specified in the award agreement. Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Granted Stock Granted During Period, Value, Share-based Compensation, Net of Forfeitures Officers' Compensation Officers' Compensation Officers Compensation, Target Bonus As Percentage Of Base Salary Officers Compensation, Target Bonus As Percentage Of Base Salary Officers Compensation, Target Bonus As Percentage Of Base Salary Target Amount For Potential Equity To Be Issued Target Amount For Potential Equity To Be Issued Target Amount For Potential Equity To Be Issued Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized Period for recognition (in years) Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition The overall period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years. Weighted-average period for recognition (in years) Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Share-based Compensation, Allocation and Classification in Financial Statements [Abstract] Share-based compensation incurred Allocated Share-based Compensation Expense Capitalized share-based compensation Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Share-based compensation expense Share-based Compensation Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Statement, Equity Components [Axis] Equity Component [Domain] Accumulated Other Comprehensive Income (Loss) [Member] Accumulated Other Comprehensive Income (Loss) [Member] Derivative, by Nature [Axis] Derivative, Name [Domain] Interest Rate Swap [Member] Fair Value by Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Fair Value, Disclosure Item Amounts [Domain] Carrying Value [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value [Member] Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Loss on Derivative Instruments, Pretax Cash Flow Hedge Loss Reclassified to Interest Expense Mortgages and notes payable, carrying value Mortgages and Notes Payable Mortgages and Notes Payable Senior notes and debentures, carrying value Senior Notes Mortgages and notes payable, fair value Mortgages and Notes Payable, Fair Value Disclosure Mortgages and Notes Payable, Fair Value Disclosure Senior notes and debentures, fair value Senior Notes and Debentures, Fair Value Disclosure Senior Notes and Debentures, Fair Value Disclosure Number of Interest Rate Derivatives Held Number of Interest Rate Derivatives Held Notional Amount of Interest Rate Cash Flow Hedge Derivatives Notional Amount of Interest Rate Cash Flow Hedge Derivatives Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Interest rate swaps Derivative Financial Instruments, Liabilities, Fair Value Disclosure Other Comprehensive Income Other Comprehensive Income (Loss), Net of Tax Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Discontinued Operations and Disposal Groups [Abstract] Summary Of The Financial Information For The Discontinued Operations Schedule Of Discontinued Operations Financial Information Table Text Block Schedule Of Discontinued Operations Financial Information Table Text Block Commitments and Contingencies Disclosure [Abstract] DISCONTINUED OPERATIONS Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Real Estate Investments [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Montrose Crossing [Member] Montrose Crossing [Member] Montrose Crossing [Member] Plaza El Segundo [Member] Plaza El Segundo [Member] Plaza El Segundo [Member] Debt Instrument [Axis] Debt Instrument, Name [Domain] New Mortgage Debt [Member] New Mortgage Debt [Member] New Mortgage Debt [Member] Real Estate Investments [Line Items] Real Estate Investments [Line Items] Real Estate Investments [Line Items] Business Acquisition Cost of Acquired Entity Cash Paid and Total Debt Assumed Business Acquisition Cost of Acquired Entity Cash Paid and Total Debt Assumed Business Acquisition Cost of Acquired Entity Cash Paid and Total Debt Assumed, if any Business Acquisition, Percentage of Voting Interests Acquired Business Acquisition, Percentage of Voting Interests Acquired Business Acquisition Cost of Acquired Entity Cash Paid and Share of Debt Assumed Business Acquisition Cost of Acquired Entity Cash Paid and Share of Debt Assumed Business Acquisition Cost of Acquired Entity Cash Paid and Our Share of Debt Assumed, if any. Debt Instrument, Fair Value Disclosure Debt Instrument, Fair Value Disclosure Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets Business Acquisition Purchase Price Allocation Amortizable Intangible Below Market Lease Liabilities Business Acquisition Purchase Price Allocation Amortizable Intangible Below Market Lease Liabilities The amount of acquisition cost of a business combination allocated to below market lease liabilities that will be amortized. Business Acquisition Purchase Price Business Acquisition Purchase Price The purchase price of the acquired entity. Business Acquisition, Cost of Acquired Entity, Cash Paid Business Acquisition, Cost of Acquired Entity, Cash Paid Debt Instrument, Face Amount Debt Instrument, Face Amount SHARE-BASED COMPENSATION PLANS Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Income Statement [Abstract] Statement [Table] Statement [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] REVENUE Revenues [Abstract] Rental income Other property income Other Real Estate Revenue Mortgage interest income Revenue Mortgage Interest Interest income earned from mortgage notes receivable. Total revenue EXPENSES Operating Expenses [Abstract] Rental expenses Direct Costs of Leased and Rented Property or Equipment Real estate taxes Real Estate Tax Expense General and administrative General and Administrative Expense Total operating expenses Operating Expenses OPERATING INCOME Operating Income (Loss) Other interest income Investment Income, Interest Interest expense Early extinguishment of debt Gains (Losses) on Extinguishment of Debt Income from real estate partnerships INCOME FROM CONTINUING OPERATIONS Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest DISCONTINUED OPERATIONS Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Discontinued operations - income Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax INCOME BEFORE GAIN ON SALE OF REAL ESTATE Income (Loss) before Gain or Loss on Sale of Properties, and Extraordinary Items Gain On Sale Of Real Estate in Real Estate Partnership Gain Loss On Sale Of Properties in Real Estate Partnership Gain loss on sale of properties in real estate partnership Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest NET INCOME ATTRIBUTABLE TO THE TRUST Net Income (Loss) Attributable to Parent Dividends on preferred shares Preferred Stock Dividends, Income Statement Impact NET INCOME AVAILABLE FOR COMMON SHAREHOLDERS Net Income (Loss) Available to Common Stockholders, Basic EARNINGS PER COMMON SHARE, BASIC Earnings Per Share, Basic [Abstract] Continuing operations Income (Loss) from Continuing Operations, Per Basic Share Discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share Gain on sale of real estate Gain on Sale of Real Estate per Basic Share Gain On Sale Of Real Estate Per Basic Share. Earnings Per Share, Basic, Total Earnings Per Share, Basic Weighted average common shares outstanding-basic Weighted Average Number of Shares Outstanding, Basic EARNINGS PER COMMON SHARE, DILUTED Earnings Per Share, Diluted [Abstract] Continuing operations Income (Loss) from Continuing Operations, Per Diluted Share Discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Gain on sale of real estate Gain on Sale of Real Estate per Diluted Share Gain On Sale Of Real Estate Per Diluted Share. Earnings Per Share, Diluted, Total Earnings Per Share, Diluted Weighted average number of common shares-diluted Weighted Average Number of Shares Outstanding, Diluted Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive Income Attributable to the Trust Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule Of Principal Components Of Rental Income Schedule of Component of Rental Income [Table Text Block] Schedule of Component of Rental Income [Table Text Block] Schedule of Minimum Rents Components Schedule Of Minimum Rents Components [Table TextBlock] Schedule of Minimum Rents Components [Table Text Block] Schedule Of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Summary Of Share Based Compensation Expense Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] COMPONENTS OF RENTAL INCOME AND EXPENSE Operating Leases Revenue And Expense Text Block The principal components of rental income and/or rental expense recognized for the period. REAL ESTATE PARTNERSHIPS Equity Method Investments Disclosure [Text Block] Weighted average unvested shares outstanding Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Anti-dilutive stock options excluded from dilutive earnings per share calculation Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Cumulative convertible preferred share, dividend rate Principles of Consolidation Consolidation, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] SHAREHOLDERS’ EQUITY Stockholders' Equity Note Disclosure [Text Block] BUSINESS AND ORGANIZATION Nature of Operations [Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Operating (including $263,583 and $263,570 of consolidated variable interest entities, respectively) Rental Properties Construction-in-progress Construction in Progress, Gross Real Estate Investment Property, At Cost, Total Real Estate Investment Property, at Cost Less accumulated depreciation and amortization (including $6,741 and $4,991 of consolidated variable interest entities, respectively) Real Estate Investment Property, Accumulated Depreciation Net real estate Cash and cash equivalents Accounts and notes receivable, net Accounts and Notes Receivable, Net Mortgage notes receivable, net Mortgage Loans on Real Estate, Commercial and Consumer, Net Investment in real estate partnership Prepaid expenses and other assets Prepaid Expense and Other Assets Debt issuance costs, net of accumulated amortization of $9,886 and $9,098, respectively Deferred Finance Costs, Net Liabilities Liabilities [Abstract] Mortgages payable (including $207,099 and $207,683 of consolidated variable interest entities, respectively) Capital lease obligations Capital Lease Obligations Notes payable Notes Payable Senior notes and debentures Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Dividends payable Dividends Payable Security deposits payable Security Deposit Liability Other liabilities and deferred credits Other liabilities and deferred credits Other liabilities & deferred credits which includes deferred revenue, prepaid rent and below market leases. Also includes liabilities not individually reported in the financial statements, or not separately disclosed in notes. Total liabilities Liabilities Commitments and contingencies (Note 7) Commitments and Contingencies Redeemable noncontrolling interest Redeemable Noncontrolling Interest, Equity, Carrying Amount Shareholders' equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred shares, authorized 15,000,000 shares, $.01 par: 5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 399,896 shares issued and outstanding Preferred Stock, Value, Issued Common shares of beneficial interest, $.01 par, 100,000,000 shares authorized, 63,909,248 and 63,544,150 shares issued and outstanding, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated dividends in excess of net income Accumulated Distributions in Excess of Net Income Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholders' equity of the Trust Stockholders' Equity Attributable to Parent Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total shareholders' equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Income from continuing operations Less: Preferred share dividends Less: Income from continuing operations attributable to noncontrolling interests Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest Less: Earnings allocated to unvested shares Earnings Allocated To Unvested Shares Earnings allocated to unvested shares Income from continuing operations available for common shareholders Income Loss From Continuing Operations Available For Common Shareholders This element represents the income or loss from continuing operations attributable to the parent after earnings allocated to unvested shares and adjustments for dividends on preferred stock. Results from discontinued operations attributable to the Trust Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Gain on sale of real estate Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes Net income available for common shareholders, basic and diluted Net income available for common shareholders, basic and diluted Net income after adjustments for dividends on preferred stock and earnings allocated to unvested shares. Stock options Incremental Common Shares Attributable to Share-based Payment Arrangements Weighted average common shares outstanding-diluted Earnings Per Share, Basic, Total Earnings Per Share, Diluted, Total Income from continuing operations attributable to the Trust Income (Loss) from Continuing Operations Attributable to Parent Debt Instruments [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Revolving Credit Facility Maturing Jul 6 2015 [Member] Revolving Credit Facility Maturing Jul 6 2015 [Member] Revolving Credit Facility Maturing Jul 6 2015 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Amount Outstanding Line of Credit Facility, Amount Outstanding Schedule of Comprehensive Income (Loss) [Table Text Block] Schedule of Comprehensive Income (Loss) [Table Text Block] Schedule Of Supplemental Disclosures Related To Consolidated Statements Of Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Taurus Investment Holdings [Member] Taurus Investment Holdings, LLC [Member] Federal Realty Investment Trust [Member] Federal Realty Investment Trust [Member] Clarion [Member] Clarion [Member] Newbury Street Partnership [Member] Newbury Street Partnership [Member] Taurus Newbury Street JV II Limited Partnership [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Ownership interest in partnership Equity Method Investment, Ownership Percentage Sales of Real Estate Sales of Real Estate Number of Real Estate Properties Sold Number of Real Estate Properties Sold Number of Real Estate Properties Sold Payments for (Proceeds from) Real Estate Partnership Investment, Net Payments for (Proceeds from) Real Estate Partnership Investment, Net Repayment Of Secured Debt FRT Repayment Of Secured Debt FRT Repayment of collateralized debt obligations for which we are the lender Number of Real Estate Properties Net income Comprehensive Income Net income attributable to noncontrolling interests Comprehensive Income Attributable to the Trust Loss Contingencies [Table] Loss Contingencies [Table] Obligation To Purchase Member One Ownership Interest [Member] Obligation To Purchase Member One Ownership Interest [Member] Obligation To Purchase Member Two Ownership Interest [Member] Purchase Of Member Two Ownership Interest [Member] Option To Purchase Preferred Interest [Member] Option To Purchase Preferred Interest [Member] Obligation To Purchase Member Three Ownership Interest [Member] Obligation To Purchase Member Three Ownership Interest [Member] Real Estate Properties [Axis] Real Estate Properties [Domain] Mercer Mall [Member] Mercer Mall [Member] Melville Mall [Member] Melville Mall [Member] Congressional Plaza [Member] Congressional Plaza [Member] Project In Southern California [Member] Project In Southern California [Member] Option By Type [Axis] Option By Type [Axis] Option By Type [Domain] Option By Type [Domain] Purchased Call Option [Member] Put Option [Member] Contractual Obligation [Axis] Contractual Obligation [Axis] Contractual Obligation [Domain] Contractual Obligation [Domain] Capital Improvement, Development, And Redevelopment Projects [Member] Capital Improvement, Development, And Redevelopment Projects [Member] Loss Contingencies by Nature of Contingency [Axis] Loss Contingency, Nature [Domain] Breach Of Contract [Member] Breach Of Contract [Member] Insurance Settlement [Member] Santana Row [Member] Santana Row Condominium Units [Member] Loss Contingencies [Line Items] Loss Contingency, Court Decision, Amount Loss Contingency, Court Decision, Amount Loss Contingency, Court Decision Loss Contingency, Estimate of Possible Loss Loss Contingency, Estimate of Possible Loss Loss Contingency Accrual, Carrying Value, Period Increase (Decrease) Loss Contingency Accrual, Carrying Value, Period Increase (Decrease) Final judgment related to a previously disclosed lawsuit Litigation Settlement, Gross Warranty Period Warranty Period Product Warranty Accrual Product Warranty Accrual, Payments Product Warranty Accrual, Payments Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Contractual Obligation Contractual Obligation Contractual Obligation Operating Leases, Future Minimum Payments Due [Abstract] 2012 Operating Leases, Future Minimum Payments Due, Current 2013 Operating Leases, Future Minimum Payments, Due in Two Years 2014 Operating Leases, Future Minimum Payments, Due in Three Years 2015 Operating Leases, Future Minimum Payments, Due in Four Years 2016 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Purchase Price Under Option Purchase Price Under Option Purchase Price Under Option Mortgage loan face amount Long-term Debt, Gross Option Indexed to Issuer's Equity, Percentage Of Indexed Ownership Interest Option Indexed to Issuer's Equity, Percentage Of Indexed Ownership Interest Option Indexed to Issuer's Equity, Percentage Of Indexed Ownership Interest Option Indexed to Issuer's Equity, Indexed Owenship Interest Ownership Interest of Other Partner in Put Option The percentage of partnership interest we are required to purchase in a put option. Estimated Maximum Liability Upon Exercise Of Option Estimated Maximum Liability Upon Exercise Of Option Estimated Maximum Liability Upon Exercise Of Option Number of Members With Purchase Options Number of Members With Purchase Options Number of Members With Purchase Options Number Of Minority Partners Under Agreement Number Of Minority Partners Under Agreement Number Of Minority Partners Under Agreement Operating partnership units, outstanding Partners' Capital Account, Units Operating partnership units outstanding, fair value Operating Partnership Units Fair Value Fair value of operating partnership units at the balance sheet date. Revenue from discontinued operations Disposal Group, Including Discontinued Operation, Revenue Income from discontinued operations FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] Components of Rental Expense [Table] Components of Rental Expense [Table] Components of Rental Expense [Table] Component of Other Operating Cost and Expense, General [Axis] Component of Other Operating Cost and Expense, General [Axis] Component of Other Expense, Nonoperating, Name [Domain] Component of Other Operating Cost and Expense, Name [Domain] Component of Operating Other Cost and Expense [Line Items] Component of Operating Other Cost and Expense [Line Items] Repairs and maintenance Cost of Property Repairs and Maintenance Utilities Utilities Costs Management fees and costs Service Management Costs Payroll Property Payroll Expense Property Payroll Expense related to property management which includes salaries and benefits. Bad debt expense Provision for Doubtful Accounts Ground rent Ground Rent Expense Ground Rent Expense Insurance Real Estate Insurance Marketing Marketing Expense Other operating Other Cost of Operating Revenue Rental expenses Statement of Cash Flows [Abstract] OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization, including discontinued operations Adjustment Depreciation And Amortization The cash flow addback for the non-cash expense of depreciation and amortization including depreciation and amortization related to discontinued operations. Gain On Sale Of Real Estate in Real Estate Partnership Early extinguishment of debt Income from real estate partnerships Other, net Other Noncash Income (Expense) Changes in assets and liabilities, net of effects of acquisitions and dispositions Increase (Decrease) in Operating Capital [Abstract] Decrease (increase) in accounts receivable Increase (Decrease) in Accounts and Other Receivables (Increase) decrease in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Decrease in accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Increase (decrease) in security deposits and other liabilities Increase Decrease In Security Deposits And Other Liabilities The net change in Security Deposits And Other Liabilities which includes security deposits, deferred revenue and prepaid rent. Also includes liabilities not individually reported in the financial statements, or not separately disclosed in notes. Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Acquisition of real estate Payments to Acquire Real Estate Capital expenditures - development and redevelopment Capital Expenditures Development Redevelopment Payments to develop or redevelop real estate assets is the process of adding improvements on or to a parcel of land. Such improvements may include drainage, utilities, subdividing, access, buildings, and any combination of these elements. In addition, the cash outflow from construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service. Capital expenditures - other Payments for Capital Improvements Investment in real estate partnerships Payments to Acquire Interest in Subsidiaries and Affiliates Distribution from real estate partnership in excess of earnings Proceeds from Distributions Received from Real Estate Partnerships Leasing costs Increase (Decrease) in Lease Acquisition Costs (Issuance) repayment of mortgage and other notes receivable, net Issuance And Repayments Of Mortgage And Other Notes Receivable Net The cash outflow from the issuance and purchase of receivables arising from the mortgage note on real estate and other notes receivable, net of repayments. Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Net borrowings under revolving credit facility, net of costs Proceeds From Repayments Of Credit Facility The net cash inflow (outflow) from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity net of costs incurred. Purchase and retirement of senior notes/debentures Repayments of Senior Debt Issuance of mortgages, capital leases and notes payable, net of costs Proceeds from Issuance of Long-term Debt and Capital Securities, Net Repayment of mortgages, capital leases and notes payable Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Issuance of common shares Dividends paid to common and preferred shareholders Dividends Paid To Common And Preferred Shareholders The cash outflow from distribution of an entity's earnings to common and preferred stockholders. PaymentsOfDividendsAndRedemptionsMinorityInterest PaymentsOfDividendsAndRedemptionsMinorityInterest The cash outflow for the return on capital for noncontrolled interest in the entity and cash outflow during the period for redemptions of noncontrolling interests. Net cash (used in) provided by financing activities Net Cash Provided by (Used in) Financing Activities Increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of year Cash and cash equivalents at end of period DEBT Debt Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Preferred Shares [Member] Preferred Stock [Member] Common Shares [Member] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Accumulated Dividends in Excess of Net Income [Member] Accumulated Distributions in Excess of Net Income [Member] Noncontrolling Interests [Member] Noncontrolling Interest [Member] Beginning balance (in shares) Shares, Outstanding Beginning balance Net income, excluding $613 attributable to redeemable noncontrolling interests Profit Loss Excluding Redeemable Noncontrolling Interests Net income (loss) excluding portion attributable to redeemable noncontrolling interests. Dividends declared to common shareholders Dividends, Common Stock, Cash Dividends declared to preferred shareholders Dividends, Preferred Stock, Cash Distributions declared to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Common shares issued (in shares) Common shares issued Stock Issued During Period, Value, New Issues Exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Shares issued under dividend reinvestment plan (in shares) Stock Issued During Period, Shares, Dividend Reinvestment Plan Shares issued under dividend reinvestment plan Stock Issued During Period, Value, Dividend Reinvestment Plan Share-based compensation expense, net (in shares) Share Based Compensation Expense Net Shares Number of shares issued during the period as a result of our long term incentive, bonus or other share based compensation plans, net of restricted share award forfeitures. Share-based compensation expense, net Share Based Compensation Expense Net Value This element represents the amount of recognized equity-based compensation related to other long-term incentive and bonus plans during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Conversion and redemption of OP units (in shares) Conversion and Redemption of Operating Partnership Units in Shares Number of shares issued during the period as a result of the conversion and redemption of operating partnership units into shares Conversion and redemption of OP units Conversion And Redemption Of Operating Partnership Units Decrease in noncontrolling interest as a result of redeeming, purchasing and/or converting to common stock the interests of Operating Partnership Units. Purchase of noncontrolling interest Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Deconsolidation of VIE Noncontrolling Interest, Decrease from Deconsolidation Contributions from noncontrolling interests Noncontrolling Interest, Increase from Business Combination Adjustment to redeemable noncontrolling interests Stockholders' Equity, Other Ending balance (in shares) Ending balance Schedule of Dividends Declared and Paid Per Share [Table Text Block] Schedule of Dividends Declared and Paid Per Share [Table Text Block] Schedule of Dividends Declared and Paid Per Share [Table Text Block] Summarized Operating Results And Financial Position Of Partnership Schedule Of Balance Sheets and Operating Results Of Unconsolidated Joint Ventures [Table Text Block] Schedule Of Balance Sheets and Operating Results Of Unconsolidated Joint Ventures [Table Text Block] Real Estate Acquisitions Dispositions Discontinued Operations Text Block Real Estate Acquisitions Dispositions Discontinued Operations Text Block Disclosure of real estate acquisitions, dispositions and discontinued operations and at year end, a summary of our real estate investments and related encumbrances. Consolidated Balance Sheets (Parenthetical) [Abstract] Consolidated Balance Sheets (Parenthetical) [Abstract] Statement, Scenario [Axis] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Operating, consolidated variable interest entities Operating Real Estate From Consolidated Variable Interest Entities Operating real estate balances from variable interest entities, or VIEs, for the periods presented. Assets held for sale/disposal (discontinued operations), consolidated variable interest entities Assets Held For Disposal From Consolidated Variable Interest Entities Assets held for disposal balances from variable interest entities, or VIEs, for the periods presented. Accumulated depreciation and amortization, consolidated variable interest entities Accumulated depreciation and amortization, consolidated variable interest entities Accumulated Depreciation And Amortization, Consolidated Variable Interest Entities. Debt issuance costs, accumulated amortization Accumulated Amortization, Deferred Finance Costs Mortgages payable, consolidated variable interest entities Mortgage Payable From Consolidated Variable Interest Entities Mortgages payable balances from variable interest entities, or VIEs, for the periods presented. Preferred shares, authorized Preferred Stock, Shares Authorized Preferred shares, par Preferred Stock, Par or Stated Value Per Share Preferred Shares, 5.417% Series 1 Cumulative Convertible liquidation preference Preferred Stock, Liquidation Preference Per Share Preferred shares, shares issued Preferred Stock, Shares Issued Preferred shares, shares outstanding Preferred Stock, Shares Outstanding Common shares of beneficial interest, par Common Stock, Par or Stated Value Per Share Common shares of beneficial interest, shares authorized Common Stock, Shares Authorized Common shares of beneficial interest, shares issued Common Stock, Shares, Issued Common shares of beneficial interest, shares outstanding Common Stock, Shares, Outstanding Document And Entity Information [Abstract] Document and Entity Information Abstract Entities [Table] Entities [Table] Entity Information [Line Items] Entity Information [Line Items] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding