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] 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 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] SHARE-BASED COMPENSATION PLANS Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Real Estate and Accumulated Depreciation Disclosure [Abstract] Schedule III - Summary of Real Estate and Accumulated Depreciation Real Estate and Accumulated Depreciation Disclosure [Text Block] Components Of Rental Income and Expense [Abstract] Components Of Rental Income And Expense [Abstract] 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 Principal Components Of Rental Expenses Schedule Of Principal Components Of Rental Expenses [Table Text Block] Schedule Of Principal Components Of Rental Expenses [Table Text Block] Secured Debt Assumed in Acquisition [Abstract] Secured Debt Assumed in Acquisition [Abstract] Secured Debt Assumed in Acquisition Secured Debt Assumed in Acquisition [Table Text Block] Secured Debt Assumed in Acquisition [Table Text Block] REAL ESTATE PARTNERSHIPS Equity Method Investments and Joint Ventures Disclosure [Text Block] Discontinued Operations and Disposal Groups [Abstract] Revenue from discontinued operations Disposal Group, Including Discontinued Operation, Revenue Income from discontinued operations Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax Earnings Per Share [Abstract] Income from continuing operations Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest Less: Preferred share dividends Preferred Stock Dividends, Income Statement Impact 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. Weighted average common shares outstanding-basic Weighted Average Number of Shares Outstanding, Basic Stock options Incremental Common Shares Attributable to Share-based Payment Arrangements Weighted average common shares outstanding-diluted Weighted Average Number of Shares Outstanding, Diluted 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 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 Income from continuing operations attributable to the Trust Income (Loss) from Continuing Operations Attributable to Parent 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] Dividends [Abstract] Schedule of Dividends Declared and Paid Per Share Schedule of Dividends Declared and Paid Per Share [Table Text Block] Schedule of Dividends Declared and Paid Per Share [Table Text Block] Schedule Of Income Tax Status Of Dividends Paid Schedule Of Income Tax Status Of Dividends Paid [Table Text Block] Schedule Of Income Tax Status Of Dividends Paid [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Melville Mall [Member] Melville Mall [Member] Melville Mall [Member] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Subsequent Event Type [Axis] Subsequent Event Type [Domain] 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 Property Ownership [Axis] Real Estate Properties [Domain] Mercer Mall [Member] Mercer Mall [Member] Congressional Plaza [Member] Congressional Plaza [Member] Project In Southern California [Member] Project In Southern California [Member] Plaza El Segundo [Member] Plaza El Segundo [Member] Montrose Crossing [Member] Montrose Crossing [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] Capital Improvement, Development, And Redevelopment Projects [Member] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Breach Of Contract [Member] Breach Of Contract [Member] Breach Of Contract [Member] Range [Axis] Range [Domain] Minimum [Member] Maximum [Member] Products and Services [Axis] Products and Services [Domain] Santana Row [Member] Santana Row Condominium Units [Member] Loss Contingencies [Line Items] Litigation Settlement, Gross Litigation Settlement, Gross 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 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 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. Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2014 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2015 Operating Leases, Future Minimum Payments, Due in Two Years 2016 Operating Leases, Future Minimum Payments, Due in Three Years 2017 Operating Leases, Future Minimum Payments, Due in Four Years 2018 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Subsequent Event [Abstract] Subsequent Event [Abstract] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Financing [Axis] Financing [Axis] Financing [Domain] Financing [Domain] Dividends [Axis] Dividends [Axis] Dividends [Domain] Dividends [Domain] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Sale [Axis] Sale [Axis] Sale [Domain] Sale [Domain] Extraordinary Item [Axis] Extraordinary Item [Axis] Extraordinary Item [Domain] Extraordinary Item [Domain] Bankruptcy of Party [Axis] Bankruptcy of Party [Axis] Bankruptcy [Domain] Bankruptcy [Domain] Loss on Receivables [Axis] Loss on Receivables [Axis] Loss on Receivables [Domain] Loss on Receivables [Domain] Product Recall [Axis] Product Recall [Axis] Product Recall [Domain] Product Recall [Domain] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Litigation Case [Axis] Litigation Case [Axis] Litigation Case Type [Domain] Litigation Case Type [Domain] New Contract [Axis] New Contract [Axis] New Contract [Domain] New Contract [Domain] Cancellation of Contract [Axis] Cancellation of Contract [Axis] Cancellation of Contract [Domain] Cancellation of Contract [Domain] Impairment in Value of Asset [Axis] Impairment in Value of Asset [Axis] Impairment in Value of Asset [Domain] Impairment in Value of Asset [Domain] Expropriation of Assets [Axis] Expropriation of Assets [Axis] Expropriation of Assets [Domain] Expropriation of Assets [Domain] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Groups, Including Discontinued Operations, Name [Domain] Disposal Groups, Including Discontinued Operations, Name [Domain] Change in Tax Status [Axis] Change in Tax Status [Axis] Change in Tax Status [Domain] Change in Tax Status [Domain] Subsequent Event [Line Items] Subsequent Event [Line Items] Subsequent Events [Text Block] Subsequent Events [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate, Property Type [Domain] Real Estate, Property Type [Domain] Commercial Real Estate [Member] Commercial Real Estate [Member] Plaza El Segundo [Member] Tower Shops January 19 2011 [Member] Tower Shops January 19 2011 [Member] Tower Shops 1/19/11 [Member] Type of Real Estate Property [Axis] Property, Plant and Equipment, Type [Axis] Type of Real Estate Property [Domain] Property, Plant and Equipment, Type [Domain] Building and Building Improvements [Member] Minor Improvements, Furniture and Equipment [Member] Minor Improvements, Furniture and Equipment [Member] Option By Type [Axis] Option By Type [Domain] Purchased Call Option [Member] Put Option [Member] Range [Axis] Range [Domain] Minimum [Member] Maximum [Member] Summary of Significant Accounting Policies [Line Items] Summary of Significant Accounting Policies [Line Items] Summary of Significant Accounting Policies [Line Items] Dividends Reinvested in Noncash Financing Transaction Dividends Reinvested in Noncash Financing Transaction Dividends reinvested in noncash financing transaction Property, Plant and Equipment, Useful Life Property, Plant and Equipment, Useful Life Operating Lease, Term Operating Lease, Term Operating Lease, Term Allowance for Doubtful Accounts Receivable Allowance for Doubtful Accounts Receivable Straight Line Rents, Collection Of Accounts Receivable, Period Straight Line Rents Collection Of Accounts Receivable Period Straight Line Rents, Collection Of Accounts Receivable, Period Deferred Rent Receivables, Net Deferred Rent Receivables, Net Depreciation Expense Real Estate Depreciation Expense Real Estate Depreciation Expense on Real Estate only Investments Classified As Cash And Cash Equivalents, Initial Maturity Investments Classified As Cash And Cash Equivalents, Initial Maturity Investments Classified As Cash And Cash Equivalents, Initial Maturity Cash, Uninsured Amount Cash, Uninsured Amount 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 Residual Profit Maxiumum Residual Profit Maxiumum Residual Profit Maxiumum received as additional interest on mortgage note receivable Master Lease Term Master Lease Term Master Lease Term in Years Secured Debt F R T Secured Debt F R T Carrying value as of the balance sheet date of collateralized debt obligations for which we are the lender. Maximum period of sale to defer gain on sale of other property, days Maximum Period On Sale Of Properties To Defer Gains Maximum period on sale of properties to defer gains. Business Acquisition, Percentage of Voting Interests Acquired Business Acquisition, Percentage of Voting Interests Acquired Real Estate Maximum Exposure to Loss Real Estate Maximum Exposure to Loss Maximum Exposure to Loss on real estate Minimum Percentage Of Taxable Income Distributed To Shareholders Minimum Percentage Of Taxable Income Distributed To Shareholders Minimum percentage of taxable income distributed to shareholders. Unrecognized Tax Benefits Unrecognized Tax Benefits Number of Properties Exceeding Segment Reporting Threshold Number of Properties Exceeding Segment Reporting Threshold Number of Properties Exceeding Segment Reporting Threshold Segment Reporting, Factors Used to Identify Entity's Reportable Segments Segment Reporting, Factors Used to Identify Entity's Reportable Segments Number of Segments Number of Reportable Segments Savings and Retirement Plans [Abstract] Savings and Retirement Plans [Abstract] Schedule of Deferred Compensation Arrangement with Individual, Postretirement Benefits [Table] Postretirement Benefits, Type of Deferred Compensation [Axis] Type of Deferred Compensation, All Types [Domain] Defined Contribution Pension [Member] Non-Qualified Deferred Compensation Plan [Member] Non-Qualified Deferred Compensation Plan [Member] Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] Defined Contribution Plan, Maximum Annual Contribution Per Employee, Amount Defined Contribution Plan, Maximum Annual Contribution Per Employee, Amount Deferred Compensation Arrangement with Individual, Employer Contribution Per Employee, Matching Percent Deferred Compensation Arrangement with Individual, Employer Contribution Per Employee, Matching Percent Deferred Compensation Arrangement with Individual, Employer Contribution Per Employee, Matching Percent Deferred Compensation Arrangement with Individual, Employer Contribution, Percent Of Eligible Earnings Defined Contribution Plan, Employer Matching Contribution, Percent Deferred Compensation Arrangement with Individual, Employer Contribution Deferred Compensation Arrangement with Individual, Employer Contribution Deferred Compensation Arrangement with Individual, Recorded Liability Deferred Compensation Arrangement with Individual, Recorded Liability Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred Shares [Member] Preferred Stock [Member] Common Shares [Member] Common Stock [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] Accumulated Other Comprehensive Income (Loss) [Member] Noncontrolling Interests [Member] Noncontrolling Interest [Member] Statement [Line Items] Statement [Line Items] Beginning balance (in shares) Shares, Outstanding Beginning balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Net income Profit Loss Excluding Redeemable Noncontrolling Interests Net income (loss) excluding portion attributable to redeemable noncontrolling interests. Other Comprehensive Income (Loss), Net of Tax Other Comprehensive Income (Loss), Net of Tax 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 (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 Debt Instruments [Abstract] Schedule of Debt Schedule of Debt [Table Text Block] Schedule of Debt Repayments [Table Text Block] Schedule of Debt Repayments [Table Text Block] Schedule of Debt Repayments [Table Text Block] Schedule of Maturities of Long-term Debt Schedule of Maturities of Long-term Debt [Table Text Block] Schedule of Future Minimum Lease Payments for Capital Leases Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] 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] DEBT Debt Disclosure [Text Block] DISCONTINUED OPERATIONS Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Schedule Of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Debt Disclosure [Abstract] 2014 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2015 Capital Leases, Future Minimum Payments Due in Two Years 2016 Capital Leases, Future Minimum Payments Due in Three Years 2017 Capital Leases, Future Minimum Payments Due in Four Years 2018 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Capital Leases, Future Minimum Payments Due Capital Leases, Future Minimum Payments Due Less amount representing interest Capital Leases, Future Minimum Payments, Interest Included in Payments Present value Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Issuance of Debt [Member] Issuance of Debt [Member] Repayment of Debt [Member] Repayment of Debt [Member] White Marsh Plaza [Member] White Marsh Plaza [Member] Crow Canyon [Member] Crow Canyon [Member] Crow Canyon [Member] Idylwood Plaza [Member] Idylwood Plaza [Member] Idylwood Plaza [Member] Leesburg Plaza [Member] Leesburg Plaza [Member] Leesburg Plaza [Member] Loehmanns Plaza [Member] Loehmanns Plaza [Member] Loehmanns Plaza [Member] Pentagon Row [Member] Pentagon