Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] 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 Accumulated Other Comprehensive Income (Loss) [Member] Noncontrolling Interests Noncontrolling Interest [Member] Statement [Line Items] 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 Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Net income, excluding amount attributable to noncontrolling interests Profit Loss Excluding Redeemable Noncontrolling Interests Net income (loss) excluding portion attributable to redeemable noncontrolling interests. Other comprehensive (loss) income - change in value of interest rate swaps 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 of shares withheld for employee taxes (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 shares withheld for employee taxes 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. Contributions from noncontrolling interests Noncontrolling Interest, Increase from Business Combination Adjustment to redeemable noncontrolling interests Stockholders' Equity, Other Ending balance (in shares) Ending balance Accounting Policies [Abstract] Minimum percentage of taxable income distributed to shareholders Minimum Percentage Of Taxable Income Distributed To Shareholders Minimum percentage of taxable income distributed to shareholders. Number of properties exceeding segment reporting threshold Number of Properties Exceeding Segment Reporting Threshold Number of Properties Exceeding Segment Reporting Threshold Segment reporting threshold Segment Reporting, Factors Used to Identify Entity's Reportable Segments Number of segments Number of Reportable Segments Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] San Antonio Center San Antonio Center [Member] San Antonio Center Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Leasable area (square feet) Area of Real Estate Property Gross value BusinessAcquisitionGrossValue Gross Value of Business Acquisition Effective interest percentage Effective Interest Acquisition Effective Interest Acquisition Mortgage loans assumed with acquisition Noncash or Part Noncash Acquisition, Debt Assumed Interest rate Debt Instrument, Interest Rate, Stated Percentage Number of downREIT operating partnership units Number of DownREIT Units Issued in Connection with Business Acquisition Number of DownREIT Units Issued in Connection with Business Acquisition Cash payments to acquire businesses Payments to Acquire Businesses, Gross Acquisition costs Business Combination, Acquisition Related Costs Savings and Retirement Plans [Abstract] Savings and Retirement Plans [Abstract] SAVINGS AND RETIREMENT PLANS Pension and Other Postretirement Benefits Disclosure [Text Block] Debt Instruments [Abstract] DEBT Debt Disclosure [Text Block] Leases [Abstract] Schedule of minimum future commercial property rentals from noncancelable operating leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Equity Method Investments and Joint Ventures [Abstract] Summarized operating results and the 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] Goodwill and Intangible Assets Disclosure [Abstract] 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 Above Market Leases [Member] Below Market Lease [Member] Below Market Lease [Member] Below Market Lease [Member] Acquired Finite-Lived Intangible Assets [Line Items] Balance of acquired above market leases Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Accumulated amortization of acquired above market leases Finite-Lived Intangible Assets, Accumulated Amortization Balance of acquired below market leases Below Market Lease, Gross Accumulated amortization of below market leases Below Market Lease, Accumulated Amortization Amortization from acquired above market leases Amortization of Intangible Assets Amortization from acquired below market lease Amortization of Below Market Lease Weighted-average amortization period Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Above Market Leases Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] 2015 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2016 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2017 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2018 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Total future amortization expense from acquired above market leases Finite-Lived Intangible Assets, Net Below Market Leases Below Market Lease, Amortization Income, Maturity Schedule [Abstract] 2015 Below Market Lease, Amortization Income, Next Twelve Months 2016 Below Market Lease, Amortization Income, Year Two 2017 Below Market Lease, Amortization Income, Year Three 2018 Below Market Lease, Amortization Income, Year Four 2019 Below Market Lease, Amortization Income, Year Five Thereafter Below Market Lease, Amortization Income, after Year Five Total future amortization expense from acquired below market leases Below Market Lease, Net Mortgage Notes Receivable [Abstract] Mortgage Notes Receivable Disclosure [Abstract] Mortgage Loans on Real Estate Schedule [Table] Mortgage Loans on Real Estate Schedule [Table] Real Estate, Type of Property [Axis] Real Estate [Domain] First Mortgage First Mortgage [Member] Second Mortgage On Hotel In San Jose, CA Second Mortgage On Hotel In San Jose, CA [Member] Second Mortgage On Hotel In San Jose, CA [Member] Mortgage Loans on Real Estate [Line Items] Mortgage Loans on Real Estate [Line Items] Number of mortgage notes receivable Mortgage Loans on Real Estate, Number of Loans Carrying amount of mortgage notes receivable Mortgage Loans on Real Estate, Carrying Amount of Mortgages Principal balance of first mortgage loan Mortgage Loans on Real Estate, Face Amount of Mortgages Valuation allowance Allowance for Loan and Lease Losses, Real Estate Weighted average interest rate Mortgage Loans on Real Estate, Interest Rate 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 Trading Symbol Trading Symbol Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding 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 Quarterly Financial Information Disclosure [Abstract] SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) Quarterly Financial Information [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Summary of share-based compensation expense Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Summary of option activity Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Summary of restricted share activity Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Schedule of common shares awarded under various compensation plans Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Amortization for acquired in-place leases during the next five years and thereafter Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Brook 35 Brook 35 [Member] Brook 35 4.50% notes Senior Notes 4 Point 50 Percent [Member] Senior Notes 4.50 Percent [Member] THE AVENUE at White Marsh THE AVENUE at White Marsh, Due 2021 [Member] THE AVENUE at White Marsh, Due 2021 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt Instrument, Face Amount Debt Instrument, Face Amount Principal balance Long-term Debt, Gross Rollforward of Redeemable Noncontrolling Interests Increase (Decrease) in Temporary Equity [Roll Forward] Beginning balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Net income Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Distributions & Redemptions Redeemable Noncontrolling Interests Distributions Redeemable Noncontrolling Interests Distributions Contributions Redeemable Noncontrolling Interests Contributions Redeemable Noncontrolling Interests Contributions Adjustment to redeemable noncontrolling interests Temporary Equity, Other Changes Ending balance Dividends [Abstract] 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 Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Federal Realty Investment Trust Federal Realty Investment Trust [Member] Federal Realty Investment Trust [Member] Schedule of Equity Method Investment, Equity Method Investee, Name [Axis] Investment, Name [Axis] Equity Method Investee, Name [Domain] Investment, Name [Domain] Federal / Lion Venture LP Federal / Lion Venture LP [Member] Federal / Lion Venture LP [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] OPERATING RESULTS Equity Method Investment, Summarized Financial Information, Income Statement [Abstract] 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. Income before gain on sale of real estate Income (Loss) before Gain or Loss on Sale of Properties, and Extraordinary Items Gain on sale of real estate Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Our share of net income from real estate partnership before gain on sale of real estate IncomeLossfromEquityInvestmentbeforegainonsalefromrealestatepartnership Income (Loss) from Equity Investment before gain on sale from real estate partnership Our share of gain on sale of real estate Gain (Loss) On Sale Of Properties in Real Estate Partnership Gain loss on sale of properties in real estate partnership ASSETS Equity Method Investment, Summarized Financial Information, Assets [Abstract] Real estate, net Real Estate Investment Property, Net Cash Cash and Cash Equivalents, at Carrying Value Other assets Other Assets Total assets Assets LIABILITIES AND PARTNERS' CAPITAL Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract] 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 Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted Stock Restricted Stock [Member] Employee Stock Option Employee Stock Option [Member] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [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 Mortgage Loans on Real Estate [Abstract] 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 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 Mortgage On Retail Buildings in Philadelphia, PA, Loan Two [Member] Mortgage On Retail Buildings in Philadelphia, PA, Loan Two [Member] Mortgage loan on a shopping center and an adjacent commercial building in Norwalk ,CT 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 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] Extension Option [Axis] Extension Option [Axis] Extension Option [Axis] Extension Option [Domain] Extension Option [Domain] Extension Option [Domain] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] Interest Rate [Axis] Interest Rate [Axis] Interest Rate [Axis] Interest Rate [Domain] Interest Rate [Domain] Interest Rate [Domain] Interest Rate One Interest Rate One [Member] Interest Rate One [Member] Interest Rate Two Interest Rate Two [Member] Interest Rate Two [Member] Prior Liens Mortgage Loans on Real Estate, Prior Liens Face Amount of Mortgages Carrying Amount of Mortgages Principal Amount of Loans Subject to delinquent Principal or Interest Mortgage Loans on Real Estate, Principal Amount of Delinquent Loans Interest Rate 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, Other Required Disclosures [Abstract] Mortgage Loans on Real Estate, Other Required Disclosures [Abstract] Aggregate tax basis for Federal tax purposes Mortgage Loans on Real Estate, Federal Income Tax Basis Interest rate Amortization schedule, period Payments of Principal and Interest Based on Amortization Schedule, Period Payments of Principal and Interest Based on Amortization Schedule, Period 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 Collection and satisfaction of loans Mortgage Loans on Real Estate, Collections of Principal Amortization of discount Mortgage Loans on Real Estate, Amortization of Premium Balance at end of year Real Estate [Abstract] Summary of real estate investments and related encumbrances Schedule of Real Estate Properties [Table Text Block] The Grove at Shrewsbury (East) Grove at Shrewsbury (East) [Member] Grove at Shrewsbury (East) [Member] The Grove at Shrewsbury (West) Grove at Shrewsbury (WEST) [Member] Grove at Shrewsbury (WEST) [Member] Principal Stated Interest Rate Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Term loan Term Loan [Member] Term Loan [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Mortgages Payable Secured Debt [Member] Notes Payable Notes Payable, Other Payables [Member] Senior Notes and Debentures Senior Notes [Member] Variable Interest Rate Debt Instrument, Basis Spread on Variable Rate 2015 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2016 Long-term Debt, Maturities, Repayments of Principal in Year Two 2017 Long-term Debt, Maturities, Repayments of Principal in Year Three 2018 Long-term Debt, Maturities, Repayments of Principal in Year Four 2019 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 change in basis points spread change in basis points spread The change in the number of basis points added to LIBOR to compute the total interest rate Real Estate Property Ownership [Axis] Real Estate Property Ownership [Axis] Real Estate Properties [Domain] Real Estate Properties [Domain] Clarion Clarion [Member] Clarion [Member] Taurus Investment Holdings Taurus Investment Holdings [Member] Taurus Investment Holdings, LLC [Member] Newbury Street Partnership Newbury Street Partnership [Member] Taurus Newbury Street JV II Limited Partnership [Member] Ownership interest in partnership Equity Method Investment, Ownership Percentage Total number of properties in the portfolio Number of Real Estate Properties Contributions Payments to Acquire Equity Method Investments Distributions Proceeds from Equity Method Investment, Dividends or Distributions Repayments of mortgage loans Repayments of Secured Debt Capital contributions from partners Proceeds from Partnership Contribution Capital contribution to acquire interest in joint venture Payments to Acquire Interest in Joint Venture Sales price Sales of Real Estate Gain on sale of portfolio Payments for (Proceeds from) Real Estate Partnership Investment, Net Number of real estate properties sold Number of Real Estate Properties Sold Number of Real Estate Properties Sold Melville Mall Melville Mall [Member] Melville Mall [Member] East Bay Bridge East Bay Bridge [Member] EastBayBridge [Member] 5.65% notes Senior 5 Point 65 Percent Notes [Member] Senior 5 Point 65 Percent Notes [Member] Accrued but unpaid interest Interest Paid RepaymentSecuredDebtIncludingPrepaymentPenalty RepaymentSecuredDebtIncludingPrepaymentPenalty Repayment of Secured Debt Cash Outflow Including Principal, Prepayment Penalty and accrued but unpaid interest Prepayment premium on mortgage loan Prepayment Premium on Mortgage Loan Prepayment Premium on Mortgage Loan Repayments of debt Repayments of Debt Operating income Operating Income (Loss) Net income NET INCOME ATTRIBUTABLE TO THE TRUST Net Income (Loss) Attributable to Parent Net income available for common shareholders Net Income (Loss) Available to Common Stockholders, Basic Earnings per common share-basic Earnings Per Share, Basic Earnings per common share-diluted Earnings Per Share, Diluted SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract] Schedule III - Summary of Real Estate and Accumulated Depreciation SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Text Block] Cash in excess of the FDIC insured limit Cash, Uninsured Amount Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Groups, Including Discontinued Operations, Name [Domain] Disposal Groups, Including Discontinued Operations, Name [Domain] Feasterville Shopping Center July 17, 2011 Feasterville Shopping Center July 17 2011 [Member] Feasterville Shopping Center 7/12/11 [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Discontinued operations - gain on sale of real estate Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Revenue from discontinued operations Disposal Group, Including Discontinued Operation, Revenue Components Of Rental Income and Expense [Abstract] Components Of Rental Income And Expense [Abstract] 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. Marketing Marketing Expense Insurance Real Estate Insurance Ground Rent Ground Rent Expense Ground Rent Expense Bad debt expense Provision for Doubtful Accounts Other operating Other Cost of Operating Revenue Total rental expenses Direct Costs of Leased and Rented Property or Equipment Fair Value Disclosures [Abstract] FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] 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] Summary of financial liabilities measured at fair value on a recurring basis Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Operating (including $282,303 and $265,138 of consolidated variable interest entities, respectively) Rental Properties Construction-in-progress Construction in Progress, Gross Real estate, at cost Real Estate Investment Property, at Cost Less accumulated depreciation and amortization (including $26,618 and $19,086 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 partnerships Prepaid expenses and other assets Prepaid Expense and Other Assets Debt issuance costs, net of accumulated amortization of $11,441 and $9,535, respectively Deferred Finance Costs, Net Liabilities Liabilities [Abstract] Mortgages payable (including $187,632 and $202,782 of consolidated variable interest entities, respectively) 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 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, 68,605,783 and 66,701,422 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 Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 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 Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Unvested at the end of year (in shares) 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, Weighted-Average Grant-Date Fair Value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value 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, 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, Weighted-Average Grant-Date Fair Value (in dollars per share) Grove at Shrewsbury and Brook 35 Grove At Shrewsbury And Brook 35 [Member] GroveatShrewsbury & Brook 35 [Member] Revolving credit facility Revolving Credit Facility [Member] Debt instrument, fair value Debt Instrument, Fair Value Disclosure Net proceeds from note offering Proceeds from Issuance of Senior Long-term Debt Redemption price Early Repayment of Senior Debt Make-whole premium Prepayment Premium On Senior Note Prepayment Premium on Senior Note. Maximum amount of borrowings outstanding Line of Credit Facility, Maximum Amount Outstanding During Period Weighted average amount of borrowings outstanding Line of Credit Facility, Average Outstanding Amount Weighted average interest rate before amortization of debt fees LineofCreditFacilityWeightedAverageInterestRateBeforeAmortizationOfDebt Fees Line of credit facility weighted average interest rate, before amortization of debt fees. Annual facility fee Line of Credit Facility, Commitment Fee Amount Revolving credit facility Long-term Line of Credit Revolving credit facility, max capacity Line of Credit Facility, Maximum Borrowing Capacity Discontinued Operations and Disposal Groups [Abstract] Summary of the financial information for the discontinued operations Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block] Common shares, declared Common Stock, Dividends, Per Share, Declared 5.417% Series 1 Cumulative Convertible Preferred shares, declared Preferred Stock, Dividends Per Share, Declared Common shares, paid Common Stock, Dividends, Per Share, Cash Paid 5.417% Series 1 Cumulative Convertible Preferred shares, paid Preferred Stock, Dividends, Per Share, Cash Paid Common shares, ordinary dividend Common Stock, Ordinary Dividends, Per Share, Cash Paid Common Stock, Ordinary 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 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, capital gain Preferred Stock, Capital Gain Dividends, Per Share, Cash Paid Preferred Stock, Capital Gain Dividends, Per Share, Cash Paid Series 1 Cumulative Convertible Preferred interest rate Preferred Stock, Dividend Rate, Percentage Common Stock, Ordinary Dividends, Tax Rate Common Stock, Ordinary Dividends, Tax Rate Common Stock, Ordinary Dividends, Tax Rate Preferred Stock, Ordinary Dividends, Tax Rate Preferred Stock, Ordinary Dividends, Tax Rate Preferred Stock, Ordinary Dividends, Tax Rate 2015 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2016 Capital Leases, Future Minimum Payments Due in Two Years 2017 Capital Leases, Future Minimum Payments Due in Three Years 2018 Capital Leases, Future Minimum Payments Due in Four Years 2019 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Future minimum lease payments 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 Nature Of Operations [Abstract] Nature Of Operations [Abstract] Number of real estate properties owned or had a majority interest in OPERATING LEASES Operating Leases of Lessor Disclosure [Text Block] Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable Collection of accounts receivable, period Straight Line Rents Collection Of Accounts Receivable Period Straight Line Rents, Collection Of Accounts Receivable, Period Accounts receivable related to straight-line rents Deferred Rent Receivables, Net Aggregate cost basis for Federal tax purposes SEC Schedule III, Real Estate, Federal Income Tax Basis Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements [Abstract] SEC Schedule III, Real Estate, Gross [Abstract] Balance at beginning of year SEC Schedule III, Real Estate, Gross Acquisitions SEC Schedule III, Real Estate, Other Acquisitions Improvements SEC Schedule III, Real Estate, Improvements Deduction during period—disposition and retirements of property and transfer to joint venture Real Estate Dispositions and Retirements Carrying amount of real estate sold, cap ex disposals, and transfers to joint venture during the period. Balance at end of year Reconciliation of Real Estate Accumulated Depreciation [Roll Forward] SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward] Balance at beginning of year SEC Schedule III, Real Estate Accumulated Depreciation Additions during period—depreciation and amortization expense SEC Schedule III, 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 Amounts attributable to redeemable noncontrolling interest Commitments and Contingencies Disclosure [Abstract] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2015 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2016 Operating Leases, Future Minimum Payments, Due in Two Years 2017 Operating Leases, Future Minimum Payments, Due in Three Years 2018 Operating Leases, Future Minimum Payments, Due in Four Years 2019 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due 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. Earnings Per Share [Abstract] EARNINGS PER SHARE Earnings Per Share [Text Block] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Building and Building Improvements Building and Building Improvements [Member] Minor Improvements, Furniture and Equipment Minor Improvements, Furniture and Equipment [Member] Minor Improvements, Furniture and Equipment [Member] Minimum Minimum [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Estimated useful lives Property, Plant and Equipment, Useful Life Real estate depreciation expense Depreciation Expense Real Estate Depreciation Expense on Real Estate only Loss Contingencies [Table] Loss Contingencies [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Member One In Plaza El Segundo Member One In Plaza El Segundo [Member] Member One In Plaza El Segundo [Member] Member Two In Plaza El Segundo Member Two In Plaza El Segundo [Member] Member Two In Plaza El Segundo [Member] Contractual Obligation [Axis] Contractual Obligation [Axis] Contractual Obligation [Domain] Contractual Obligation [Domain] Capital improvement, development, and redevelopment projects Capital Improvement, Development, And Redevelopment Projects [Member] Capital Improvement, Development, And Redevelopment Projects [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Mercer Mall Mercer Mall [Member] Mercer Mall [Member] Congressional Plaza Congressional Plaza [Member] Congressional Plaza [Member] Project In Southern California Project In Southern California [Member] Project In Southern California [Member] Montrose Crossing Montrose Crossing [Member] Montrose Crossing [Member] Plaza El Segundo Plaza El Segundo [Member] Plaza El Segundo [Member] The Grove at Shrewsbury The Grove at Shrewsbury [Member] The Grove at Shrewsbury Option By Type [Axis] Option By Type [Axis] Option By Type [Domain] Option By Type [Domain] Put Option Put Option [Member] Loss Contingencies [Line Items] Reserves for warranties and general liability Product Warranty Accrual Payments from reserves Product Warranty Accrual, Payments Letters of credit outstanding, amount Letters of Credit Outstanding, Amount Contractual obligations Contractual Obligation Purchase price under option Purchase Price Under Option Purchase Price Under Option Maximum partnership percentage required to purchase Option Indexed to Issuer's Equity, Percentage Of Indexed Ownership Interest Option Indexed to Issuer's Equity, Percentage Of Indexed Ownership Interest Indexed ownership interest percentage 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 the put option Estimated Liability Upon Exercise Of Option Estimated 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. Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Derivative, by Nature [Axis] Derivative, by Nature [Axis] Derivative, Name [Domain] Derivative, Name [Domain] Interest Rate Swap Interest Rate Swap [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [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] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Number of interest rate swap agreements Number of Interest Rate Derivatives Held Notional amount Derivative, Notional Amount Interest rate Derivative, Fixed Interest Rate Interest rate swap liability Derivative Liability Other comprehensive (loss) income - change in value of interest rate swaps Interest expense Minimum annual payments Operating Leases of Lessee Disclosure [Table Text Block] Real Estate and Accumulated Depreciation, by Property [Table] SEC Schedule III, Real Estate and Accumulated Depreciation, by Property [Table] 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] 150 Post Street Post Street 150 [Member] Post Street 150 [Member] 29th Place 29th Place [Member] 29th Place [Member] Andorra Andorra [Member] Andorra [Member] Assembly Row/Assembly Square Market Place Assembly Square Market Place Assembly Row [Member] Assembly Square Market Place Assembly Row [Member] The Avenue at White Marsh THE AVENUE at White Marsh [Member] THE AVENUE at White Marsh [Member] Bala Cynwyd Bala Cynwyd [Member] Bala Cynwyd [Member] Barracks Road Barracks Road [Member] Barracks Road [Member] Bethesda Row Bethesda Row [Member] Bethesda Row [Member] Brick Plaza Brick Plaza [Member] Brick Plaza [Member] Bristol Plaza Bristol [Member] Bristol [Member] Chelsea Commons Chelsea [Member] Chelsea [Member] Colorado Blvd Colorado Blvd [Member] Colorado Blvd [Member] Courthouse Center Courthouse Center [Member] Courthouse Center [Member] Courtyard Shops Courtyard Shops [Member] Courtyard Shops [Member] Crossroads Crossroads [Member] Crossroads [Member] Crow Canyon Commons Crow Canyon [Member] Crow Canyon [Member] Darien Darien [Member] Darien [Member] Dedham Plaza Dedham Plaza [Member] Dedham Plaza [Member] Del Mar Village Del Mar Village [Member] Del Mar Village [Member] Eastgate Eastgate [Member] Eastgate [Member] Elllisburg Elllisburg Circle [Member] Elllisburg Circle [Member] Escondido Promenade Escondido Promenade [Member] Former Mervyns Parcel, Escondido Promenade [Member] Falls Plaza Falls Plaza [Member] Falls Plaza [Member] Federal Plaza Federal Plaza [Member] Federal Plaza [Member] Finley Square Finley Square [Member] Finley Square [Member] Flourtown Flourtown [Member] Flourtown [Member] Fresh Meadows Fresh Meadows [Member] Fresh Meadows [Member] Friendship Center Friendship Ctr [Member] Friendship Ctr [Member] Gaithersburg Square Gaithersburg Square [Member] Gaithersburg Square [Member] Garden Market Garden Market [Member] Garden Market [Member] Governor Plaza Governor Plaza [Member] Governor Plaza [Member] Graham Park Plaza Graham Park [Member] Graham Park Gratiot Plaza Gratiot Plaza [Member] Gratiot Plaza [Member] Greenwich Avenue Greenwich Avenue [Member] Greenwich Avenue [Member] Hauppauge Hauppauge [Member] Hauppauge [Member] Hermosa Avenue Hermosa Ave [Member] Hermosa Ave [Member] Hollywood Blvd. Hollywood Blvd [Member] Hollywood Blvd [Member] Houston Street Houston Street [Member] Houston Street [Member] Huntington Huntington [Member] Huntington [Member] Huntington Square HuntingtonSquare [Member] Huntington Square [Member] Idylwood Plaza Idylwood Plaza [Member] Idylwood Plaza [Member] Kings Court Kings Court [Member] Kings Court [Member] Lancaster Lancaster [Member] Lancaster [Member] Langhorne Square Langhorne Square [Member] Langhorne Square [Member] Laurel Laurel [Member] Laurel [Member] Lawrence Park Lawrence Park [Member] Lawrence Park [Member] Leesburg Plaza Leesburg Plaza [Member] Leesburg Plaza [Member] Linden Square Linden Square [Member] Linden Square [Member] Mount Vernon/South Valley/7770 Richmond Hwy, Mount Vernon [Member] Mount Vernon [Member] Town Center of New Britain Town Center of New Britain [Member] Town Center of New Britain [Member] North Dartmouth North Dartmouth [Member] North Dartmouth [Member] Northeast Northeast [Member] Northeast [Member] North Lake Commons North Lake Commons [Member] North Lake Commons [Member] Old Keene Mill Old Keene Mill [Member] Old Keene Mill [Member] Old Town Center Old Town Center [Member] Old Town Center [Member] Pan Am Shopping Center Pan Am Shopping Center [Member] Pan Am Shopping Center [Member] Pentagon Row Pentagon Row [Member] Pentagon Row [Member] Perring Plaza Perring Plaza [Member] Perring Plaza [Member] Pike & Rose Pike & Rose [Member] Pike & Rose Pike 7 Pike 7 [Member] Pike 7 [Member] Queen Anne Plaza Queen Anne Plaza [Member] Queen Anne Plaza [Member] Quince Orchard Plaza Quince Orchard Plaza [Member] Quince Orchard Plaza [Member] Rockville Town Square Rockville Town Square [Member] Rockville Town [Member] Rollingwood Apts. Rollingwood Apartments [Member] Rollingwood Apartments [Member] Sam's Park and Shop Sams Park and Shop [Member] Sams Park and Shop [Member] Santana Row Santana Row [Member] Santana Row Condominium Units [Member] Saugus Saugus [Member] Saugus [Member] Shirlington Shirlington [Member] Shirlington [Member] The Shoppes At Nottingham Square Shoppes At Nottingham Square [Member] Shoppes At Nottingham Square [Member] Third Street Promenade Third Street Promenade [Member] Third Street Promenade [Member] Tower Tower [Member] Tower [Member] Tower Shops Tower Shops January 19 2011 [Member] Tower Shops 1/19/11 [Member] Troy Troy [Member] Troy [Member] Tyson's Station Tyson Station [Member] Tyson Station [Member] Westgate Center Westgate Mall [Member] Westgate Mall [Member] White Marsh Plaza White Marsh Plaza [Member] White Marsh Plaza [Member] White Marsh Other White Marsh Other [Member] White Marsh Other [Member] Wildwood Wildwood [Member] Wildwood [Member] Willow Grove Willow Grove [Member] Willow Grove [Member] Willow Lawn Willow Lawn [Member] Willow Lawn [Member] Wynnewood Wynnewood [Member] Wynnewood [Member] Real Estate and Accumulated Depreciation [Line Items] SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items] Encumbrances SEC Schedule III, Real Estate and Accumulated Depreciation, Amount of Encumbrances Initial cost to company, Land SEC Schedule III, Real Estate and Accumulated Depreciation, Initial Cost of Land Initial cost to company, Buildings and Improvements SEC Schedule III, Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements Cost Capitalized Subsequent to Acquisition SEC Schedule III, Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs Gross amount at which carried at close of period, Land SEC Schedule III, Real Estate and Accumulated Depreciation, Carrying Amount of Land Gross amount at which carried at close of period, Buildings and Improvements SEC Schedule III, Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements Gross