Stockholders' Equity Note [Abstract] Summary of dividends declared and paid per share Dividends Declared [Table Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] At The Market Equity Program At The Market Equity Program [Member] At The Market Equity Program [Member] Stock Issuance Costs by Type [Axis] Stock Issuance Costs by Type [Axis] Stock Issuance Costs by Type [Axis] Stock Issuance Costs by Type [Domain] Stock Issuance Costs by Type [Domain] [Domain] for Stock Issuance Costs by Type [Axis] Commissions Commissions [Member] Commissions [Member] Other offering expenses Other Offering Costs [Member] Other Offering Costs [Member] Class of Stock [Line Items] Class of Stock [Line Items] Aggregate offering price of common share Aggregate Offering Price Of Common Share Maximum aggregate offering price of common shares. Shares issued (in shares) Stock Issued During Period, Shares, New Issues Weighted average price per common share Weighted Average Price Per Common Share Weighted average price per common share Net cash proceeds of common stock Proceeds from Issuance of Common Stock Commissions related to sales of common shares Payments of Stock Issuance Costs Remaining capacity to issue Remaining Capacity To Issue Remaining $ Capacity Of Shares To Issue Fair Value Disclosures [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type Long-term Debt, Type [Domain] Mortgages payable and notes payable Mortgages Payable And Notes Payable [Member] Mortgages Payable And Notes Payable [Member] Senior notes and debentures Senior Notes And Debentures [Member] Senior Notes And Debentures [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair value of long-term debt Long-term Debt, Fair Value Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock Class of Stock [Domain] 5.417% Series 1 Cumulative Convertible Preferred 5.417% Series 1 Cumulative Convertible Preferred [Member] Five point Four One Seven Percentage Series One Cumulative Convertible Preferred Stock [Member] 5.0% Series C Cumulative Redeemable Preferred 5.0% Series C Cumulative Redeemable Preferred [Member] Five point Zero Percentage Series C Redeemable Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Operating real estate, 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. Construction-in-progress, consolidated variable interest entities Constructioninprogresofconsolidatedvariableieestentity Construction-in-progress oc consolidated variable interest entity Accumulated depreciation and amortization, consolidated variable interest entities Accumulated depreciation and amortization, consolidated variable interest entities Accumulated depreciation and amortization related to real estate, Consolidated Variable Interest Entities. 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 value Preferred Stock, Par or Stated Value Per Share Preferred shares, percentage Preferred Stock, Dividend Rate, Percentage Preferred shares, 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 value 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 Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent event Subsequent Event [Member] Option By Type [Axis] Option By Type [Axis] Option By Type [Axis] Option By Type [Domain] Option By Type [Domain] Option By Type [Domain] Option to increase credit facility through accordion feature Option to increase credit facility through accordion feature [Member] Option to increase credit facility through accordion feature Subsequent Event [Line Items] Subsequent Event [Line Items] Maximum borrowing capacity under revolving credit facility Line of Credit Facility, Maximum Borrowing Capacity Revolving credit facility basis spread over LIBOR Debt Instrument, Basis Spread on Variable Rate Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash and Cash Equivalents Total cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents SUBSEQUENT EVENT Subsequent Events [Text Block] Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Fair Value, recurring Fair Value, Recurring [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swap Interest Rate Swap [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated other comprehensive loss AOCI Attributable to Parent [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] One of our equity method investees Equity Method Investee [Member] Number of interest rate swap agreements Number of Interest Rate Derivatives Held Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax Summary of carrying amount and fair value of financial instruments Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Commitments and Contingencies Disclosure [Abstract] downREIT operating partnership units, outstanding Partners' Capital Account, Units downREIT operating partnership units outstanding, fair value Operating Partnership Units Fair Value Fair value of operating partnership units at the balance sheet date. Earnings Per Share [Abstract] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Weighted average unvested shares outstanding Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Anti-dilutive stock options Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Cumulative convertible preferred shares, dividend rate Debt Instruments [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Mortgage loan Mortgages [Member] Fixed rate senior unsecured notes Senior Notes [Member] Term loan Term loan [Member] Term loan [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument Debt Instrument, Name [Domain] Rollingwood Apartments Rollingwood Apartments [Member] Rollingwood Apartments [Member] 3.20% Senior note 3.2% Senior Note [Member] 3.2% Senior Note [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Principal amount of mortgage loan repayment Repayments of Secured Debt Senior notes issued Senior Notes Interest rate Debt Instrument, Interest Rate, Stated Percentage Note offering percent Note Offering Percent Note offering percent of principal amount Debt yield to maturity rate Debt Securities, Held-to-maturity, Maturity, after 10 Years, Weighted Average Yield Net proceeds from senior note offering Proceeds from Issuance of Senior Long-term Debt Repayment of unsecured term loan Repayments of Unsecured Debt Maximum amount outstanding under revolving credit facility Line of Credit Facility, Maximum Amount Outstanding During Period Weighted average interest rate, before amortization of debt fees LineofCreditFacilityWeightedAverageInterestRateBeforeAmortizationOfDebt Fees Line of credit facility weighted average interest rate, before amortization of debt fees. Weighted average borrowings outstanding Line of Credit Facility, Average Outstanding Amount Outstanding balance on revolving credit facility Long-term Line of Credit EARNINGS PER SHARE Earnings Per Share [Text Block] Statement of Stockholders' Equity [Abstract] Preferred Shares Preferred Stock [Member] Common Shares Common Stock [Member] Statement, Equity Components [Axis] 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) Income Noncontrolling Interests Noncontrolling Interest [Member] 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 January 1 adoption of new accounting standard - See Note 2 Cumulative Effect on Retained Earnings, Net of Tax Net income, excluding amounts attributable to redeemable noncontrolling interests Profit Loss Excluding Redeemable Noncontrolling Interests Net income (loss) excluding portion attributable to redeemable noncontrolling interests. Other comprehensive (loss) income - change in fair value of interest rate swaps Dividends declared to common shareholders Dividends, Common Stock, Cash Dividends declared to preferred shareholders Dividends, Preferred Stock, Cash Distributions declared to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Shares issued Stock Issued During Period, Value, New Issues Exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Shares issued under dividend reinvestment plan (in shares) Stock Issued During Period, Shares, Dividend Reinvestment Plan Shares issued under dividend reinvestment plan Stock Issued During Period, Value, Dividend Reinvestment Plan Share-based compensation expense, net of forfeitures (in shares) Share Based Compensation Expense Net Shares Number of shares issued during the period as a result of our long term incentive, bonus or other share based compensation plans, net of restricted share award forfeitures. Share-based compensation expense, net of forfeitures Share Based Compensation Expense Net Value This element represents the amount of recognized equity-based compensation related to other long-term incentive and bonus plans during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Shares withheld for employee taxes (in shares) Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Shares withheld for employee taxes Share-based Payment Arrangement, Decrease for Tax Withholding Obligation 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 Increase (Decrease) in noncontrolling interest as a result of redeeming, purchasing and/or converting to common stock the interests of Operating Partnership Units. Adjustment to redeemable noncontrolling interests Stockholders' Equity, Other Contributions from noncontrolling interests Contributions from noncontrolling interests Contributions from noncontrolling interests Ending balance (in shares) Ending balance 5.0% Series C Cumulative Redeemable Preferred Shares, (stated at liquidation preference $25,000 per share), 6,000 shares issued and outstanding 5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 399,896 shares issued and outstanding ASSETS Assets [Abstract] Operating (including $1,703,069 and $1,701,804 of consolidated variable interest entities, respectively) Rental Properties Construction-in-progress (including $78,633 and $51,313 of consolidated variable interest entities, respectively) Construction in Progress, Gross Assets held for sale Real Estate Held-for-sale Real estate, at cost, total Real Estate Investment Property, at Cost Less accumulated depreciation and amortization (including $312,416 and $292,374 of consolidated variable interest entities, respectively) Real Estate Investment Property, Accumulated Depreciation Net real estate Real Estate Investment Property, Net Accounts and notes receivable, net Accounts and Financing Receivable, after Allowance for Credit Loss Mortgage notes receivable, net Mortgage Loans on Real Estate, Commercial and Consumer, Net Investment in partnerships Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Operating lease right of use assets Operating Lease, Right-of-Use Asset Finance lease right of use assets Finance Lease, Right-of-Use Asset Prepaid expenses and other assets Prepaid Expense and Other Assets TOTAL ASSETS Assets Liabilities Liabilities [Abstract] Mortgages payable, net (including $441,469 and $444,388 of consolidated variable interest entities, respectively) Secured Debt Capital lease obligations Capital Lease Obligations Notes payable, net Notes Payable Senior notes and debentures, net Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Dividends payable Dividends Payable Security deposits payable Security Deposit Liability Operating lease liabilities Operating Lease, Liability Finance lease liabilities Finance Lease, Liability Other liabilities and deferred credits Deferred Credits and Other Liabilities Total liabilities Liabilities Commitments and contingencies (Note 6) Commitments and Contingencies Redeemable noncontrolling interests Redeemable Noncontrolling Interest, Equity, Carrying Amount Shareholders’ equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred shares, authorized 15,000,000 shares, $.01 par: Preferred Stock, Value, Issued Common shares of beneficial interest, $.01 par, 100,000,000 shares authorized, 74,950,197 and 74,249,633 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 TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY Liabilities and Equity Cover page. Entities [Table] Entities [Table] Common Shares of Beneficial Interest Entity Information [Line Items] Entity Information [Line Items] Document Type Document Type Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Commission File Number Entity File Number Name of Registrant Entity Registrant Name State of Organization Entity Incorporation, State or Country Code IRS Employer Identification No. Entity Tax Identification Number Entity Address, Address Entity Address, Address Line One Entity Address, City Entity Address, City or Town Entity Address, State Entity Address, State or Province Entity Address, Zip Code Entity Address, Postal Zip Code Registrant's Telephone Area Code City Area Code Registrant's Telephone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Schedule of earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Accounting Policies [Abstract] Schedule of lease cost Lease, Cost [Table Text Block] Supplemental disclosures related to the Consolidated Statements Of Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Reconciliation of cash, cash equivalents, and restricted cash Schedule of Cash and Cash Equivalents [Table Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Recently Adopted Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] DEBT Debt Disclosure [Text Block] Nature Of Operations [Abstract] Nature Of Operations [Abstract] Number of real estate properties Number of Real Estate Properties Minimum percentage of taxable income distributed to shareholders Minimum Percentage Of Taxable Income Distributed To Shareholders Minimum percentage of taxable income distributed to shareholders. Share-based Payment Arrangement [Abstract] Summary of share-based compensation expense included in net income Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Abstract] Grants of common shares and options Share-based Payment Arrangement, Expense Capitalized share-based compensation Share-based Payment Arrangement, Amount Capitalized Share-based compensation expense Share-based Payment Arrangement, Noncash Expense New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Number of properties subject to ground leases Number of Properties Subject to Ground Leases Cumulative impact to accumulated dividends in excess of net income Capitalized initial direct costs of leases excluding external leasing commissions Capitalized initial direct costs of leases, excluding external leasing commissions Capitalized