Row [Member] Pentagon Row [Member] Senior275PercentNotes [Member] [Member] Senior275PercentNotes [Member] [Member] Senior275PercentNotes [Member] [Member] Senior 5.40 Percent Notes [Member] Senior 5.40 Percent Notes [Member] Senior 5.40 Percent Notes [Member] Senior395percentnotes [Member] Senior395percentnotes [Member] Senior395percentnotes [Member] Senior 5.95 Percent Notes [Member] Senior 5.95 Percent Notes [Member] Senior 5.95 Percent Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Repayment of mortgage loan Repayments of Secured Debt Prepayment Premium on Mortgage Loan Prepayment Premium on Mortgage Loan Prepayment Premium on Mortgage Loan Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Basis Points Spread Basis Points Spread The number of basis points added to LIBOR to compute the total interest rate. Revolving credit facility, maximum outstanding Line of Credit Facility, Maximum Amount Outstanding During Period Line of credit facility, weighted average amount outstanding Line of Credit Facility, Average Outstanding Amount Line of credit facility weighted average interest rate before amortization of debt fees LineofCreditFacilityWeightedAverageInterestRateBeforeAmortizationOfDebt Fees Line of credit facility weighted average interest rate, before amortization of debt fees. Line of Credit Facility, Commitment Fee Amount Line of Credit Facility, Commitment Fee Amount Line of credit facility, amount outstanding Line of Credit Facility, Amount Outstanding Long-term Debt, Gross Debt Instrument, Face Amount Debt Instrument, Face Amount Stated Interest Rate Debt Instrument, Interest Rate, Stated Percentage Proceeds from Issuance of Senior Long-term Debt Proceeds from Issuance of Senior Long-term Debt Senior notes and debentures Senior Notes Early Repayment of Senior Debt Early Repayment of Senior Debt Prepayment Premium On Senior Note Prepayment Premium On Senior Note Prepayment Premium on Senior Note. Interest Paid Interest Paid ACQUIRED IN-PLACE LEASES [Abstract] ACQUIRED IN-PLACE LEASES [Abstract] Schedule of Acquired Finite-Lived Intangible Assets by Major Class Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Statement of Cash Flows [Abstract] Montrose Crossing [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] 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, 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 Gain (Loss) on Sale of Properties Gain on deconsolidation of VIE Discontinued Operation Gain On Deconsolidation Of Variable Interest Entity Gain resulting from the deconsolidation of a variable interest entity Early extinguishment of debt Gains (Losses) on 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 (decrease) in accounts receivable Increase (Decrease) in Accounts and Other Receivables Decrease (increase) in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Increase (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 Proceeds from sale of real estate Proceeds from Sale of Real Estate Held-for-investment 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 Distribution from sale of real estate partnership properties Payments for (Proceeds from) Real Estate Partnership Investment, Net 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 repayments 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 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 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 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 Operating Leases [Abstract] Operating Leases [Abstract] Property Subject to or Available for Operating Lease, by Major Property Class [Table] Real Estate Investments by Property Type [Axis] Real Estate Investments by Property Type [Axis] Real Estate Investments by Property Type [Axis] Real Estate Investments, Property Type [Domain] Real Estate Investments, Property Type [Domain] Real Estate Investments, Property Type [Domain] Residential Real Estate [Member] Residential Real Estate [Member] Property Subject to or Available for Operating Lease [Line Items] Number of Real Estate Properties Number of Real Estate Properties Number of States in which Entity Has Properties Number of States in which Entity Operates Number Of Leases Number Of Leases Number Of Leases Percent of Annualized Base Rent Percent of Annualized Base Rent Maximum Percent of Annualized Base Rent Maximum Operating Leases, Future Minimum Payments Receivable [Abstract] 2014 Operating Leases, Future Minimum Payments Receivable, Current 2015 Operating Leases, Future Minimum Payments Receivable, in Two Years 2016 Operating Leases, Future Minimum Payments Receivable, in Three Years 2017 Operating Leases, Future Minimum Payments Receivable, in Four Years 2018 Operating Leases, Future Minimum Payments Receivable, in Five Years Thereafter Operating Leases, Future Minimum Payments Receivable, Thereafter Total Operating Leases, Future Minimum Payments Receivable Accounting Policies [Abstract] Principles of Consolidation Consolidation, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Revenue Recognition and Accounts Receivable Revenue Recognition and Accounts Receivable [Policy Text Block] Disclosure of accounting policy for revenue recognition for operating leases and trade and other accounts receivable. Includes how an entity determines the level of its allowance for doubtful accounts. Real Estate Real Estate Policy [Policy Text Block] Disclosure of accounting policty for real estate which includes basis, depreciation methods, estimated useful lives and real estate depreciation expense, the entity's capitalization policy including its accounting treatment for costs incurred for repairs and maintenance activities, policy for capitalizing certain costs including interest costs, how impairments are assessed and recognized, policy for recognizing sales of real estate and policy for business combinations including purchase price allocation and treatment of acquisition costs. Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Prepaid Expenses and Other Assets Prepaid Expenses and Other Assets [Policy Text Block] Description of entity's accounting policy related to prepaid expenses and other assets. Debt Issuance Costs Debt, Policy [Policy Text Block] Derivatives Instruments Derivatives, Policy [Policy Text Block] Mortgage Notes Receivable Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block] Share Based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Variable Interest Entities Consolidation, Variable Interest Entity, Policy [Policy Text Block] Redeemable Noncontrolling Interests Redeemable Noncontrolling Interests [Policy Text Block] Redeemable Noncontrolling Interests [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Segment Information Segment Reporting, Policy [Policy Text Block] Selected Quarterly Financial data (Unaudited) [Abstract] Selected Quarterly Financial data (Unaudited) [Abstract] SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) Quarterly Financial Information [Text Block] Real Estate Investments, Net [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Real Estate Property Ownership [Axis] Real Estate Properties [Domain] Real Estate and Accumulated Depreciation, Description of Property [Axis] Name of Property [Axis] Real Estate and Accumulated Depreciation, Name of Property [Domain] Name of Property [Domain] Forest Hills [Member] Forest Hills [Member] Forest Hills [Member] Shirlington [Member] Shirlington [Member] Shirlington [Member] Darien [Member] Darien [Member] Darien [Member] Fifth Avenue [Member] Fifth Avenue [Member] Fifth Avenue [Member] LandParcelAdjacenttoAssemblyRow [Member] LandParcelAdjacenttoAssemblyRow [Member] Land Parcel Adjacent to Assembly Row [Member] Land Contiguous with Montrose Crossing [Member] Land Contiguous with Montrose Crossing [Member] Land Contiguous with Montrose Crossing [Member] Crossroads (Office Building) [Member] Crossroads (Office Building) [Member] Crossroads (Office Building) [Member] [Member] EastBayBridge [Member] EastBayBridge [Member] EastBayBridge [Member] ResidentialPropertyAdjacentToSantanaRow [Member] ResidentialPropertyAdjacentToSantanaRow [Member] ResidentialPropertyAdjacentToSantanaRow [Member] HuntingtonSquare [Member] Huntington Square [Member] Escondido Promenade [Member] Escondido Promenade [Member] Former Mervyns Parcel, Escondido Promenade [Member] Bethesda Row [Member] Bethesda Row [Member] Real Estate Investments [Line Items] Real Estate Investments [Line Items] Real Estate Investments [Line Items] Mortgage loan face amount Leasable area (square feet) Area of Real Estate Property 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. Number of Real Estate Properties Acquired NumberofRealEstatePropertiesAcquired Number of Real Estate Properties Acquired NumberofResidentialUnits NumberofResidentialUnits Number of Residential Units Acquisition costs Business Combination, Acquisition Related Costs Proceeds from sale of buildings Sales of Real Estate Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Area of Land Area of Land Land Acquisition Purchase Price Land Acquisition Purchase Price Land Acquisition Purchase Price Land Acquisition Our Share of Purchase Price Land Acquisition Our Share of Purchase Price Land Acquisition Our Share of Purchase Price 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 Purchase Price Business Acquisition Purchase Price The purchase price of the acquired entity. Long-term Debt, Fair Value Long-term Debt, Fair Value Consolidated Balance Sheets (Parenthetical) [Abstract] Consolidated Balance Sheets (Parenthetical) [Abstract] 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] Statement, Scenario [Axis] 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. 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, 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 Stock, Shares, Outstanding Common Stock, Shares, Outstanding Mortgage Loans on Real Estate [Abstract] Mortgage Loans on Real Estate Schedule [Table] Mortgage Loans on Real Estate Schedule [Table] Extension Option [Axis] Extension Option [Axis] Extension Option [Axis] Extension Option [Domain] Extension Option [Domain] Extension Option [Domain] Mortgage loan on a shopping center and an adjacent commercial building in Norwalk ,CT [Member] Mortgage loan on a shopping center and an adjacent commercial building in Norwalk ,CT [Member] Mortgage loan on a shopping center and an adjacent commercial building in Norwalk ,CT [Member] Mortgage On Restaurant In Rockville, MD [Member] Mortgage On Restaurant In Rockville, MD [Member] Mortgage On Restaurant In Rockville, MD [Member] Extension Option One [Member] Extension Option One [Member] Extension Option One [Member] Extension Option Two [Member] Extension Option Two [Member] Extension Option Two [Member] Interest Rate [Axis] Interest Rate [Axis] Interest Rate [Axis] Interest Rate [Domain] Interest Rate [Domain] Interest Rate [Domain] Interest Rate One [Member] Interest Rate One [Member] Interest Rate One [Member] Interest Rate Two [Member] Interest Rate Two [Member] Interest Rate Two [Member] Mortgage Loans on Real Estate, Description, Type of Property [Axis] Mortgage Loans on Real Estate, Name, Property Type [Domain] Mortgage On Retail Buildings in Philadelphia, PA, Loan One [Member] Mortgage On Retail Buildings in Philadelphia, PA, Loan One [Member] Mortgage On Retail Buildings in Philadelphia, PA, Loan One [Member] Mortgage On Retail Buildings in Philadelphia, PA, Loan Two [Member] Mortgage On Retail Buildings in Philadelphia, PA, Loan Two [Member] Mortgage On Retail Buildings in Philadelphia, PA, Loan Two [Member] Second Mortgage On Hotel In San Jose, CA [Member] Second Mortgage On Hotel In San Jose, CA [Member] Second Mortgage On Hotel In San Jose, CA [Member] Mortgage Loans on Real Estate, Description, Loan Category [Axis] Mortgage Loans on Real Estate, Description, Loan Category [Axis] Mortgage Loans on Real Estate, Loan Category [Domain] Mortgage Loans on Real Estate, Loan Category [Domain] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Domain] Mortgage Loans on Real Estate, Loan Type [Domain] Mortgage Loans on Real Estate, Original Loan Amount [Axis] Mortgage Loan, Original Amount [Axis] Mortgage Loans on Real Estate, Original Loan Amount [Domain] Mortgage Loans on Real Estate, Original Loan Amount [Domain] Mortgage Loans on Real Estate [Line Items] Mortgage Loans on Real Estate [Line Items] Mortgage Loans on Real Estate, Participation Plus Interest Rate, Interest Rate Mortgage Loans on Real Estate, Participation Plus Interest Rate, Interest Rate Mortgage Loans on Real Estate, Participation Plus Interest Rate, Interest Rate Prior Liens Mortgage Loans on Real Estate, Prior Liens Face Amount of Mortgages Mortgage Loans on Real Estate, Face Amount of Mortgages Carrying Amount of Mortgages Mortgage Loans on Real Estate, Carrying Amount of Mortgages Principal Amount of Loans Subject to delinquent Principal or Interest Mortgage Loans on Real Estate, Principal Amount of Delinquent Loans Mortgage Loans on Real Estate, Other Required Disclosures [Abstract] Mortgage Loans on Real Estate, Other Required Disclosures [Abstract] Mortgage Loans on Real Estate, Federal Income Tax Basis Mortgage Loans on Real Estate, Federal Income Tax Basis Payments of Principal and Interest Based on Amortization Schedule, Period Payments of Principal and Interest Based on Amortization Schedule, Period Payments of Principal and Interest Based on Amortization Schedule, Period Mortgage Loans on Real Estate, Interest Rate, Increase in Subsequent Year of Extension Mortgage Loans on Real Estate, Interest Rate, Increase in Subsequent Year of Extension Mortgage Loans on Real Estate, Interest Rate, Increase in Subsequent Year of Extension Extension Option Period Extension Option Period Extension Option Period Mortgage Loans on Real Estate, Interest Rate Mortgage Loans on Real Estate, Interest Rate Movement in Mortgage Loans on Real Estate [Roll Forward] Movement in Mortgage Loans on Real Estate [Roll Forward] Balance at beginning of year Mortgage Loans on Real Estate Issuance of loans Mortgage Loans on Real Estate, New Mortgage Loans Real Estate Deconsolidation of VIE Real Estate Deconsolidation of VIE Decrease to Real Estate due to Deconsolidation of VIE Collection and satisfaction of loans Mortgage Loans on Real Estate, Collections of Principal Amortization of discount /loan fee Mortgage Loans on Real Estate, Amortization of Premium Balance at end of year Real Estate and Accumulated Depreciation, by Property [Table] Real Estate and Accumulated Depreciation, by Property [Table] Real Estate and Accumulated Depreciation [Line Items] Real Estate and Accumulated Depreciation [Line Items] Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements [Abstract] Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements [Abstract] Balance at beginning of year Real Estate, Gross Acquisitions Real Estate, Other Acquisitions Improvements Real Estate, Improvements Real Estate Deconsolidation of VIE Deduction during period - disposition and retirements of property Real Estate Dispositions and Retirements Carryiing amount of real estate sold and cap ex disposals during the period. Balance at end of year Real Estate and Accumulated Depreciation, Other Required Disclosures [Abstract] Real Estate and Accumulated Depreciation, Other Required Disclosures [Abstract] Real Estate, Federal Income Tax Basis Real Estate, Federal Income Tax Basis Reconciliation of Real Estate Accumulated Depreciation [Roll Forward] Reconciliation of Real Estate Accumulated Depreciation [Roll Forward] Balance at beginning of year Real Estate Accumulated Depreciation Additions during period—depreciation and amortization expense Real Estate Accumulated Depreciation, Depreciation Expense Deductions during period—disposition and retirements of property Real Estate Accumulated Depreciation Dispositions and Retirements Real Estate Accumulated Depreciation Dispositions and Retirements Balance at end of year Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Restricted Stock [Member] Restricted Stock [Member] Stock Award [Member] Stock Award [Member] Award Type [Axis] Award Type [Domain] Award Type [Domain] Stock Options [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 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 Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Outstanding at the beginning of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Outstanding at the beginning of year, Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Granted, Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercised (in shares) Exercised, Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Forfeited or expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Forfeited or Expired, Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Outstanding at the end of year (in shares) Outstanding at the end of year, Weighted-Average Exercise Price (in dollars per share) Outstanding at the end of year, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Exercisable at the end of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Exercisable, Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Exercisable, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Unvested at the beginning of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested at the beginning of year, Weighted-Average Grant-Date Fair Value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period 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 Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Vested, Weighted-Average Grant-Date Fair Value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Forfeited, Weighted-Average Grant-Date Fair Value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Unvested at the end of year (in shares) Unvested at the end of year, Weighted-Average Grant-Date Fair Value (in dollars per share) Redeemable Noncontrolling Interest, by Legal Entity [Table] Redeemable Noncontrolling Interest, by Legal Entity [Table] Redeemable Noncontrolling Interest [Line Items] Redeemable Noncontrolling Interest [Line Items] Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Beg Bal Redeemable Noncontrolling Interest, Equity, Carrying Value Redeemable Noncontrolling Interest, Equity, Carrying Amount Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Redeemable Noncontrolling Interests Distributions & Redemptions Redeemable Noncontrolling Interests Distributions Redeemable Noncontrolling Interests Distributions Redeemable Noncontrolling Interests Contributions Redeemable Noncontrolling Interests Contributions Redeemable Noncontrolling Interests Contributions Adjustments to redeemable noncontrolling interests Temporary Equity, Other Changes End Bal Redeemable Noncontrolling Interest, Equity, Carrying Amount Interest Paid [Abstract] Interest Paid [Abstract] Total interest costs incurred Interest Costs Incurred Interest capitalized Interest Costs Capitalized Interest expense Cash paid for interest, net of amounts capitalized Interest Paid, Net Cash (refunded) paid for income taxes Income Taxes Paid, Net Mortgage loan assumed/entered into with acquisition Loans Assumed Deconsolidation of VIE NonCash Deconsolidation Of Variable Interest Entity Non-cash investing amount related to the deconsoliation of a variable interest entity. Capital lease obligations Capital Lease Obligations Incurred Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Above Market Leases [Member] Below Market Leases [Member] Acquired Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets, Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Acquired Below Market Lease Accumulated Amortization AcquiredBelowMarketLeaseAccumulatedAmortization The accumulated amount of amortization of acquired 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. Amortization For Acquired In Place Leases [Abstract] Amortization For Acquired In Place Leases [Abstract] 2014 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2015 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2016 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2017 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2018 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Finite-Lived Intangible Assets, Future Amortization Expense Finite-Lived Intangible Assets, Net 2014 Future Recognition of Deferred Revenue, Year One Future Recognition of Deferred Revenue, Year One 2015 Future Recognition of Deferred Revenue, Year Two Future Recognition of Deferred Revenue, Year Two 2016 Future Recognition of Deferred Revenue, Year Three Future Recognition of Deferred Revenue, Year Three 2017 Future Recognition of Deferred Revenue, Year Four Future Recognition of Deferred Revenue, Year Four 2018 Future Recognition of Deferred Revenue, Year Five Future Recognition of Deferred Revenue, Year Five Thereafter Future Recognition of Deferred Revenue, after Five Years Future Recognition of Deferred Revenue, after Five Years Future Recognition of Deferred Revenue Future Recognition of Deferred Revenue Future Recognition of Deferred Revenue Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Amounts attributable to redeemable noncontrolling interest Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest [Table Text Block] Schedule Of Supplemental Disclosures Related To Consolidated Statements Of Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Post Street 150 [Member] Post Street 150 [Member] 29th Place [Member] 29th Place [Member] Andorra [Member] Andorra [Member] Assembly Square Market Place Assembly Row [Member] Assembly Square Market Place Assembly Row [Member] THE AVENUE at White Marsh [Member] THE AVENUE at White Marsh [Member] Bala Cynwyd [Member] Bala Cynwyd [Member] Barracks Road [Member] Barracks Road [Member] Brick Plaza [Member] Brick Plaza [Member] Bristol [Member] Bristol [Member] Chelsea [Member] Chelsea [Member] Colorado Blvd [Member] Colorado Blvd [Member] Courthouse Center [Member] Courthouse Center [Member] Courtyard Shops [Member] Courtyard Shops [Member] Crossroads [Member] Crossroads [Member] Dedham Plaza [Member] Dedham Plaza [Member] Del Mar Village [Member] Del Mar Village [Member] Eastgate [Member] Eastgate [Member] Elllisburg Circle [Member] Elllisburg Circle [Member] Falls Plaza [Member] Falls Plaza [Member] Federal Plaza [Member] Federal Plaza [Member] Finley Square [Member] Finley Square [Member] Flourtown [Member] Flourtown [Member] Fresh Meadows [Member] Fresh Meadows [Member] Friendship Ctr [Member] Friendship Ctr [Member] Gaithersburg Square [Member] Gaithersburg Square [Member] Garden Market [Member] Garden Market [Member] Governor Plaza [Member] Governor Plaza [Member] Gratiot Plaza [Member] Gratiot Plaza [Member] Greenwich Avenue [Member] Greenwich Avenue [Member] Hauppauge [Member] Hauppauge [Member] Hermosa Ave [Member] Hermosa Ave [Member] Hollywood Blvd [Member] Hollywood Blvd [Member] Houston Street [Member] Houston Street [Member] Huntington [Member] Huntington [Member] Kings Court [Member] Kings Court [Member] Lancaster [Member] Lancaster [Member] Langhorne Square [Member] Langhorne Square [Member] Laurel [Member] Laurel [Member] Lawrence Park [Member] Lawrence Park [Member] Linden Square [Member] Linden Square [Member] Mid Pike Plaza [Member] Mid Pike Plaza [Member] Mount Vernon [Member] Mount Vernon [Member] Town Center of New Britain [Member] Town Center of New Britain [Member] North Dartmouth [Member] North Dartmouth [Member] Northeast [Member] Northeast [Member] North Lake Commons [Member] North Lake Commons [Member] Old Keene Mill [Member] Old Keene Mill [Member] Old Town Center [Member] Old Town Center [Member] Pan Am Shopping Center [Member] Pan Am Shopping Center [Member] Perring Plaza [Member] Perring Plaza [Member] Pike 7 [Member] Pike 7 [Member] Queen Anne Plaza [Member] Queen Anne Plaza [Member] Quince Orchard Plaza [Member] Quince Orchard Plaza [Member] Rockville Town Square [Member] Rockville Town [Member] Rollingwood Apartments [Member] Rollingwood Apartments [Member] Sams Park and Shop [Member] Sams Park and Shop [Member] Saugus [Member] Saugus [Member] Shoppes At Nottingham Square [Member] Shoppes At Nottingham Square [Member] Third Street Promenade [Member] Third Street Promenade [Member] Tower [Member] Tower [Member] Troy [Member] Troy [Member] Tyson Station [Member] Tyson Station [Member] Westgate Mall [Member] Westgate Mall [Member] White Marsh Other [Member] White Marsh Other [Member] Wildwood [Member] Wildwood [Member] Willow Grove [Member] Willow Grove [Member] Willow Lawn [Member] Willow Lawn [Member] Wynnewood [Member] Wynnewood [Member] Encumbrances Real Estate and Accumulated Depreciation, Amount of Encumbrances Initial cost to company, Land Real Estate and Accumulated Depreciation, Initial Cost of Land Initial cost to company, Buildings and Improvements Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements Cost Capitalized Subsequent to Acquisition Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs Gross amount at which carried atclose of period, Land Real Estate and Accumulated Depreciation, Carrying Amount of Land Gross amount at which carried atclose of period, Buildings and Improvements Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements Gross amount at which carried atclose of period, Total Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements Accumulated Depreciation and Amortization Real Estate and Accumulated Depreciation, Accumulated Depreciation Life on which depreciation in latest income statements is computed Real Estate and Accumulated Depreciation, Life Used for Depreciation Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Operating (including $265,138 and $264,506 of consolidated variable interest entities, respectively) Rental Properties Construction-in-progress Construction in Progress, Gross Assets held for sale/disposal (discontinued operations) Real Estate Held-for-sale Real Estate Investment Property, At Cost, Total Real Estate Investment Property, at Cost Less accumulated depreciation and amortization (including $19,086 and $12,024 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 $9,535 and $10,140, respectively Deferred Finance Costs, Net Liabilities Liabilities [Abstract] Mortgages payable (including $202,782 and $205,299 of consolidated variable interest entities, respectively) Capital lease obligations Capital Lease Obligations Notes payable Notes Payable 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 9) Commitments and Contingencies Redeemable Noncontrolling Interests 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, 66,701,422 and 64,815,446 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 OPERATING LEASES Operating Leases of Lessor Disclosure [Text Block] Nature Of Operations [Abstract] Nature Of