amount at which carried at close of period, Total Accumulated Depreciation and Amortization Life on which depreciation in latest income statements is computed SEC Schedule III, Real Estate and Accumulated Depreciation, Life Used for Depreciation Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Name of Property Name of Property Second Mortgage Second Mortgage [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Master lease term Lessor Leasing Arrangements, Operating Leases, Term of Contract 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. Ownership percentage Business Acquisition, Percentage of Voting Interests Acquired Maximum exposure to loss Real Estate Maximum Exposure to Loss Maximum Exposure to Loss on real estate SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] ACQUIRED IN-PLACE LEASES Intangible Assets Disclosure [Text Block] Summary of total debt outstanding Schedule of Debt [Table Text Block] Conctractual terms of secured mortgage loans assumed in acquisition Secured Debt Assumed in Acquisition [Table Text Block] Secured Debt Assumed in Acquisition [Table Text Block] Schedule of loans or debt securities refinanced or issued during the period Debt Refinanced Or Issued During The Period [Table Text Block] [Table Text Block] for Debt Refinanced Or Issued During The Period [Table] Schedule of repaid loans or debt securities Schedule of Debt Repayments [Table Text Block] Schedule of Debt Repayments [Table Text Block] Schedule of principal payments on mortgages payable, notes payable, senior notes and debentures Schedule of Maturities of Long-term Debt [Table Text Block] Schedule of future minimum lease payments and their present value for property under capital leases Schedule of Future Minimum Lease Payments for Capital Leases [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. Schedule of earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] SUBSEQUENT EVENT Subsequent Events [Text Block] Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [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] Retail and commercial Commercial Real Estate [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Operating lease, term Operating Lease, Term Operating Lease, Term SUPPLEMENTAL DISCLOSURES: Supplemental Cash Flow Information [Abstract] Total interest costs incurred Interest Costs Incurred Interest capitalized Interest Costs Capitalized Cash paid for interest, net of amounts capitalized Interest Paid, Net Cash paid (refunded) 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 ValueofdownREITOperatingPartnershipUnitsIssuedinConnectionwithBusinessAcquisition Value of downREIT Operating Partnership Units Issued in Connection with Business Acquisition Mortgage loans refinanced Refinanceofmortgageloan Refinance of mortgage loan Repayment of note payable with public funding/related construction-in-progress offset repaymentofnotepayablewithpublicfunding 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 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 of consolidated variable interest entities Accumulated depreciation and amortization, consolidated variable interest entities Accumulated Depreciation And Amortization, Consolidated Variable Interest Entities. Accumulated amortization of debt issuance costs Accumulated Amortization, Deferred Finance Costs Mortgages payable - consolidated variable interest entities Mortgage Payable From Consolidated Variable Interest Entities Mortgages payable balances from variable interest entities, or VIEs, for the periods presented. Preferred shares, authorized Preferred Stock, Shares Authorized Preferred shares, par Preferred Stock, Par or Stated Value Per Share Preferred Shares, 5.417% Series 1 Cumulative Convertible liquidation preference Preferred Stock, Liquidation Preference Per Share Preferred shares, shares issued Preferred Stock, Shares Issued Preferred shares, shares outstanding Preferred Stock, Shares Outstanding Common shares of beneficial interest, par Common Stock, Par or Stated Value Per Share Common shares of beneficial interest, shares authorized Common Stock, Shares Authorized Common shares of beneficial interest, shares issued Common Stock, Shares, Issued Common shares of beneficial interest, shares outstanding Common Stock, Shares, Outstanding REAL ESTATE PARTNERSHIPS Equity Method Investments and Joint Ventures Disclosure [Text Block] Stockholders' Equity Note [Abstract] SHAREHOLDERS’ EQUITY Stockholders' Equity Note Disclosure [Text Block] Interest rate swaps associated with cash flow hedges to be reclassified within the next twelve months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Residual profit maximum Residual Profit Maximum Residual Profit Maximum received as additional interest on mortgage note receivable Income from discontinued operations Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax SHARE-BASED COMPENSATION PLANS Disclosure of Compensation Related Costs, Share-based Payments [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 Real estate taxes Real Estate Tax Expense General and administrative General and Administrative Expense Total operating expenses Operating Expenses OPERATING INCOME Other interest income Interest Income, Other Interest expense Early extinguishment of debt Gains (Losses) on Extinguishment of Debt Income from real estate partnerships INCOME FROM CONTINUING OPERATIONS Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest DISCONTINUED OPERATIONS Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Discontinued operations - income Results from discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, 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 Dividends on preferred shares Preferred Stock Dividends, Income Statement Impact NET INCOME AVAILABLE FOR COMMON SHAREHOLDERS EARNINGS PER COMMON SHARE, BASIC Earnings Per Share, Basic [Abstract] Continuing operations Income (Loss) from Continuing Operations, Per Basic Share Discontinued operations Income (Loss) from Discontinued Operations and Disposal of 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 COMMON SHARE, BASIC Weighted average common shares outstanding, basic Weighted Average Number of Shares Outstanding, Basic EARNINGS PER COMMON SHARE, DILUTED Earnings Per Share, Diluted [Abstract] Continuing operations Income (Loss) from Continuing Operations, Per Diluted Share Discontinued operations Income (Loss) from Discontinued Operations and Disposal of 