Real estate: Real Estate Abstract Real Estate Abstract. Condensed Consolidated Balance Sheets [Abstract] ASSETS Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value, Total Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash and Cash Equivalents, at Carrying Value Total assets Total assets Assets LIABILITIES Liabilities [Abstract] Total liabilities Liabilities, Total Liabilities EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Liberty Property Trust shareholders' equity Stockholders' Equity Attributable to Parent [Abstract] Common Stock, Value, Issued Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common Stock, Value, Issued, Total Common shares of beneficial interest, $.001 par value, 183,987,000 shares authorized; 114,642,717 (includes 1,249,909 in treasury) and 113,875,211 (includes 1,249,909 in treasury) shares issued and outstanding as of June 30, 2010 and December 31, 2009, respectively Additional paid-in capital Additional Paid in Capital, Total Additional Paid in Capital, Beginning Balance Additional Paid in Capital, Ending Balance Additional Paid in Capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive (loss) income Distributions in excess of net income Accumulated Distributions in Excess of Net Income Treasury Stock, Value Common shares in treasury, at cost, 1,249,909 shares as of June 30, 2010 and December 31, 2009 Treasury Stock, Value, Ending Balance Treasury Stock, Value, Beginning Balance Common shares in treasury, at cost, 1,249,909 shares as of June 30, 2009 and December 31, 2008 Common shares in treasury, at cost, 1,249,909 shares as of June 30, 2010 and December 31, 2009 Total Liberty Property Trust shareholders' equity Stockholders' Equity Attributable to Parent, Total Stockholders' Equity Attributable to Parent, Beginning Balance Stockholders' Equity Attributable to Parent, Ending Balance Stockholders' Equity Attributable to Parent Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Ending Balance Beginning Balance Total equity Total liabilities and equity Liabilities and Stockholders' Equity Condensed Consolidated Statements of Cash Flows [Abstract] OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Amortization of deferred financing costs Amortization of Financing Costs Noncash compensation Share-based Compensation, Total Share-based Compensation Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Increase (Decrease) in Restricted Cash for Operating Activities Restricted cash Restricted cash Increase (Decrease) in Accounts Receivable Accounts receivable Accounts receivable Increase (Decrease) in Deferred Rent Receivables Deferred rent receivable Deferred rent receivable Accounts payable Increase (Decrease) in Accounts Payable, Total Increase (Decrease) in Accounts Payable Accrued interest Increase (Decrease) in Interest Payable, Net Other liabilities Increase (Decrease) in Other Operating Liabilities Other 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] Payments to Acquire Equity Method Investments Investments in and advances to unconsolidated joint ventures Investments in unconsolidated joint ventures Investment in development in progress Payments to Develop Real Estate Assets Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from Issuance of Common Stock Net proceeds from issuance of Common Shares Repayments of unsecured notes Repayments of Unsecured Debt Proceeds from credit facility Proceeds from Long-term Lines of Credit Repayments on credit facility Repayments of Long-term Lines of Credit Increase in deferred financing costs Payments of Financing Costs, Total Payments of Financing Costs Payments of Dividends, Common Stock Distribution paid on Common Shares Distribution paid on common shares Net Cash Provided by (Used in) Financing Activities Net cash used in financing activities Cash and Cash Equivalents, Period Increase (Decrease) Cash and Cash Equivalents, Period Increase (Decrease), Total Net (decrease) increase in cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents Effect of Exchange Rate on Cash and Cash Equivalents, Total (Decrease) increase in cash and cash equivalents related to foreign currency translation Operating real estate Sum of the carrying amounts as of the balance sheet date of all operating real estate assets. Operating real estate Land and land improvements Aggregate of the carrying amounts as of the balance sheet date of investments in land and land improvements included in operating real estate. Land and land improvements Deferred Financing And Leasing Costs Net Of Accumulated Amortization Deferred financing and leasing costs, net of accumulated