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. Stockholders' Equity Note [Abstract] Summary of dividends declared and paid per share Dividends Declared [Table Text Block] Statement of Stockholders' Equity [Abstract] Net income attributable to redeemable noncontrolling interests Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Dividends declared to common shareholders (in dollars per share) Common Stock, Dividends, Per Share, Declared Share-based Payment Arrangement [Abstract] SHARE-BASED COMPENSATION PLANS Share-based Payment Arrangement [Text Block] Leases [Abstract] Finance Lease, Amortization of right-of-use assets Finance Lease, Right-of-Use Asset, Amortization Finance Lease, Interest on lease liabilities Finance Lease, Interest Expense Operating lease cost Operating Lease, Cost Variable lease cost Variable Lease, Cost Total Lease Cost Lease, Cost 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 Earnings Per Share [Abstract] EARNINGS PER SHARE Earnings Per Share [Text Block] Dividends [Abstract] Dividends Payable [Table] Dividends Payable [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] Dividends Dividends Payable [Line Items] Dividends paid per common share Common Stock, Dividends, Per Share, Cash Paid Preferred shares, percentage Preferred Stock, Dividend Rate, Percentage 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 Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Weighted average unvested shares outstanding Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Anti-dilutive stock options Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Cumulative convertible preferred shares, dividend rate Summary of share-based compensation expense included in net income Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Accounting Policies [Abstract] Total interest costs incurred Interest Costs Incurred Interest capitalized Interest Costs Capitalized Adjustment Interest expense 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 issued with acquisition Value of downREIT Operating Partnership Units Issued With Acq. of Noncontrolling Interest Value of downREIT Operating Partnership Units Issued With Acq. of Noncontrolling Interest Mortgage loans assumed with acquisition Noncash or Part Noncash Acquisition, Debt Assumed 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 Debt Instruments [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Option By Type [Axis] Option By Type [Axis] Option By Type [Axis] Option By Type [Domain] Option By Type [Domain] Option By Type [Domain] Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] Hoboken 2 Buildings Hoboken 2 Buildings [Member] Hoboken 2 Buildings Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type Long-term Debt, Type [Domain] Mortgage loan Mortgages [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument Debt Instrument, Name [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Mortgage loan assumed with acquisition Mortgage loan fair value Long-term Debt, Fair Value Interest rate Debt Instrument, Interest Rate, Stated Percentage Maximum amount outstanding under revolving credit facility Line of Credit Facility, Maximum Amount Outstanding During Period Maximum borrowing capacity under revolving credit facility Line of Credit Facility, Maximum Borrowing Capacity 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 Real Estate [Abstract] Schedule of Significant Acquisitions [Table] Schedule of Business Acquisitions, by Acquisition [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] 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] Shopping center in Fairfax, Virginia Fairfax Junction [Member] Fairfax Junction Hoboken Hoboken [Member] Hoboken [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 DownREIT operating units issued to fund acquisition downREIT partnership units issued in acquisition The number of downREITpartnership units issued in an acquisition. Ownership interest in joint venture Equity Method Investment, Ownership Percentage Above market leases Finite-lived Intangible Assets Acquired Below market leases Below Market Lease, Acquired 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. Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Less: Preferred share dividends Preferred Stock Dividends, Income Statement Impact Less: Income from operations attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest 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 and diluted Weighted Average Number of Shares Outstanding, Basic and Diluted Earnings per common share, basic and diluted Earnings Per Share, Basic and Diluted DEBT Debt Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Other liabilities and deferred credits other liabilities and deferred credits [Member] other liabilities and deferred credits Long-term Debt, Type Mortgage payable 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] Fair Value, Balance Sheet Grouping, Financial Statement Captions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Number of interest rate swap agreements Number of Interest Rate Derivatives Held Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax Notional amount of derivative liability Derivative Liability, Notional Amount Mortgage payable Long-term Debt, Gross Fixed interest rate on derivative Derivative, Fixed Interest Rate Derivative Liability Derivative Liability Amount reclassified from other comprehensive loss to interest expense (less than) Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Derivative Asset Derivative Asset BUSINESS AND ORGANIZATION Nature of Operations [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] 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 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. 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] Decrease (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 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 Capital Expenditures - Other Payments to improve operating real estate that is not included in development or redevelopment. Such improvements may include drainage, utilities, subdividing, access, buildings, and any combination of these elements. Costs associated with property sold under threat of condemnation Costs associated with lease buyout for a property sold The cash outflow related to a tenant lease buyout, which related to the sale of a property. 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 (Issuance) repayment of mortgage and other notes receivable, net Issuance And Repayments Of Mortgage And Other Notes Receivable Net The cash outflow from the issuance and purchase of receivables arising from the mortgage note on real estate and other notes receivable, net of repayments. Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Net borrowings under revolving credit facility, including costs Proceeds from (Repayments of) Lines of Credit 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 Proceeds from Issuance of Common Stock Dividends paid to common and preferred shareholders Dividends Paid To Common And Preferred Shareholders The cash outflow from distribution of an entity's earnings to common and preferred stockholders. 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 provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Increase (decrease) 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, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash at end of period 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] Number of Interest Rate Derivatives Held Fair value of long-term debt Statement of Financial Position [Abstract] 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 $1,751,718 and $1,676,866 of consolidated variable interest entities, respectively) Rental Properties Construction-in-progress (including $84,034 and $102,583 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 $306,861 and $296,165 of consolidated variable interest entities, respectively) Real Estate Investment Property, Accumulated Depreciation Net real estate Real Estate Investment Property, Net Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts and notes receivable, net Accounts and 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 $476,944 and $469,184 of consolidated variable interest entities, respectively) Secured Debt Notes payable, net Notes Payable Senior notes and debentures, net Unsecured Debt 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, 75,622,504 and 75,540,804 shares issued and outstanding, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated dividends in excess of net income Accumulated Distributions in Excess of Net Income Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholders’ equity of the Trust Stockholders' Equity Attributable to Parent Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total shareholders’ equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY Liabilities and Equity Subsequent Events [Abstract] SUBSEQUENT EVENT Subsequent Events [Text Block] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Cover [Abstract] Entities [Table] Entities [Table] Common Shares of Beneficial Interest Common Stock [Member] 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 Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract] Restricted cash Restricted Cash and Cash Equivalents Total cash, cash equivalents, and restricted cash 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] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent event Subsequent Event [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] 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. Net cash proceeds of common stock Remaining capacity to issue Remaining Capacity To Issue Remaining $ Capacity Of Shares To Issue SHAREHOLDERS’ EQUITY Stockholders' Equity Note Disclosure [Text Block] Lease, Cost [Table Text Block] Lease, Cost [Table Text Block] OPERATING & FINANCE LEASES Operating & Finance Leases [Text Block] Operating & Finance Leases [Text Block] Preferred Shares Preferred Stock [Member] Common Shares 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 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 - 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 (in shares) Stock Issued During Period, Shares, New Issues Shares issued Stock Issued During Period, Value, New Issues 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. Contributions from noncontrolling interests Contributions from noncontrolling interests Contributions from noncontrolling interests Adjustment to redeemable noncontrolling interests Stockholders' Equity, Other Ending balance (in shares) Ending balance 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] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] 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 OPERATING INCOME Operating Income (Loss) OTHER INCOME/(EXPENSE) Other Income and Expenses [Abstract] Other interest income Interest Income, Other Interest expense Loss from partnerships NET INCOME Net income attributable to noncontrolling interests NET INCOME ATTRIBUTABLE TO THE TRUST Net Income (Loss) Attributable to Parent Dividends on preferred shares NET INCOME AVAILABLE FOR COMMON SHAREHOLDERS Net Income (Loss) Available to Common Stockholders, Basic EARNINGS PER COMMON SHARE, BASIC: Earnings Per Share, Basic [Abstract] Net income available for common shareholders Earnings Per Share, Basic Weighted average number of common shares Weighted Average Number of Shares Issued, 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 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, 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 Schedule of earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Summary of carrying amount and fair value of financial instruments Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Summary of financial (liabilities) assets that are measured at fair value on a recurring basis Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] 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] ASU 2016-13 Accounting Standards Update 2016-13 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Cumulative impact to accumulated dividends in excess of net income Cumulative Effect of New Accounting Principle in Period of Adoption Expected losses included in rental expenses Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease) Subsequent Event [Table] Subsequent Event [Table] Term loan Term loan [Member] Term loan [Member] A building in Pasadena, California Colorado Blvd [Member] Colorado Blvd [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Sales price of real estate Sales price of real estate The gross sales price of real estate sold. Note payable Basis points over LIBOR Debt Instrument, Basis Spread on Variable Rate REAL ESTATE Real Estate Acquisitions Dispositions Text Block Disclosure of real estate acquisitions and dispositions, and at year end, a summary of our real estate investments and related encumbrances. Share-based 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