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[Domain] Global GRAB Technologies, Inc. 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Pyrotek Special Effects, Inc. And Gladstone Alternative Pyrotek Special Effects, Inc. And Gladstone Alternative Income Fund [Member] Pyrotek Special Effects, Inc. 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Price Award Exercise Price Related Party Transaction [Axis] Related Party Transaction [Axis] Fair Value, Recurring Fair Value, Recurring [Member] Document Quarterly Report Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates [Table] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Fair value, measurement input Investment Company, Investment Owned, Measurement Input BORROWINGS Debt Disclosure [Text Block] Cost Total cost basis of investments held as of June 30, 2026: Investment Owned, Cost Gross Additions Investments in and Advances to Affiliates, at Fair Value, Gross Additions Interest payable Interest Payable Repayments of long-term debt Repayments of Long-Term Debt 5.00% 2026 Notes 5.00% Notes Due 2026 [Member] 5.00% Notes Due 2026 Base management fee Management Fee Expense Borrowings outstanding at cost Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Deferred financing costs, net Debt Issuance Costs, Net Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] FINANCIAL HIGHLIGHTS Investment Company, Financial Highlights [Text Block] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Total gain (loss) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Measurement Input Type [Domain] Measurement Input Type [Domain] Related Party Fees Related Party Fees [Policy Text Block] Related Party Fees Purchase of investments Purchase of investments Payment for Purchase, Investment, Operating Activity Ratio of net investment income to average net assets – annualized Investment Company, Investment Income (Loss) Ratio, after Incentive Allocation Greater Than 50% But Less Than or Equal to 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Actually Paid vs. Net Income [Text Block] Entity Central Index Key Weighted Average Weighted Average [Member] Total investments and cash equivalents, fair value Investment Owned And Money Market Funds, At Fair Value Investment Owned And Money Market Funds, At Fair Value All Adjustments to Compensation All Adjustments to Compensation [Member] Equity [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Net cash provided by (used in) operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation DISTRIBUTIONS Investment Company, Distribution to Shareholders [Abstract] Thereafter Principal Repayment And Maturity Of Investments, After Year Four Principal Repayment And Maturity Of Investments, After Year Four Income Statement [Abstract] ANALYSIS OF NET ASSETS Equity, Attributable to Parent [Abstract] Document Transition Report Ownership [Axis] Ownership [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Schedule of Investments [Line Items] Schedule of Investments [Line Items] 6.875% 2028 Notes 6.875% Notes Due 2028 [Member] 6.875% Notes Due 2028 Investment, Name [Axis] Investment, Name [Axis] EXPENSES Operating Expenses [Abstract] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Cumulative net unrealized appreciation Investment, Tax Basis, Unrealized Gain Credits to fees from Adviser - other Investment Company, Voluntary Fee Waived Net realized and unrealized loss Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax Total net unrealized (depreciation) appreciation Net unrealized (depreciation) appreciation of investments and other Debt and Equity Securities, Unrealized Gain (Loss) Investment company, cash distributions paid to common stockholders from capital gains Investment Company, Cash Distributions Paid To Common Stockholders From Capital Gains, Percent Investment Company, Cash Distributions Paid To Common Stockholders From Capital Gains, Percent Debt instrument, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Senior security, indebtedness, asset coverage amount Investment Company, Senior Security, Indebtedness, Asset Coverage Amount Investment Company, Senior Security, Indebtedness, Asset Coverage Amount Investment, reference rate and spread Investment, Basis Spread, Variable Rate City Area Code Variable Rate [Domain] Variable Rate [Domain] Document Information [Table] All Individuals All Individuals [Member] SUBSEQUENT EVENTS Subsequent Events [Text Block] Reversal of previously recorded (appreciation) depreciation upon realization Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Asset, Reversal Of Previously Recorded (Appreciation) Depreciation Upon 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Hobbs Co. – Atlanta, LLC (“J.R. Hobbs”) B+T, Diligent, Edge [Member] B+T, Diligent, Edge Name Forgone Recovery, Individual Name Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Cash equivalents Money Market Funds, Fair Value Disclosure Money Market Funds, Fair Value Disclosure Total net realized loss Net realized loss on investments Net realized gain (loss) Debt and Equity Securities, Realized Gain (Loss) Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Statement [Line Items] Statement [Line Items] TOTAL ASSETS Assets Net accretive effect of equity offering (in USD per share) Investment Company, Net Accretive Effective Of Equity Offering Investment Company, Net Accretive Effective Of Equity Offering Common stock, dividends, paid, ordinary (in USD per share) Common Stock, Dividends, Per Share, Paid, Ordinary Common Stock, 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Schedule of Fair Value Measurement Inputs and Valuation Techniques Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Common stock, outstanding (in shares) Common stock outstanding at end of period (in shares) Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Investment Type Concentration Risk Investment Type Concentration Risk [Member] Investment Type Concentration Risk Fair Value Measurements of Borrowings Using Significant Unobservable Inputs (Level 3) Reported in Consolidated Statements of Assets and Liabilities Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] Entity Current Reporting Status Net cash (used in) provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Control investments Control Investments Investment, Affiliated Issuer, Controlled [Member] Total Shareholder Return Amount Total Shareholder Return Amount Interest income Interest Income, Operating, Paid in Cash Investment company, distributions paid subsequent to fiscal year-end, classified in prior year, ordinary income Investment Company, Distributions Paid Subsequent to Fiscal Year-End, Classified in Prior Year, Ordinary Income Investment Company, Distributions Paid Subsequent to Fiscal Year-End, Classified in Prior Year, Ordinary Income SOFR, Thereafter Secured Overnight Financing Rate (SOFR), Thereafter [Member] Secured Overnight Financing Rate (SOFR), Thereafter Ownership [Domain] Ownership [Domain] Schedule of Distributions to Common Stockholders Schedule of Subsequent Events [Table Text Block] Net investment income, diluted (in USD per share) Investment Company, Investment Income (Loss), Per Share, Diluted CASH FLOWS FROM FINANCING ACTIVITIES Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Line of credit facility, available Availability Line of Credit Facility, Remaining Borrowing Capacity Diversified/Conglomerate Manufacturing Diversified/Conglomerate Manufacturing [Member] Diversified/Conglomerate Manufacturing Unused fee percentage Line of Credit Facility, Unused Capacity, Commitment Fee Percentage 7.125% Notes due 2031 7.125% Notes Due 2031 [Member] 7.125% Notes Due 2031 Financial Instruments [Domain] Financial Instruments [Domain] Total investment return Investment Company, Total Return, Market Value Leisure, Amusement, Motion Pictures, and Entertainment Leisure, Amusement, Motion Pictures, And Entertainment [Member] Leisure, Amusement, Motion Pictures, And Entertainment Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Underlying Securities Award Underlying Securities Amount Issuance of common stock Stock Issued During Period, Value, New Issues Cargo Transport Cargo Transport [Member] Cargo Transport (Decrease) increase in interest payable Increase (Decrease) in Interest Payable, Net Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Cost percentage Investment Owned, Percent Of Cost Basis Investment Owned, Percent Of Cost Basis Schedule of Investment Company, Financial Highlights Investment Company, Financial Highlights [Table Text Block] Cash Cash Accordion feature, increase limit Line of Credit Facility, Accordion Feature, Increase Limit Line of Credit Facility, Accordion Feature, Increase Limit Borrowings: Debt and Lease Obligation [Abstract] Principal repayments of investments Proceeds From Principal Repayments Of Investments, Operating Activity Proceeds From Principal Repayments Of Investments, Operating Activity Investment, interest rate, paid in cash Investment, Interest Rate, Paid in Cash Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Table] Number of investment portfolio company Number Of Investment Portfolio Company Number Of Investment Portfolio Company Escrow holdbacks Escrow Deposit Sale of Stock [Axis] Sale of Stock [Axis] Title of Individual [Axis] Title and Position [Axis] Investment portfolio, debt investments, intended percent Investment Portfolio, Debt Investments, Intended Percent Investment Portfolio, Debt Investments, Intended Percent Investment portfolio, equity investments, intended percent Investment Portfolio, Equity Investments, Intended Percent Investment Portfolio, Equity Investments, Intended Percent Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Current Fiscal Year End Date Shares Principal Shares Investment Owned, Balance, Shares Revolving Line of Credit Revolving Line Of Credit [Member] Revolving Line Of Credit 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Concepts Acquisition, Inc. Home Concepts Acquisition, Inc. [Member] Home Concepts Acquisition, Inc. Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Administration fee Administrative Fees Expense Unrealized appreciation (depreciation) Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Liability, Unrealized Appreciation (Depreciation) Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Liability, Unrealized Appreciation (Depreciation) Common stock, issued (in shares) Common Stock, Shares, Issued Measure: Measure [Axis] Percentage threshold of qualified assets representing total assets in order to acquire non-qualified assets Percentage Threshold of Qualified Assets Representing Total Assets In Order To Acquire Non-Qualified Assets Percentage Threshold of Qualified Assets Representing Total Assets In Order To Acquire Non-Qualified Assets Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Registration Statement on Form N-2 (File No. 333-277452) Registration Statement on Form N-2 (File No. 333-277452) [Member] Registration Statement on Form N-2 (File No. 333-277452) INVESTMENTS IN AND ADVANCES TO AFFILIATES Investments in and Advances to Affiliates, Schedule of Investments [Text Block] OPERATIONS Net Income (Loss), Including Portion Attributable to Noncontrolling Interest [Abstract] Number of industries that have made investments Number Of Industries Invested In Number Of Industries Invested In Net unrealized depreciation (appreciation) of other Unrealized Gain (Loss), Other, Accumulated Depreciation (Appreciation), Before Tax Unrealized Gain (Loss), Other, Accumulated Depreciation (Appreciation), Before Tax Related Party Related Party [Member] Class of Stock [Line Items] Class of Stock [Line Items] Allowance for uncollectible receivables Investment Company, Allowance For Uncollectible Receivables Investment Company, Allowance For Uncollectible Receivables Administrator The Administrator [Member] The Administrator Entity Interactive Data Current Long-Term Debt Long-Term Debt [Member] Variable Rate [Axis] Variable Rate [Axis] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Percentage of acquired non-qualifying assets of total assets Percentage of Acquired Non-qualifying Assets of Total Assets Percentage of Acquired Non-qualifying Assets of Total Assets Investment Owned, at Cost Investment Owned, At Cost [Member] Investment Owned, At Cost Entity Small Business Termination Date Trading Arrangement Termination Date Investment and cash equivalents, net assets, percentage Investment Owned And Money Market Funds, Net Assets, Percentage Investment Owned And Money Market Funds, Net Assets, Percentage Subsequent Events [Abstract] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Investment, Unaffiliated and Affiliated Issuer, Excluding Other Investment, Unaffiliated And Affiliated Issuer, Excluding Other [Member] Investment, Unaffiliated And Affiliated Issuer, Excluding Other Document Type O 2026 M3 Dividends O 2026 M3 Dividends [Member] O 2026 M3 Dividends Transfers Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value as of Grant Date Award Grant Date Fair Value Collateral Pledged Collateral Pledged [Member] NET ASSET VALUE PER SHARE (in USD per share) Net asset value at beginning of period (in USD per share) Net asset value at end of period (in USD per share) SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Electronics Electronics [Member] Electronics Cash and cash equivalents Cash and Cash Equivalents [Member] Arrangement Duration Trading Arrangement Duration Subsequent Event [Line Items] Subsequent Event [Line Items] Uncollectible receivables allowance, minimum required day for uncollectible adjustment Uncollectible Receivables Allowance, Minimum Required Day For Uncollectible Adjustment Uncollectible Receivables Allowance, Minimum Required Day For Uncollectible Adjustment  Proceeds from issuance of long-term debt Proceeds from Issuance of Long-Term Debt Local Phone Number Canada CANADA Distribution per common share (in USD per share) Common Stock, Dividends, Per Share, Declared, Ordinary Common Stock, Dividends, Per Share, Declared, Ordinary Entity Address, Postal Zip Code Entity Registrant Name O 2027 M1 Dividends O 2027 M1 Dividends [Member] O 2027 M1 Dividends Net unrealized depreciation (in USD per share) Investment Company, Unrealized Gain (Loss) on Investment, Per Share Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Commitments and contingencies Commitments and Contingencies Less Than or Equal to 50% of Commitment Less Than Or Equal To 50% Of Commitment [Member] Less Than Or Equal To 50% Of Commitment Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Increase in accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Net decrease in net assets from distributions Investment Company, Dividend Distribution Executive Category: Executive Category [Axis] Changes in assets and liabilities: Increase (Decrease) in Operating Liabilities [Abstract] Counterparty Name [Axis] Counterparty Name [Axis] Other Commitments [Table] Other Commitments [Table] Fees due to related party Total related party fees due Accounts Payable, Other All Award Types Award Type [Domain] Net realized loss (in USD per share) Investment Company, Realized Gain (Loss) on Investment, Per Share Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Common stock, dividends, paid, supplemental (in USD per share) Common Stock, Dividends, Per Share, Paid, Supplemental Common Stock, Dividends, Per Share, Paid, Supplemental Revenue multiple Measurement Input, Revenue Multiple [Member] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Investment company, capital gains-based incentive fees Investment Company, Capital Gains-Based Incentive Fees, Percentage Investment Company, Capital Gains-Based Incentive Fees, Percentage Preferred Equity Preferred equity Preferred Equity [Member] Preferred Equity Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities PEO Name PEO Name Geographical [Axis] Geographical [Axis] Restricted cash Restricted Cash Other, net (in USD per share) Investment Company, Net Asset Value Per Share, Other Increase (Decrease), Net Investment Company, Net Asset Value Per Share, Other Increase (Decrease), Net Fair Value Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] Greater Than 65% of Commitment Greater Than 65% Of Commitment [Member] Greater Than 65% Of Commitment Investment, Issuer Affiliation [Axis] Investment, Issuer Affiliation [Axis] Weighted-average interest rate Line of Credit Facility, Interest Rate During Period Common Stock ATM Program Common Stock ATM Program [Member] Common Stock ATM Program Debt Commitment [Axis] Debt Covenants [Axis] Debt Covenants Other assets, net Other Assets Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Cash distributions to common stockholders from net realized gains (in USD per share) Investment Company, Distribution To Shareholders From Net Realized Gains, Per Share Investment Company, Distribution To Shareholders From Net Realized Gains, Per Share B+T Group Acquisition, Inc. ("B+T"), Diligent Delivery Systems ("Diligent") and Edge Adhesives Holdings, Inc. ("Edge") B+T Group Acquisition, Inc. ("B+T"), Diligent Delivery Systems ("Diligent") and Edge Adhesives Holdings, Inc. ("Edge") [Member] B+T Group Acquisition, Inc. ("B+T"), Diligent Delivery Systems ("Diligent") and Edge Adhesives Holdings, Inc. ("Edge") (Increase) decrease in due from administrative agent Increase (Decrease) in Due from Related Parties Entity Tax Identification Number Amount of Investment Income Interest and Dividend Income, Securities, Operating West US West Region [Member] Amortization of deferred financing costs and discounts Amortization Of Deferred Financing Costs And Discounts Amortization Of Deferred Financing Costs And Discounts Liability Class [Axis] Liability Class [Axis] Number of states or countries which have invested in the company location Number Of States Or Countries Where Portfolio Company Investments Are Located Number Of States Or Countries Where Portfolio Company Investments Are Located Notes payable, net of unamortized deferred financing costs of $7,815 and $8,460, respectively Notes Payable Other Commitments [Line Items] Other Commitments [Line Items] Revenue Recognition Revenue [Policy Text Block] CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD CASH, CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD Total cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Entity Incorporation, State or Country Code Cash equivalents, net assets, percentage Money Market Funds, Net Assets, Percentage Money Market Funds, Net Assets, Percentage Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Capital loss carryforwards Investment Company, Distributable Earnings (Loss), Accumulated Capital Loss Carryforward Borrowings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Gladstone Alternative Gladstone Alternative Income Fund ("GALT") [Member] Gladstone Alternative Income Fund ("GALT") Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Accrued capital gains-based incentive fee Accrued Capital Gains-Based Incentive Fee Accrued Capital Gains-Based Incentive Fee ORGANIZATION Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Debt Instrument [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Subsequent Event [Table] Subsequent Event [Table] Revenue Measurement Input, Revenue [Member] Measurement Input, Revenue Investment portfolio, debt investments, actual percent Investment Portfolio, Debt Investments, Actual Percent Investment Portfolio, Debt Investments, Actual Percent Distributions to common stockholders from net realized gains Investment Company, Distribution, Long-Term Capital Gain Investment company, capital gains-based incentive fees reversal Investment Company, Capital Gains-Based Incentive Fees Payable Investment Company, Capital Gains-Based Incentive Fees Payable Principal Amount per Note Debt Instrument, Principal Amount Per Note Debt Instrument, Principal Amount Per Note 2029 Principal Repayment And Maturity Of Investments, Year Two Principal Repayment And Maturity Of Investments, Year Two Other less than 2.0% Other Sectors [Member] Other Sectors Schedule of Debt Schedule of Debt [Table Text Block] Customer [Domain] Customer [Domain] Investment, Name [Domain] Investment, Name [Domain] Average total assets subject to base management fee Assets under Management, Average Balance Long-Term Debt, Type [Domain] Long-Term Debt, Type [Domain] Credits to fees from Adviser - other Investment Company, Credits To Fees From Adviser, Other Investment Company, Credits To Fees From Adviser, Other Base management and loan servicing fee due to Adviser, net of credits Investment Company, Base Management And Loan Servicing Fee Due To Adviser, Net Of Credits Investment Company, Base Management And Loan Servicing Fee Due To Adviser, Net Of Credits Measurement Input Type [Axis] Measurement Input Type [Axis] Statistical Measurement [Axis] Statistical Measurement [Axis] Increase (decrease) in fee due to related party Increase (Decrease) in Due to Related Parties Insider Trading Arrangements [Line Items] Base management fee (as a percent) Management and Service Fees, Base Rate Fair value percentage Investment Owned, Percent Of Fair Value Investment Owned, Percent Of Fair Value Government Assistance [Line Items] Government Assistance [Line Items] Award Type Award Type [Axis] Deferred financing costs from line of credit Payments of Financing Costs Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Cumulative gross unrealized appreciation for federal income tax purposes Investment, Tax Basis, Unrealized Gain (Loss) Net unrealized depreciation of investments Unrealized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction Price Change, Operating, before Tax Total distributable earnings Retained Earnings (Accumulated Deficit) Sale of stock, aggregate offering price authorized Sale Of Stock, Aggregate Offering Price Authorized Sale Of Stock, Aggregate Offering Price Authorized Advisory Agreement Advisory Agreement [Member] Advisory Agreement 2028 Principal Repayment And Maturity Of Investments, Year One Principal Repayment And Maturity Of Investments, Year One Northeast US Northeast Region [Member] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Summary of Investment Holdings [Table] Investment Holdings [Table] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Common Stock, $0.001 par value per share Common Stock [Member] Total Investment Company, Financial Support to Investee Contractually Required, Not Provided, Amount Units Principal Units Investment Owned, Percentage Investment Owned, Percentage Ratio of net investment income (loss) to average net assets – annualized Investment Company, Investment Income (Loss) Ratio, before Incentive Allocation Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Securities, aggregate value authorized Sale Of Stock, Aggregate Value Of Securities Authorized Sale Of Stock, Aggregate Value Of Securities Authorized Gladstone Securities, LLC Gladstone Securities, LLC [Member] Gladstone Securities, LLC Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Percentage of total investments Percentage of Total Investments Concentration Risk, Percentage Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Oil and Gas Oil And Gas 1 [Member] Oil And Gas 1 Incentive fee Net total incentive fee Net Total Incentive Fee Net Total Incentive Fee Equity Awards Adjustments Equity Awards Adjustments [Member] O 2027 M4 Dividends O 2027 M4 Dividends [Member] O 2027 M4 Dividends Employee Stock Option Share-Based Payment Arrangement, Option [Member] Industry Sector [Domain] Industry Sector [Domain] Notes Payable Notes Payable, Other Payables [Member] Increase in other liabilities Increase (Decrease) in Other Operating Liabilities Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Asset Class [Axis] Asset Class [Axis] Investment owned, percent of net assets Investment Owned, Net Assets, Percentage Related Party [Domain] Related and Nonrelated Parties [Domain] Net increase in net assets from capital activity Investment Company, Capital Activity, Increase (Decrease) Investment Company, Capital Activity, Increase (Decrease) Tabular List, Table Tabular List [Table Text Block] Capital gains-based incentive fee Capital Gains-Based Incentive Fee Capital Gains-Based Incentive Fee Capital in excess of par value Additional Paid in Capital Schedule of Cash Distributions to Common Stockholders Investment Company, Cash Distributions Paid To Common Stockholders [Table Text Block] Investment Company, Cash Distributions Paid To Common Stockholders Incentive fee base on minimum rate of return required on investment Investment Company, Incentive Fee When Pre-Inventive Fee Net Investment Income Does Not Exceed Hurdle Rate Investment Company, Incentive Fee When Pre-Inventive Fee Net Investment Income Does Not Exceed Hurdle Rate Name Awards Close in Time to MNPI Disclosures, Individual Name Investment, Identifier [Axis] Investment, Identifier [Axis] Covenant, required minimum net worth of mandatory redeemable term preferred stock, plus percent of all equity and subordinated debt raised, minus percent of any equity or subordinated debt redeemed or retired Debt Instrument, Covenant, Net Worth Of Mandatory Redeemable Term Preferred Stock, Plus Percent Of All Equity And Subordinated Debt Raised, Minus Any Equity Or Subordinated Debt Redeemed or Retired Debt Instrument, Covenant, Net Worth Of Mandatory Redeemable Term Preferred Stock, Plus Percent Of All Equity And Subordinated Debt Raised, Minus Any Equity Or Subordinated Debt Redeemed or Retired SOFR, Tranche One Secured Overnight Financing Rate (SOFR), Tranche One [Member] Secured Overnight Financing Rate (SOFR), Tranche One Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Adjustments to reconcile net (decrease) increase in net assets resulting from operations to net cash provided by (used in) operating activities: Adjustments To Reconcile Net Assets From Operations To Cash Provided By (Used In) Operating Activities [Abstract] Adjustments To Reconcile Net Assets From Operations To Cash Provided By (Used In) Operating Activities O 2027 M2 Dividends O 2027 M2 Dividends [Member] O 2027 M2 Dividends Covenant, required minimum net worth of mandatory redeemable term preferred stock Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock Total from equity capital activity (in USD per share) Investment Company, Distribution to Shareholders, Per Share Debt instrument, measurement input Debt Instrument, Measurement Input REGISTRATION STATEMENT AND COMMON EQUITY OFFERINGS Registration Statement And Common Equity Offerings [Text Block] Registration Statement And Common Equity Offerings TEV Total Enterprise Value [Member] Total Enterprise Value Adjustment to Compensation: Adjustment to Compensation [Axis] Class of Stock [Domain] Class of Stock [Domain] Percentage of pre-incentive fee net investment income is less than the hurdle rate Investment Company, Percentage Of Pre-Incentive Fee Net Investment Income Exceeds The Hurdle Rate Investment Company, Percentage Of Pre-Incentive Fee Net Investment Income Exceeds The Hurdle Rate Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount CASH PAID FOR INTEREST Interest Paid, Excluding Capitalized Interest, Operating Activity Statement of Cash Flows [Abstract] Repayments Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales Investment company, pre-incentive fee net investment income, percent threshold of net assets Investment Company, Pre-Incentive Fee Net Investment Income, Percent Threshold Of Net Assets Investment Company, Pre-Incentive Fee Net Investment Income, Percent Threshold Of Net Assets Midwest US Midwest Region [Member] Ratio of net expenses to average net assets – annualized Investment Company, Expense Ratio after Incentive Allocation Credit Facility [Axis] Credit Facility [Axis] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Investment Valuation Policy Investment, Policy [Policy Text Block] Name Measure Name Base management fee, percent fee Management And Service Fees, Percent Of Fee Credits Against Base Management Fee Management And Service Fees, Percent Of Fee Credits Against Base Management Fee Geographic Regions Risk Geographic Regions Concentration Risk [Member] Geographic Regions Concentration Risk Government Assistance [Table] Government Assistance [Table] Pay vs Performance Disclosure [Line Items] Five Largest Portfolio Investments Five Largest Portfolio Investments [Member] Five Largest Portfolio Investments Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Buildings and Real Estate Buildings And Real Estate [Member] Buildings And Real Estate Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Entity Filer Category Net base management fee Net Base Management Fee Net Base Management Fee Investment company, capital gains-based incentive fees Investment Company, Capital Gains-Based Incentive Fees Paid To The Adviser Investment Company, Capital Gains-Based Incentive Fees Paid To The Adviser Dividends [Axis] Dividends [Axis] Interest receivable Interest Receivable Name Trading Arrangement, Individual Name Net proceeds from the sale and recapitalization of investments Proceeds From Sale And Recapitalization of Investments, Net, Operating Activity Proceeds From Sale And Recapitalization of Investments, Net, Operating Activity Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Company Selected Measure Amount Company Selected Measure Amount Investments, Debt and Equity Securities [Abstract] Unused line of credit commitments Unused lines of Credit [Member] Covenant, required minimum net worth of mandatory redeemable term preferred stock, plus percent of all equity and subordinated debt raised Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock, Plus Percent Of All Equity And Subordinated Debt Raised Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock, Plus Percent Of All Equity And Subordinated Debt Raised Change in unrealized (depreciation) appreciation attributable to investments still held Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) Entity Address, Address Line Two Stock, Class of Stock [Table] Stock, Class of Stock [Table] Net (decrease) increase in net assets from operations Net (decrease) increase in net assets resulting from operations Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Total investment income Gross Investment Income, Operating Other due to Adviser Other Due To Adviser [Member] Other Due To Adviser Non-PEO NEO Non-PEO NEO [Member] Entity Address, Address Line One Investments in and Advances to Affiliates, at Fair Value [Roll Forward] Investments in and Advances to Affiliates, at Fair Value [Roll Forward] Net realized loss on investments Realized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction Price Change, Operating, before Tax Customer Concentration Risk Customer Concentration Risk [Member] Award Timing Method Award Timing Method [Text Block] NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Portfolio turnover ratio Investment Company, Portfolio Turnover Covenant, required minimum net worth of mandatory redeemable term preferred stock, minus percent of any equity or subordinated debt redeemed or retired Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock, Minus Percent Of Any Equity Or Subordinated Debt Redeemed Or Retired Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock, Minus Percent Of Any Equity Or Subordinated Debt Redeemed Or Retired Credits to fees from Adviser - other Investment Company, Credits To Incentive Fees From Adviser, Other Investment Company, Credits To Incentive Fees From Adviser, Other Numerator: net (decrease) increase in net assets resulting from operations Net Income (Loss) Attributable to Parent Long-Term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Total Investments [Member] 2030 Principal Repayment And Maturity Of Investments, Year Three Principal Repayment And Maturity Of Investments, Year Three Statement [Table] Statement [Table] Restatement Determination Date: Restatement Determination Date [Axis] O 2027 M3 Dividends O 2027 M3 Dividends [Member] O 2027 M3 Dividends DHE Computer Systems Acquisition, Inc. DHE Computer Systems Acquisition, Inc. [Member] DHE Computer Systems Acquisition, Inc. For the remaining nine months ending March 31, 2027 Principal Repayment And Maturity Of Investments, Remainder Of Fiscal Year Principal Repayment And Maturity Of Investments, Remainder Of Fiscal Year PSI Molded PSI Molded Plastics, Inc. [Member] PSI Molded Plastics, Inc. Proceeds from issuance of common stock, net of discounts, commissions, and offering costs Proceeds (Payments) From Issuance Of Common Stock, Net Proceeds (Payments) From Issuance Of Common Stock, Net INVESTMENT INCOME Revenues [Abstract] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Financial Support to Nonconsolidated Legal Entity [Domain] Financial Support to Nonconsolidated Legal Entity [Domain]