Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic and Diluted [Table] Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Liberty Property Limited Partnership [Member] Liberty Property Limited Partnership [Member] Limited Partnership. Earnings Per Share, Basic and Diluted [Line Items] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Earnings Per Share [Text Block] Earnings Per Share [Text Block] Stock Option Exercises [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Commitments and Contingencies Disclosure [Abstract] Supply Commitment [Table] Supply Commitment [Table] Supply Commitment [Axis] Supply Commitment [Axis] Supply Commitment Arrangement [Domain] Supply Commitment Arrangement [Domain] Construction in Progress [Member] Construction in Progress [Member] Development Not Yet Commenced [Member] Development Not Yet Commenced [Member] A planned development project that currently does not have any costs classified on the balance sheet as Development or Construction in Progress. Buildings and land parcels [Member] Land, Buildings and Improvements [Member] Tenant Improvements [Member] Leasehold Improvements [Member] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Comcast Innovation and Technology Center [Member] Comcast Innovation and Technology Center [Member] Comcast Innovation and Technology Center is composed of two equity method investments: 1) Liberty Property 18th & Arch, LP 2) Liberty Property 18th & Arch Hotel, LLC Supply Commitment [Line Items] Supply Commitment [Line Items] Net Rentable Area Net Rentable Area Number of Real Estate Properties Number of Real Estate Properties Total anticipated development cost Anticipated Aggregate Investment Total anticipated cost of investment in assets including but not limited to assets under construction. Development in Process Development in Process Deferred Costs, Leasing, Gross Deferred Costs, Leasing, Gross Remaining amount committed or obligated to pay for the benefit of current or future tenants Supply Commitment, Remaining Minimum Amount Committed Tenant improvements not yet completed Supply Commitment, Remaining Maximum Amount Committed Supply Commitment, Remaining Maximum Amount Committed Comcast Innovative and Technology Center [Abstract] Comcast Innovative and Technology Center [Abstract] Comcast Innovative and Technology Center [Abstract] Number of equity method investments Number of equity method investments Number of equity method investments Number of stories in a high-rise building Number of stories in a high-rise building Number of stories in a high-rise building Number of hotel rooms Number of hotel rooms Number of hotel rooms in a hotel Anticipated investment in joint ventures Anticipated investment in joint ventures Anticipated balance in investment in unconsolidated joint ventures after development is completed. Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage Disposal Group, Including Discontinued Operation, Long Lived Assets [Abstract] Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block] Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Summary of Derivative Instruments [Abstract] Summary of Derivative Instruments [Abstract] Interest Rate Derivatives [Abstract] Interest Rate Derivatives [Abstract] Number of interest rate swap contracts Number of Interest Rate Derivatives Held aggregate notional amount Derivative, Notional Amount Termination value of interest rate swap, including accrued interest Assets Needed for Immediate Settlement, Aggregate Fair Value Interest Rate Cash Flow Hedges [Abstract] Interest Rate Cash Flow Hedges [Abstract] Change in fair value of swaps as a decrease to other comprehensive income Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss) Amount of loss reclassified into interest expense from AOCI Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion Ineffective portion of the change in the fair value of swaps as an adjustment to interest expense Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness Fair value of interest rate swaps Interest Rate Cash Flow Hedge Liability at Fair Value Amount estimated to be reclassified from accumulated other comprehensive income as an adjustment to interest expense Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Stock Option Exercises [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Stock Option [Member] Employee Stock Option [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common Units [Member] Common Class B [Member] Stock Option Exercises [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Amount of Options Exercises in Period Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Stockholders' Equity Attributable to Noncontrolling Interest [Abstract] Redeemable Noncontrolling Interest, by Legal Entity [Table] Redeemable Noncontrolling Interest, by Legal Entity [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Redeemable Noncontrolling Interest [Line Items] Redeemable Noncontrolling Interest [Line Items] Common units, units outstanding not held by the trust Noncontrolling Interest, Operating Partnership, Limited Partners' Common Units Outstanding Noncontrolling Interest of the Trust relating to the Operating Partnership. The amount of units owned by limited partners' which are outstanding. Market value of common units based on closing price Redeemable Noncontrolling Interest, Equity, Common, Fair Value Document and Entity Information [Abstract] Document And Entity Information. Entities [Table] Entities [Table] Entity Information [Line Items] Entity Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Income from continuing operations net of noncontrolling interest Income (Loss) from Continuing Operations Attributable to Parent Less: Preferred unit distributions Preferred Stock Dividends, Income Statement Impact Income from Continuing Operations available to Common Unitholders Income from Continuing Operations available to Common Unitholders Income from Continuing Operations available to Common Unitholders Discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Net income available to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted Average Number of Shares Outstanding, Basic Weighted Average Number of Shares Outstanding, Basic Dilutive units for long-term compensation plans Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted Average Number of Shares Outstanding, Diluted Weighted Average Number of Shares Outstanding, Diluted Earnings Per Share, Basic [Abstract] Earnings Per Share, Basic [Abstract] Income from Continuing Operations, Per Basic Share Income (Loss) from Continuing Operations, Per Basic Share Income from Discontinued Operations, Per Basic Share Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share Income per common share - basic Earnings Per Share, Basic Earnings Per Share, Diluted [Abstract] Earnings Per Share, Diluted [Abstract] Income from Continuing Operations, Per Diluted Share Income (Loss) from Continuing Operations, Per Diluted Share Income from Discontinued Operations, Per Diluted Share Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share Income per common share - diluted Earnings Per Share, Diluted Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Groups, Including Discontinued Operations, Name [Domain] Disposal Groups, Including Discontinued Operations, Name [Domain] Discontinued Operations [Member] Discontinued Operations [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] Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract] Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract] Revenues Disposal Group, Including Discontinued Operation, Revenue Operating expenses Disposal Group, Including Discontinued Operation, Operating Expense Interest and other income Disposal Group, Including Discontinued Operation, Other Income Interest expense Disposal Group, Including Discontinued Operation, Interest Expense Depreciation and amortization Disposal Group, Including Discontinued Operation, Depreciation and Amortization Income before gain on property dispositions Discontinued Operations excluding Gain on Sale Discontinued Operations excluding Gain on Sale Gain on property dispositions Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Net income Debt Instrument, Fair Value Disclosure [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] 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] Estimate of Fair Value Measurement [Member] Estimate of Fair Value Measurement [Member] Portion at Other than Fair Value Measurement [Member] Portion at Other than Fair Value Measurement [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value by Liability Class [Axis] Liability Class [Axis] Fair Value, Liabilities, Measured on Recurring Basis, Unobservable Input Reconciliation, by Liability Class [Domain] Fair Value by Liability Class [Domain] Mortgage Loans Mortgage Loans on Real Estate [Member] Unsecured Notes Unsecured Debt [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term Debt, Fair Value Long-term Debt, Fair Value 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] Senior Notes [Member] Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 5.125% Senior Notes [Member] 5.125% Senior Notes [Member] 5.125% Senior Notes [Member] 3.75% Senior Notes [Member] 3.75% Senior Notes [Member] 3.75% Senior Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Unsecured Notes [Abstract] Unsecured Debt [Abstract] Debt Instrument, Repurchased Face Amount Debt Instrument, Face Amount Debt Instrument, Face Amount Interest Rate Debt Instrument, Interest Rate, Stated Percentage 2015 Operating Leases, Future Minimum Payments, Remainder of Fiscal Year 2016 Operating Leases, Future Minimum Payments, Due in Two Years 2017 Operating Leases, Future Minimum Payments, Due in Three Years 2018 Operating Leases, Future Minimum Payments, Due in Four Years 2019 Operating Leases, Future Minimum Payments, Due in Five Years 2020 through 2034 Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Other Expenses [Abstract] Other Expenses [Abstract] Operating ground lease expense Operating Ground Lease Expense Operating Ground Lease Expense Income Statement [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Gain on property dispositions Statement of Stockholders' Equity [Abstract] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] General Partners Equity [Member] General Partners Equity [Member] General Partners Equity. Common Shares Of Beneficial Interest [Member] Common Shares Of Beneficial Interest [Member] Common Shares Of Beneficial Interest [Member] Additional Paid-In Capital [Member] Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income (Loss) [Member] Distributions in Excess of Net Income [Member] Accumulated Distributions in Excess of Net Income [Member] Common Shares Held in Treasury [Member] Treasury Stock [Member] Total Liberty Property Trust Shareholders' Equity [Member] Parent [Member] Noncontrolling interest operating partnership-Common [Member] Noncontrolling interest operating partnership Common [Member] Noncontrolling Interest Operating Partnership. Noncontrolling interest-consolidated joint ventures [Member] Noncontrolling interest-consolidated joint ventures [Member] Noncontrolling Interest Consolidated Joint Ventures. Total Equity [Member] Stockholders' Equity, Total [Member] Beginning Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests Net proceeds from the issuance of common shares Stock Issued During Period, Value, New Issues Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income (Mezzanine) Temporary Equity, Net Income Distributions (Mezzanine) Temporary Equity, Other Changes Redemption of limited partners common units for common shares Stock Issued During Period, Value, Conversion of Units Contributions from partners Partners' Capital Account, Contributions Distributions Dividends Distributions to partners Partners' Capital Account, Distributions Share-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Other comprehensive loss - foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax Other comprehensive loss - derivative instruments Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Redemption of noncontrolling interests - common units Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests, Common Units Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests, Common Units Ending Balance Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Supplemental Cash Flow Information [Abstract] Supplemental Disclosure to Statements of Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Ownership interest in operating partnership - Limited Partnership Noncontrolling Interest, Ownership Percentage by Parent Common shares [Member] Common Class A [Member] Discontinued operations net of noncontrolling interest Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Dilutive shares for long-term compensation plans Weighted Average Number of Shares Outstanding, Diluted Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Land and land improvements Land and Land Improvements Building and improvements Investment Building and Building Improvements Less accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Operating real estate Operating real estate Sum of the carrying amounts as of the balance sheet date of all operating real estate assets. Development in progress Land held for development Land Available for Development Net real estate Real Estate Investment Property, Net Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash and Cash Equivalents Accounts receivable Accounts Receivable, Net Deferred rent receivable Deferred Rent Receivables, Net Deferred financing and leasing costs, net of accumulated amortization (2015, $173,076; 2014, $169,468) Deferred costs, net Deferred costs, including deferred leasing and financing costs and intangible assets including to intangible market rent and intangible leases net of accumulated amortization. Investments in and advances to unconsolidated joint ventures Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Assets held for sale Disposal Group, Including Discontinued Operation, Assets Prepaid expenses and other assets Prepaid Expense and Other Assets Total assets Assets LIABILITIES Liabilities [Abstract] Mortgage loans Secured Debt Unsecured notes Unsecured Debt Credit facility Long-term Line of Credit Accounts payable Accounts Payable Accrued interest Interest Payable Dividend and distributions payable Dividends Payable Other liabilities Other Liabilities Total liabilities Liabilities Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of March 31, 2015 and December 31, 2014 Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 150,367,813 (includes 1,249,909 in treasury) and 149,807,179 (includes 1,249,909 in treasury) shares issued and outstanding as of March 31, 2015 and December 31, 2014, respectively Common Stock, Value, Issued General partner’s equity - 149,117,904 (net of 1,249,909 treasury units) and 148,557,270 (net of 1,249,909 treasury units) common units outstanding as of March 31, 2015 and December 31, 2014, respectively General Partners' Capital Account Limited partners' equity Limited Partners' Capital Account Additional paid-in capital Additional Paid in Capital Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Distributions in excess of net income Accumulated Distributions in Excess of Net Income Common shares in treasury, at cost, 1,249,909 shares as of March 31, 2015 and December 31, 2014 Treasury Stock, Value Total Liberty Property Trust shareholders' equity Stockholders' Equity Attributable to Parent Noncontrolling interest - operating partnership Noncontrolling interest - operating partnerships Noncontrolling Interest in Operating Partnerships Noncontrolling interest - consolidated joint ventures Noncontrolling Interest in Joint Ventures Total equity Total liabilities, noncontrolling interest - operating partnership and equity Liabilities and Equity Noncontrolling Interests Noncontrolling Interest Disclosure [Text Block] Supplemental Disclosure to Statements of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Interest rate swaps [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Foreign Currency Translation: Cumulative Translation Adjustment Summary [Roll Forward] Beginning balance Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Ending balance Derivative Instruments: Cumulative Cash Flow Hedge Adjustment Summary [Roll Forward] Cumulative Cash Flow Hedge Adjustment Summary [Roll Forward] Beginning balance Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Unrealized loss Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Reclassification adjustment Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Ending balance Total accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total Accumulated Other Comprehensive Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total Less: portion included in noncontrolling interest - operating partnership Accumulated Other Comprehensive Income (Loss), Attributable to Noncontrolling Interest, Total Accumulated Other Comprehensive Income (Loss), Attributable to Noncontrolling Interest, Total Total accumulated other comprehensive (loss) income included in shareholders' equity/owners' equity Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Intersegment Eliminations [Member] Intersegment Eliminations [Member] Operating Segments [Member] Operating Segments [Member] Discontinued Operations [Member] Segment Reconciling Items [Member] Corporate, Non-Segment [Member] Corporate, Non-Segment [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Carolinas [Member] Carolinas [Member] Carolinas Reportable Segment Chicago Milwaukee [Member] Chicago Milwaukee [Member] Chicago Milwaukee Reportable Segment Houston [Member] Houston [Member] Houston Reportable Segment Lehigh Central PA [Member] Lehigh Central PA [Member] Lehigh Central PA [Member] Minnesota [Member] Minnesota [Member] Minnesota Reportable Segment Orlando [Member] Orlando [Member] Orlando reportable segment Philadelphia [Member] Philadelphia [Member] Philadelphia [Member] Richmond Hampton Roads [Member] Richmond Hampton Roads [Member] Richmond Hampton Roads Reportable Segment South Florida [Member] South Florida [Member] South Florida Reportable Segment Southeastern PA [Member] Southeastern PA [Member] Southeastern PA Tampa [Member] Tampa [Member] Tampa - Reportable segment United Kingdom [Member] United Kingdom [Member] United Kingdom Member. Other Segments [Member] Other Segments [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] North America [Member] North America [Member] European Union [Member] European Union [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Operating revenue Revenues Net operating income Operating Income (Loss) Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Interest expense Interest Expense Depreciation and amortization expense Depreciation, Depletion and Amortization Impairment - real estate assets Impairment of Real Estate Gain on property dispositions Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Equity in earnings of unconsolidated joint ventures Income (Loss) from Equity Method Investments General and administrative expense General and Administrative Expense Discontinued operations excluding interest and gain on property dispositions Income taxes Income Tax Expense (Benefit) Other Other Nonoperating Income (Expense) Income from continuing operations Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest Legal Matters [Abstract] Loss Contingency, Quantities [Abstract] Loss Contingency, Pending Claims, Number Loss Contingency, Pending Claims, Number Other [Abstract] Other Liabilities, Unclassified [Abstract] Letter of credit obligations Letters of Credit Outstanding, Amount Segment Reporting, Measurement Disclosures [Abstract] Schedule of Segment Reporting Information, by Segment, Revenue and Net Operating Income [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table Text Block] New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] Accumulated Other Comprehensive Income (Loss) Note [Text Block] Comprehensive Income (Loss) Note [Text Block] Long-term Purchase Commitment [Table] Long-term Purchase Commitment [Table] 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] Land Purchases [Member] Capital Addition Purchase Commitments [Member] Long-term Purchase Commitment [Line Items] Long-term Purchase Commitment [Line Items] Remaining amount commitment to future land purchases Purchase Commitment, Remaining Minimum Amount Committed Schedule of Antidilutive Options Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock Option [Member] Equity Option [Member] Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Options Excluded from Computation of Earnings Per Share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Future Minimum Rental Payments Operating Leases of Lessee Disclosure [Table Text Block] Temporary Equity Disclosure [Abstract] Temporary Equity, by Class of Stock [Table] Temporary Equity, by Class of Stock [Table] Temporary Equity [Line Items] Temporary Equity [Line Items] Schedule of Temporary Equity [Table Text Block] Temporary Equity [Table Text Block] Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Asset Impairment Charges [Text Block] Asset Impairment Charges [Text Block] Series I 2 [Member] Redeemable Preferred Stock [Member] Cumulative redeemable preferred units of the Operating Partnership outstanding Units Temporary Equity, Shares Outstanding Liquidation Preference Temporary Equity, Redemption Price Per Share Dividend Rate Preferred Stock, Dividend Rate, Percentage Common shares [Member] OPERATING REVENUE Revenues [Abstract] Rental Operating Leases, Income Statement, Lease Revenue Operating expense reimbursement Tenant Reimbursements Total operating revenue OPERATING EXPENSE Operating Expenses [Abstract] Rental property Direct Costs of Leased and Rented Property or Equipment Real estate taxes Real Estate Tax Expense General and administrative Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Impairment - real estate assets Total operating expenses Costs and Expenses Operating income OTHER INCOME (EXPENSE) Nonoperating Income (Expense) [Abstract] Other income Other Income Total other income (expense) Nonoperating Income (Expense) Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Gain on property dispositions Income from continuing operations Discontinued operations (including net gain on property dispositions of $46,115 for the three months ended March 31, 2014) Net income Noncontrolling interest – operating partnership Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable Noncontrolling interest - consolidated joint ventures Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Nonredeemable Preferred unit distributions Noncontrolling Interest in Net Income (Loss) Preferred Unit Holders, Redeemable Net income available to common shareholders Comprehensive income attributable to common shareholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Other comprehensive (loss) income - foreign currency translation Other comprehensive (loss) income Other Comprehensive Income (Loss), Net of Tax Total comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: comprehensive income attributable to noncontrolling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income attributable to common shareholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent Earnings per common share Basic: Income from continuing operations Income from discontinued operations Income per common share - basic Diluted: Income from continuing operations Income from discontinued operations Income per common share - diluted Distributions per common share or unit Common Stock, Dividends, Per Share, Declared Weighted average number of common shares outstanding Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Basic Diluted Net income allocated to general partners Net Income (Loss) Allocated to General Partners Net income allocated to limited partners Net Income (Loss) Allocated to Limited Partners Amounts attributable to common shareholders Income Amounts Attributable to Parent, Disclosures [Abstract] Income from continuing operations Discontinued operations Fair Value, by Balance Sheet Grouping [Table Text Block] Limited Partners' Equity of the Operating Partnership [Abstract] Limited Partners' Equity of the Operating Partnership [Abstract] Schedule of Limited Partners' Capital Account by Class [Table] Schedule of Limited Partners' Capital Account by Class [Table] Limited Partners' Capital Account [Line Items] Limited Partners' Capital Account [Line Items] Limited Partners' Capital Account, Units Outstanding Limited Partners' Capital Account, Units Outstanding market value of the outstanding common units market value of the outstanding common units Market value of the limited partners' outstanding common units as of period end based on the closing price of the common shares of the trust. Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Land, Buildings and Improvements [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Acquisitions [Abstract] Acquisitions [Abstract] Any type of acquisition by the entity. Number of real estate properties acquired Number of real estate properties acquired Number of real estate properties acquired Dispositions [Abstract] Dispositions [Abstract] Any type of disposition by the entity, including dispositions both classified as discontinued operations and not discontinued operations. Proceeds from Sale of Property Proceeds from Sale of Property, Plant, and Equipment Number of Real Estate Properties Sold Number of Real Estate Properties Sold Number of Real Estate Properties Sold Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Amortized Cost on Deferred Financing and Leasing Costs Amortized Cost on Deferred Financing and Leasing Costs Amortized cost on deferred financing and leasing costs. Noncontrolling Interest Operating Partnership Common Units Outstanding Temporary Equity, Shares Outstanding Common Stock, Par or Stated Value 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 Treasury Stock, Shares Treasury Stock, Shares Disclosure of Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Debt Disclosure [Text Block] Debt Disclosure [Text Block] Stockholders' Equity Note Disclosure [Text Block] Statement of Cash Flows [Abstract] 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 Amortization of deferred financing costs Amortization of Financing Costs Equity in earnings of unconsolidated joint ventures Gain on property dispositions Gain (Loss) on Sale of Properties Share-based compensation/Non-cash compensation Share-based Compensation Other Other Operating Activities, Cash Flow Statement Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Restricted cash Increase (Decrease) in Restricted Cash for Operating Activities Accounts receivable Increase (Decrease) in Accounts Receivable Deferred rent receivable Straight Line Rent Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable Increase (Decrease) in Accounts Payable Accrued interest Increase (Decrease) in Interest Payable, Net Other liabilities Increase (Decrease) in Other Operating Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Investment in operating properties - acquisitions Payments to Acquire Buildings Investment in operating properties - other Payments for Capital Improvements Investments in and advances to unconsolidated joint ventures Payments to Acquire Equity Method Investments Distributions from unconsolidated joint ventures Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Net proceeds from disposition of properties/land Proceeds from Sale of Real Estate Held-for-investment Net (advances on) proceeds from public reimbursement receivable/escrow Proceeds from Collection of Other Receivables Investment in development in progress Payments to Develop Real Estate Assets Investment in land held for development Payments To Acquire And Develop Land The cash outflow associated with the purchase of or development of land held for investment. Investment in deferred leasing costs Payments for Leasing Costs Net cash (used in) provided by investing activities Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Net proceeds from issuance of common shares Proceeds from Issuance of Common Stock Proceeds from unsecured notes Proceeds from Issuance of Unsecured Debt Repayment of unsecured notes Repayments of Unsecured Debt Repayments of mortgage loans Repayments of Secured Debt Proceeds from credit facility Proceeds from Long-term Lines of Credit Repayments on credit facility Repayments of Long-term Lines of Credit Payment of deferred financing costs Payments of Financing Costs Capital contributions Proceeds from Contributed Capital Distributions to partners Payments of Capital Distribution Distribution paid on common shares Payments of Ordinary Dividends, Common Stock Distribution paid on units Payments of Ordinary Dividends, Noncontrolling Interest Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net (decrease) increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect (Decrease) increase in cash and cash equivalents related to foreign currency translation Effect of Exchange Rate on Cash and Cash Equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Schedule of Preferred Units [Table] Preferred Units [Line Items] Noncontrolling Interest Disclosure [Text Block] Segment Information Segment Reporting Disclosure [Text Block] Write off of fully depreciated/amortized property and deferred costs Write off of fully depreciated property and deferred costs Write off of fully depreciated property and deferred costs Write off of depreciated property and deferred costs due to sale Write Off Of Depreciated Property And Deferred Costs Due To Sale Write Off Of Depreciated Property And Deferred Costs Due To Sale Unrealized loss on cash flow hedge Unrealized gain (loss) on cash flow hedge, non cash transaction Unrealized gain (loss) on cash flow hedge, non cash transaction Changes in accrued development capital expenditures Construction in Progress Expenditures Incurred but Not yet Paid Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]