initial direct costs of leases, excluding external leasing commissions BUSINESS AND ORGANIZATION Nature of Operations [Text Block] Statement of Cash Flows [Abstract] OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Adjustment Depreciation And Amortization The cash flow addback for the non-cash expense of depreciation and amortization including depreciation and amortization related to discontinued operations. Gain on sale of real estate, net Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes Loss from partnerships Income (Loss) from Equity Method Investments Other, net Other Noncash Income (Expense) Changes in assets and liabilities, net of effects of acquisitions and dispositions: Increase (Decrease) in Operating Capital [Abstract] Proceeds from new market tax credit transaction, net of deferred costs Proceeds from new market tax credit transaction, net of deferred costs Proceeds from new market tax credit transaction, net of deferred costs Increase in accounts receivable, net Increase (Decrease) in Accounts and Other Receivables Decrease in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Decrease in accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities (Decrease) 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 the sale of real estate and real estate partnership interests Proceeds from the sale of real estate and real estate partnership interests Investment in partnerships Payments to Acquire Interest in Subsidiaries and Affiliates Distribution from partnerships in excess of earnings Proceeds from Distributions Received from Real Estate Partnerships Leasing costs Increase (Decrease) in Lease Acquisition Costs Repayment (issuance) of mortgage and other notes receivable, net Issuance And Repayments Of Mortgage And Other Notes Receivable Net The cash outflow from the issuance and purchase of receivables arising from the mortgage note on real estate and other notes receivable, net of repayments. Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Net borrowings under revolving credit facility, net of costs Proceeds from (Repayments of) Lines of Credit Issuance of senior notes, net of costs Repayment of mortgages, finance leases and notes payable Repayment of Long-term Debt, Long-term Lease Obligation, and Capital Security Issuance of common shares, net of costs 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. Shares withheld for employee taxes Payment, Tax Withholding, Share-based Payment Arrangement Contributions from noncontrolling interests Proceeds from Noncontrolling Interests 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 used in financing activities Net Cash Provided by (Used in) Financing Activities Increase in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents, and restricted cash at beginning of year Cash, cash equivalents, and restricted cash at end of period FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] Real Estate [Abstract] Schedule of Significant Acquisitions [Table] Schedule of Business Acquisitions, by Acquisition [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] Condominiums Condominiums [Member] Condominiums [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Amortization of above market leases Above Market Leases [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets Other Assets [Member] Other Liabilities Other Liabilities [Member] Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] Fairfax Junction Fairfax Junction [Member] Fairfax Junction Free State Shopping Center Free State Shopping Center [Member] [Member] Free State Shopping Center [Member] [Member] A land parcel at Northeast shopping center Northeast [Member] Northeast [Member] Free State Shopping Center and a land parcel at Northeast Free State Shopping Center and a land parcel at Northeast [Member] Free State Shopping Center and a land parcel at Northeast [Member] Assembly Row and Pike & Rose Assembly Row and Pike & Rose [Member] Assembly Row and Pike & Rose [Member] Significant Acquisition and Dispositions Business Acquisition [Line Items] Square footage of real estate property Area of Real Estate Property Purchase price of real estate acquisition Purchase price of real estate acquisition Purchase price of real estate acquisition Above market leases Finite-lived Intangible Assets Acquired Below market leases Below Market Lease, Acquired Proceeds from sale Proceeds from Sale of Real Estate Gain on sale Gain (Loss) on Sale of Properties Number of condominium units sold Number of condominium units sold Number of condominium units sold Gain on sale of real estate, net of income tax Taxes related to the sale of condominiums Gain (Loss) on Sale of Properties, Applicable Income Taxes Dividends [Abstract] Dividends Payable [Table] Dividends Payable [Table] Dividends Dividends Payable [Line Items] Dividends declared to common shareholders (in dollars per share) Common Stock, Dividends, Per Share, Declared Dividends paid per common share Common Stock, Dividends, Per Share, Cash Paid Dividends declared per preferred shares Preferred Stock, Dividends Per Share, Declared Dividends paid per preferred share Preferred Stock, Dividends, Per Share, Cash Paid Percentage of depository shares Percentage Of Depository Shares Percentage of shares equivalent to depository share Net income attributable to redeemable noncontrolling interests Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Income Statement [Abstract] REVENUE Revenues [Abstract] Rental income Operating Leases, Income Statement, Lease Revenue Mortgage interest income Revenue Mortgage Interest Interest income earned from mortgage notes receivable. Total revenue Revenues EXPENSES Operating Expenses [Abstract] Rental expenses Direct Costs of Leased and Rented Property or Equipment Real estate taxes Real Estate Tax Expense General and administrative General and Administrative Expense Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Total operating expenses Operating Expenses Gain on sale of real estate, net of tax OPERATING INCOME Operating Income (Loss) OTHER INCOME/(EXPENSE) Other Income and Expenses [Abstract] Other interest income Interest Income, Other Interest expense Interest Expense Income (loss) from partnerships NET INCOME Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest NET INCOME ATTRIBUTABLE TO THE TRUST Net Income (Loss) Attributable to Parent Dividends on preferred shares Preferred Stock Dividends, Income Statement Impact NET INCOME AVAILABLE FOR COMMON SHAREHOLDERS Net Income (Loss) Available to Common Stockholders, Basic EARNINGS PER COMMON SHARE, BASIC: Earnings Per Share, Basic [Abstract] Net income available for common shareholders Earnings Per Share, Basic Weighted average number of common shares Weighted Average Number of Shares Outstanding, Basic EARNINGS PER COMMON SHARE, DILUTED: Earnings Per Share, Diluted [Abstract] Net income available for common shareholders Earnings Per Share, Diluted Weighted average number of common shares Weighted Average Number of Shares Outstanding, Diluted COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest COMPREHENSIVE INCOME ATTRIBUTABLE TO THE TRUST Comprehensive Income (Loss), Net of Tax, Attributable to Parent LEASE COST: Lease, Cost [Abstract] Amortization of right-of-use assets - finance leases Finance Lease, Right-of-Use Asset, Amortization Interest on lease liabilities - finance leases Finance Lease, Interest Expense Operating lease cost Operating Lease, Cost Variable lease cost Variable Lease, Cost Total lease cost Lease, Cost Cash paid for amounts included in the measurement of lease liabilities Cash Flow, Operating Activities, Lessee [Abstract] Operating cash flows for finance leases Finance Lease, Interest Payment on Liability Operating cash flows for operating leases Operating Lease, Payments Financing cash flows for finance leases Finance Lease, Principal Payments Weighted-average remaining lease term - finance leases Finance Lease, Weighted Average Remaining Lease Term Weighted-average remaining lease term - operating leases Operating Lease, Weighted Average Remaining Lease Term Weighted-average discount rate - finance leases Finance Lease, Weighted Average Discount Rate, Percent Weighted-average discount rate - operating leases Operating Lease, Weighted Average Discount Rate, Percent SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] SHAREHOLDERS’ EQUITY Stockholders' Equity Note Disclosure [Text Block] REAL ESTATE Real Estate Acquisitions Dispositions Text Block Disclosure of real estate acquisitions and dispositions, and at year end, a summary of our real estate investments and related encumbrances. Less: Preferred share dividends Less: Income from operations attributable to noncontrolling interests Less: Earnings allocated to unvested shares Earnings Allocated To Unvested Shares Earnings allocated to unvested shares 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 Total interest costs incurred Interest Costs Incurred Interest capitalized Interest Costs Capitalized Adjustment Interest expense Cash paid for interest, net of amounts capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Cash paid for income taxes Income Taxes Paid, Net DownREIT operating partnership units redeemed for common shares Redemptionofoperatingpartnershipunitsforcommonshares Redemption of operating partnership units for common shares Shares issued under dividend reinvestment plan Dividends Reinvested in Noncash Financing Transaction Dividends reinvested in noncash financing transaction SHARE-BASED COMPENSATION PLANS Share-based Payment Arrangement [Text Block]