Commitments and Contingencies Disclosure [Abstract] 2017 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2018 Capital Leases, Future Minimum Payments Due in Two Years 2019 Capital Leases, Future Minimum Payments Due in Three Years 2020 Capital Leases, Future Minimum Payments Due in Four Years 2021 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Total Capital Leases, Future Minimum Payments Due SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract] 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 at cost SEC Schedule III, Real Estate Accumulated Depreciation, Depreciation Expense Retirements or sales SEC Schedule III, Real Estate Accumulated Depreciation, Real Estate Sold Property held for sale SEC Schedule III, Real Estate Accumulated Depreciation, Other Deductions Balance at end of year Business Combinations [Abstract] Business Combinations Business Combination Disclosure [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Rental Revenues [Member] Rental Revenues [Member] Rental Revenues [Member] Depreciation and Amortization [Member] Depreciation and Amortization [Member] Depreciation and Amortization [Member] Interest Expense [Member] Interest Expense [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] Above-Market Leases [Member] Leases, Acquired-in-Place, Market Adjustment [Member] In Place Leases [Member] Leases, Acquired-in-Place [Member] Below-Market Assumed Mortgages [Member] Mortgages, Acquired In Place, Market Adjustment [Member] This element represents the identifiable intangible asset or liability established for an assumed above or below-market mortgage acquired in an acquisition. Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] 2017 amortization/(accretion) Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2018 amortization/(accretion) Finite-Lived Intangible Assets, Amortization Expense, Year Two 2019 amortization/(accretion) Finite-Lived Intangible Assets, Amortization Expense, Year Three 2020 amortization/(accretion) Finite-Lived Intangible Assets, Amortization Expense, Year Four 2021 amortization/(accretion) Finite-Lived Intangible Assets, Amortization Expense, Year Five Amortization (accretion) Amortization of Intangible Assets Identified Intangible Assets And Liabilities Intangible Assets Disclosure [Text Block] Accounting Policies [Abstract] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer Concentration Risk [Member] Customer Concentration Risk [Member] Houston Texas Geographic Concentration [Member] Houston Texas Geographic Concentration [Member] Houston, Texas Geographic Concentration [Member] Other Parts of Texas Geographic Concentration [Member] Other Parts of Texas Geographic Concentration [Member] Other Parts of Texas Geographic Concentration [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Sales Revenue, Services, Net [Member] Sales Revenue, Services, Net [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] 90-Day London Interbank Offered Rate (LIBOR) [Member] Ninety-Day London Interbank Offered Rate (LIBOR) [Member] Ninety-Day London Interbank Offered Rate (LIBOR) [Member] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Building [Member] Building [Member] Parking Lot Surfacing And Equipment [Member] Parking Lot Surfacing And Equipment [Member] Parking Lot Surfacing And Equipment [Member] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Service Based Awards [Member] Service Based Awards [Member] Service-Based Awards [Member] Share Awards [Member] Restricted Stock [Member] Market Based Awards [Member] Market Based Awards [Member] Market-Based Awards [Member] Market-Based Awards Relative To FTSE NAREIT U.S. Shopping Center Index [Member] Market Based Awards Relative To FTSE NAREIT United States Shopping Center Index [Member] Market-Based Awards Relative To FTSE NAREIT United States Shopping Center Index [Member] Market-Based Awards Relative To Three-Year Absolute TSR [Member] Market Based Awards Relative To Three Year Absolute Total Shareholder Return [Member] Market-Based Awards Relative To Three-Year Absolute Total Shareholder Return [Member] Share Options [Member] Employee Stock Option [Member] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Retirement Plan [Member] Pension Plan [Member] Defined Contribution Plan Name [Axis] Defined Contribution Plan Name [Axis] Defined Contribution Plan Name [Domain] Defined Contribution Plan Name [Domain] Supplemental Retirement Plan, Defined Contribution Plan [Member] Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] Supplemental Retirement Plan, Defined Contribution Plan, New Balance Annual Additions [Member] Supplemental Retirement Plan, Defined Contribution Plan, New Balance Annual Additions [Member] Supplemental Retirement Plan, Defined Contribution Plan, New Balance Annual Additions [Member] Supplemental Retirement Plan, Defined Contribution Plan, Old Balance Annual Addtions [Member] Supplemental Retirement Plan, Defined Contribution Plan, Old Balance Annual Additions [Member] Supplemental Retirement Plan, Defined Contribution Plan, Old Balance Annual Additions [Member] Savings and Investment Plan, Defined Contribution Plan [Member] Savings and Investment Plan, Defined Contribution Plan [Member] Savings and Investment Plan, Defined Contribution Plan [Member] Deferred Compensation Arrangement with Individual, Share-based Payments, by Title of Individual [Axis] Title of Individual [Axis] Title of Individual with Relationship to Entity [Domain] Relationship to Entity [Domain] Officer [Member] Officer [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Square footage of operating properties (in square feet) Area of Real Estate Property Concentrations of risk Concentration Risk, Percentage Real estate asset, estimated useful life Property, Plant and Equipment, Useful Life Single purpose entity, ownership percentage Special Purpose Entity, Percent Of Ownership Special Purpose Entity, Percent Of Ownership Vesting period (years) for share options and awards Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Percentage allocation of market based awards Percentage Allocation Of Market Based Awards To Period Relative Total Shareholder Return Percentage Allocation Of Market Based Awards To Period Relative Total Shareholder Return Market based awards, hurdle comparison Percentage Allocation Of Market Based Awards, Hurdle Comparison Percentage Allocation Of Market Based Awards, Hurdle Comparison Maximum term of option award (years) Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Defined benefit plan, service credit percentage Defined Benefit Plan, Service Credit, Percentage Percent applied to compensation to determine service credit amount. Defined benefit plan, interest credit rate Defined Benefit Plan, Interest Credit, Percentage Interest credit percentage for calculating defined benefits. Defined benefit plan, vesting period (years) Defined Benefit Plan, Vesting Period The vesting term over which an employee's right to be eligible to receive payments from a defined benefit plan which is no longer contingent on satisfaction of a service condition. Number of retirement plans Number Of Retirement Plans Number Of Retirement Plans Defined contribution plan, service credit percentage Defined Contribution Plan, Service Credit, Percentage Defined Contribution Plan, Service Credit, Percentage Defined contribution plan, interest credit percentage Defined Contribution Plan, Interest Credit, Percentage Defined Contribution Plan, Interest Credit, Percentage Defined contribution plan, vesting period Defined Contribution Plan, Vesting Period Defined Contribution Plan Vesting Period Defined contribution plan, basis spread on variable rate Defined Contribution Plan, Basis Spread on Variable Rate Defined Contribution Plan, Basis Spread on Variable Rate Defined contribution plan, minimum annual contribution per employee, percent Defined Contribution Plan, Minimum Annual Employee Contributions Per Employee, Percent Minimum percentage of employee gross pay the employee may contribute to a defined contribution plan. Defined contribution plan, employer matched rate of employee contributions, percentage Defined Contribution Plan, Employer Matching Contribution, Percent of Match Defined contribution plan, employer matching contribution, percent Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Number of foreign operations Number of Foreign Operations Number of Foreign Operations Number of reportable segments Number of Reportable Segments Finite-Lived Intangible Assets and Liabilities [Axis] Finite-Lived Intangible Assets and Liabilities [Axis] Finite-Lived Intangible Assets and Liabilities [Axis] Finite-Lived Intangible Assets and Liabilities [Domain] Finite-Lived Intangible Assets And Liabilities [Domain] Finite-Lived Intangible Assets and Liabilities [Domain] Above-market leases [Member] Above Market Leases [Member] Below-Market Assumed Mortgages [Member] Below Market Mortgages [Member] Below-Market Mortgages [Member] Above-Market Assumed Mortgages [Member] Above Market Mortgages [Member] Above-Market Mortgages [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets [Member] Other Assets [Member] Debt, Net [Member] Debt [Member] Unamortized Debt And Lease Costs, Net [Member] Deferred Costs, Leasing and Finance, Net [Member] Deferred Costs, Leasing and Finance, Net Other Liabilities, Net [Member] Other Liabilities [Member] Above-market leases (included in Other Assets, net) Finite-Lived Intangible Asset, Off-market Lease, Favorable, Gross Identified intangible assets/liabilities, accumulated (amortization) accretion Finite-Lived Intangible Assets, Accumulated Amortization Below-market assumed mortgages (included in Debt, net) Below Market Mortgage, Acquired Below Market Mortgage, Acquired In place leases (included in Unamortized Lease Costs, net) Finite-Lived Intangible Asset, Acquired-in-Place Leases Identified intangible assets, net Finite-Lived Intangible Assets, Net Below-market leases (included in Other Liabilities, net) Below Market Lease, Gross Below-market leases - Accumulated Amortization Below Market Lease, Accumulated Amortization Above-market assumed mortgages (included in Debt, net) Above Market Mortgage, Gross This element represents a liability associated with the acquisition of an off-market mortgage when the terms of the mortgage are unfavorable to the market terms for the mortgage at the date of acquisition. Identified intangible liabilities, net Finite-Lived Intangible Liabilities, Net Amount after amortization of liabilities, excluding financial assets and goodwill, lacking physical substance with a finite life. Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Joint Venture [Member] Corporate Joint Venture [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Collection of Outstanding Receivable [Member] Collection of Outstanding Receivable [Member] Collection of Outstanding Receivable [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Series of Individually Immaterial Business Acquisitions [Member] Series of Individually Immaterial Business Acquisitions [Member] Business Combination Achieved in Stages [Member] Business Combination Achieved in Stages [Member] Business Combination Achieved in Stages [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Equity Method Investee [Member] Equity Method Investee [Member] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] 50% Owned Unconsolidated Real Estate Joint Venture [Member] 50% Owned Unconsolidated Real Estate Joint Venture [Member] 50% Owned Unconsolidated Real Estate Joint Venture [Member] 51% Owned Real Estate joint venture [Member] 51% Owned Real Estate joint venture [Member] 51% Owned Real Estate joint venture [Member] Unconsolidated Real Estate Joint Venture [Member] Unconsolidated Real Estate Joint Venture [Member] Unconsolidated Real Estate Joint Venture [Member] 90% Owned Real Estate Joint Venture [Member] 90% Owned Real Estate Joint Venture [Member] 90% Owned Real Estate Joint Venture [Member] 20% Owned Unconsolidated Real Estate Joint Venture [Member] 20% Owned Unconsolidated Real Estate Joint Venture [Member] 20% Owned Unconsolidated Real Estate Joint Venture [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Ownership percentage in joint ventures Equity Method Investment, Ownership Percentage Net basis differentials for equity method investments Equity Method Investment, Difference Between Carrying Amount and Underlying Equity Impairment loss Equity Method Investment, Summarized Financial Information, Asset Impairment Charges The amount of asset impairment charges reported by an equity method investment of the entity. Fees earned from real estate joint ventures and partnerships Revenue from Related Parties Increase (decrease) in accounts receivable, related party Increase (Decrease) in Accounts Receivable, Related Parties Repayments of long-term debt Repayments of Long-term Debt Number of centers sold Number of Real Estate Properties Sold The number of real estate properties, buildings or undeveloped land parcels sold during the period. Proceeds from sale and disposition of property Gross Proceeds From Sale Of Real Estate Gross cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period. Gain on sale of property Gain (Loss) on Sale of Properties Number of real estate properties acquired Number of Real Estate Properties Acquired Number of Real Estate Properties Acquired Gross payments to acquire real estate Gross Payments to Acquire Real Estate Gross purchase price from the acquisition of a piece of land, anything permanently fixed to it, including buildings, structures on it and so forth; includes real estate intended to generate income for the owner; excludes real estate acquired for use by the owner. Percentage of voting interest acquired Business Acquisition, Percentage of Voting Interests Acquired Equity interest in joint venture Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value Recognized identifiable assets acquired and liabilities assumed, land Equity Method Investment, Summarized Financial Information, Real Estate Investment Property, at Cost The amount of real estate property assets reported by an equity method investment of the entity. Equity interest in joint venture (percent) Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage Number of real estate properties Number of Real Estate Properties Assets held by joint venture Assets Debt held by joint venture Long-term Debt Proceeds from business acquisition Proceeds to Acquire Businesses, Gross The cash inflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. Gain from sale of real estate joint venture and partnership interests Equity Method Investment, Realized Gain (Loss) on Disposal Derivative Instruments and Hedging Activities Disclosure [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest Rate Contracts [Member] Interest Rate Contract [Member] Forward Starting Interest Contract [Member] Forward Starting Interest Contract [Member] Forward Starting Interest Contract [Member] Interest Rate Swap [Member] Interest Rate Swap [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow Hedging [Member] Cash Flow Hedging [Member] Fair Value Hedging [Member] Fair Value Hedging [Member] Equity Components [Axis] Equity Components [Axis] Equity Components [Domain] Equity Component [Domain] Gain (Loss) On Cash Flow Hedges [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Number of interest rate contracts Number of Interest Rate Derivatives Held Notional amount of interest rate fair value hedge derivatives Derivative, Notional Amount Derivative, fixed interest rate Derivative, Fixed Interest Rate Derivative, swap rate period (In years) Derivative, Remaining Maturity Derivative, forward interest rate Derivative, Forward Interest Rate Payments for derivative instrument Payments for Derivative Instrument, Financing Activities Derivative instruments, loss recognized in other comprehensive income (loss), effective portion Derivative Instruments, Loss Recognized in Other Comprehensive Income (Loss), Effective Portion Gain on cash flow hedge Other Comprehensive Income (Loss), Realized Gain (Loss) on Derivatives Arising During Period, Net of Tax Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in realized deferred hedging gain (loss). Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Cash flow hedge gain (loss) to be amortized within 12 months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Number of interest rate derivatives terminated Number of Interest Rate Derivatives Terminated Number of Interest Rate Derivatives Terminated Proceeds from extinguishment of derivative instrument Proceeds from Derivative Instrument, Financing Activities Derivative, variable rate Derivative, Variable Interest Rate Valuation and Qualifying Accounts [Abstract] Valuation And Qualifying Accounts Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Revenues Business Acquisition, Pro Forma Revenue Net income Business Acquisition, Pro Forma Net Income (Loss) Net income attributable to common shareholders - basic Business Acquisitions, Pro Forma Net Income Attributable to Common Shareholders, Basic Business Acquisitions, Pro Forma Net Income Attributable to Common Shareholders, Basic Net income attributable to common shareholders - diluted Business Acquisitions, Pro Forma Net Income Attributable to Common Shareholders, Diluted Business Acquisitions, Pro Forma Net Income Attributable to Common Shareholders, Diluted Earnings per share – basic (usd per share) Business Acquisition, Pro Forma Earnings Per Share, Basic Earnings per share – diluted (usd per share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Compensation and Retirement Disclosure [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan, Equity Investments by Sector Concentration Risk [Member] Defined Benefit Plan, Equity Investments by Sector Concentration Risk [Member] Defined Benefit Plan, Equity Investments by Sector Concentration Risk [Member] Equity Investment Portfolio, Total [Member] Equity Investment Portfolio, Total [Member] Equity Investment Portfolio, Total [Member] Equity Securities by Industry [Axis] Industry Sector [Axis] Equity Securities, Industry [Domain] Industry Sector [Domain] Technology Sector [Member] Technology Sector [Member] Financial Services Sector [Member] Financial Services Sector [Member] Consumer Cyclical Goods Sector [Member] Consumer Cyclical Goods Sector [Member] Consumer Cyclical Gods Sector [Member] Healthcare Sector [Member] Healthcare Sector [Member] Industrial Sector [Member] Industrial Sector [Member] Industrial Sector [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Defined benefit plan, long-term rate of return on assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Defined benefit plan, estimated future employer contribution in next fiscal year Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year Defined contribution plan, compensation expense Defined Contribution Plan, Cost Recognized Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Property Real Estate Investment Property, at Cost Accumulated Depreciation Real Estate Investment Property, Accumulated Depreciation Property Held for Sale, net Real Estate Held For Sale Net Net carrying amount as of the balance sheet date of investments in land and buildings held for sale, excluding real estate considered to be inventory of the entity. Property, net Real Estate Investment Property, Net Investment in Real Estate Joint Ventures and Partnerships, net Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures Total Real Estate Investments, Net Unamortized Lease Costs, net Deferred Costs, Leasing and In Place Leases, Net For an unclassified balance sheet, represents costs incurred by the lessor that are (a) costs to originate a lease incurred in transactions with independent third parties that (i) result directly from and are essential to acquire that lease and (ii) would not have been incurred had that leasing transaction not occurred and (b) certain costs directly related to specified activities performed by the lessor for that lease. Those activities are: evaluating the prospective lessee's financial condition; evaluating and recording guarantees, collateral, and other security arrangements; negotiating lease terms; preparing and processing lease documents; and closing the transaction. This element is net of accumulated amortization. Furthermore, the aggregate sum of gross carrying value the amount of value allocated by a lessor (acquirer) to lease agreements which exist at acquisition of a leased property. Such amount may include the value assigned to existing tenant relationships and excludes the market adjustment component of the value assigned for above or below-market leases acquired., less accumulated amortization and any impairment charges. Such amount may include the value assigned to existing tenant relationships and excludes the market adjustment component of the value assigned for above or below-market leases acquired Accrued Rent and Accounts Receivable (net of allowance for doubtful accounts of $6,700 in 2016 and $6,072 in 2015) Accounts and Notes Receivable, Net Cash and Cash Equivalents Cash and Cash Equivalents, at Carrying Value Restricted Deposits and Mortgage Escrows Other Restricted Assets Other, net Prepaid Expense and Other Assets Total Assets LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Debt, net Debt and Capital Lease Obligations Accounts Payable and Accrued Expenses Accounts Payable and Accrued Liabilities Other, net Other Liabilities Total Liabilities Liabilities Commitments and Contingencies (see Note 20) Commitments and Contingencies Deferred Compensation Share Awards Temporary Equity, Carrying Amount, Attributable to Parent Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Shareholders' Equity: Stockholders' Equity Attributable to Parent [Abstract] Common Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 275,000; shares issued and outstanding: 128,072 in 2016 and 123,951 in 2015 Common Stock, Value, Issued Additional Paid-In Capital Additional Paid in Capital Net Income Less Than Accumulated Dividends Accumulated Distributions in Excess of Net Income Additional Paid-In Capital Total Shareholders' Equity Stockholders' Equity Attributable to Parent Noncontrolling Interests Stockholders' Equity Attributable to Noncontrolling Interest Total Equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total Liabilities and Equity Liabilities and Equity Consolidated variable interest entities' assets and debt included in the above balances (see Note 15): Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract] Property, net Variable Interest Entity, Consolidated, Carrying Amount, Property, Net For a consolidated VIE, the net book value of real estate property held for investment purposes. Accrued Rent and Accounts Receivable, net Variable Interest Entity, Consolidated, Carrying Amount, Accounts Receivable, net For a consolidated VIE, the amount of fees and other revenue, excluding investment income receivable, earned but not yet received, which were recognized in conformity with revenue recognition criteria based on estimates or specific contractual terms. Also, the amount due from customers for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection. Finally, the cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, expected to be recognized in income or expense over the term of the leased property, by the lessor or lessee, respectively. Such receivable should be reduced by allowances attributable to, for instance, credit risk associated with a lessee. Cash and Cash Equivalents Variable Interest Entity, Consolidated, Carrying Amount, Cash And Cash Equivalents For a consolidated VIE, cash and cash equivalents includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents. Investment in Real Estate Joint Ventures and Partnerships, net Variable Interest Entity, Consolidated, Carrying Amount, Investment in Real Estate Join Ventures and Partnerships, Net Variable Interest Entity, Consolidated, Carrying Amount, Investment in Real Estate Join Ventures and Partnerships, Net Debt, net Variable Interest Entity, Consolidated, Carrying Amount, Debt, net For a consolidated VIE, sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations. Leases, Operating [Abstract] Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [Table] Parties to Contractual Arrangement [Axis] Lease Arrangement, Type [Axis] Parties to Contractual Arrangement [Domain] Lease Arrangement, Type [Domain] Small Tenant [Member] Small Tenant [Member] Represents Retail Tenants with space under 10,000 square feet Large Tenant [Member] Large Tenant [Member] Represents Retail Tenants with space over 10,000 square feet Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Lease Term Lessor Leasing Arrangements, Operating Leases, Term of Contract Quarterly Financial Information Disclosure [Abstract] Schedule of Selected Quarterly Financial Information [Table] Schedule of Selected Quarterly Financial Information [Table] Schedule of Selected Quarterly Financial Information [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] 6.5% Series F Preferred Shares [Member] Series F Preferred Stock [Member] Schedule of Selected Quarterly Financial Information [Line Items] Schedule of Selected Quarterly Financial Information [Line Items] [Line Items] for Schedule of Selected Quarterly Financial Information [Table] Revenues Real Estate Revenue, Net Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income attributable to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Earnings per common share - basic (in dollars per share) Earnings Per Share, Basic Earnings per common share - diluted (in dollars per share) Earnings Per Share, Diluted Gain on sale of properties and real estate joint venture and partnership interests and on acquisitions Gain (Loss) on Disposition of Other Assets Debt extinguishment costs Gain (Loss) on Extinguishment of Debt Redemption costs of preferred shares Other Preferred Stock Dividends and Adjustments Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Real Estate [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Business Acquisition [Line Items] Number of acquired centers Number of Businesses Acquired Investment in new development projects Payments to Develop Real Estate Assets Property acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Number of real estate properties classified as held for sale Number of Real Estate Properties Classified as Held For Sale Number of Real Estate Properties Classified as Held For Sale Property held for sale Real Estate Held-for-sale Discontinued Operations and Disposal Groups [Abstract] Revenues, net Disposal Group, Including Discontinued Operation, Revenue Depreciation and amortization Disposal Group, Including Discontinued Operation, Depreciation and Amortization Operating expenses Disposal Group, Including Discontinued Operation, Operating Expense Real estate taxes, net Disposal Group, Including Discontinued Operation, Real Estate Taxes Net Disposal group including discontinued operation, real estate taxes net General and administrative Disposal Group, Including Discontinued Operation, General and Administrative Expense Interest, net Disposal Group, Including Discontinued Operation, Interest Expense Provision for income taxes Discontinued Operation, Tax Effect of Income (Loss) from Discontinued Operation During Phase-out Period Operating income from discontinued operations Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax Gain on sale of property from discontinued operations Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Income from Discontinued Operations Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Related Party Transactions [Abstract] Related Parties Related Party Transactions Disclosure [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Consolidated Variable Interest Entities [Member] Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member] Unconsolidated Variable Interest Entities [Member] Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Summary Of Variable Interest Entities Schedule of Variable Interest Entities [Table Text Block] Leasing Operations Operating Leases of Lessor Disclosure [Text Block] Supplemental Cash Flow Elements [Abstract] Non-cash Investing and Financing Activities [Table] Non-cash or Part Noncash Investing and Financing Activities [Table] Non-cash or Part Noncash Investing and Financing Activities [Table] Non-cash Investing and Financing Activities [Axis] Non-cash Investing and Financing Activities [Axis] Non-cash Investing and Financing Activities [Axis] Non-Cash Investing and Financing Activites [Domain] Non-Cash Investing and Financing Activites [Domain] Non-Cash Investing and Financing Activites [Domain] Property Acquisitions And Investments In Unconsolidated Real Estate Joint Ventures [Member] Property Acquisitions And Investments In Unconsolidated Real Estate Joint Ventures [Member] Property Acquisitions And Investments In Unconsolidated Real Estate Joint Ventures [Member] Sale Of Property And Property Interest [Member] Sale Of Property And Property Interest [Member] Sale Of Property And Property Interest [Member] Consolidation of Joint Venture [Member] Consolidation of Joint Venture [Member] Consolidation of Joint Venture [Member] Noncash or Part Noncash Acquisitions [Line Items] Noncash or Part Noncash Acquisitions [Line Items] Accrued property construction costs Construction in Progress Expenditures Incurred but Not yet Paid Increase in equity for the acquisition of noncontrolling interests in consolidated real estate joint ventures Noncash or Part Noncash Acquisition, Investments Acquired Exchange of operating partnership units for common shares Noncash or Part Noncash Acquisition, Operating Partnership Units Acquired Noncash or Part Noncash Acquisition, Operating Partnership Units Acquired Decrease in notes receivable from real estate joint ventures and partnerships in association with our contribution in an unconsolidated real estate joint venture Other Significant Noncash Transaction, Value of Consideration Given Reduction of debt service guaranty liability Debt Reduction The value of debt reduced in noncash investing or financing activities. Increase in property, net Noncash or Part Noncash Acquisition, Fixed Assets Acquired Decrease in real estate joint ventures and partnerships - investments Noncash or Part Noncash Acquisition, Equity Method Investments Acquired The amount of an equity method investment that an Entity acquires in a noncash (or part noncash) acquisition. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Increase in debt, net Noncash or Part Noncash Acquisition, Debt Assumed Decrease in property, net Noncash or Part Noncash Divestiture, Fixed Assets Divested The amount of fixed assets that an Entity divests in a noncash (or part noncash) divestiture. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Decrease in real estate joint ventures and partnerships - investments Noncash or Part Noncash Divestiture, Equity Method Investments Divested The amount of an equity method investment that an Entity divests in a noncash (or part noncash) divestiture. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Decrease in other, net Noncash or Part Noncash Divestiture, Other Investing Activity, Divested The amount of other investing activities that an Entity divests in a noncash (or part noncash) divestiture. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Decrease in debt, net due to debt assumption Noncash or Part Noncash Divestiture, Debt Divested The amount of debt that an Entity divests in disposing a business in a noncash (or part noncash) divestiture. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Increase in security deposits Noncash or Part Noncash Acquisition, Security Deposits Assumed The amount of security deposits that an entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition that are not presented as a separate disclosure or otherwise listed in the existing taxonomy. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Increase in noncontrolling interests Noncash or Part Noncash Acquisition, Noncontrolling Interests Assumed The amount of noncontrolling interests that an entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition that are not presented as a separate disclosure or otherwise listed in the existing taxonomy. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Increase in restricted deposits and mortgage escrows Noncash or Part Noncash Acquisition, Restricted Deposits and Escrows Assets Acquired Noncash or Part Noncash Acquisition, Restricted Deposits and Escrows Assets Acquired Increase in security deposits Noncash or Part Noncash Divestiture, Security Deposits Divested The amount of security deposits that another entity assumes in divesting a business or in consideration for an asset sold in a noncash (or part noncash) divestiture that are not presented as a separate disclosure or otherwise listed in the existing taxonomy. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Decrease in equity associated with deferred compensation plan (see Note 1) Noncash or Part Noncash Transaction, Decrease in Equity Associated with Deferred Compensation Plan Noncash or Part Noncash Transaction, Decrease in Equity Associated with Deferred Compensation Plan Offsetting Assets [Table] Offsetting Assets [Table] Offsetting Assets [Line Items] Offsetting Assets [Line Items] Gross Amounts Recognized, Assets Derivative Asset, Fair Value, Gross Asset Gross Amounts Offset In Balance Sheet, Assets Derivative Asset, Fair Value, Gross Liability Net Amounts Presented in Balance Sheet, Assets Derivative Asset Gross Amounts Not Offset in Balance Sheet, Financial Instruments, Assets Derivative, Collateral, Obligation to Return Securities Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received, Assets Derivative, Collateral, Obligation to Return Cash Net Amount, Assets Derivative Asset, Fair Value, Amount Offset Against Collateral Gross Amounts Recognized, Liabilities Derivative Liability, Fair Value, Gross Liability Gross Amounts Offset In Balance Sheet, Liabilities Derivative Liability, Fair Value, Gross Asset Net Amounts Presented in Balance Sheet, Liabilities Derivative Liability Gross Amounts Not Offset in Balance Sheet, Financial Instruments, Liabilities Derivative, Collateral, Right to Reclaim Securities Gross Amounts Not Offset in Balance Sheet, Cash Collateral Received, Liabilities Derivative, Collateral, Right to Reclaim Cash Net Amount, Liabilities Derivative Liability, Fair Value, Amount Offset Against Collateral Land Land Land held for development Land Available for Development Land under development Land under development The current amount of land and land improvement expenditures for a real estate project that has not yet been completed. Buildings and improvements Investment Building and Building Improvements Construction in-progress Construction in Progress, Gross Total Contingent rental income Operating Leases, Income Statement, Contingent Revenue 2017 Operating Leases, Future Minimum Payments Receivable, Current 2018 Operating Leases, Future Minimum Payments Receivable, in Two Years 2019 Operating Leases, Future Minimum Payments Receivable, in Three Years 2020 Operating Leases, Future Minimum Payments Receivable, in Four Years 2021 Operating Leases, Future Minimum Payments Receivable, in Five Years Thereafter Operating Leases, Future Minimum Payments Receivable, Thereafter Total Operating Leases, Future Minimum Payments Receivable Increase in revenues Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Increase in net income attributable to common shareholders Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual In place leases Identifiable Intangible Assets And Liabilities Associated With Acquisition Of Property Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule Of Future Amortization Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Long-Term Incentive Plan [Member] Long Term Incentive Plan Options And Awards [Member] Incremental common shares attributable to options and awards issued under the Long Term Incentive Plan. 2010 Restated LT Incentive Plan Stock Options and Awards [Member] Two Thousand Ten Amended and Restated Long Term Incentive Plan [Member] 2010 Amended and Restated Long Term Incentive Plan Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Plan common shares authorized (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Plan common shares available for future grants (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Net compensation expense for share options and restricted shares Allocated Share-based Compensation Expense Net capitalized compensation expense Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Total intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Unrecognized compensation cost, share options Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Unrecognized compensation cost, restricted shares Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Weighted average expected amortization period for unrecognized compensation cost (in years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Debt Disclosure [Abstract] Schedule Of Debt Schedule of Debt [Table Text Block] Grouping Of Debt Between Fixed And Variable As Well As Secured And Unsecured Schedule of Grouping of Debt in Fixed and Variable As Well As Secured and Unsecured [Table Text Block] Schedule of Grouping of Debt in Fixed and Variable As Well As Secured and Unsecured [Table Text Block] Schedule Of Credit Facilities Schedule of Line of Credit Facilities [Table Text Block] Principal Payments Of Debt Schedule of Maturities of Long-term Debt [Table Text Block] 2017 Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year 2018 Long-term Debt, Maturities, Repayments of Principal in Year Two 2019 Long-term Debt, Maturities, Repayments of Principal in Year Three 2020 Long-term Debt, Maturities, Repayments of Principal in Year Four 2021 Long-term Debt, Maturities, Repayments of Principal in Year Five 2022 Long-term Debt, Maturities, Repayments of Principal in Year Six Amount of long-term debt maturing in year six following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates. 2023 Long-term Debt, Maturities, Repayments of Principal in Year Seven Amount of long-term debt maturing in year seven following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates. 2024 Long-term Debt, Maturities, Repayments of Principal in Year Eight Amount of long-term debt maturing in year eight following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates. 2025 Long-term Debt, Maturities, Repayments of Principal in Year Nine Amount of long-term debt maturing in year nine following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates. 2026 Long-term Debt, Maturities, Repayments of Principal in Year Ten Amount of long-term debt maturing in year ten following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates. Thereafter Long-term Debt, Maturities, Repayments of Principal in Year Thereafter Amount of long-term debt maturing after ten years following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates. Total Class of Stock Disclosures [Abstract] Schedule of Market Equity Distributions Schedule of Market Equity Distributions [Table Text Block] Schedule of Market Equity Distributions [Table Text Block] Schedule Of Future Minimum Rental Income Schedule of Future Minimum Payments Receivable for Operating Leases [Table Text Block] Tabular disclosure of future minimum payments receivable required in the aggregate and for each of the five succeeding fiscal years for operating leases having initial or remaining noncancelable lease terms in excess of one year as of the balance sheet date. Schedule Of Contingent Rental Income Schedule Of Contingent Rental Income for Operating Leases [Table Text Block] Tabular disclosure of contingent rental revenue recognized for the period under operating leases, based on the occurrences of an event or condition. Projected benefit obligation Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation Accumulated benefit obligation Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation Fair value of plan assets Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets Schedule of Long-term Debt, By Type [Table] Schedule of Long-term Debt, By Type [Table] Schedule of Long-term Debt, By Type [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] As To Interest Rate [Member] As To Interest Rate [Member] As To Interest Rate [Member] As To Collateralization [Member] As To Collateralization [Member] As To Collateralization [Member] Schedule of Long-term Debt, By Type [Line Items] Schedule of Long-term Debt, By Type [Line Items] [Line Items] for Schedule of Long-term Debt, By Type Fixed-rate debt (1) Long-term Debt, Percentage Bearing Fixed Interest, Amount Variable-rate debt Long-term Debt, Percentage Bearing Variable Interest, Amount Unsecured debt (1) Unsecured Debt Secured debt (1) Secured Debt Total Statement of Comprehensive Income [Abstract] Net Income Other Comprehensive Income (Loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Net unrealized gain (loss) on investments, net of taxes Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Realized gain on investments Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Realized (loss) gain on derivatives Net unrealized (loss) gain on derivatives Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Reclassification adjustment of derivatives and designated hedges into net income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Retirement liability adjustment Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Total Other Comprehensive Income (Loss), Net of Tax 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 Adjusted for Noncontrolling Interests Comprehensive Income (Loss), Net of Tax, Attributable to Parent Equity [Abstract] Preferred Dividends Declared Per Share Dividends Declared [Table Text Block] Change in classification Reclassifications of Temporary to Permanent Equity Change in redemption value Temporary Equity, Accretion to Redemption Value Diversification of share awards Temporary Equity, Other Changes Balance at December 31, 2016 Temporary Equity, Carrying Amount, Period Increase (Decrease) Long-term Purchase Commitment [Table] Long-term Purchase Commitment [Table] DownREIT [Member] DownREIT [Member] DownREIT [Member] Category of Item Purchased [Axis] Category of Item Purchased [Axis] Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-term Purchase Commitment, Category of Item Purchased [Domain] Capital Additions [Member] Capital Addition Purchase Commitments [Member] Development Addition [Member] Development Addition Purchase Commitment [Member] Development Addition Purchase Commitment[Member] Long-term Purchase Commitment [Line Items] Long-term Purchase Commitment [Line Items] Operating leases, term range, in years Lessee Leasing Arrangements, Operating Leases, Term of Contract Operating leases, rental expense Operating Leases, Rent Expense, Net Capital leases, total assets Capital Leased Assets, Gross Capital leases, accumulated depreciation Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation Capital leases, future minimum payments Capital leases, future minimum payments, interest Capital Leases, Future Minimum Payments, Interest Included in Payments Capital leases, future minimum payments, present value of net minimum payments Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments Number of real estate joint ventures Number of Real Estate Joint Ventures Number of Real Estate Joint Ventures Shares issued in exchange of interests Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Aggregate redemption value Redeemable Noncontrolling Interest, Equity, Common, Fair Value Purchase contract, commitment Long-term Purchase Commitment, Amount Purchase contract, period (in months) Long-term Purchase Commitment, Period Future investment amount Future Payments to Develop Real Estate Assets Future Payments to Develop Real Estate Assets Mortgage Loans on Real Estate [Abstract] Mortgage Loans On Real Estate Mortgage Loans on Real Estate, by Loan Disclosure [Text Block] Assets Held by VIEs Variable Interest Entity, Consolidated, Carrying Amount, Assets Assets Held as Collateral for Debt Variable Interest Entity, Consolidated, Assets Held As Collateral Variable Interest Entity's (VIE) assets considered as collateral on debt included in the statement of financial position of the reporting entity. This element is applicable for variable interests whether the reporting entity has a controlling financial interest (primary beneficiary) or not. Maximum Risk of Loss (2) Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Number of VIE's guaranteed by company Variable Interest Entity, Qualitative or Quantitative Information, Number of VIE's Guaranteed by Company Variable Interest Entity, Qualitative or Quantitative Information, Number of VIE's Guaranteed by Company Transactions Related to Acquisitions Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Pro Forma Impact of Acquisitions Business Acquisition, Pro Forma Information [Table Text Block] Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block] Basis Of Presentation Basis of Accounting, Policy [Policy Text Block] Revenue Recognition Revenue Recognition Leases, Operating [Policy Text Block] Property Property, Plant and Equipment, Policy [Policy Text Block] Real Estate Joint Ventures And Partnerships Equity Method Investments, Policy [Policy Text Block] Unamortized Lease Costs, net Deferred Charges, Policy [Policy Text Block] Accrued Rent And Accounts Receivable, Net Trade and Other Accounts Receivable, Policy [Policy Text Block] Cash And Cash Equivalents Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Restricted Deposits And Mortgage Escrows Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Other Assets, Net Other Assets, Policy [Policy Text Block] Disclosure of accounting policy for other assets. This disclosure may include (1) the basis at which such other assets are carried in the entity's statements of financial position (2) how the level of the valuation allowance for other assets is determined (3) when impairments, charge-offs or recoveries are recognized for such other assets (4) amortization and depreciation methods (5) the treatment of any premiums or discounts or unearned income and (6) the entity's income recognition policies for other assets, including those that are impaired, past due or placed on nonaccrual status. Derivatives And Hedging Derivatives, Policy [Policy Text Block] Sales Of Real Estate Revenue Recognition, Real Estate Transactions, Policy [Policy Text Block] Impairment Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy [Policy Text Block] Interest Capitalization Interest Capitalization, Policy [Policy Text Block] Interest Expense In Discontinued Operations Interest Expense Allocated to Discontinued Operations, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Share-Based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Retirement Benefit Plans Pension and Other Postretirement Plans, Pensions, Policy [Policy Text Block] Fair Value Measurements Fair Value of Financial Instruments, Policy [Policy Text Block] Reportable Segments Segment Reporting, Policy [Policy Text Block] Newly Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Real Estate and Accumulated Depreciation SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Text Block] Valuation and Qualifying Accounts Disclosure [Table] Valuation and Qualifying Accounts Disclosure [Table] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves [Domain] Valuation Allowances and Reserves [Domain] Allowance For Doubtful Accounts [Member] Allowance for Doubtful Accounts [Member] Tax Valuation Allowance [Member] Valuation Allowance of Deferred Tax Assets [Member] Valuation and Qualifying Accounts Disclosure [Line Items] Valuation and Qualifying Accounts Disclosure [Line Items] Movement in Valuation Allowances and Reserves [Roll Forward] Movement in Valuation Allowances and Reserves [Roll Forward] Balance at beginning of period Valuation Allowances and Reserves, Balance Charged to costs and expenses Valuation Allowances and Reserves, Additions for Charges to Cost and Expense Deductions Valuation Allowances and Reserves, Deductions Balance at end of period Effect Of Changes In Ownership Interest In Subsidiaries On Consolidated Equity Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table Text Block] Asset Impairment Charges [Abstract] Impairment Asset Impairment Charges [Text Block] Discontinued Operations Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Derivatives And Hedging Derivative Instruments and Hedging Activities Disclosure [Text Block] Share Options And Awards Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Statement of Cash Flows [Abstract] Capitalized interest paid Interest Paid, Capitalized Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Operating Activities [Axis] Operating Activities [Axis] Operating Activities [Domain] Operating Activities [Domain] Discontinued Operations [Member] Discontinued Operations [Member] Real Estate Location By State [Axis] Real Estate Location By State [Axis] Real Estate Location By State [Axis] Real Estate Location By State [Domain] Real Estate Location By State [Domain] Real Estate Location By State [Domain] Georgia [Member] Georgia [Member] Georgia [Member] Florida [Member] Florida [Member] Florida [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] Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected volatility, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Expected volatility, maximum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum Expected life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Risk-free interest rate, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Risk-free interest rate, maximum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Allowance for doubtful accounts Allowance for Doubtful Accounts, Premiums and Other Receivables Common Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 275,000; shares issued and outstanding: 123,951 in 2015 and 122,489 in 2014 Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Common shares of beneficial interest, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common shares of beneficial interest, shares authorized (in shares) Common Stock, Shares Authorized Common shares of beneficial interest, shares issued (in shares) Common Stock, Shares, Issued Common shares of beneficial interest, shares outstanding (in shares) Common Stock, Shares, Outstanding Service-Based Awards [Member] Market-Based Awards Relative To Three-Year Absolute TSR Trust Manager Awards [Member] Trust Manager Awards [Member] Trust Manager Awards [Member] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Unvested restricted share awards, outstanding beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested restricted share awards, granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Unvested restricted share awards, vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Unvested restricted share awards, forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Unvested restricted share awards, outstanding end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted average grant date fair value, outstanding beginning of period (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 Weighted average grant date fair value, granted (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 Weighted average grant date fair value, vested (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 Weighted average grant date fair value, forfeited (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 Weighted average grant date fair value, outstanding end of period (in dollars per share) Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Equity Method Investments [Member] Equity Method Investments [Member] Revenues, net Equity Method Investment, Summarized Financial Information, Revenue Expenses: Equity Method Investment, Summarized Financial Information, Expenses [Abstract] Equity Method Investment, Summarized Financial Information, Expenses [Abstract] Depreciation and amortization Equity Method Investment, Summarized Financial Information, Cost of Services, Depreciation and Amortization The amount of depreciation and amortization reported by an equity method investment of the entity. Interest, net Equity Method Investment, Summarized Financial Information, Interest and Debt Expense The amount of the interest and debt expense reported by an equity method investment of the entity. Operating Equity Method Investment, Summarized Financial Information, Other Cost and Expense, Operating The amount of the other operating costs and expenses reported by an equity method investment of the entity. Real estate taxes, net Equity Method Investment, Summarized Financial Information, Real Estate Tax Expense The amount of the real estate tax expense reported by an equity method investment of the entity. General and administrative Equity Method Investment, Summarized Financial Information, General and Administrative Expense The amount of general and administrative expenses reported by an equity method investment of the entity. Provision for income taxes Equity Method Investment, Summarized Financial Information, Income Tax Expense (Benefit) The amount of income tax expense (benefit) reported by an equity method investment of the entity. Total Equity Method Investment, Summarized Financial Information, Cost of Sales Gain on sale of non-operating property Other Nonoperating Gains (Losses) Gain on dispositions Gain (Loss) on Sale of Properties, before Applicable Income Taxes Net Income Equity Method Investment, Summarized Financial Information, Net Income (Loss) Commitments And Contingencies Commitments Contingencies and Guarantees [Text Block] Investment In Real Estate Joint Ventures And Partnerships Equity Method Investments and Joint Ventures Disclosure [Text Block] Fair Value Disclosures [Abstract] Assets And Liabilities Measured On Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule Of Fair Value Disclosures Fair Value, by Balance Sheet Grouping [Table Text Block] Quantitative Information About Significant Unobservable Inputs (Level 3) Used Fair Value Inputs, Assets And Liabilities, Quantitative Information [Table Text Block] Tabular disclosure of quantitative information about the inputs used in the fair value measurement of assets and liabilities. This disclosure may include, but is not limited to, the fair value of the asset or liability, valuation technique used to measure fair value, the inputs used to measure fair value, the ranges of the inputs, and the weighted averages of the inputs 2017 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2018 Operating Leases, Future Minimum Payments, Due in Two Years 2019 Operating Leases, Future Minimum Payments, Due in Three Years 2020 Operating Leases, Future Minimum Payments, Due in Four Years 2021 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Interest Expense, Net [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Amount of (Gain) Loss Recognized in Other Comprehensive Income on Derivative (Effective Portion) Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Amount of Gain (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing) Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Preferred Shares of Beneficial Interest Preferred Stock [Member] Common Shares of Beneficial Interest Common Stock [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Net Income Less Than Accumulated Dividends Accumulated Distributions in Excess of Net Income [Member] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Noncontrolling Interests Noncontrolling Interest [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance Shares issued under benefit plans, net Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Dividends paid – common shares Dividends, Common Stock, Cash Dividends paid – preferred shares Dividends, Preferred Stock, Cash Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Contributions from noncontrolling interests Noncontrolling Interest, Increase from Contributions made by Noncontrolling Interest Holders Increase in noncontrolling interest balance from receipt of contributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, by the noncontrolling interest holders. Acquisition of noncontrolling interests Disposition of noncontrolling interests Noncontrolling Interest, Decrease from Deconsolidation Other comprehensive loss Other, net Stockholders' Equity, Other Redemption of preferred shares Stock Redeemed or Called During Period, Value Issuance of common shares, net Stock Issued During Period, Value, New Issues Shares issued in exchange for noncontrolling interests Noncontrolling Interest, Decrease from Issuance of Parent Shares Noncontrolling Interest, Decrease from Issuance of Parent Shares Change in redemption value of deferred compensation plan Diversification of share awards within deferred compensation plan Stockholders' Equity, Deferred Compensation, Change in Redemption Value Stockholders' Equity, Deferred Compensation, Change in Redemption Value Diversification of share awards within deferred compensation plan Adjustments to Additional Paid in Capital, Deferred Compensation Adjustments to Additional Paid in Capital, Deferred Compensation Ending balance Income Tax Disclosure [Abstract] Ordinary income Percentage Of Ordinary Income Percentage of ordinary income Capital gain distributions Percentage Of Capital Gain Distributions Percentage of capital gain distributions Return of capital (nontaxable distribution) Percentage of Return of Capital, Nontaxable Distribution Percentage of Return of Capital, Nontaxable Distribution Total Percentage Of Ordinary Income And Capital Gain Distributions Percentage of ordinary income and capital gain distributions Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table] Exercise Price Range [Axis] Exercise Price Range [Axis] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] $11.85 - $17.78 [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Eleven Point Eight Five To Dollar Seventeen Point Seven Eight [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Eleven Point Eight Five To Dollar Seventeen Point Seven Eight [Member] $17.79 - $26.69 [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Seventeen Point Seven Nine To Dollar Twenty Six Point Sixty Nine [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Seventeen Point Seven Nine To Dollar Twenty Six Point Sixty Nine [Member] $26.70 - $40.05 [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Twenty Six Point Seven Zero To Dollar Forty Point Zero Five [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Twenty Six Point Seven Zero To Dollar Forty Point Zero Five [Member] $40.06 - $49.62 [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Forty Point Zero Six To Dollar Forty Nine Point Sixty Two [Member] Share Based Compensation, Shares Authorized Under Stock Option Plans, Exercise Price Range, Dollar Forty Point Zero Six To Dollar Forty Nine Point Sixty Two [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] Range of exercise prices, lower (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Range of exercise prices, upper (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Share option outstanding, number (in shares) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options Share option outstanding, weighted average remaining contractual life (years) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term Share option outstanding, weighted average exercise price (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price Share option outstanding, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Share option exercisable, number (in shares) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options