Gross leasable area (square feet) Area of Real Estate Property Key Information for Leases Schedule of Investment Property Leases [Table Text Block] Schedule of Investment Property Leases [Table Text Block] Performance incentive plan payment Performance Incentive Plan Payment Performance Incentive Plan Payment Total other expenses (revenues) Other Nonoperating Income (Expense) 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 Amortization of notes payable discount Amortization of Debt Discount (Premium) Shares of common stock (in shares) Stock Issued During Period, Shares, Dividend Reinvestment Plan Accounting Policies [Line Items] Accounting Policies [Line Items] [Line Items] for Accounting Policies [Table] Changes in Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Lease Accounting, Lessee Lessee, Leases [Policy Text Block] Accounted for using the direct financing method Direct Financing Lease, Net Investment in Lease Debt costs Debt Issuance Costs, Gross Statistical Measurement [Domain] Statistical Measurement [Domain] LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Line of Credit Line of Credit [Member] Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block] Preferred Stock Preferred Stock [Member] Current Fiscal Year End Date Current Fiscal Year End Date 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 Earnings from operations Operating Income (Loss) Payment of debt issuance costs Payment of debt issuance costs Stock issuance costs Payments of Debt Issuance Costs Entity Address, Postal Zip Code Entity Address, Postal Zip Code Variable Rate [Domain] Variable Rate [Domain] Variable Rate [Axis] Variable Rate [Axis] Restricted shares, net of forfeitures Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures ASSETS Assets [Abstract] Less amount funded Real Estate Investment, Funding Commitments, Amount Funded Real Estate Investment, Funding Commitments, Amount Funded Accounting Policies [Abstract] Accounting Policies [Abstract] Entity Shell Company Entity Shell Company Cover [Abstract] Cover [Abstract] DRIP DRIP [Member] DRIP [Member] Document Type Document Type Accumulated deficit Retained Earnings (Accumulated Deficit) Mortgages payable, including unamortized premium and net of unamortized debt costs Secured Debt Operating lease – ROU assets Operating Lease, Right-of-Use Asset Fair value of forward starting swaps Loss deferred in other comprehensive income Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Accrued rental income Accrued Rental Income Accrued Rental Income Discount Debt Instrument, Unamortized Discount Loss on early extinguishment of debt Gain (Loss) on Extinguishment of Debt Financial Instruments, Owned, at Fair Value [Abstract] Financial Instruments, Owned, at Fair Value [Abstract] Rental income Total lease income Lease Income Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Period for improvements to construction commitments Period for Improvements to Construction Commitments Period for Improvements to Construction Commitments Number of sold properties Number Of Disposed Properties Continuing Operations Number Of Disposed Properties, Continuing Operations 5.200% Series F, 138,000 shares issued and outstanding, at stated liquidation value of $2,500 per share Preferred Stock, Value, Issued Real estate Lease, Cost Total operating expenses Operating Expenses Other comprehensive income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Document Quarterly Report Document Quarterly Report Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Payment for early extinguishment of debt Payment of make-whole premium Payment for Debt Extinguishment or Debt Prepayment Cost Other Payments for (Proceeds from) Other Investing Activities Intangible lease liabilities (included in other liabilities): Other Liabilities [Abstract] Accumulated Other Comprehensive Income (Loss) [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Depositary Shares, each representing one-hundredth of a share of 5.200% Series F Preferred Stock, $0.01 par value 5.200% Series F, 138,000 shares issued and outstanding, at stated liquidation value of $2,500 per share Series F Preferred Stock Series F Preferred Stock [Member] Accounting Policies [Table] Accounting Policies [Table] Accounting Policies [Table] 2022 Notes Notes Payable Due October 2022 [Member] Notes Payable Due October 2022 [Member] 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. Entity File Number Entity File Number Statement [Line Items] Statement [Line Items] Fair Value Deferred In Other Comprehensive Income Cash Flow Hedges Derivative Instruments at Fair Value, Net Forecast [Member] Forecast [Member] Class of Stock [Domain] Class of Stock [Domain] Basic and Diluted Earnings: Earnings Per Share, Basic and Diluted [Abstract] Accounted for using the operating method Payments to Acquire Real Estate Held-for-investment Proceeds from line of credit payable Proceeds from Long-term Lines of Credit Document Fiscal Period Focus Document Fiscal Period Focus Accrued rental income allowance Deferred Lease Income, Allowances Deferred Lease Income, Allowances Statement [Table] Statement [Table] Statistical Measurement [Axis] Statistical Measurement [Axis] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Repayment of line of credit payable Repayments of Long-term Lines of Credit ATM ATM Equity Program [Member] ATM Equity Program [Member] Principles of Consolidation Consolidation, Policy [Policy Text Block] Series E Preferred Stock Series E Preferred Stock [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] 2050 Notes Notes Payable Due April 2050 [Member] Notes Payable Due April 2050 [Member] Mortgage loan Real Estate Loan [Member] Impairment losses – real estate, net of recoveries Impairment losses – real estate, net of recoveries Impairment of Real Estate Shares of common stock (in shares) Sale of Stock, Number of Shares Issued in Transaction Line of Credit Payable Debt Disclosure [Text Block] Proceeds from issuance of common stock Net proceeds Proceeds from Issuance of Common Stock Rental Income Operating Lease, Lease Income [Table Text Block] Schedule of Common Stock Issuances Pursuant to DRIP Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Weighted average number of common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Amendment Flag Amendment Flag Line of credit payable Line of credit payable Long-term Line of Credit Amortization of interest rate hedges Reclassification to interest expense Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Schedule of Common Stock Issuances Pursuant to Equity Programs Schedule of Sale of Stock by Subsidiary or Equity Method Investee Disclosure [Table Text Block] AOCI, cash flow hedges Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Credit Losses on Financial Instruments Credit Loss, Financial Instrument [Policy Text Block] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Real Estate Commitments Real Estate Funding Commitments [Table Text Block] Real Estate Funding Commitments [Table Text Block] Proceeds from notes payable Proceeds from Issuance of Other Long-term Debt Work in progress accrual balance Capital Expenditures Incurred but Not yet Paid Subsequent Events Subsequent Events [Text Block] Local Phone Number Local Phone Number Lease Income [Abstract] Lease Income [Abstract] Lease Accounting, Lessor Lessor, Leases [Policy Text Block] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Below-market in-place leases Below Market Lease, Gross Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Axis] Interest costs capitalized Interest Costs Capitalized Property Portfolio: Real Estate Investment Property, at Cost [Abstract] Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Interest rate cash flow hedge gain (loss) to be reclassified over next 12 months, net Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Land and improvements Land and Land Improvements Aggregate notional amount Aggregate Notional Amount Derivative, Notional Amount Amortization expense, in-place leases Amortization of Intangible Assets Line of Credit Facility [Table] Line of Credit Facility [Table] Entity Current Reporting Status Entity Current Reporting Status Buildings and improvements Investment Building and Building Improvements Director compensation (in shares) Stock Issued During Period, Shares, Issued for Services Below-market in-place leases, net Below Market Lease, Net Other liabilities Other Liabilities Restricted shares, net of forfeitures (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Equity Plan Name [Domain] Equity Plan Name [Domain] Equity Plan Name [Domain] Impact of COVID-19, requested rent deferral Lessor Lease, Rent Deferral Due To Covid-19, Term Lessor Lease, Rent Deferral Due To Covid-19, Term Total assets Assets Scenario [Axis] Scenario [Axis] Land and improvements Inventory, Land Held-for-sale Leases, net Finite-Lived Intangible Assets, Net Liability Fair Value When Terminated Cash Flow Hedge Derivative Instrument Liabilities at Fair Value Subsequent Event Type [Axis] Subsequent Event Type [Axis] Equity Plan Name [Axis] Equity Plan Name [Axis] Equity Plan Name [Axis] Valuation adjustments – available-for-sale securities OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Lessor, Lease, Description [Table] Lessor, Lease, Description [Table] Entity Small Business Entity Small Business Dividends declared and paid: Dividends [Abstract] Interest expense Interest Expense Accrued interest payable Interest Payable Other Stockholders' Equity, Other Depreciation and amortization Depreciation, Depletion and Amortization Entity Filer Category Entity Filer Category Preferred stock, stated liquidation value per share (in dollars per share) Preferred Stock, Liquidation Preference Per Share 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. Real Estate Dispositions 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 held for sale Real estate held for sale Inventory, Real Estate, Held-for-sale Total liabilities Liabilities 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 Entity Address, City or Town Entity Address, City or Town Schedule of Dividends Declared and Paid Schedule of Dividends Declared and Paid [Table Text Block] Schedule of Dividends Declared and Paid [Table Text Block] Debt costs accumulated amortization Accumulated Amortization of Debt Issuance Costs, Line of Credit Arrangements Net earnings attributable to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Real Estate [Abstract] Real Estate [Abstract] States Number of States in which Entity Operates Document Fiscal Year Focus Document Fiscal Year Focus Allowance for credit loss Financing Receivable, Allowance for Credit Loss Other Increase (Decrease) in Other Operating Assets and Liabilities, Net Common stock dividends per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Debt Instrument [Axis] Debt Instrument [Axis] Capital in Excess of Par Value Additional Paid-in Capital [Member] Number of properties Real Estate Investment Funding Construction Commitments, Number Of Properties Real Estate Investment Funding Construction Commitments, Number Of Properties Debt costs accumulated amortization Accumulated Amortization, Debt Issuance Costs Other assets Other Assets Class of Stock [Line Items] Class of Stock [Line Items] Work in progress for buildings and improvements Development in Process 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] Gain on disposition of real estate Gains (Losses) on Sales of Investment Real Estate Fair Value Measurement Fair Value of Financial Instruments, Policy [Policy Text Block] Less accumulated depreciation and amortization Inventory, Real Estate, Held-For-Sale, Accumulated Depreciation Inventory, Real Estate, Held-For-Sale, Accumulated Depreciation Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding 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. Subsequent event Subsequent Event [Member] Notes Payable to Banks Notes Payable to Banks [Member] Reclassification Reclassification, Comparability Adjustment [Policy Text Block] Common stock, shares authorized (in shares) Total allowable shares (in shares) Common Stock, Shares Authorized 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] Additions to real estate: Payments to Acquire Real Estate [Abstract] Number of properties classified as held for sale Number Of Properties Classified As Held For Sale Number Of Properties Classified As Held For Sale Interest and other income from real estate transactions Interest Income, Operating Document Period End Date Document Period End Date Entity Registrant Name Entity Registrant Name Income Statement [Abstract] Income Statement [Abstract] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Amortization expense, above- and below-market leases Amortization of above and below Market Leases Use of Estimates Use of Estimates, Policy [Policy 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] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Building and improvements Inventory, Building, Held-for-sale Inventory, Building, Held-for-sale Scenario [Domain] Scenario [Domain] Collectability analysis, period used Financing Receivable, Historical Collectability Trend Analysis, Period Financing Receivable, Historical Collectability Trend Analysis, Period Entity Tax Identification Number Entity Tax Identification Number Net earnings Net earnings Net earnings Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Trading Symbol Trading Symbol Reclassifications from accumulated other comprehensive income to net earnings Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Number of properties sold Number Of Disposed Properties Number Of Disposed Properties Entity Information [Line Items] Entity Information [Line Items] Real Estate Held for Sale Disclosure of Long Lived Assets Held-for-sale [Table Text Block] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Increase (decrease) in accrued interest payable Increase (Decrease) in Interest Payable, Net Intangible lease assets (included in other assets): Intangible Assets, Net (Excluding Goodwill) [Abstract] Other comprehensive income (loss) Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Loans Payable Loans Payable [Member] Leasehold interests Tenant Improvements In-place leases Leases, Acquired-in-Place [Member] City Area Code City Area Code Realized gain – available-for-sale securities Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax 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] Equity Components [Axis] Equity Components [Axis] Title of 12(b) Security Title of 12(b) Security Debt Costs Deferred Charges, Policy [Policy Text Block] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Minimum Minimum [Member] 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. Average price per share (net) (in dollars per share) Sale of Stock, Average Price Per Share Sale of Stock, Average Price Per Share Issuance of common stock: Stock Issued During Period, New Issues [Abstract] Stock Issued During Period, New Issues [Abstract] Remaining commitment Real Estate Investment, Funding Commitments, Remaining Commitment Real Estate Investment, Funding Commitments, Remaining Commitment Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Revenues: Revenues [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Less impairment Accumulated Impairment Real Estate Held For Sale Accumulated Impairment Real Estate Held For Sale Subsequent Event Type [Domain] Subsequent Event Type [Domain] General and administrative Restricted Cash and Investments, Restricted Cash and Cash Held in Escrow, Current Restricted Cash and Investments, Restricted Cash and Cash Held in Escrow, Current Derivative [Table] Derivative [Table] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Decrease in other comprehensive income Supplemental Change In Other Comprehensive Income Supplemental change in other comprehensive income Real estate subject to operating leases, gross Real Estate Investment Property, at Cost Decrease in other liabilities Increase (Decrease) in Other Operating Liabilities Direct financing Number Of Investment Properties Leased Under Direct Financing Leases Number of Investment Properties leased under the direct financing method Other expenses (revenues): Other Nonoperating Income (Expense) [Abstract] Receivables allowance Allowance for Doubtful Accounts, Premiums and Other Receivables Payment of common stock dividends Common stock dividends Payments of Ordinary Dividends, Common Stock Effective Rate Debt Instrument, Interest Rate, Effective Percentage Assets Held-for-sale Disposal Group, Held-for-sale, Not Discontinued Operations [Member] Real estate portfolio: Investments [Abstract] Accrued rental income, net of allowance of $7,481 and $1,842, respectively Deferred Rent Receivables, Net Preferred stock dividends declared and paid Dividends, Preferred Stock, Cash Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Rental income from operating leases Operating Lease, Lease Income Adjustments for New Accounting Pronouncements [Axis] Accounting Standards Update [Axis] Preferred stock, $0.01 par value. Authorized 15,000,000 shares Preferred Stock, Including Additional Paid in Capital [Abstract] Gain on disposition of real estate Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Increase in accrued rental income Straight Line Rent ASC 842 Accounting Standards Update 2016-02 [Member] Weighted average number of shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Receivables, net of allowance of $3,085 and $506, respectively Accounts and Financing Receivable, after Allowance for Credit Loss Percent of deferred rent due by December 31, 2021 Lessor Lease, Percent Of Rent Due By Second Half Of Year Two Lessor Lease, Percent Of Rent Due By Second Half Of Year Two Common stock dividends (in dollars per share) Common stock dividends declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Principal amount Debt Instrument, Face Amount Debt costs, net of accumulated amortization of $16,356 and $15,574, respectively Debt Issuance Costs, Line of Credit Arrangements, Net Entities [Table] Entities [Table] Equity [Abstract] Equity [Abstract] Decrease (increase) in receivables Increase (Decrease) in Receivables Supplemental disclosure of noncash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Entity Central Index Key Entity Central Index Key Entity Emerging Growth Company Entity Emerging Growth Company Subsequent Event [Line Items] Subsequent Event [Line Items] Accrued rental income Deferred Rent Receivables, Gross Deferred Rent Receivables, Gross Amortization of deferred compensation Amortization Of Deferred Compensation Amortization of deferred compensation Derivative Contract [Domain] Derivative Contract [Domain] Proceeds from the disposition of real estate Proceeds from Sale of Real Estate Held-for-investment Diluted (in shares) Weighted average number of shares outstanding used in diluted earnings per share (in shares) Weighted Average Number of Shares Outstanding, Diluted Basic (in dollars per share) Earnings Per Share, Basic Weighted average remaining lease term Weighted Average Remaining Lease Term Weighted Average Remaining Lease Term Debt Disclosure [Abstract] Debt Disclosure [Abstract] Option to increase facility size Line of Credit Facility, Accordion Feature, Increase Limit Line of Credit Facility, Accordion Feature, Increase Limit Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Total properties Investment Properties Total Investment Properties Total Payment of preferred stock dividends Payments of Ordinary Dividends, Preferred Stock and Preference Stock Amortization of interest rate hedges Amortization of Deferred Hedge Gains Stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Common stock, $0.01 par value. Authorized 375,000,000 shares; 173,407,606 and 171,694,209 shares issued and outstanding, respectively Common Stock, Value, Issued Straight line rent adjustments Straight Line Rent Adjustments Disposal Group Name [Axis] Disposal Group Name [Axis] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] (Loss) earnings attributable to noncontrolling interests Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest 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] Subsequent Event [Table] Subsequent Event [Table] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Comprehensive income attributable to NNN Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Percent of deferred rent due Lessor Lease, Percent Of Rent Deferred Lessor Lease, Percent Of Rent Deferred Stock issuance costs Stock Issuance Costs Stock issuance costs Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Common stock, shares issued (in shares) Total shares issued (in shares) Common Stock, Shares, Issued Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Notes Payable [Abstract] Notes Payable [Abstract] 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] Operating lease – lease liabilities Operating Lease, Liability Director compensation Stock Issued During Period, Value, Issued for Services Notes payable redeemed Extinguishment of Debt, Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Total stockholders’ equity of NNN Stockholders' Equity Attributable to Parent Stock issuance costs Payments of Stock Issuance Costs Total liabilities and equity Liabilities and Equity Repayment of notes payable Repayments of Other Long-term Debt Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Notes payable, net of unamortized discount and unamortized debt costs Notes Payable Total  Stockholders’ Equity Parent [Member] Mortgage receivable Financing Receivable, after Allowance for Credit Loss General and administrative General and Administrative Expense Percent of rent collected for previous quarter Lessor Lease, Percent Of Rent Collected For Previous Quarter Lessor Lease, Percent Of Rent Collected For Previous Quarter Type of Adoption [Domain] Accounting Standards Update [Domain] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Real Estate Portfolio and Impairment Real Estate, Policy [Policy Text Block] Equity Component [Domain] Equity Component [Domain] Liabilities: Liabilities [Abstract] Entity Address, Address Line One Entity Address, Address Line One Percentage rent Variable Lease, Income Real Estate Real Estate Disclosure [Text Block] Net earnings attributable to NNN Net earnings attributable to NNN Net earnings attributable to NNN Net Income (Loss) Attributable to Parent Entity Address, State or Province Entity Address, State or Province Change in operating assets and liabilities, net of assets acquired and liabilities assumed: Increase (Decrease) in Operating Capital [Abstract] Noncontrolling interest distributions Payments to Noncontrolling Interests LIBOR London Interbank Offered Rate (LIBOR) [Member] Net other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Lease classification: Leases [Abstract] Initial lease term Lessor, Lease, Term Of Contract Lessor, Lease, Term Of Contract Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Operating expenses: Operating Expenses [Abstract] Aggregate purchase price Notes Payable Net Price At Issuance Notes Payable Net Price At Issuance Net earnings per share of common stock: Earnings Per Share [Abstract] Impact of COVID-19, requested rent deferral, period of payment Lessor Lease, Rent Deferral Due To Covid-19, Period Of Payment Lessor Lease, Rent Deferral Due To Covid-19, Period Of Payment Above-market in-place leases Above Market Leases [Member] Disposal Groups, Including Discontinued Operations, Name [Domain] Disposal Group Name [Domain] Leasing transaction costs Lease, Transaction Cost Lease, Transaction Cost Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Entity Interactive Data Current Entity Interactive Data Current Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Real estate subject to operating leases, net, before work in progress Real Estate Investment Property, Net, Before Development In Process Real Estate Investment Property, Net, Before Development In Process Net earnings used in basic and diluted earnings per share Net Income (Loss) Available to Common Stockholders, Diluted Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Principal payments received on mortgages and notes receivable Proceeds from Collection of Notes Receivable Redemption price, percent of principal amount Debt Instrument, Redemption Price, Percentage Stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Real estate held-for-sale Real Estate Held-for-sale Common Stock, $0.01 par value Common Stock Common Stock [Member] Property, Plant and Equipment, Type [Domain] Long-Lived Tangible Asset [Domain] Above-market and below-market in-place leases Above Market And Below Market Leases [Member] Above Market And Below Market Leases [Member] Real Estate Subject to Operating Leases Property, Plant and Equipment [Table Text Block] Dividend rate Preferred Stock, Dividend Rate, Percentage Less: accumulated amortization Below Market Lease, Accumulated Amortization Intangible Assets, Lease Liabilities, and Related Amortization Schedule of Finite-Lived Intangible Assets And Below-Market Lease Liabilities, And Future Amortization [Table Text Block] Schedule of Finite-Lived Intangible Assets And Below-Market Lease Liabilities, And Future Amortization [Table Text Block] Line of credit facility available for future borrowings Line of Credit Facility, Remaining Borrowing Capacity Asset under construction Asset under Construction [Member] Leases Finite-Lived Intangible Assets, Gross Lessor, Lease, Description [Line Items] Lessor, Lease, Description [Line Items] Less: Unvested restricted stock (in shares) Weighted Average Number of Shares, Restricted Stock Stated interest rate Debt Instrument, Interest Rate, Stated Percentage Preferred stock dividends per depositary share (in dollars per share) Preferred Stock, Dividends, Per Share, Cash Paid Net increase (decrease) in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Less: Unvested contingent restricted shares (in shares) Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares Dividends Less: preferred stock dividends Preferred stock dividends Dividends, Preferred Stock Basic (in shares) Weighted average number of shares outstanding used in basic earnings per share (in shares) Weighted Average Number of Shares Outstanding, Basic Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Subsequent Events [Abstract] Subsequent Events [Abstract] Other dilutive securities (in shares) Incremental Common Shares Attributable To Dilutive Effect, Other Incremental Common Shares Attributable To Dilutive Effect, Other Revolving credit facility weighted average interest rate Line of Credit Facility, Interest Rate During Period Interest paid, net of amount capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Notes Payable Notes Payable [Text Block] Notes Payable [Text Block] ATM equity program (in shares) Stock Issued During Period, Shares, Other Total equity Balances Balances Stockholders' equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Organization and Summary of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Right-of-use assets recorded in connection with lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Preferred stock dividends (in dollars per share) Preferred Stock, Dividends Per Share, Declared Capital in excess of par value Additional Paid in Capital Total revenues Revenues Class of Stock [Axis] Class of Stock [Axis] Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Forward Swap Forward Swap [Member] Forward Swap [Member] Diluted (in dollars per share) Earnings Per Share, Diluted Total commitment Real Estate Investment, Funding Commitments Real Estate Investment, Funding Commitments Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Amortization of mortgages payable premium Amortization of Mortgages Premium Amortization of Mortgages Premium Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Revolving credit facility weighted average outstanding balance Line of Credit Facility, Average Outstanding Amount Percent of tenants with rent deferral agreements Lessor Lease, Percent Of Tenants With Rent Deferral Agreements Lessor Lease, Percent Of Tenants With Rent Deferral Agreements Derivative [Line Items] Derivative [Line Items] Interest and other income Investment Income, Net 2030 Notes Notes Payable Due April 2030 [Member] Notes Payable Due April 2030 [Member] Increase in other assets Increase (Decrease) in Other Operating Assets Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Settlement of forward starting swaps Gain (Loss) on Sale of Derivatives Revolving credit facility borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Less: accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Repayment of mortgages payable Repayments of Secured Debt Maximum Maximum [Member] Amortization of debt costs Amortization of Debt Issuance Costs Security Exchange Name Security Exchange Name Property Subject to or Available for Operating Lease [Line Items] Property Subject to or Available for Operating Lease [Line Items] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized   Noncontrolling Interests Noncontrolling Interest [Member] Common stock dividends declared and paid Dividends, Common Stock, Cash Retained Earnings (Deficit) Retained Earnings [Member] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Percent of deferred rent due by June 30, 2021 Lessor Lease, Percent Of Rent Due By First Half Of Year Two Lessor Lease, Percent Of Rent Due By First Half Of Year Two Document Transition Report Document Transition Report Percent of rent collected for current month Lessor Lease, Percent Of Rent Collected For Current Month Lessor Lease, Percent Of Rent Collected For Current Month Basic and Diluted Weighted Average Shares Outstanding: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Mortgage receivable issued in connection with real estate transactions Notes Issued Asset Fair Value When Terminated Cash Flow Hedge Derivative Instrument Assets at Fair Value Less accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Fair value of notes payable Notes Payable, Fair Value Disclosure Earned income from direct financing leases Direct Financing Lease, Lease Income Gain on disposition of real estate Gain (Loss) on Sale of Properties Fair Value of Financial Instruments Financial Instruments Disclosure [Text Block] 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. Term of rent deferred Lessor Lease, Average Term Of Rent Deferred Lessor Lease, Average Term Of Rent Deferred Operating Number Of Investment Properties Leased Under Operating Leases Total number of Investment Properties leased under operating leases Accounted for using the operating method, net of accumulated depreciation and amortization Accounted for using the operating method, net of accumulated depreciation and amortization Real Estate Investment Property, Net ATM equity program Stock Issued During Period, Value, Other New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract]