Real Estate [Abstract] Real Estate Real Estate Disclosure [Text Block] Financial Instruments, Owned, at Fair Value [Abstract] Fair value of notes payable Notes Payable, Fair Value Disclosure Statement of Cash Flows [Abstract] Statement [Table] Statement [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Series D Depositary Share Series D Depositary Share [Member] Series D Depositary Share [Member] Series E Depositary Share Series E Depositary Share [Member] Series E Depositary Share Series F Preferred Stock Series F Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net earnings Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net earnings 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, Depletion and Amortization Impairment losses – real estate and other charges, net of recoveries Impairment Losses and Other Charges Impairment Losses and Other Charges Amortization of notes payable discount Amortization of Debt Discount (Premium) Amortization of debt costs Amortization of Debt Issuance Costs Amortization of mortgages payable premium Amortization of Mortgages Premium Amortization of Mortgages Premium Amortization of interest rate hedges Amortization of Deferred Hedge Gains Settlement of forward starting swaps Gain (Loss) on Sale of Derivatives Gain on disposition of real estate Gain (Loss) on Sale of Properties Performance incentive plan expense Performance Incentive Plan Expense The aggregate amount of noncash, equity-based and long-term incentive based employee remuneration. This may include the value of stock options, amortization of restricted stock, amortization of long term incentive compensation and adjustment for officers compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. Performance incentive plan payment Performance Incentive Plan Payment Performance Incentive Plan Payment Change in operating assets and liabilities, net of assets acquired and liabilities assumed: Increase (Decrease) in Operating Capital [Abstract] Decrease in real estate leased to others using the direct financing method Increase Decrease In Direct Financing And Sales Type Leases The net change during the reporting period consisting of: (a) minimum lease payments due on direct financing and sales-type leases, (b) unguaranteed residual value, and (c) any unamortized initial direct costs on direct financing leases; less: (i) executory costs, (ii) unearned income, and (iii) the accumulated allowance for uncollectible minimum lease payments. Decrease (increase) in receivables Increase (Decrease) in Receivables Increase in accrued rental income Straight Line Rent Increase in other assets Increase (Decrease) in Other Operating Assets Increase in accrued interest payable Increase (Decrease) in Interest Payable, Net Increase (decrease) in other liabilities Increase (Decrease) in Other Operating Liabilities Other Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash 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] Proceeds from the disposition of real estate Proceeds from Sale of Real Estate Held-for-investment Additions to real estate: Payments to Acquire Real Estate [Abstract] Accounted for using the operating method Payments to Acquire Real Estate Held-for-investment Principal payments on mortgages and notes receivable Proceeds from Collection of Notes Receivable Other Payments for (Proceeds from) Other Investing Activities Net cash 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] Proceeds from line of credit payable Proceeds from Long-term Lines of Credit Repayment of line of credit payable Repayments of Long-term Lines of Credit Repayment of mortgages payable Repayments of Secured Debt Proceeds from notes payable Proceeds from Notes Payable Payment of debt costs Payments of Debt Issuance Costs Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Stock issuance costs Payments of Stock Issuance Costs Redemption of Series D preferred stock Payments for Repurchase of Redeemable Preferred Stock Payment of Series D, E and F preferred stock dividends Payments of Ordinary Dividends, Preferred Stock and Preference Stock Payment of common stock dividends Payments of Ordinary Dividends, Common Stock Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash, cash equivalents and restricted cash Cash and Cash Equivalents, Period Increase (Decrease) Cash, cash equivalents and restricted cash at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and restricted cash at end of period Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Interest paid, net of amount capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Taxes received Income Taxes Paid, Net Supplemental disclosure of noncash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Increase (decrease) in other comprehensive income Supplemental Change In Other Comprehensive Income Supplemental change in other comprehensive income Change in lease classification (direct financing lease to operating lease) Change In Lease Classification, From Direct Financing Lease To Operating Lease Change In Lease Classification, From Direct Financing Lease To Operating Lease Change in lease classification (operating lease to direct financing lease) Change In Lease Classification, From Operating Lease To Direct Financing Lease Change In Lease Classification, From Operating Lease To Direct Financing Lease Restricted cash and cash held in escrow Restricted Cash and Investments, Restricted Cash and Cash Held in Escrow, Current Restricted Cash and Investments, Restricted Cash and Cash Held in Escrow, Current Classification of Investment Property Leases Schedule of Investment Property Leases [Table Text Block] Schedule of Investment Property Leases [Table Text Block] Summary of Real Estate Subject to Operating Leases Schedule of Property Subject to or Available for Operating Lease [Table Text Block] Disclosure of Long Lived Assets Held-for-sale Disclosure of Long Lived Assets Held-for-sale [Table Text Block] Disclosure of Long Lived Assets Held-for-sale, Gains Recognized Disclosure of Long Lived Assets Held-for-sale, Gains Recognized [Table Text Block] Disclosure of Long Lived Assets Held-for-sale, Gains Recognized [Table Text Block] Real Estate Funding Commitments Real Estate Funding Commitments [Table Text Block] Real Estate Funding Commitments [Table Text Block] Debt Disclosure [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Line of Credit Line of Credit [Member] Letter of Credit Letter of Credit [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Revolving credit facility borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Revolving credit facility weighted average outstanding balance Line of Credit Facility, Average Outstanding Amount Revolving credit facility weighted average interest rate Line of Credit Facility, Interest Rate During Period Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Option to increase facility size Line of Credit Facility, Accordion Feature, Increase Limit Line of Credit Facility, Accordion Feature, Increase Limit Line of credit payable Long-term Line of Credit Line of credit facility available for future borrowings Line of Credit Facility, Remaining Borrowing Capacity Line of credit facility, undrawn letters of credit Line of Credit Facility, Current Borrowing Capacity Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Subsequent Event [Table] Subsequent Event [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 2021 Notes Two Thousand Twenty One Notes [Member] Two Thousand Twenty One Notes [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Principal Debt Instrument, Face Amount Stated Rate Debt Instrument, Interest Rate, Stated Percentage Debt instrument, redemption price, percentage Debt Instrument, Redemption Price, Percentage Debt repayment, make whole amount Payment for Debt Extinguishment or Debt Prepayment Cost Accounting Policies [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Gains or (Losses) on Cash Flow Hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Gains on Available-for-Sale Securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Total AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Beginning balance, December 31, 2017 Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Other comprehensive income Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Reclassifications from accumulated other comprehensive income to net earnings Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Net current period other comprehensive income Other Comprehensive Income (Loss), Net of Tax Ending balance, September 30, 2018 Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] In-place leases, net Leases, Acquired-in-Place [Member] Mortgages Mortgages [Member] Notes Payable to Banks Notes Payable to Banks [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Interest costs capitalized Interest Costs Capitalized Amortization of above and below market leases Amortization of above and below Market Leases Acquired-in-place leases Amortization of Intangible Assets Debt costs Debt Issuance Costs, Gross Debt costs accumulated amortization Accumulated Amortization, Debt Issuance Costs Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Series D Preferred Stock Series D Preferred Stock [Member] Series E Preferred Stock Series E Preferred Stock [Member] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Basic and Diluted Earnings: Earnings Per Share, Basic and Diluted [Abstract] Net earnings attributable to NNN Net Income (Loss) Attributable to Parent Less: preferred stock dividends Dividends, Preferred Stock Excess of redemption value over carrying value of Series D preferred shares redeemed Preferred Stock Redemption Premium Net earnings attributable to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Less: Earnings allocated to unvested restricted shares Earnings Attributable To Unvested Restricted Shares Using the Two-Class Method Earnings attributable to unvested shares using the two-class method Net earnings used in basic and diluted earnings per share Net Income (Loss) Available to Common Stockholders, Diluted Basic and Diluted Weighted Average Shares Outstanding: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted average number of shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Less: Unvested restricted stock (in shares) Weighted Average Number of Shares, Restricted Stock Less: Unvested contingent restricted shares (in shares) Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares Weighted average number of shares outstanding used in basic earnings per share (in shares) Weighted Average Number of Shares Outstanding, Basic Other dilutive securities (in shares) Incremental Common Shares Attributable To Dilutive Effect, Other Incremental Common Shares Attributable To Dilutive Effect, Other Weighted average number of shares outstanding used in diluted earnings per share (in shares) Weighted Average Number of Shares Outstanding, Diluted Organization and Summary of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Number of properties classified as held for sale Number Of Properties Classified As Held For Sale Number Of Properties Classified As Held For Sale Number of properties sold Number of Properties Sold Number of Properties Sold Land and improvements Inventory, Land Held-for-sale Building and improvements Inventory, Building, Held-for-sale Inventory, Building, Held-for-sale Real estate held-for-sale Real Estate Held-for-sale Less accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Less impairment Accumulated Impairment Real Estate Held For Sale Accumulated Impairment Real Estate Held For Sale Real estate held for sale Inventory, Real Estate, Held-for-sale Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Groups, Including Discontinued Operations, Name [Domain] Disposal Group Name [Domain] Assets Held-for-sale Disposal Group, Held-for-sale, Not 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] Number of sold properties - gain on disposition of real estate Number Of Disposed Properties Continuing Operations Number Of Disposed Properties, Continuing Operations Gain on disposition of real estate Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Notes Payable [Abstract] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest Rate Swap Interest Rate Swap [Member] Notes Payable Due October 2028 Notes Payable Due October 2028 [Member] Notes Payable Due October 2028 [Member] Notes Payable Due October 2048 Notes Payable Due October 2048 [Member] Notes Payable Due October 2048 [Member] Purchase price Proceeds from Issuance of Debt Unamortized discount Debt Instrument, Unamortized Discount Effective interest rate Debt Instrument, Interest Rate, Effective Percentage Number of derivative financial instruments outstanding Number of Interest Rate Derivatives Held Notional amount Derivative, Notional Amount Liability amount from termination of hedge agreement Cash Flow Hedge Derivative Instrument Liabilities at Fair Value Proceeds from debt issuance, net of issuance costs Proceeds from Debt, Net of Issuance Costs Debt repayment, make whole amount Debt Instrument, Redemption Make-Whole Amount Debt Instrument, Redemption Make-Whole Amount Document And Entity Information [Abstract] Document and Entity Information [Abstract] 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 Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business 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 Property Subject to or Available for Operating Lease, by Major Property Class [Table] Property Subject to or Available for Operating Lease, by Major Property Class [Table] Major Property Class [Axis] Major Property Class [Axis] Major Property Class [Domain] Major Property Class [Domain] Land and improvements Land Improvements [Member] Buildings and improvements Building Improvements [Member] Leasehold interests Leasehold Interests Member Leasehold Interests [Member] Work in progress Construction in Progress [Member] Asset under Construction Asset under Construction [Member] Property Subject to or Available for Operating Lease [Line Items] Property Subject to or Available for Operating Lease [Line Items] Land and improvements Land Buildings and improvements Investment Building and Building Improvements Leasehold interests Leasehold Interests Aggregate carrying amounts as of the balance sheet date of investments in leasehold interests Real estate subject to operating leases, gross Real Estate Subject to Operating Leases, Gross Real Estate Subject to Operating Leases, Gross Less accumulated depreciation and amortization Property Subject to or Available for Operating Lease, Accumulated Depreciation Real estate subject to operating leases before work in process Real Estate Subject To Operating Leases Before Work In Process Real Estate Subject To Operating Leases Before Work In Process Work in progress for buildings and improvements Development in Process Accounted for using the operating method, net of accumulated depreciation and amortization Real Estate Investment Property, Net Equity [Abstract] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Line of Credit Payable Line Of Credit Facilities [Text Block] Disclosure of short-term or long-term contractual arrangements with lenders, including letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Schedule of Finite-Lived Intangible Assets by Major Class [Table] Schedule of Finite-Lived Intangible Assets [Table] Above-market in-place leases, net Above Market Leases [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Intangible lease assets (included in Other assets): Intangible Assets, Net (Including Goodwill) [Abstract] Leases Finite-Lived Intangible Assets, Gross Less: accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Leases, net Finite-Lived Intangible Assets, Net Intangible lease liabilities (included in Other liabilities): Intangible Liabilities Net Including Goodwill Abstract [Abstract] Intangible Liabilities Net Including Goodwill Abstract [Abstract] Below-market in-place leases Below Market Lease, Gross Less: accumulated amortization Below Market Lease, Accumulated Amortization Below-market in-place leases, net Below Market Lease, Net Summary of NNN's Investment Portfolio Schedule Of Investment Properties [Table Text Block] Schedule of number of Investment Property Holdings and gross leasable area and number of states located Intangible Assets and Liabilities Schedule of Finite-lived Intangible Lease Assets and Related Amortization [Table Text Block] Schedule of Finite-lived Intangible Lease Assets and Related Amortization [Table Text Block] Computation of Basic and Diluted Earnings Per Share Schedule Of Computation Of Earnings Per Share Basic And Diluted [Table Text Block] Represents the calculation of the numerator and denominator used in basic and diluted earnings per share calculation. Schedule of AOCI Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Notes Payable Notes Payable [Text Block] Notes Payable [Text Block] Number of properties Real Estate Investment Funding Construction Commitments, Number Of Properties Real Estate Investment Funding Construction Commitments, Number Of Properties Period for improvements to construction commitments Period for Improvements to Construction Commitments Period for Improvements to Construction Commitments Total commitment Real Estate Investment, Funding Commitments Real Estate Investment, Funding Commitments Less amount funded Real Estate Investment, Funding Commitments, Amount Funded Real Estate Investment, Funding Commitments, Amount Funded Remaining commitment Real Estate Investment, Funding Commitments, Remaining Commitment Real Estate Investment, Funding Commitments, Remaining Commitment Fair Value of Financial Instruments Financial Instruments Disclosure [Text Block] Property Subject to or Available for Operating Lease [Axis] Property Subject to or Available for Operating Lease [Axis] Property Subject to or Available for Operating Lease [Domain] Property Subject to or Available for Operating Lease [Domain] Operating Property Subject to Operating Lease [Member] Direct financing Property Subject To Direct Financing Member Property Subject To Direct Financing [Member] Building portion – direct financing/land portion – operating Building Portion Subject To Direct Financing Land Portion Subject To Operating Lease Member Building Portion Subject To Direct Financing Land Portion Subject To Operating Lease [Member] Property Subject to or Available for Operating Lease [Line Items] Lease classification: Leases [Abstract] Operating Number Of Investment Properties Leased Under Operating Leases Total number of Investment Properties leased under operating leases Direct financing Number Of Investment Properties Leased Under Direct Financing Leases Number of Investment Properties leased under the direct financing method Building portion – direct financing/land portion – operating Number Of Investment Properties Leased Under Direct Financing And Operating Leases Number Of Investment Properties Leased Under Direct Financing And Operating Leases. Weighted average remaining lease term (years) Weighted Average Remaining Lease Term Weighted Average Remaining Lease Term Number of renewal options, or more Number of Renewal Options Number of Renewal Options Schedule of Stock Issuance Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Schedule of ATM Program Schedule of At The Market Equity Program [Table Text Block] Schedule of At The Market Equity Program [Table Text Block] Schedule of Stock by Class Schedule of Stock by Class [Table Text Block] Schedule of Dividends Declared and Paid Schedule of Dividends Declared and Paid [Table Text Block] Schedule of Dividends Declared and Paid [Table Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Equity Plan Name [Axis] Equity Plan Name [Axis] Equity Plan Name [Axis] Equity Plan Name [Domain] Equity Plan Name [Domain] Equity Plan Name [Domain] DRIP DRIP [Member] DRIP [Member] 2018 ATM ATM Equity Program 2018 [Member] ATM Equity Program 2018 [Member] 2016 ATM ATM Equity Program 2016 [Member] ATM Equity Program 2016 [Member] ATM Equity Programs ATM Equity Program [Member] ATM Equity Program [Member] Class of Stock [Line Items] Class of Stock [Line Items] Total allowable shares (in shares) Common Stock, Shares Authorized Shares of common stock (in shares) Stock Issued During Period, Shares, Dividend Reinvestment Plan Net proceeds Total shares issued (in shares) Common Stock, Shares, Issued Shares of common stock (in shares) Stock Issued During Period, Shares, New Issues Average price per share (net) (in dollars per share) Sale of Stock, Average Stock Price Per Share Sale of Stock, Average Stock Price Per Share Net proceeds Stock Issued During Period, Value, New Issues Stock issuance costs Dividends Per depository share (in dollars per share) Preferred Stock, Dividends, Per Share, Cash Paid Common stock Dividends Common stock Per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Dividend rate Preferred Stock, Dividend Rate, Percentage Common stock, dividends, per share, declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Statement of Financial Position [Abstract] Receivables allowance Allowance for Doubtful Accounts, Premiums and Other Receivables Accrued rental income allowance Allowance Rental Income The valuation allowance as of the balance sheet date to reduce the gross amount of accrued rent receivable to estimated net realizable value, which would be presented in parentheses on the face of the balance sheet. Debt costs accumulated amortization Accumulated Amortization of Debt Issuance Costs, Line of Credit Arrangements Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, depositary shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, depositary shares outstanding (in shares) Preferred Stock, Shares Outstanding Preferred stock, stated liquidation value per share (in dollars per share) Preferred Stock, Liquidation Preference Per Share Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common stock, shares issued (in shares) Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Impairment losses – real estate and other charges, net of recoveries Impairment Losses and Other Charges, Net of Recoveries Impairment Losses and Other Charges, Net of Recoveries ASSETS Assets [Abstract] Real estate portfolio: Investments [Abstract] Accounted for using the operating method, net of accumulated depreciation and amortization Accounted for using the direct financing method Net Investment in Direct Financing and Sales Type Leases Real estate held for sale Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Receivables, net of allowance of $1,034 and $1,119, respectively Accounts and Notes Receivable, Net Accrued rental income, net of allowance of $1,842 and $1,936, respectively Deferred Rent Receivables, Net Debt costs, net of accumulated amortization of $13,734 and $12,667, respectively Debt Issuance Costs, Line of Credit Arrangements, Net Other assets Other Assets Total assets Assets LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Liabilities: Liabilities [Abstract] Line of credit payable Mortgages payable, including unamortized premium and net of unamortized debt costs Secured Debt Notes payable, net of unamortized discount and unamortized debt costs Notes Payable Accrued interest payable Interest Payable Other liabilities Other Liabilities Total liabilities Liabilities Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.01 par value. Authorized 15,000,000 shares Preferred Stock, Value, Issued Common stock, $0.01 par value. Authorized 375,000,000 shares; 158,933,104 and 153,577,028 shares issued and outstanding, respectively Common Stock, Value, Issued Capital in excess of par value Additional Paid in Capital Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity of NNN Stockholders' Equity Attributable to Parent Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Total liabilities and equity Liabilities and Equity Derivative [Table] Derivative [Table] Treasury Lock Treasury Lock [Member] Forward Swap Forward Swap [Member] Forward Swap [Member] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Derivative [Line Items] Derivative [Line Items] Number of interest rate derivatives terminated Number Of Interest Rate Derivatives Terminated Number of interest rate derivative instruments terminated by the entity during the period. Aggregate Notional Amount Liability (Asset) Fair Value When Terminated Liability (Asset) Fair Value When Terminated Cash Flow Hedge Derivative Instrument Assets at Fair Value Fair Value Deferred In Other Comprehensive Income Cash Flow Hedges Derivative Instruments at Fair Value, Net Fair value of interest rate hedges recognized in other comprehensive income Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Interest expense Interest Expense Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Principles of Consolidation Consolidation, Policy [Policy Text Block] Real Estate Portfolio Real Estate, Policy [Policy Text Block] Debt Costs Deferred Charges, Policy [Policy Text Block] Revenue Recognition Revenue Recognition, Policy [Policy Text Block] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Fair Value Measurement Fair Value of Financial Instruments, Policy [Policy Text Block] New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Reclassification Reclassification, Policy [Policy Text Block] Property Portfolio: Real Estate Investment Property, at Cost [Abstract] Total properties Investment Properties Total Investment Properties Total Gross leasable area (square feet) Area of Real Estate Property States Number of States in which Entity Operates Income Statement [Abstract] Revenues: Revenues [Abstract] Rental income from operating leases Operating Leases, Income Statement, Minimum Lease Revenue Earned income from direct financing leases Capital Leases, Income Statement, Direct Financing Lease Revenue Percentage rent Operating Leases, Income Statement, Percentage Revenue Real estate expense reimbursement from tenants Operating Lease Income Statement, Real Estate Expense Reimbursement From Tenants Operating Lease Income Statement, Real Estate Expense Reimbursement From Tenants Interest and other income from real estate transactions Interest Income, Operating Total revenues Revenues Operating expenses: Operating Expenses [Abstract] General and administrative General and Administrative Expense Real estate Direct Costs of Leased and Rented Property or Equipment Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Impairment losses – real estate and other charges, net of recoveries Impairment Losses and Other Charges, Continuing Operations Impairment Losses and Other Charges, Continuing Operations Retirement severance costs Severance Costs Total operating expenses Operating Expenses Earnings from operations Operating Income (Loss) Other expenses (revenues): Other Nonoperating Income (Expense) [Abstract] Interest and other income Investment Income, Net Total other expenses (revenues) Other Nonoperating Income (Expense) Earnings before gain on disposition of real estate Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Gain on disposition of real estate Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes Net earnings Earnings attributable to noncontrolling interests Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest Net earnings attributable to NNN Dividends Net earnings per share of common stock: Earnings Per Share [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Weighted average number of common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Diluted (in shares) Other comprehensive income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Amortization of interest rate hedges Amortization Of Interest Rate Hedges Amortization of interest rate hedges Fair value of forward starting swaps Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Net gain (loss) – available-for-sale securities Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Comprehensive income attributable to NNN Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block]