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 COMMON SHARE, DILUTED Weighted average number of common shares, diluted Weighted Average Number of Shares Outstanding, Diluted Comprehensive Income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income attributable to noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest COMPREHENSIVE INCOME ATTRIBUTABLE TO THE TRUST Comprehensive Income (Loss), Net of Tax, Attributable to Parent DISCONTINUED OPERATIONS Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Rollforward table of the redeemable noncontrolling interest Redeemable Noncontrolling Interest [Table Text Block] Schedule of supplemental disclosures related to the Consolidated Statements Of Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Subsidiary, Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock, Name of Transaction [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 [Line Items] Class of Stock [Line Items] Preferred shares, liquidation preference per share Preferred shares, par value Conversion price per share Convertible Preferred Stock, Conversion Price Per Share Convertible Preferred Stock, Conversion Price Per Share Aggregate offering price of common shares 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 Proceeds from Issuance 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 BUSINESS AND ORGANIZATION Nature of Operations [Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Stock Award Stock Award [Member] Stock Award [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Performance Incentive Plan 2010 Performance Incentive Plan 2010 [Member] Performance Incentive Plan 2010 [Member] Long Term Incentive Plan 2001 Long Term Incentive Plan 2001 [Member] Long Term Incentive Plan 2001 [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 Number of shares authorized Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Contractual term (in years) Share Based Compensation Arrangement By Share Based Payment Award Contractual Period Contractual period as to when the equity-based award expires as specified in the award agreement. Number of options granted in period Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Total cash received from options exercised Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options Total intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Weighted-average grant-date fair value of stock awarded Total vesting-date fair value of shares vested during the year Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Total unrecognized compensation cost related to unvested share-based compensation arrangements Employee Service Share-based Compensation, Nonvested Awards, 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 Weighted-average period for recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition 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 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] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Fifth Avenue Fifth Avenue [Member] Fifth Avenue [Member] Forest Hills Forest Hills [Member] Forest Hills [Member] Land Parcel Adjacent to Assembly Row LandParcelAdjacenttoAssemblyRow [Member] Land Parcel Adjacent to Assembly Row [Member] Land Contiguous with Montrose Crossing Land Contiguous with Montrose Crossing [Member] Land Contiguous with Montrose Crossing [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Effective economic interest percentage Effective Economic Interest Acquisition Effective Economic Interest in Acquisition Net assets acquired allocated to above market leases Finite-lived Intangible Assets Acquired Net assets acquired allocated to below market leases Below Market Lease, Acquired Mandatorily redeemable noncontrolling interested classified as a liability Price to Acquire Non-Controlling Interest Price to Acquire Non-Controlling Interest Business acquisition purchase price Business Combination, Consideration Transferred Proceeds from sale Area of land Area of Land Land acquisition purchase price Land Acquisition Purchase Price Land Acquisition Purchase Price Land acquistion, share of purchase price Land Acquisition Our Share of Purchase Price Land Acquisition Our Share of Purchase Price Summary 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] Summary of income tax status of dividends per share paid Schedule Of Income Tax Status Of Dividends Paid [Table Text Block] Schedule Of Income Tax Status Of Dividends Paid [Table Text Block] Income from continuing operations Less: Preferred share dividends Less: Income from continuing operations attributable to noncontrolling interests Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest Less: Earnings allocated to unvested shares Earnings Allocated To Unvested Shares Earnings allocated to unvested shares Income from continuing operations available for common shareholders Income Loss From Continuing Operations Available For Common Shareholders This element represents the income or loss from continuing operations attributable to the parent after earnings allocated to unvested shares and adjustments for dividends on preferred stock. Results from discontinued operations attributable to the Trust Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent 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 Stock options Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average common shares outstanding—diluted EARNINGS PER COMMON SHARE, BASIC EARNINGS PER COMMON SHARE, DILUTED Income from continuing operations attributable to the Trust Income (Loss) from Continuing Operations Attributable to Parent Schedule IV - Mortgage Loans on Real Estate Mortgage Loans on Real Estate, by Loan Disclosure [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Fair Value Measurement [Domain] Portion at Fair Value Measurement 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 [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 Statement of Cash Flows [Abstract] OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization, including discontinued operations Adjustment Depreciation And Amortization The cash flow addback for the non-cash expense of depreciation and amortization including depreciation and amortization related to discontinued operations. Gain on sale of real estate 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) decrease in accounts receivable, net Increase (Decrease) in Accounts and Other Receivables (Increase) decrease in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets 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 Proceeds from sale of real estate in real estate partnership 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 (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 Redemption and retirement of senior notes Repayments of Senior Debt Issuance of mortgages, capital leases and notes payable, net of costs Proceeds from Issuance of Long-term Debt and Capital Securities, Net Repayment of mortgages, capital leases and notes payable Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Issuance of common shares Dividends paid to common and preferred shareholders Dividends Paid To Common And Preferred Shareholders The cash outflow from distribution of an entity's earnings to common and preferred stockholders. 