Discontinued Operations and Disposal Groups [Abstract] Schedule of Disposal Group Disposal Groups, Including Discontinued Operations [Table Text Block] Share-based Compensation [Abstract] Summary of Stock Award Activity Share-based Compensation, Activity [Table Text Block] Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Mortgages Mortgages [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt, net Long-term Debt Weighted average interest rate Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate Deferred financing costs, net Debt Issuance Costs, Net Statement of Financial Position [Abstract] Allowance for accounts and rent receivables Allowance for Doubtful Accounts Receivable Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Segment Reporting [Abstract] Concentration Risk [Table] Concentration Risk [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Other Corporate, Non-Segment [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Retail Retail [Member] Multi-Tenant Office Multi-Tenant Office [Member] Multi-Tenant Office [Member] Net Lease Net Lease [Member] Net Lease [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] Number of business segments (in segments) Number of Operating Segments Number of impaired assets Number of Leased Assets, as Lessor, Impaired Number of Leased Assets, as Lessor, Impaired Number of leased assets Number of Leased Assets, as Lessor Number of Leased Assets, as Lessor Payables and Accruals [Abstract] Accrued real estate taxes Taxes Payable Accrued compensation Employee-related Liabilities Accrued interest payable Interest Payable Other accrued expenses Other Accrued Liabilities Total accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Income Statement [Abstract] Statement [Table] Statement [Table] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Tenant recovery income Real Estate, Tenant Recovery [Member] Real Estate, Tenant Recovery [Member] Other property income Real Estate, Other [Member] Total revenues Real Estate [Member] Statement [Line Items] Statement [Line Items] Revenues Revenues [Abstract] Rental income Operating Leases, Income Statement, Lease Revenue Total revenues Revenue from Contract with Customer, Excluding Assessed Tax Expenses Operating Expenses [Abstract] Property operating expenses Cost of Goods and Services Sold Real estate taxes Real Estate Tax Expense Depreciation and amortization Depreciation and Amortization, Net of Lease Inducements Depreciation and Amortization, Net of Lease Inducements General and administrative expenses General and Administrative Expense Provision for asset impairment Asset Impairment Charges Total expenses Operating Expenses Operating income Operating Income (Loss) Interest income Investment Income, Interest and Dividend Gain (loss) on sale of investment properties Gain (Loss) on Sale of Properties, before Applicable Income Taxes (Loss) gain on extinguishment of debt Gain (Loss) on Extinguishment of Debt Other income Other Nonoperating Gains (Losses) Interest expense Interest Expense Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax benefit Income Tax Expense (Benefit) Net income Net Income (Loss) Attributable to Parent Net income per common share, basic and diluted (in dollars per share) Earnings Per Share, Basic and Diluted Weighted average number of common shares outstanding, basic and diluted (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Pro Forma Pro Forma [Member] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Triangle Center Triangle Center [Member] Triangle Center [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] Pro forma revenue Pro forma net income from continuing operations and attributable to the registrant Pro forma net income from continuing operations and attributable to the registrant per common share, basic and diluted (in dollars per share) Assets Assets [Abstract] Investment properties Real Estate Investment Property, Net [Abstract] Land Land Building and other improvements Investment Building and Building Improvements Construction in progress Development in Process Total Real Estate Investment Property, at Cost Less accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Net investment properties Real Estate Investment Property, Net Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash and escrows Restricted Cash Accounts and rents receivable (net of allowance of $1,047 and $850, respectively) Accounts Receivable, Net Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Deferred costs and other assets Deferred Costs and Other Assets Total assets Assets Liabilities Liabilities [Abstract] Mortgage loans, net Accounts payable and accrued expenses Intangible liabilities, net Below Market Lease, Net Other liabilities Other Liabilities Total liabilities Liabilities Commitments and contingencies (Note 13) Commitments and Contingencies Stockholders’ Equity Stockholders' Equity Attributable to Parent [Abstract] Common stock, $0.01 par value, 1,000,000,000 shares authorized, 871,537,188 and 868,423,581 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated distributions in excess of net income Accumulated Distributions in Excess of Net Income Total stockholders’ equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and stockholders' equity Liabilities and Equity Schedule of Accounts Payable and Accrued Expenses Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Share Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Accounting Policies [Abstract] Cash and cash equivalents Restricted cash Total cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Pro Forma Financial Information Pro Forma Financial Information, Discontinued Operations And Disposal Groups [Text Block] Pro Forma Financial Information, Discontinued Operations And Disposal Groups [Text Block] Asset Acquisitions [Abstract] Asset Acquisitions [Abstract] Schedule of Asset Acquisitions, by Acquisition [Table] Schedule of Asset Acquisitions, by Acquisition [Table] Schedule of Asset Acquisitions, by Acquisition [Table] Name of Property [Axis] Name of Property [Axis] Name of Property [Domain] Name of Property [Domain] The Lafayette The Lafayette [Member] The Lafayette [Member] 1620 Central Street 1620 Central Street [Member] 1620 Central Street [Member] Kenilworth Court Kenilworth Court [Member] Kenilworth Court [Member] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Multi-family Multifamily [Member] Schedule of Asset Acquisitions, by Acquisition [Line Items] Schedule of Asset Acquisitions, by Acquisition [Line Items] [Line Items] for Schedule of Asset Acquisitions, by Acquisition [Table] Payments to Acquire Real Estate Payments to Acquire Real Estate Accounts Payable and Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Statement of Cash Flows [Abstract] Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Cash paid for taxes Income Taxes Paid Supplemental schedule of non-cash investing and financing activities: Other Noncash Investing and Financing Items [Abstract] Non-cash accruals for capital expense and investment in development Capital Expenditures Incurred but Not yet Paid Mortgage loans payable and related obligations settled Transfer Mortgage Payable And Related Obligations Settled Transfer Mortgage Payable And Related Obligations Settled Real estate transferred to mortgage lender Real Estate Owned, Transfer to Real Estate Owned Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Nonrecurring Fair Value, Measurements, Nonrecurring [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Investment properties Property, Plant, and Equipment, Fair Value Disclosure Provision for impairment Acquired Properties Asset Acquisitions [Text Block] Asset Acquisitions [Text Block] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Amortization and Accretion, Net Amortization of above and below market leases, net Amortization of above and below Market Leases Amortization of debt discounts and financing costs Amortization of Debt Issuance Costs and Discounts Straight-line rental (expense) income Straight Line Rent Loss (gain) on extinguishment of debt (Gain) loss on sale of investment properties, net Gain (Loss) on Sale of Properties Non-cash stock-based compensation expense Share-based Compensation Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts and rents receivable, net Increase (Decrease) in Receivables Settlement of balance due from InvenTrust Increase (Decrease) in Due from Related Parties, Current Deferred costs and other assets Increase (Decrease) in Deferred Charges Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Net cash flows provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures and tenant improvements Payments to Acquire and Develop Real Estate Investment in development Payments to Develop Real Estate Assets Proceeds from sale of investment properties, net Proceeds from Sale of Real Estate Held-for-investment Acquisition of investment properties Proceeds from insurance settlement Proceeds from Insurance Settlement, Investing Activities Payment of leasing fees Payments for Leasing Costs Net cash flows used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Payoff of mortgage debt Repayments of Notes Payable, Paid Off Repayments of Notes Payable, Paid Off Prepayment penalties on the payoff of mortgage debt Payment for Debt Extinguishment or Debt Prepayment Cost Principal payments of mortgage debt Repayments of Mortgage, Principal Repayments of Mortgage, Principal Payment for tax withholding for share-based compensation Payments Related to Tax Withholding for Share-based Compensation Net cash flows used in financing activities Net Cash Provided by (Used in) Financing Activities Net 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 period Cash, cash equivalents and restricted cash, at end of period Earnings Per Share [Abstract] Earnings Per Share Earnings Per Share [Text Block] Segment Reporting Segment Reporting Disclosure [Text Block] Number of properties acquired Number Of Real Estate Properties Acquired Number Of Real Estate Properties Acquired Acquisition of investment properties Capitalized transaction costs Asset Acquisition, Capitalized Transaction Costs Asset Acquisition, Capitalized Transaction Costs Summary of Net Property Operations Schedule of Segment Reporting Information, by Segment [Table Text Block] Statement of Stockholders' Equity [Abstract] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Distributions in Excess of Net Income Accumulated Distributions in Excess of Net Income [Member] Beginning balance Beginning balance (in shares) Shares, Outstanding Net income Share-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options Share-based compensation (in shares) Stock Issued During Period, Shares, Share-based Compensation, Gross Common stock repurchased and retired Stock Repurchased and Retired During Period, Value Common stock repurchased and retired (in shares) Stock Repurchased and Retired During Period, Shares Ending balance (in shares) Ending balance Schedule of Cash and Restricted Cash Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Operating segments Operating Segments [Member] Reconciling items Segment Reconciling Items [Member] Operating Segments And Corporate, Non-Segment Operating Segments And Corporate, Non-Segment [Member] Operating Segments And Corporate, Non-Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Operating expenses and real estate taxes Cost of Real Estate Revenue and Real Estate Tax Expense Cost of Real Estate Revenue and Real Estate Tax Expense Net operating income Operating Income (Loss), Net of Non-Allocated Expenses Operating Income (Loss), Net of Non-Allocated Expenses Non-allocated expenses General and Administrative Expense, Depreciation and Amortization General and Administrative Expense, Depreciation and Amortization Other income and expenses Income Tax Expense, Interest Expense and Other Loss Income Tax Expense, Interest Expense and Other Loss Provision for asset impairment Total assets Capital expenditures Payments For Capital Expenditures Payments For Capital Expenditures Numerator: Net Income (Loss), Including Portion Attributable to Noncontrolling Interest [Abstract] Denominator: Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Weighted average shares outstanding - basic and diluted (in shares) Basic and diluted income per share: Earnings Per Share, Basic and Diluted [Abstract] Net income per common share (in dollars per share) 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 2016-18 Accounting Standards Update 2016-18 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Increase in beginning balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Beginning Balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Beginning Balance Increase in ending balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Ending Balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Ending Balance Scheduled Maturities of Mortgage Indebtedness Schedule of Maturities of Long-term Debt [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Conversion of Stock [Table] Conversion of Stock [Table] Common stock Conversion of Stock [Line Items] Conversion of Stock [Line Items] Shares issued for each share held at date of spin-off (in shares) Number of Shares Issued in Spinoff for Each Share Owned in Former Parent Number of Shares Issued in Spinoff for Each Share Owned in Former Parent Number of assets (in property) Number of Real Estate Properties Parcels of land Number of Parcels of Land Number of Parcels of Land Fair Value, Assets Measured on Nonrecurring Basis Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Schedule of the Fair Value of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Entity Filer Category Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Entity Current Reporting Status Entity Current Reporting Status Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Small Business Entity Small Business Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus 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] Incentive Award Plan Incentive Award Plan [Member] Incentive Award Plan [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Executive Officer Executive Officer [Member] Two Executive Officers Two Executive Officers [Member] Two Executive Officers [Member] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Incentive awards Performance Shares [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Aggregate value of shares granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested Number of employees affected Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Number of Employees Affected Incremental compensation cost, plan modification Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost Number of shares authorized to grant (up to) (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Shares available for future issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Stock Awards Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Ending balance (in shares) Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price 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 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 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 Ending balance (in dollars per share) Stock-based compensation expense Allocated Share-based Compensation Expense Unrecognized compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Payment for tax withholding for share-based compensation Common stock repurchased and retired (in shares) Common stock repurchased and retired (in dollars per share) Stock Repurchased And Retired During Period, Per Share Stock Repurchased And Retired During Period, Per Share Schedule Of Asset Acquisitions Schedule Of Asset Acquisitions [Table Text Block] Schedule Of Asset Acquisitions [Table Text Block] 2018 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2019 Long-term Debt, Maturities, Repayments of Principal in Year Two 2020 Long-term Debt, Maturities, Repayments of Principal in Year Three 2021 Long-term Debt, Maturities, Repayments of Principal in Year Four Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Total Long-term Debt, Gross Weighted average interest rate Interest Costs Incurred [Abstract] 2018 Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Next 12 Months Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Next 12 Months 2019 Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Year Two Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Year Two 2020 Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Year Three Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Year Three 2021 Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Year Four Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, Year Four Thereafter Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, After Year Five Long-term Debt, Maturities, Repayments of Principal, Weighted Average Interest Rate, After Year Five Total Disposed Properties Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Organization Nature of Operations [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Discount rate Measurement Input, Discount Rate [Member] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Long-term debt Long-term Debt [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Measurement input percentage Long-term Debt, Measurement Input Dulles Executive Plaza Asset Dulles Executive Plaza Asset [Member] Dulles Executive Plaza Asset [Member] AT&T-Hoffman Estates Asset AT&T-Hoffman Estates Asset [Member] AT&T-Hoffman Estates Asset [Member] AT&T-St. Louis Asset AT&T-St. Louis [Member] AT&T-St. Louis [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Spinoff Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Spinoff [Member] Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member] Net gain on sale of investment properties Extinguishment of debt Extinguishment of Debt, Amount Gain on extinguishment of debt Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] 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] Estimated Fair Value Estimate of Fair Value Measurement [Member] Mortgages payable Long-term Debt, Fair Value Reconciliation of Net (Loss) Income to Basic and Diluted EPS Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Revenue Recognition Revenue Recognition Leases, Operating [Policy Text Block] Share Based Compensation Compensation Related Costs, Policy [Policy Text Block] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Recently Issued Accounting Pronouncements and Recently Adopted Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Mortgage Loans, Net Debt Disclosure [Text Block] Buckhorn Plaza Buckhorn Plaza [Member] Buckhorn Plaza [Member] Rolling Plains Rolling Plains [Member] Rolling Plains [Member] Gross Disposition Price Disposal Group, Including Discontinued Operation, Consideration