Document and Entity Information. Document and Entity Information [Abstract] Mortgage interest Interest recorded on mortgage notes receivable based on the interest rates in each note. Mortgage interest Straight-line rent Revenue recorded to smooth out tenant rents over the life of each lease in accordance with GAAP. Straight-line rent Repayments on notes and bonds payable Repayments on notes and bonds payable Repayments on notes and bonds payable Repayments on notes and bonds payable. Straight-line rent receivable. Straight Line Rent Receivable Straight-line rent receivable Summary Of Significant Accounting Policies. Summary of Significant Accounting Policies [Abstract] Real Estate and Mortgage Notes Receivable Investments. Real Estate and Mortgage Notes Receivable Investments [Abstract] Acquisitions And Dispositions. Acquisitions and Dispositions [Abstract] Acquisitions And Dispositions Acquisitions And Dispositions Acquisitions and Dispositions Commitments And Contingencies. Commitments and Contingencies [Abstract] Taxable Income. Taxable Income [Abstract] Fair Value Of Financial Instruments. Fair Value of Financial Instruments [Abstract] Personal property Personal property. Personal property Cumulative net income attributable to common stockholders. Cumulative net income attributable to common stockholders Cumulative net income attributable to common stockholders Assets held for sale and discontinued operations, net. Assets held for sale and discontinued operations net Assets held for sale and discontinued operations, net Master lease rent Rents earned during the period from master leases based on the terms of the contractual arrangements. Master lease rent Other Operating Income. Other Operating Income Text Block Other Operating Income Other Operating Income. Other Operating Income [Abstract] Cumulative dividends Dividends paid or payable to stockholders. Cumulative dividends Cumulative dividends Property Operating Income Property operating Rents earned, tenant reimbursements, and other tenant revenue from leases in multi-tenanted buildings based on the terms of the contractual arrangements. Real Estate and Mortgage Notes Receivable Investments Text Block Real Estate and Mortgage Notes Receivable Investments Disclosure of real estate and mortgage notes receivable investments. Straight-line rent liability Straight line rent liabilty. Straight-line rent liability Remeasurement Gain of Equity Interest Re-measurement gain of equity interest upon acquisition Re-measurement gain of equity interest upon acquisition Remeasurement gain of equity interest upon acquisition of additional interest in joint venture. Payment of partial pension settlement Payment of partial pension settlement Payment of partial pension settlement. Payment of partial pension settlement Net proceeds repayments on unsecured credit facility Net borrowings (repayments) on unsecured credit facilities Net borrowings on unsecured credit facilities Net borrowings (repayments) on unsecured credit facilities Impairments Impairments Impairments Impairment of properties included in discontinued operations. Gain on sales of real estate properties Gain on sales of real estate properties Gain on sales of real estate properties Gain on sales of real estate properties Gain on sales of real estate properties included in discontinued operations. Bad debt, net Provision for bad debts, net Bad debt, net Provision For Doubtful Accounts Income Statement Provision for doubtful accounts on income statement. Less accumulated depreciation Less accumulated depreciation Less accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Investments in unconsolidated joint venture Investments in unconsolidated joint venture Additional paid-in capital Additional Paid in Capital, Common Stock Amortization Amortization Amortization of Deferred Charges Impairment Impairments Asset Impairment Charges Asset Impairment Charges, Total Balance Sheets [Abstract] Balance Sheets Net income (loss) attributable to common stockholders Earnings Per Share, Basic Cash and cash equivalents, end of period Cash and cash equivalents, beginning of period Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents, at Carrying Value, Total Capitalized interest Cash Paid for Capitalized Interest Interest paid Interest Paid Accounts payable and accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities, Total Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Common stock, authorized shares Common Stock, Shares Authorized Common stock, issued shares Common Stock, Shares, Issued Common Stock, Shares, Issued, Total Common stock, outstanding shares Common Stock, Shares, Outstanding Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Common stock, $.01 par value; 150,000,000 shares authorized; 64,149,158 and 60,614,931 shares issued and outstanding at September 30, 2010 and December 31, 2009, respectively Common Stock, Value, Issued Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common Stock, Value, Issued, Total Property operating Direct Costs of Leased and Rented Property or Equipment Notes and Bonds Payable Debt Disclosure [Text Block] Debt issuance costs Debt issuance costs Debt issuance and assumption costs Payments of Debt Issuance Costs Other Assets Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Text Block] Defined Benefit Pension Plans [Abstract] Construction in progress Construction in progress Development in Process Net income (loss) attributable to common stockholders Earnings Per Share, Diluted Income (loss) from discontinued operations Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax, Total Repurchase of notes payable Repurchase of notes payable Early Repayment of Senior Debt Equity in losses from unconsolidated joint ventures Stock-based compensation Share-based Compensation Share-based Compensation, Total Loss on extinguishment of debt Loss on extinguishment of debt Gains (Losses) on Extinguishment of Debt Gains (Losses) on Extinguishment of Debt, Total General and administrative General and Administrative Expense General and Administrative Expense, Total Statements of Income [Abstract] Income from continuing operations Income (Loss) from Continuing Operations, Per Diluted Share Income from continuing operations Income (Loss) from Continuing Operations, Per Basic Share Income (Loss) from Continuing Operations, Per Outstanding Share, Total INCOME (LOSS) FROM DISCONTINUED OPERATIONS Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest DISCONTINUED OPERATIONS Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Discontinued operations Discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Discontinued operations Discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share Taxable Income Income Tax Disclosure [Text Block] State income taxes paid, net of refunds Income Taxes Paid, Net Income Taxes Paid, Net, Total Other assets Increase (Decrease) in Other Operating Assets Interest expense Interest expense Interest Expense Interest Expense, Total Buildings, improvements and lease intangibles Investment Building and Building Improvements Investment Building and Building Improvements, Total Land Total liabilities Total liabilities Liabilities Liabilities: Liabilities [Abstract] Liabilities of discontinued operations Liabilities of Disposal Group, Including Discontinued Operation Liabilities of Disposal Group, Including Discontinued Operation, Total Total liabilities and equity Liabilities and Stockholders' Equity LIABILITIES AND EQUITY Liabilities and Stockholders' Equity [Abstract] Notes and bonds payable Long-term Debt Long-term Debt, Total Noncontrolling interests Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities [Abstract] Net cash provided by (used in) investing activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities [Abstract] Net cash provided by operating activities Net cash provided by operating activities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities OPERATING ACTIVITIES Net Cash Provided by (Used in) Operating Activities [Abstract] NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS Net Income (Loss) Available to Common Stockholders, Basic Increase (decrease) in cash and cash equivalents Increase in cash and cash equivalents Increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Total other income expense Total other income (expense) Nonoperating Income (Expense) OTHER INCOME (EXPENSE) Nonoperating Income (Expense) [Abstract] Notes and Bonds Payable [Abstract] Total Revenue Total Revenue Revenues REVENUES Revenues [Abstract] Other assets, net Other assets, net Other Assets Other liabilities Other Liabilities Interest and Other income, net Interest and other income, net Other Nonoperating Income Other operating Other operating Other Real Estate Revenue Quarterly dividends paid Payments of Dividends, Common Stock Preferred stock, authorized shares Preferred Stock, Shares Authorized Preferred stock, issued shares Preferred Stock, Shares Issued Preferred Stock, Shares Issued, Total Preferred stock, outstanding shares Preferred Stock, Shares Outstanding Preferred Stock, Shares Outstanding, Ending Balance Preferred Stock, Shares Outstanding, Beginning Balance Preferred stock, par value Preferred Stock, Par or Stated Value Per Share Mortgage notes receivable Mortgage Loans on Real Estate Mortgage Loans on Real Estate, Ending Balance Mortgage Loans on Real Estate, Beginning Balance Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Capital contributions received from noncontrolling interests Proceeds from Noncontrolling Interests Proceeds from sales of real estate Proceeds from Sale of Property Held-for-sale Bad debt, net Provision for bad debt, net Bad debt, net Provision for Doubtful Accounts Acquisition and development of real estate properties Acquisition and development of real estate properties Payments to Acquire and Develop Real Estate Payments to Acquire and Develop Real Estate, Total Funding of mortgages and notes receivable Payments to Acquire Notes Receivable Real Estate Properties,Total Real Estate Properties,Total Real Estate Investment Property, at Cost Total real estate properties, net Real Estate Investment Property, Net Real Estate Investment Property, Net, Total Payments For Repurchase Of Common Stock Common stock redemptions Distributions to noncontrolling interest holders Distributions to noncontrolling interest holders Distributions to noncontrolling interest holders Payments to Noncontrolling Interests Defined Benefit Pension Plans Schedule of Defined Benefit Plans Disclosures [Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Statements of Cash Flows [Abstract] Equity issuance costs Equity issuance costs Stockholders' Equity [Abstract] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Supplemental Cash Flow Information: Supplemental Cash Flow Information [Abstract] Mortgage notes payable assumed upon acquisition (adjusted to fair value) Notes Assumed Mortgage note payable disposed of upon sale of joint venture interest Notes Reduction WEIGHTED AVERAGE COMMON SHARES OUTSTANDING - DILUTED WEIGHTED AVERAGE COMMON SHARES OUTSTANDING - DILUTED Weighted Average Number of Shares Outstanding, Diluted WEIGHTED AVERAGE COMMON SHARES OUTSTANDING - BASIC WEIGHTED AVERAGE COMMON SHARES OUTSTANDING - BASIC Weighted Average Number of Shares Outstanding, Basic Total assets Assets DIVIDENDS DECLARED, PER COMMON SHARE, DURING THE PERIOD DIVIDENDS DECLARED, PER COMMON SHARE, DURING THE PERIOD Common Stock, Dividends, Per Share, Declared ASSETS Assets [Abstract] Fair Value of Financial Instruments Fair Value, by Balance Sheet Grouping [Text Block] Accumulated other comprehensive loss Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax, Beginning Balance Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax, Total Proceeds from mortgages and notes receivable repayments Proceeds from mortgages and notes receivable repayments Proceeds from Sale and Collection of Notes Receivable Depreciation Depreciation, Nonproduction Real estate properties: Real Estate Investment Property, Net [Abstract] EXPENSES Operating Expenses [Abstract] Total Expense Total Expense Operating Expenses BASIC EARNINGS (LOSS) PER COMMON SHARE: Earnings Per Share, Basic [Abstract] DILUTED EARNINGS (LOSS) PER COMMON SHARE: Earnings Per Share, Diluted [Abstract] Other liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Common stock, par value Common Stock, Par or Stated Value Per Share Total stockholders' equity Total stockholders' equity Stockholders' Equity Attributable to Parent Stockholders' Equity Attributable to Parent, Ending Balance Stockholders' Equity Attributable to Parent, Beginning Balance Preferred stock, $.01 par value; 50,000,000 shares authorized;none issued and outstanding Preferred Stock, Value, Issued Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred Stock, Value, Issued, Total Invoices accrued for construction, tenant improvement and other capitalized costs Capital Expenditures Incurred but Not yet Paid Other Assets [Abstract] NET INCOME Net income NET INCOME (LOSS) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Less: Net income attributable to noncontrolling interests Less: Net income attributable to noncontrolling interests Less: Net (income) loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest INCOME FROM CONTINUING OPERATIONS INCOME FROM CONTINUING OPERATIONS Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest Depreciation and amortization Depreciation, Depletion and Amortization Depreciation, Depletion and Amortization, Total Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance Commitments and Contingencies Adjustments to reconcile net income to cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities Accounts Payable and Accrued Liabilities, Total Amendment Flag Current Fiscal Year End Date Document Period End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Registrant Name Entity Central Index Key Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Document Type