amortization (2010, $118,545; 2009, $108,403) Aggregate of the carrying amounts as of the balance sheet date of deferred financing and leasing costs, net of accumulated amortization. Building and improvements Investment Building and Building Improvements, Total Investment Building and Building Improvements Less accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Land held for development Land Available for Development Net real estate Real Estate Investment Property, Net, Total Real Estate Investment Property, Net Restricted cash Restricted Cash and Cash Equivalents Accounts receivable Accounts Receivable, Net, Total Accounts Receivable, Net Deferred rent receivable Deferred Rent Receivables, Net Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures, Total Investments in and advances to unconsolidated joint ventures Prepaid expenses and other assets Prepaid Expense and Other Assets Credit facility Line of Credit Facility, Amount Outstanding Accounts payable Accounts Payable, Total Accounts Payable Accrued interest Interest Payable Dividend and distributions payable Dividends Payable Operating expense reimbursement Tenant Reimbursements Total operating revenue Real Estate Revenue, Net Revenues [Abstract] 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 General and Administrative Expense, Total General and Administrative Expense Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Operating income Operating Income (Loss) Operating income OTHER INCOME (EXPENSE) Nonoperating Income (Expense) [Abstract] Gains (Losses) on Extinguishment of Debt Debt extinguishment gain Gains (Losses) on Extinguishment of Debt, Total Debt extinguishment gain Interest expense Interest Expense Total other income (expense) Nonoperating Income (Expense) Income before 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, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest Gain (Loss) on Disposition of Assets Gain (Loss) on Disposition of Assets, Total Gain (loss) on property dispositions Income taxes Income Tax Expense (Benefit), Total Income Tax Expense (Benefit) Income (Loss) from Equity Method Investments Equity in earnings of unconsolidated joint ventures Equity in earnings of unconsolidated joint ventures Equity in earnings of unconsolidated joint ventures Income from continuing operations Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest, Total Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Discontinued operations (including net gain on property dispositions of $2,408 and $3,670 for the three months ended June 30, 2010 and 2009, respectively) Discontinued operations (including net gain on property dispositions of $XXX and $1XXX for the six months ended June 30, 2010 and 2009, respectively) Noncontrolling interest - operating partnership Net Income (Loss) Attributable to Noncontrolling Interest, Operating Partnerships Noncontrolling interest - consolidated joint ventures Net Income (Loss) Attributable to Noncontrolling Interest, Joint Venture Partners Net income available to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Discontinued operations Discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Income from continuing operations Income (Loss) from Continuing Operations Attributable to Parent, Total Income (Loss) from Continuing Operations Attributable to Parent Amounts attributable to common shareholders Income Amounts Attributable to Parent, Disclosures [Abstract] Diluted Weighted Average Number of Shares Outstanding, Diluted, Total Weighted Average Number of Shares Outstanding, Diluted Basic Weighted Average Number of Shares Outstanding, Basic, Total Weighted Average Number of Shares Outstanding, Basic Weighted average number of common shares outstanding Weighted Average Number of Shares Outstanding, Diluted, Disclosure Items [Abstract] Distributions per common share Common Stock, Dividends, Per Share, Cash Paid Earnings Per Share, Diluted Income per common unit - diluted Income from discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Income from continuing operations Income (Loss) from Continuing Operations, Per Diluted Share Distributions per common share Diluted: Earnings Per Share, Diluted [Abstract] Earnings Per Share, Basic Income per common unit - basic Income from discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share Income from continuing operations Income (Loss) from Continuing Operations, Per Outstanding Share, Total Income (Loss) from Continuing Operations, Per Basic Share Basic: Earnings Per Share, Basic [Abstract] Earnings per common share Earnings Per Share [Abstract] Accumulated amortization on deferred financing and leasing costs Amortized Cost on Deferred Financing and Leasing Costs Amortized cost on deferred financing and leasing costs. Common shares, par value Common Stock, Par or Stated Value Per Share Common shares, shares authorized Common Stock, Shares Authorized Common shares, shares issued Common Stock, shares, Issued, Total Common Stock, Shares, Issued Common shares, shares outstanding Common Stock, Shares, Outstanding, Beginning Balance Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding Treasury stock, shares Treasury Stock, Shares, Beginning Balance Treasury Stock, Shares, Ending Balance Treasury Stock, Shares Net gain on property dispositions included in discontinued operations Net gain on property dispositions included in discontinued operation Net gain on property dispositions included in discontinued operation. Organization and Basis of Presentation [Abstract] Organization and Basis of Presentation [Abstract] Organization and Basis of Presentation. Segment Information [Abstract] Segment Information [Abstract] Segment Information. SFAS No 144 Accounting for the Impairment or Disposal of Long Lived Assets [Abstract] SFAS No 144 Accounting for the Impairment or Disposal of Long Lived Assets [Abstract] SFASNo 144 Accounting for the Impairment or Disposal of Long Lived Assets. Disclosure of Fair Value of Financial Instruments [Abstract] Disclosure of Fair Value of Financial Instruments [Abstract] Disclosure of Fair Value of Financial Instruments. Organization and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Segment Information Segment Reporting Disclosure [Text Block] Accounting for the Impairment or Disposal of Long-Lived Impairment or Disposal of Long-Lived Assets, Policy [Text Block] Noncontrolling interests Noncontrolling Interest Disclosure [Text Block] Disclosure of Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Recently Issued Accounting Standards Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Supplemental Disclosure to Statements of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Distributions To Shareholders Distributions The total of distributions to shareholders during the period. Noncash compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Value Foreign currency translation adjustment Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, before Tax, Total Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, before Tax Condensed Consolidated Statement of Equity [Abstract] Statement of Equity [Abstract] Condensed Consolidated Statements of Operations [Abstract] Statements of Operations [Abstract] Distributions from unconsolidated joint ventures Equity Method Investment, Dividends or Distributions Gain (Loss) on Sale of Properties Gain on property dispositions Gain on property dispositions Investment in deferred leasing costs The cash outflow associated with the investment in deferred leasing costs. Investment in deferred leasing costs Investment in deferred leasing costs Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Statement [Line Items] Noncontrolling Interest in Operating Partnerships Statement [Table] Common units; 3,943,224 and 4,011,354 outstanding as of June 30, 2010 and December 31, 2009, respectively COMMON SHARES OF BENEFICIAL INTEREST 4,017,354 and 4,074,967 common units outstanding as of June 30, 2009 and December 31, 2008, respectively 9,740,000 preferred units outstanding as of June 30, 2010 and December 31, 2009 9,740,000 preferred units outstanding as of June 30, 2009 and December 31, 2008 Statement, Equity Components [Axis] Equity Component [Domain] TOTAL LIBERTY PROPERTY TRUST SHAREHOLDERS' EQUITY ADDITIONAL PAID-IN CAPITAL Additional Paid-In Capital COMMON SHARES HELD IN TREASURY Common Shares Held in Treasury DISTRIBUTIONS IN EXCESS OF NET INCOME Distributions in Excess of Net Income ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME SFAS No 144 Accounting for the Impairment or Disposal of Long Lived Assets [Abstract] Increase in deferred financing costs Repayments on credit facility Repayments of unsecured notes Investment in deferred leasing costs Investment in development in progress Distributions in excess of net income Noncontrolling interest - operating partnership Noncontrolling interest operating partnership Abstract Noncontrolling interest - operating partnership. Net proceeds from the issuance of common shares Stock Issued During Period, Value, New Issues Income taxes Interest expense Noncontrolling interest - operating partnership Noncontrolling interest - consolidated joint ventures Development in progress Development in Process Unsecured notes Unsecured Debt, Total Unsecured Debt Other liabilities Other Liabilities ASSETS Noncontrolling interest - operating partnership Noncontrolling interest - operating partnership, common units outstanding, shares Rental Operating Leases, Income Statement, Lease Revenue, Total Operating Leases, Income Statement, Lease Revenue Total operating expenses Costs and Expenses Interest and other income Interest and other income Comprised of management and other fee income, interest income, and other income not classified elsewhere. Noncontrolling interest - operating partnership, preferred units outstanding Preferred Units, Outstanding Proceeds from mortgage loans Proceeds from Issuance of Secured Debt Repayments of mortgage loans Repayments of Secured Debt Noncontrolling interests [Abstract] Noncontrolling interests [Abstract] Recently Issued Accounting Standards [Abstract] Recently Issued Accounting Standards [Abstract] Supplemental Disclosure to Statements of Cash Flows [Abstract] Supplemental Disclosure to Statements of Cash Flows [Abstract] Noncontrolling interest - operating partnership, common units outstanding Noncontrolling Interest Operating Partnership Common Units Outstanding Noncontrolling Interest Operating Partnership Common Units Outstanding. Distributions from unconsolidated joint ventures Equity Method Investment Dividends Or Distributions Investing Equity method investment dividends or distributions investing. Distribution paid on units Payments of Dividends, Noncontrolling Interest Fee Interest And Other Income SFS 144 Accounting For Impairment Or Disposal Of Long-lived Assets [Abstract] Less accumulated depreciation NONCONTROLLING INTEREST - OPERATING PARTNERSHIP - COMMON Noncontrolling Interest Operating Partnership. Document and Entity Information [Abstract] Document And Entity Information. Proceeds From Grant Receivables Escrow Net proceeds from advances in grant receivable/escrow The cash inflow associated with grants receivable and the release of cash held in escrow. NONCONTROLLING INTEREST - OPERATING PARTNERSHIP - PREFERRED NonControlling Interest Operating Partnership Preferred. Document Fiscal Year Focus Document Fiscal Period Focus NONCONTROLLING INTEREST- CONSOLIDATED JOINT VENTURES Noncontrolling Interest Consolidated Joint Ventures. Payments for Capital Improvements Investment in properties Investment in properties Payments To Acquire And Develop Land Investment in land held for development Investment in land held for development The cash outflow associated with the purchase of or development of land held for investment. Minority Interest In Real Estate Joint Ventures Noncontrolling interest - consolidated joint ventures Carrying amount of the equity interests owned by external partners in joint ventures included in the entity's consolidated financial statements. Proceeds from Sale of Real Estate Held-for-investment Proceeds from Sale of Real Estate Held-for-investment, Total Net proceeds from disposition of properties/land Limited Partners' Capital Account Limited Partners' Capital Account, Total Limited partners' equity General Partners' Capital Account, Value General partner's equity - common units, 114,642,717 and 113,875,211 units outstanding as of June 30, 2010 and December 31, 2009, respectively Limited Partners' Capital Account [Abstract] Limited partners' equity Net Income (Loss) Attributable to Noncontrolling Interest, Preferred Unit Holders Preferred unit distributions Preferred unit distributions Preferred unit distributions Net Income (Loss) Allocated to General Partners Net income allocated to general partners Net Income (Loss) Allocated to Limited Partners Net income allocated to limited partners Proceeds from Contributed Capital Capital contributions Payments of Capital Distribution Distributions to partners Distributions to partners Distributions to partners Partners' Capital Notes Disclosure [Text Block] Limited partners' equity Limited partners' equity [Abstract] NONCONTROLLING INTEREST GENERAL PARTNER'S EQUITY General Partners Equity. Partners' Capital Account, Contributions Contributions from partners Partners' Capital Account, Exchanges and Conversions Redemption of limited partners common units for common shares Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Redemption of noncontrolling interests- common units Partners' Capital Account, Distributions Distributions to partners Depreciation, Depletion and Amortization Depreciation, Depletion and Amortization, Total Depreciation and amortization Legal Entity [Axis] Entity [Domain] Limited Partners' Capital Account, Units Issued