Share option exercisable, weighted average exercise price (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price Share option exercisable, weighted average exercisable average life (years) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term Share option exercisable, intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Schedule Of Minimum Rental Payments For Operating Leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule Of Future Minimum Revenues Under Subleases Schedule Of Future Minimum Rental Revenues Under Subleases For Operating Leases [Table Text Block] Tabular disclosure of future minimum sublease payments receivable and for each of the five succeeding fiscal years for operating leases having initial or remaining noncancelable lease terms in excess of one year and the total minimum rentals to be received in the future under noncancelable subleases as of the balance sheet date. Schedule Of Annual Future Minimum Lease Payments For Capital Leases Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Equity [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Gain On Investments [Member] Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Gain On Cash Flow Hedges [Member] Defined Benefit Pension Plan [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Beginning balance Change excluding amounts reclassified from accumulated other comprehensive loss Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified from accumulated other comprehensive loss Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Net other comprehensive loss (income) Ending balance Line of Credit Facility [Table] Line of Credit Facility [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Unsecured Revolving Credit Facility [Member] Revolving Credit Facility [Member] Letter of Credit [Member] Letter of Credit [Member] Unsecured Facility [Member] Unsecured And Uncommitted Overnight Facility [Member] Unsecured and Uncommitted Overnight Facility [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Balance outstanding Long-term Line of Credit Available balance Line of Credit Facility, Remaining Borrowing Capacity Letter of credit outstanding under facility Line of Credit Facility, Current Borrowing Capacity Variable interest rate Line of Credit Facility, Interest Rate at Period End Maximum balance outstanding during the year Line of Credit Facility, Maximum Amount Outstanding During Period Weighted average balance Line of Credit Facility, Average Outstanding Amount Year-to-date weighted average interest rate (excluding facility fee) Line of Credit Facility, Interest Rate During Period Schedule Of Reconciling Net Income Adjusted For Noncontrolling Interests To REIT Taxable Income Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Schedule Of Cash Dividends Distributed To Common Shareholders Schedule Of Cash Dividends Distributed To Common Shareholders [Table Text Block] Schedule of cash dividends distributed to common shareholders [Table Text Block] Schedule Of Deferred Tax Assets And Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule Of Income Tax Provision Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Newly Issued Accounting Pronouncements New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward] SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward] Balance at beginning of year SEC Schedule III, Real Estate, Gross Additions at cost SEC Schedule III, Real Estate, Additions Amount of additions including acquisition or improvement to real estate investments for entities with a substantial portion of business acquiring and holding investment real estate. Retirements or sales SEC Schedule III, Real Estate, Cost of Real Estate Sold Property held for sale SEC Schedule III, Real Estate, Transfer to Held for Sale Amount of real estate investments transferred to held for sale. Impairment loss SEC Schedule III, Real Estate, Write-down or Reserve, Amount Impairment loss Earnings Per Share [Abstract] Continuing Operations: Continuing Operations [Abstract] Continuing Operations [Abstract] Income from continuing operations Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Net income attributable to noncontrolling interests Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest Dividends on preferred shares Preferred Stock Dividends, Income Statement Impact Redemption costs of preferred shares Income from continuing operations attributable to common shareholders – basic Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent Income attributable to operating partnership units Dilutive Securities, Effect on Basic Earnings Per Share, Dilutive Convertible Securities Income from continuing operations attributable to common shareholders – diluted Net Income (Loss) Attributable to Parent, Diluted Discontinued Operations: Income from discontinued operations Net loss attributable to noncontrolling interests Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest Income from discontinued operations attributable to common shareholders – basic and diluted Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Net Income: Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Net Income Attributable to Common Shareholders Net income attributable to common shareholders – diluted Net Income (Loss) Available to Common Stockholders, Diluted Denominator: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted average shares outstanding – basic (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of dilutive securities: Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract] Share options and awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Operating partnership units (in shares) Incremental Common Shares Attributable to Dilutive Effect of Equity Unit Purchase Agreements Weighted average shares outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Common Shares Of Beneficial Interest Stockholders' Equity Note Disclosure [Text Block] Dividends Payable [Table] Dividends Payable [Table] Dividends Payable [Line Items] Dividends Payable [Line Items] Preferred shares of beneficial interest, dividend per share (in dollars per share) Preferred Stock, Dividends Per Share, Declared Mortgage Loans on Real Estate Schedule [Table] Mortgage Loans on Real Estate Schedule [Table] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Shopping Center [Member] Retail Site [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] First Mortgages [Member] First Mortgage [Member] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Domain] Mortgage Loans on Real Estate, Loan Type [Domain] College Park Realty Company [Member] College Park Realty Company [Member] College Park Realty Company [Member] Mortgage Loans on Real Estate [Line Items] Mortgage Loans on Real Estate [Line Items] State Mortgage Loans on Real Estate, Geographic Location of Property Interest Rate Mortgage Loans on Real Estate, Interest Rate Final Maturity Date Mortgage Loans on Real Estate, Final Maturity Date Periodic Payment Terms Mortgage Loans on Real Estate, Periodic Payment Terms Face Amount of Mortgages Mortgage Loans on Real Estate, Face Amount of Mortgages Carrying Amount of Mortgages Mortgage Loans on Real Estate, Carrying Amount of Mortgages Aggregate cost for federal income tax purposes Mortgage Loans on Real Estate, Federal Income Tax Basis Defined Benefit Plan, Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Plan Asset Categories [Domain] Plan Asset Categories [Domain] Cash and Short-Term Investments [Member] Cash and Cash Equivalents [Member] U.S. Stocks [Member] Equity Funds [Member] International Stocks [Member] Equity Funds, Foreign [Member] Equity Funds, Foreign [Member] U.S. Bonds [Member] Debt Securities [Member] International Bonds [Member] Debt Securities, Foreign [Member] Debt Securities, Foreign [Member] Other Securities [Member] Other Securities [Member] Other Securities [Member] Portfolio, Actual asset allocation Defined Benefit Plan, Actual Plan Asset Allocations Benchmark, Target asset allocation Defined Benefit Plan, Target Plan Asset Allocations Summary Of Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] ATM Equity Program [Member] ATM Equity Program [Member] ATM Equity Program [Member] Quarterly Rate Per Share [Member] Quarterly Rate Per Share [Member] Quarterly Rate Per Share [Member] Class of Stock [Line Items] Class of Stock [Line Items] Equity issuances amount available for issuance Equity Issuances Amount Available For Issuance Equity Issuances Amount Available For Issuance Maximum borrowing capacity under credit facility Line of Credit Facility, Maximum Borrowing Capacity