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) Increase 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 year Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Products and Services [Axis] Products and Services [Domain] Residential Residential Real Estate [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Operating Leases, Income Statement, Lease Revenue [Abstract] Operating Leases, Income Statement, Lease Revenue [Abstract] 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 MORTGAGE NOTES RECEIVABLE Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Summary of quarterly financial data Schedule of Quarterly Financial Information [Table Text Block] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Schedule of Real Estate Properties [Table] Schedule of Real Estate Properties [Table] Retail and mixed-use properties Retail And Mixed-Use Properties [Member] Retail And Mixed-Use Properties [Member] Retail properties under capital leases Retail Properties Under Capital Leases [Member] Retail Properties Under Capital Leases [Member] Residential Real Estate Properties [Line Items] Real Estate Properties [Line Items] Cost Accumulated Depreciation and Amortization Property Subject to or Available for Operating Lease, by Major Property Class [Table] Property Subject to or Available for Operating Lease [Line Items] 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] 2015 Operating Leases, Future Minimum Payments Receivable, Current 2016 Operating Leases, Future Minimum Payments Receivable, in Two Years 2017 Operating Leases, Future Minimum Payments Receivable, in Three Years 2018 Operating Leases, Future Minimum Payments Receivable, in Four Years 2019 Operating Leases, Future Minimum Payments Receivable, in Five Years Thereafter Operating Leases, Future Minimum Payments Receivable, Thereafter Total Operating Leases, Future Minimum Payments Receivable 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 Mortgages Payable THE AVENUE at White Marsh THE AVENUE at White Marsh, Due 2015 [Member] THE AVENUE at White Marsh, Due 2015 [Member] Rollingwood Apartments Chelsea Escondido (municipal bonds) Municipal Bonds [Member] Various Various Notes Payable [Member] Various Notes Payable [Member] 6.20% notes Senior 6.20 Percent Notes [Member] Senior 6.20 Percent Notes [Member] 5.90% notes Senior 5.90 Percent Notes [Member] Senior 5.90 Percent Notes [Member] 3.00% notes Senior300PercentNotes [Member] Senior300PercentNotes [Member] 2.75% notes Senior 2 Point 75 Percent Notes [Member] Senior 2 Point 75 Percent Notes [Member] 3.95% notes Senior395percentnotes [Member] Senior395percentnotes [Member] 7.48% debentures Debentures 7.48 Percent [Member] Debentures 7.48 Percent [Member] 6.82% medium term notes Medium Term Notes 6.82 Percent [Member] Medium Term Notes 6.82 Percent [Member] Net unamortized premium (discount) Debt Instrument, Unamortized Discount (Premium), Net Special Assessment Bond Municipal Debt Securities, at Carrying Value Other Notes Payable Other Notes Payable Total debt and capital lease obligations Debt and Capital Lease Obligations Schedule of Deferred Compensation Arrangement with Individual, Postretirement Benefits [Table] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Axis] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Domain] Pension Plan Pension Plan [Member] Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits [Member] Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] Maximum annual contribution per employee Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount Employer match as a percent Deferred Compensation Arrangement with Individual, Employer Contribution Per Employee, Matching Percent Deferred Compensation Arrangement with Individual, Employer Contribution Per Employee, Matching Percent Maximum of employer match as a percentage of employee eligible earnings Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Employer contribution expense Deferred Compensation Arrangement with Individual, Employer Contribution Liability to participants Deferred Compensation Arrangement with Individual, Recorded Liability Straight-line rents Straight Line Rent Net amortization of above and below market leases Amortization of above and below Market Leases 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 Granted (in shares) Exercised (in shares) Forfeited or expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Outstanding at the end of year (in shares) Exercisable at the end of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, 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, 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, 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, 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, Weighted-Average Exercise Price (in dollars per share) Exercisable at the end of the year, Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Outstanding at the end of year, Weighted-Average Remaining Contractual Term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Exercisable at the end of year, Weighted-Average Remaining Contractual Term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Outstanding at the end of year, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Exercisable at the end of year, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value 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 Property, Plant and Equipment, Policy [Policy Text Block] 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] Derivative 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] Recently Adopted and Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block]