Operations [Abstract] ACQUIRED IN-PLACE LEASES Intangible Assets Disclosure [Text Block] Schedule Of Real Estate Investments And Related Encumbrances Schedule of Real Estate Properties [Table Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Mortgage Notes Receivable [Abstract] Mortgage Notes Receivable Disclosure [Abstract] MORTGAGE NOTES RECEIVABLE Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Real Estate Investments [Table] Real Estate Investments [Table] Real Estate Investments [Table] Retail And Mixed-Use Properties [Member] Retail And Mixed-Use Properties [Member] Retail Properties Under Capital Leases [Member] Retail Properties Under Capital Leases [Member] Residential [Member] Cost Accumulated Depreciation and Amortization Schedule IV - Mortgage Loans on Real Estate Mortgage Loans on Real Estate, by Loan Disclosure [Text Block] First Mortgage [Member] First Mortgage [Member] Mortgage Loans on Real Estate, Number of Loans Mortgage Loans on Real Estate, Number of Loans Mortgage Loans on Real Estate, Carrying Amount of Mortgages Principal balance of first mortgage loan Allowance for Loan and Lease Losses, Real Estate Allowance for Loan and Lease Losses, Real Estate Mortgage Loans, Weighted Average Interest Rate Mortgage loan carrying balance The carrying amount of the oustanding balance due under the mortgage loan prior to refinancing. Maturity date of first mortgage loan Mortgage Loans on Real Estate, Final Maturity Date Cash received as part of refinancing Mortgage Loan On Real Estate Refinancing Payment The amount of cash received at refinancing of a mortgage note receivable related to a previously consolidated VIE. Mortgage Loan Fair Value Mortgage Loan Fair Value The original fair value of the mortgage loan receivable. Discontinued operations - gain on deconsolidation of VIE COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] 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 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 Income from real estate partnerships INCOME FROM CONTINUING OPERATIONS DISCONTINUED OPERATIONS Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Discontinued operations - income Discontinued operation - gain on sale of real estate Results from discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest INCOME BEFORE GAIN ON SALE OF REAL ESTATE Income (Loss) before Gain or Loss on Sale of Properties, and Extraordinary Items Gain Loss On Sale Of Properties 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 NET INCOME AVAILABLE FOR COMMON SHAREHOLDERS Net Income (Loss) Available to Common Stockholders, Basic EARNINGS PER COMMON SHARE, BASIC Earnings Per Share, Basic [Abstract] Earnings Per Share, Basic, Total EARNINGS PER COMMON SHARE, DILUTED Earnings Per Share, Diluted [Abstract] Earnings Per Share, Diluted, Total Weighted average number of common shares-diluted Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive Income (Loss), Net of Tax, Attributable to Parent BUSINESS AND ORGANIZATION Nature of Operations [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 [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 Components of Rental Income [Table] Components of Rental Income [Table] Components of Rental Income [Table] 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 SAVINGS AND RETIREMENT PLANS Pension and Other Postretirement Benefits Disclosure [Text Block] Earnings Per Share Narrative [Table] Earnings Per Share Narrative [Table] Earnings Per Share Narrative [Table] Earnings Per Share Narrative [Line Items] 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 excluded from dilutive earnings per share calculation Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Cumulative convertible preferred share, dividend rate Taurus Investment Holdings [Member] Taurus Investment Holdings, LLC [Member] Federal Realty Investment Trust [Member] Federal Realty Investment Trust [Member] Clarion [Member] Clarion [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Loan Secured By Two Buildings [Member] Loan Secured By Two Buildings [Member] Loan Secured By Two Buildings [Member] Loan Secured by One Building [Member] Loan Secured by One Building [Member] Loan Secured by One Building [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 Total number of properties in the portfolio Sales of Real Estate Business Acquisition Cost of Acquired Entity Cash Paid and Total Debt Assumed Contributed towards acquisition of property Payments to Acquire Equity Method Investments Equity Method Investment, Dividends or Distributions Proceeds from Equity Method Investment, Dividends or Distributions Secured loan Loan interest rate Debt Instrument, Interest Rate Terms 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 EARNINGS PER SHARE Earnings Per Share [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Term Loan [Member] Term Loan [Member] Term Loan [Member] Accumulated Other Comprehensive Income (Loss) [Member] Derivative, by Nature [Axis] Derivative, Name [Domain] Interest Rate Swap [Member] 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 2 [Member] Fair Value, Inputs, Level 2 [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] Mortgages and notes payable, carrying value Mortgages and Notes Payable Mortgages and Notes Payable Senior notes and debentures, carrying value 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 Notes payable Notional Amount of Interest Rate Cash Flow Hedge Derivatives Derivative, Fixed Interest Rate Derivative, Fixed Interest Rate Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Interest Expense Cash Flow Hedge Loss Reclassified to Interest Expense Interest rate swaps Derivative Financial Instruments, Liabilities, Fair Value Disclosure FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] 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 Stockholders' Equity Note [Abstract] Stockholders' Equity [Table] Stockholders' Equity [Table] Stockholders' Equity [Table] 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 [Member] Commissions [Member] Commissions [Member] Other Offering Costs [Member] Other Offering Costs [Member] Other Offering Costs [Member] 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] Preferred Stock, Liquidation Preference Per Share Common Stock, Shares, Issued 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 Weighted average price per common share Weighted Average Price Per Common Share Weighted average price per common share Net cash proceeds of common stock Commissions related to sales of common shares Payments of Stock Issuance Costs Remaining Capacity To Issue Remaining Capacity To Issue Remaining $ Capacity Of Shares To Issue Dividends [Table] Dividends [Table] Dividends [Line Items] Dividends [Line Items] Common shares, declared Common Stock, Dividends, Per Share, Declared 5.417% Series 1 Cumulative Convertible Preferred, Declared (in dollars per share) Preferred Stock, Dividends Per Share, Declared Common shares, ordinary dividend Common Stock, Ordinary Dividends, Per Share, Cash Paid Common Stock, Ordinary Dividends, Per Share, Cash Paid Common shares, ordinary dividend eligible for 15% rate Common Stock, Ordinary Dividends Eligible For 15 Percent Tax Rate, Per Share, Cash Paid Common Stock, Ordinary Dividends Eligible For 15 Percent Tax Rate, Per Share, Cash Paid Common shares, return of capital Common Stock, Return Of Capital Dividends, Per Share, Cash Paid Common Stock, Return Of Capital Dividends, Per Share, Cash Paid Common shares, capital gain Common Stock, Capital Gain Dividends, Per Share, Cash Paid Common Stock, Capital Gain Dividends, Per Share, Cash Paid Common shares, paid Common Stock, Dividends, Per Share, Cash Paid 5.417% Series 1 Cumulative Convertible Preferred shares, ordinary dividend Preferred Stock, Ordinary Dividends, Per Share, Cash Paid Preferred Stock, Ordinary Dividends, Per Share, Cash Paid 5.417% Series 1 Cumulative Convertible Preferred shares, ordinary dividend eligible for 15 % rate Preferred Stock, Ordinary Dividends Eligible For 15 Percent Tax Rate, Per Share, Cash Paid Preferred Stock, Ordinary Dividends Eligible For 15 Percent Tax Rate, Per Share, Cash Paid 5.417% Series 1 Cumulative Convertible Preferred shares, capital gain Preferred Stock, Capital Gain Dividends, Per Share, Cash Paid Preferred Stock, Capital Gain Dividends, Per Share, Cash Paid 5.417% Series 1 Cumulative Convertible Preferred shares, paid Preferred Stock, Dividends, Per Share, Cash Paid Common Stock, Ordinary Dividends, Tax Rate Common Stock, Ordinary Dividends, Tax Rate Preferred Stock, Ordinary Dividends, Tax Rate Preferred Stock, Ordinary Dividends, Tax Rate DIVIDENDS Dividends Disclosure [Text Block] This text block may be used to disclose all or some of the information related to dividends declared, dividends paid, and the tax status of dividends as of the financial reporting date. Schedule of Quarterly Financial Information Schedule of Quarterly Financial Information [Table Text Block] Schedule of Future Minimum Rental Payments for Operating Leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Summary Of Share Based Compensation Expense Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of Share-based Compensation, Stock Options, Activity Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Disclosure of Share-based Compensation Arrangements by Share-based Payment Award Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] GroveatShrewsbury & Brook 35 [Member] GroveatShrewsbury & Brook 35 [Member] GroveatShrewsbury & Brook 35 [Member] GroveatShrewsbury [Member] GroveatShrewsbury [Member] GroveatShrewsbury [Member] Brook 35 [Member] Brook 35 [Member] Brook 35 [Member] Grove at Shrewsbury (WEST) [Member] Grove at Shrewsbury (WEST) [Member] Grove at Shrewsbury (WEST) [Member] Repayments of Secured Debt Business Acquisition, Cost of Acquired Entity, Purchase Price Business Acquisition, Cost of Acquired Entity, Purchase Price Effective Economic Interest Acquisition Effective Economic Interest Acquisition Effective Economic Interest in Acquisition Noncash or Part Noncash Acquisition, Debt Assumed Noncash or Part Noncash Acquisition, Debt Assumed Operating partnership units, outstanding Number of DownREIT Units Issued in Connection with Business Acquisition Number of DownREIT Units Issued in Connection with Business Acquisition Business Acquisition, Cost of Acquired Entity, Cash Paid Business Acquisition, Cost of Acquired Entity, Cash Paid Price to Acquire Non-Controlling Interest Price to Acquire Non-Controlling Interest Price to Acquire Non-Controlling Interest Straight-line rents Straight Line Rent Amortization of above and below Market Leases Amortization of above and below Market Leases Operating Leases of Lessee Disclosure Operating Leases of Lessee Disclosure [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 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. 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 Operating Income Net income attributable to the Trust Net income available for common shareholders Earnings per common share—basic Earnings per common share—diluted Senior Notes [Member] Senior Notes [Member] Mortgages Payable [Member] Secured Debt [Member] Notes Payable, Other Payables [Member] Notes Payable, Other Payables [Member] 2014 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2015 Long-term Debt, Maturities, Repayments of Principal in Year Two 2016 Long-term Debt, Maturities, Repayments of Principal in Year Three 2017 Long-term Debt, Maturities, Repayments of Principal in Year Four 2018 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Long-term Debt Long-term Debt SHAREHOLDERS’ EQUITY Stockholders' Equity Note Disclosure [Text Block] Secured Debt [Member] Municipal Bonds [Member] Municipal Bonds [Member] Revolving Credit Facility [Member] Various Notes Payable [Member] Various Notes Payable [Member] Senior 5.65 Percent Notes [Member] Senior 5.65 Percent Notes [Member] Senior 6.20 Percent Notes [Member] Senior 6.20 Percent Notes [Member] Senior 5.90 Percent Notes [Member] Senior 5.90 Percent Notes [Member] Senior300PercentNotes [Member] Senior300PercentNotes [Member] Senior300PercentNotes [Member] Debentures 7.48 Percent [Member] Debentures 7.48 Percent [Member] Medium Term Notes 6.82 Percent [Member] Medium Term Notes 6.82 Percent [Member] Debt Instrument, Interest Rate Terms Net unamortized premium (discount) Debt Instrument, Unamortized Discount (Premium), Net Total debt and capital lease obligations Debt and Capital Lease Obligations Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Stock Options [Member] Stock Option [Member] Stock Option [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Long Term Incentive Plan 2001 [Member] Long Term Incentive Plan 2001 [Member] Long Term Incentive Plan 2001 [Member] Performance Incentive Plan 2010 [Member] Performance Incentive Plan 2010 [Member] Performance Incentive Plan 2010 [Member] Related Party [Axis] Related Party [Domain] Stock Award [Member] 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 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. Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures 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, 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 Years Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition Years Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition