Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Operating (including $355,241 and $282,303 of consolidated variable interest entities, respectively) Rental Properties Construction-in-progress Construction in Progress, Gross Real estate, at cost, total Real Estate Investment Property, at Cost Less accumulated depreciation and amortization (including $30,099 and $26,618 of consolidated variable interest entities, respectively) Real Estate Investment Property, Accumulated Depreciation Net real estate Real Estate Investment Property, Net Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value 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 partnerships Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Prepaid expenses and other assets Prepaid Expense and Other Assets Debt issuance costs, net of accumulated amortization of $11,796 and $11,441, respectively Deferred Finance Costs, Net TOTAL ASSETS Assets LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities and Equity [Abstract] Liabilities Liabilities [Abstract] Mortgages payable (including $179,303 and $187,632 of consolidated variable interest entities, respectively) Secured Debt Capital lease obligations Capital Lease Obligations Notes payable Notes Payable Senior notes and debentures Senior Notes 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 Deferred Credits and Other Liabilities Total liabilities Liabilities Commitments and contingencies (Note 7) Commitments and Contingencies Redeemable noncontrolling interests 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, 69,120,797 and 68,605,783 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 TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities and Equity Fair Value Disclosures [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Mortgages and Notes Payable Mortgages Payable And Notes Payable [Member] Mortgages Payable And Notes Payable [Member] Senior Notes and Debentures Senior Notes And Debentures [Member] Senior Notes And Debentures [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair value of long-term debt Long-term Debt, Fair Value Income Statement [Abstract] REVENUE Revenues [Abstract] 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. Other property income Other Real Estate Revenue Mortgage interest income Revenue Mortgage Interest Interest income earned from mortgage notes receivable. Total revenue Revenues 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 Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Total operating expenses Operating Expenses OPERATING INCOME Operating Income (Loss) Other interest income Interest Income, Other Interest expense Interest Expense Early extinguishment of debt Gains (Losses) on Extinguishment of Debt Income from real estate partnerships Income (Loss) from Equity Method Investments INCOME FROM CONTINUING OPERATIONS Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest Gain on sale of real estate Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes NET INCOME Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 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 (in usd per share) Income (Loss) from Continuing Operations, Per Basic Share Gain on sale of real estate (in usd per share) Gain on Sale of Real Estate per Basic Share Gain On Sale Of Real Estate Per Basic Share. Earnings per common share, basic (in usd per share) Earnings Per Share, Basic Weighted average number of common shares, basic (in shares) Weighted Average Number of Shares Outstanding, Basic EARNINGS PER COMMON SHARE, DILUTED Earnings Per Share, Diluted [Abstract] Continuing operations (in usd per share) Income (Loss) from Continuing Operations, Per Diluted Share Gain on sale of real estate (in usd per share) Gain on Sale of Real Estate per Diluted Share Gain On Sale Of Real Estate Per Diluted Share. Earnings per common share, diluted (in usd per share) Earnings Per Share, Diluted Weighted average number of common shares, diluted (in shares) 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 Debt Instruments [Abstract] DEBT Debt Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Net income, excluding $1,758 attributable to redeemable noncontrolling interests Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Accounts Payable and Accrued Expenses Accounts Payable and Accrued Liabilities [Member] Derivative, by Nature [Axis] Derivative, by Nature [Axis] Derivative, Name [Domain] Derivative, Name [Domain] Interest Rate Swap Interest Rate Swap [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Financial liabilities Derivative Liability Nature Of Operations [Abstract] Nature Of Operations [Abstract] Number of real estate properties owned or had a majority interest in 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. Real Estate [Abstract] Schedule of Significant Acquisitions [Table] Schedule of Business Acquisitions, by Acquisition [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] Above Market Leases Above Market Leases [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] San Antonio Center San Antonio Center [Member] San Antonio Center The Grove at Shrewsbury GroveatShrewsbury [Member] GroveatShrewsbury [Member] CocoWalk CocoWalk [Member] CocoWalk Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] Houston Street Houston Street [Member] Houston Street Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Other Assets Other Assets [Member] Other Liabilities Other Liabilities [Member] General and Administrative Expenses General and Administrative Expense [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] CocoWalk LLC Subsidiaries [Member] Significant Acquisitions Business Acquisition [Line Items] Square footage of real estate property Area of Real Estate Property Gross value of business acquisition BusinessAcquisitionGrossValue Gross value of business acquisition. Effective interest of acquisition Effective Interest Acquisition Effective Interest Acquisition Mortgage loans assumed with acquisition Noncash or Part Noncash Acquisition, Debt Assumed Number of downREIT operating partnership units assumed in acquisition Number of downREIT Operating Partnership Units Issued in Connection with Business Acquisition Number of downREIT Operating Partnership Units Issued in Connection with Business Acquisition Cash paid in acquisition Payments to Acquire Businesses, Gross Acquired above market leases Finite-lived Intangible Assets Acquired Acquired below market leases Below Market Lease, Acquired Purchase price Business Combination, Consideration Transferred Contributions from noncontrolling interests Noncontrolling Interest, Increase from Business Combination Current period acquisition costs Business Combination, Acquisition Related Costs Price to acquire non-controlling interest Price to Acquire Non-Controlling Interest Price to Acquire Non-Controlling Interest Proceeds from sale Sales of Real Estate Gain (loss) on sale of real estate Gain (Loss) on Disposition of Real Estate Amount of difference between the carrying amount and the sales price of real estate properties sold. Net real estate Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Term loan TermLoan [Member] TermLoan [Member] Number of interest rate swap agreements Number of Interest Rate Derivatives Held Notional amount of interest rate swap agreements Derivative Liability, Notional Amount Principal amount of term loan Other Notes Payable Variable portion of interest rate Derivative, Fixed Interest Rate Effective interest rate Debt Instrument, Interest Rate, Effective Percentage Interest rate cash flow hedge loss to be reclassified within next 12 months, net Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Fair value of interest rate swaps Other comprehensive income (loss) - change in value of interest rate swaps Other Comprehensive Income (Loss), Net of Tax Interest expense reclassified from other comprehensive loss Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Statement of Cash Flows [Abstract] OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] Net income 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 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 Gain (Loss) on Sale of Properties 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] Increase in accounts receivable Increase (Decrease) in Accounts and Other Receivables Decrease in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets (Decrease) increase in accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Increase 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 Proceeds from sale of real estate Proceeds from Sale of Real Estate Held-for-investment Investment in real estate partnership 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 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. Issuance of senior notes, net of costs Proceeds from Issuance of Senior Long-term Debt Redemption and retirement of senior notes Repayments of Senior Debt Repayment of mortgages, capital leases and notes and other payables Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Issuance of common shares Proceeds from Issuance of Common Stock 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. Distributions to and redemptions of noncontrolling interests 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 provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities 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 BUSINESS AND ORGANIZATION Nature of Operations [Text Block] Components Of Rental Income and Expense [Abstract] Components Of Rental Income And Expense [Abstract] COMPONENTS OF RENTAL INCOME Operating Leases Revenue And Expense Text Block The principal components of rental income and/or rental expense recognized for the period. Accounting Policies [Abstract] Schedule of Supplemental Cash Flow Disclosures Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Operating (including $355,241 and $282,303 of consolidated variable interest entities, respectively) Operating Real Estate From Consolidated Variable Interest Entities Operating real estate balances from variable interest entities, or VIEs, for the periods presented. Less accumulated depreciation and amortization (including $30,099 and $26,618 of consolidated variable interest entities, respectively) Accumulated depreciation and amortization, consolidated variable interest entities Accumulated depreciation and amortization related to real estate, Consolidated Variable Interest Entities. Debt issuance costs, net of accumulated amortization of $11,796 and $11,441, respectively Accumulated Amortization, Deferred Finance Costs Mortgages payable (including $179,303 and $187,632 of consolidated variable interest entities, respectively) 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, percentage Preferred Stock, Dividend Rate, Percentage 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 Statement [Table] Statement [Table] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred Shares Preferred Stock [Member] Common Shares Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Dividends in Excess of Net Income Accumulated Distributions in Excess of Net Income [Member] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Noncontrolling Interests Noncontrolling Interest [Member] Statement Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance (in shares) Shares, Outstanding Beginning balance Net income, excluding $1,758 attributable to redeemable noncontrolling interests Profit Loss Excluding Redeemable Noncontrolling Interests Net income (loss) excluding portion attributable to redeemable noncontrolling interests. Other comprehensive loss - change in value of interest rate swaps 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) Stock Issued During Period, Shares, New Issues 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 of forfeitures (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 of forfeitures 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). Shares withheld for employee taxes (in shares) Common shares withheld for employee taxes Common shares withheld for employee taxes from vesting Shares withheld for employee taxes Shares withheld for employee taxes net value Shares withheld for employee taxes net value 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. Adjustment to redeemable noncontrolling interests Stockholders' Equity, Other Ending balance (in shares) Ending balance Subsequent Events [Abstract] SUBSEQUENT EVENTS Subsequent Events [Text Block] Stockholders' Equity Note [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] At The Market Equity Program At The Market Equity Program [Member] At The Market Equity Program [Member] Stock Issuance Costs by Type [Axis] Stock Issuance Costs by Type [Axis] Stock Issuance Costs by Type [Axis] Stock Issuance Costs by Type [Domain] Stock Issuance Costs by Type [Domain] [Domain] for Stock Issuance Costs by Type [Axis] Commissions Commissions [Member] Commissions [Member] Other Offering Costs Other Offering Costs [Member] Other Offering Costs [Member] Class of Stock Class of Stock [Line Items] Aggregate offering price (in usd) Aggregate Offering Price Of Common Share Maximum aggregate offering price of common shares. Weighted average price per share Weighted Average Price Per Common Share Weighted average price per common share Proceeds from issuance of stock Stock issuance costs Payments of Stock Issuance Costs Remaining capacity to issue (in usd) Remaining Capacity To Issue Remaining $ Capacity Of Shares To Issue Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Mortgages Mortgages [Member] Senior Notes Senior Notes [Member] Line of Credit Line of Credit [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] 4.50% Senior notes 4.50% Senior notes [Member] 4.50% Senior notes 6.20% Senior Notes 6.20% Senior notes [Member] 6.20% Senior notes Debt Instrument Debt Instrument [Line Items] Principal Long-term Debt, Gross Fair value Debt Instrument, Fair Value Disclosure Stated interest rate Debt Instrument, Interest Rate, Stated Percentage Note offering percent of principal amount Note Offering Percent Note offering percent of principal amount Debt yield to maturity percent Debt yield to maturity percent Debt yield to maturity percent Repayments of debt Repayments of Debt Redemption price Early Repayment of Senior Debt Make-whole premium Prepayment premium on senior note Cash outflow for prepayment premium on senior note Accrued but unpaid interest Interest Paid Maximum borrowing capacity under revolving credit facility Line of Credit Facility, Maximum Borrowing Capacity Maximum amount outstanding under revolving credit facility Line of Credit Facility, Maximum Amount Outstanding During Period Weighted average interest rate, before amortization of debt fees LineofCreditFacilityWeightedAverageInterestRateBeforeAmortizationOfDebt Fees Line of credit facility weighted average interest rate, before amortization of debt fees. Weighted average borrowings outstanding Line of Credit Facility, Average Outstanding Amount Outstanding balance of revolving credit facility Long-term Line of Credit Commitments and Contingencies Disclosure [Abstract] downREIT operating partnership units, outstanding Partners' Capital Account, Units downREIT operating partnership units outstanding, fair value Operating Partnership Units Fair Value Fair value of operating partnership units at the balance sheet date. Schedule of Extinguishment of Debt [Table] Schedule of Extinguishment of Debt [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Barracks Road Barracks Road [Member] Barracks Road [Member] Brick Plaza Brick Plaza [Member] Brick Plaza [Member] Wynnewood Wynnewood [Member] Wynnewood [Member] Lawrence Park Lawrence Park [Member] Lawrence Park [Member] Wildwood Wildwood [Member] Wildwood [Member] Hauppauge Hauppauge [Member] Hauppauge [Member] Extinguishment of Debt Extinguishment of Debt [Line Items] Repayments of debt Extinguishment of Debt, Amount COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Equity Method Investments and Joint Ventures [Abstract] Summarized Operating Results and Financial Position of the 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] Schedule of Minimum Rents [Table] Schedule of Minimum Rents [Table] Schedule of Minimum Rents [Table] Amortization of above market leases Amortization of below market leases BelowMarketLease [Member] BelowMarketLease [Member] Minimum Rent Minimum Rent [Line Items] Minimum Rent [Line Items] Straight-line rents Straight Line Rent Amortization of above and below market leases Amortization of above and below Market Leases Document And Entity Information [Abstract] Document and Entity Information Abstract 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 Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding SUPPLEMENTAL DISCLOSURES: Supplemental Cash Flow Information [Abstract] Total interest costs incurred Interest Costs Incurred Interest capitalized Interest Costs Capitalized Adjustment Interest expense Cash paid for interest, net of amounts capitalized Interest Paid, Net Cash paid for income taxes Income Taxes Paid, Net NON-CASH INVESTING AND FINANCING TRANSACTIONS: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] DownREIT operating partnership units issued with acquisition ValueofdownREITOperatingPartnershipUnitsIssuedinConnectionwithBusinessAcqu Value of downREIT Operating Partnership Units Issued in Connection with Business Acquisition Mortgage loan refinanced Refinance of mortgage loan Refinance of mortgage loan Repayment of note payable with public funding/related construction-in-progress offset Repayment of Note Payable with Public Funding Settlement of note payable with public funding Shares issued under dividend reinvestment plan Dividends Reinvested in Noncash Financing Transaction Dividends reinvested in noncash financing transaction Prepayment premium on senior note Payments of Debt Extinguishment Costs Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Share-based Compensation, Allocation and Classification in Financial Statements [Abstract] Grants of shares and options 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 Schedule of Extinguishment of Debt Schedule of Extinguishment of Debt [Table Text Block] Earnings Per Share [Abstract] NUMERATOR Numerator [Abstract] Numerator [Abstract] Net income Less: Preferred share dividends 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. Gain on sale of real estate Gain (Loss) on sale of properties & real estate partnership properties, net of applicable income taxes This element represents the amount of gain (loss) on sale of properties and real estate partnership properties during the reporting period net of the applicable income taxes realized. 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. DENOMINATOR Denominator [Abstract] Denominator [Abstract] Weighted average common shares outstanding—basic (in shares) Stock options (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average common shares outstanding—diluted (in shares) Continuing operations (in usd per share) Gain on sale of real estate (in usd per share) Continuing operations (in usd per share) Gain on sale of real estate (in usd per share) Income from continuing operations attributable to the Trust Income (Loss) from Continuing Operations Attributable to Parent Earnings Per Share Narrative [Table] Earnings Per Share Narrative [Table] Earnings Per Share Narrative [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] 5.417% Series 1 Cumulative Convertible Preferred Shares 5.417% Series 1 Cumulative Convertible Preferred [Member] Five point Four One Seven Percentage Series One Cumulative Convertible Preferred Stock [Member] Earnings Per Share Narrative Earnings Per Share Narrative [Line Items] Earnings Per Share Narrative [Line Items] Weighted average unvested shares outstanding Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Anti-dilutive stock options Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Cumulative convertible preferred shares, dividend rate EARNINGS PER SHARE Earnings Per Share [Text Block] Stockholders' Equity [Table] Stockholders' Equity [Table] Stockholders' Equity [Table] Dividends declared per common share Common Stock, Dividends, Per Share, Declared Dividends paid per common share Common Stock, Dividends, Per Share, Cash Paid Dividends declared per preferred share Preferred Stock, Dividends Per Share, Declared Dividends paid per preferred share Preferred Stock, Dividends, Per Share, Cash Paid Schedule of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] REAL ESTATE Real Estate Acquisitions Dispositions Text Block Disclosure of real estate acquisitions and dispositions, and at year end, a summary of our real estate investments and related encumbrances. SHARE-BASED COMPENSATION PLANS Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Federal Realty Investment Trust Federal Realty Investment Trust [Member] Federal Realty Investment Trust [Member] Investment, Name [Axis] Investment, Name [Domain] Federal Realty Investment Trust / ING Clarion Partners Partnership Federal Realty Investment Trust / ING Clarion Partners Partnership [Member] Federal Realty Investment Trust / ING Clarion Partners Partnership [Member] Schedule of Equity Method Investments Schedule of Equity Method Investments [Line Items] OPERATING RESULTS Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Revenue Expenses Expenses [Abstract] Expenses [Abstract] Other operating expenses Other Expenses Interest expense Total expenses Total Expenses Total expenses including operating expenses, interest expense, depreciation and amortization, and other expenses. Our share of net income from real estate partnership BALANCE SHEETS Balance Sheet Related Disclosures [Abstract] Real estate, net Cash Other assets Other Assets Mortgages payable Other liabilities Other Liabilities Partners’ capital Partners' Capital Our share of unconsolidated debt Share Of Unconsolidated Debt Share Of Unconsolidated Debt Our investment in real estate partnership ING Clarion Partners Clarion [Member] Clarion [Member] Ownership interest in Partnership Equity Method Investment, Ownership Percentage Number of real estate properties owned by partnership SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Components of Rental Income [Table] Components of Rental Income [Table] Components of Rental Income [Table] Products and Services [Axis] Products and Services [Domain] Retail and Commercial Commercial Real Estate [Member] Residential 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 Summary of Carrying Value and Fair Value of Financial Instruments Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Summary of Financial Liabilities Measured on a Recurring Basis Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] REAL ESTATE PARTNERSHIPS Equity Method Investments and Joint Ventures Disclosure [Text Block] Summary of Dividends Declared and Paid Per Share Dividends Declared [Table Text Block] Summary of Share-Based Compensation Expense Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] SHAREHOLDERS’ EQUITY Stockholders' Equity Note Disclosure [Text Block] 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 Schedule Of Minimum Rents Components [Table TextBlock] Schedule of Minimum Rents Components [Table Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Subsequent Event [Table] Subsequent Event [Table] Pike 7 Plaza Pike Seven Plaza [Member] Pike Seven Plaza [Member] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Land Land [Member] Subsequent Event Subsequent Event [Line Items] Number of buildings Number Of Buildings Number Of Buildings Weighted average interest rate of debt retired Debt, Weighted Average Interest Rate