Common stock dividends paid (in USD per share) Common Stock, Dividends, Per Share, Cash Paid SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] Classification of Investments, Investment Valuation Policy, and Realized Gain or Loss and Unrealized Appreciation or Depreciation of Portfolio Investments Investment, Policy [Policy Text Block] Non-Control/Non-Affiliate investments Investment, Unaffiliated Issuer [Member] Sale of stock, weighted-average gross price per share (in USD per share) Sale of Stock, Weighted-Average Gross Price Per Share Sale of Stock, Weighted-Average Gross Price Per Share Chemicals, Plastics, and Rubber Chemicals, Plastics, and Rubber [Member] Chemicals, Plastics, and Rubber Gross receivables from portfolio companies Investment Company, Gross Receivables From Portfolio Companies Investment Company, Gross Receivables From Portfolio Companies Award Timing Predetermined Award Timing Predetermined [Flag] Related Party Transaction [Axis] Related Party Transaction [Axis] 8.00% Notes Due 2028 8.00% Notes Due 2028 [Member] 8.00% Notes Due 2028 Asset Class [Axis] Asset Class [Axis] Common Equity/ Equivalents Common equity/equivalents Common Equity/Equivalents [Member] Common Equity/Equivalents Dividend income: Dividend Income, Operating, Paid in Cash Securities Act File Number Capital in excess of par value Additional Paid-in Capital [Member] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Deferred financing costs from line of credit Payments of Financing Costs 7.875% Notes Due 2030 7.875% Notes Due 2030 [Member] 7.875% Notes Due 2030 Investment company, percentage of net capital gains distribution Investment Company, Percentage Of Net Capital Gains Distribution Investment Company, Percentage Of Net Capital Gains Distribution Tabular List, Table Tabular List [Table Text Block] Credits to base management fee – loan servicing fee Investment Company, Credits To Base Management Fee, Loan Servicing Fee Investment Company, Credits To Base Management Fee, Loan Servicing Fee Accumulated net realized gain (loss) in excess of distributions Accumulated Long-term Capital Gains [Member] Accumulated Long-term Capital Gains Borrowings: Debt and Lease Obligation [Abstract] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] 6.50% Series C Cumulative Term Preferred Stock due 2022 [Member] 6.50% Series C Cumulative Term Preferred Stock due 2022 Mandatorily redeemable preferred stock Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] Total debt Debt Securities [Member] Schedule of Principal Balances of Unused Line of Credit Schedule of Principal Balances of Unused Line of Credit And Delayed Draw Term Debt Commitments And Guaranties [Table Text Block] Schedule of Principal Balances of Unused Line of Credit And Delayed Draw Term Debt Commitments And Guaranties Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Total investment return Investment Company, Total Return, Market Value Adjustment to Compensation: Adjustment to Compensation [Axis] RELATED PARTY TRANSACTIONS Related Party Transactions Disclosure [Text Block] Government Assistance [Table] Government Assistance [Table] Schedule of Line of Credit Facilities Schedule of Line of Credit Facilities [Table Text Block] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] (Decrease) increase in accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Stock, Class of Stock [Table] Stock, Class of Stock [Table] Discount Rate Measurement Input, Discount Rate [Member] Telecommunications Telecommunications [Member] Telecommunications (Increase) decrease in interest receivable Increase (Decrease) in Accrued Interest Receivable, Net Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] South US South Region [Member] EBITDA multiple Measurement Input, EBITDA Multiple [Member] Measurement Input Type [Domain] Measurement Input Type [Domain] Adjustment to Compensation, Amount Adjustment to Compensation Amount Affiliated Entity Affiliated Entity [Member] Percentage of Total Investments Concentration Risk, Percentage Total underwriting discounts, commissions, and offering costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Decrease (increase) in other assets, net Increase (Decrease) in Other Operating Assets Net unrealized appreciation of other Unrealized Gain (Loss), Other, Accumulated Depreciation, Before Tax Unrealized Gain (Loss), Other, Accumulated Depreciation, Before Tax Consolidation Consolidation, Policy [Policy Text Block] Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Other general and administrative expenses Other General and Administrative Expense Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Net realized gain (loss): Net realized loss (gain) on investments and other Debt and Equity Securities, Realized Gain (Loss) Cash and cash equivalents Cash and Cash Equivalents [Member] Average net assets Investment Company, Average Net Assets TOTAL NET ASSETS NET ASSETS, BEGINNING OF YEAR NET ASSETS, END OF YEAR Equity, Attributable to Parent O 2025 M3 Dividends O 2025 M3 Dividends [Member] O 2025 M3 Dividends Measurement Frequency [Axis] Measurement Frequency [Axis] Distributions to common stockholders from net investment income ($0.99, $0.64, and $1.08 per share, respectively) Investment Company, Distribution, Ordinary Income Insider Trading Policies and Procedures [Line Items] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Total from investment operations (in USD per share) Investment Company, Investment Income (Loss) from Operations, Per Share Notes payable, fair value disclosure Notes Payable, Fair Value Disclosure Fair Value, Recurring Fair Value, Recurring [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Investment company, excess expense reimbursable Investment Company, Reimbursable Excess Expense Fees due to related party Accounts Payable, Other Maximum Maximum [Member] O 2025 M5 Dividends O 2025 M5 Dividends [Member] O 2025 M5 Dividends Accounting Policies [Abstract] Risks Related to Our External Financing [Member] Risks Related to Our External Financing Effect of equity capital activity Effect Of Equity Capital Activity [Abstract] Effect Of Equity Capital Activity Notes 2028 Four Point Eight Seven Five [Member] Notes 2028 Four Point Eight Seven Five O 2024 M9 Dividends O 2024 M9 Dividends [Member] O 2024 M9 Dividends Concentration Risk Type [Domain] Concentration Risk Type [Domain] Credits to base management fee – loan servicing fee Investment Company, Contractual Fee Waived Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Investment company, deemed distribution approach, notice period Investment Company, Deemed Distribution Approach, Notice Period Investment Company, Deemed Distribution Approach, Notice Period Debt Instrument [Line Items] Debt Instrument [Line Items] Investment, Identifier [Axis] Investment, Identifier [Axis] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Investments at fair value Fair Value Investments owned, fair value Beginning balance Ending balance Investment Owned, Fair Value Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Net realized (loss) gain on investments Realized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction Price Change, Operating, before Tax Control investments Investment, Affiliated Issuer, Controlled [Member] LIABILITIES Liabilities [Abstract] Investment Holdings [Table] Investment Holdings [Table] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] O 2025 M2 Dividends O 2025 M2 Dividends [Member] O 2025 M2 Dividends Entity Shell Company Schedule of Investment Concentrations Summary Investment Holdings [Table Text Block] Net Realized Gain (Loss) For Period Debt And Equity Securities, Realized Gain (Loss), Excluding Portfolio Companies No Longer In The Portfolio Debt And Equity Securities, Realized Gain (Loss), Excluding Portfolio Companies No Longer In The Portfolio Percentage of principal amount redeemed Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Weighted-average borrowings outstanding Long-Term Debt, Average Amount Outstanding Schedule of Long-Term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] 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] Statement of Stockholders' Equity [Abstract] 6.75% Series B Cumulative Term Preferred Stock [Member] 6.75% Series B Cumulative Term Preferred Stock Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Cash Cash Cash Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Unamortized deferred financing costs Less: Unamortized deferred financing costs Debt Issuance Costs, Gross Measurement Input Type [Axis] Measurement Input Type [Axis] Securities, remaining capacity of aggregate value authorized Sale of Stock, Remaining Capacity of Aggregate Value of Securities Authorized Sale of Stock, Remaining Capacity of Aggregate Value of Securities Authorized Investment, Issuer Affiliation [Axis] Investment, Issuer Affiliation [Axis] Name Measure Name Issuances / originations Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances Due from administrative agent Other Receivables Secured Debt [Member] Schedule of Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Base management fee Management Fee Expense Class of Stock [Line Items] Class of Stock [Line Items] Industry Sector [Domain] Industry Sector [Domain] Document Fiscal Period Focus Increase (decrease) due to reclassifications of permanent differences Investment Company, Tax Reclassification, Increase (Decrease) Total investments and cash equivalents, cost Investment Owned, At Cost And Money Market Funds, At Carrying Value Investment Owned, At Cost And Money Market Funds, At Carrying Value Award Timing Method Award Timing Method [Text Block] Home and Office Furnishings, Housewares, and Durable Consumer Products Home and Office Furnishings, Housewares, and Durable Consumer Products [Member] Home and Office Furnishings, Housewares, and Durable Consumer Products Net increase in net assets resulting from operations, basic (in USD per share) Basic net increase in net assets resulting from operations per weighted-average common share (in USD per share) Income (Loss) from Continuing Operations, Per Basic Share Revenue multiple Measurement Input, Revenue Multiple [Member] Other Other Investment Companies [Member] Award Type Award Type [Axis] Total borrowings Long-Term Debt TOTAL ASSETS Assets Cash equivalents, principal Money Market Funds, Principal Amount Money Market Funds, Principal Amount Investment, Name [Domain] Investment, Name [Domain] Trading Symbol Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Geographical [Domain] Geographical [Domain] Investment Portfolio Benchmark Investment Portfolio Benchmark [Member] Investment Portfolio Benchmark Federal Income Taxes Income Tax, Policy [Policy Text Block] Per Common Share Data: Investment Company, Per Share Data [Abstract] Investment Company, Per Share Data Entity Address, City or Town CASH FLOWS FROM OPERATING ACTIVITIES Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] O 2024 M8 Dividends O 2024 M8 Dividends [Member] O 2024 M8 Dividends Concentration Risk Type [Axis] Concentration Risk Type [Axis] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Statement of Income Location, Balance [Domain] Statement of Income Location, Balance [Domain] Remaining capacity of authorized offering price Sale Of Stock, Remaining Capacity Of Authorized Offering Price Sale Of Stock, Remaining Capacity Of Authorized Offering Price SOFR, Tranche Two Secured Overnight Financing Rate (SOFR), Tranche Two [Member] Secured Overnight Financing Rate (SOFR), Tranche Two Interest expense on borrowings Interest Expense, Borrowings Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Investments in and Advances to Affiliates, Activity [Line Items] Investments in and Advances to Affiliates, Activity [Line Items] Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) [Member] Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) Finance Finance [Member] Finance Entity Emerging Growth Company Entity Common Stock, Shares Outstanding Principal amount Investment Owned, Balance, Principal Amount Repayments on line of credit Repayments of Lines of Credit Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Deferred financing costs, net Debt Issuance Costs, Net Document Financial Statement Error Correction [Flag] O 2025 M6 Dividends O 2025 M6 Dividends [Member] O 2025 M6 Dividends Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Borrowings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Mining, Steel, Iron and Non-Precious Metals Mining, Steel, Iron and Non-Precious Metals Total [Member] Mining, Steel, Iron and Non-Precious Metals Total Related Party Related Party [Member] Common stock, shares, outstanding (in shares) Common stock outstanding at end of period (in shares) Common Stock, Shares, Outstanding 4.875% Notes Due 2028 4.875% Notes Due 2028 [Member] 4.875% Notes Due 2028 Distributions to common stockholders from cumulative realized gains ($0.51, $1.02, and $1.12 per share, respectively) Investment Company, Distribution, Long-Term Capital Gain Document Information [Table] PEO PEO [Member] Schedule of Investments Classified by Contractual Maturity Date Investments Classified by Contractual Maturity Date [Table Text Block] Investment company, target percentage of taxable income to distribute to shareholders (up to) Investment Company, Target Percentage Of Taxable Income To Distribute To Shareholders Investment Company, Target Percentage Of Taxable Income To Distribute To Shareholders O 2024 M11 Dividends O 2024 M11 Dividends [Member] O 2024 M11 Dividends 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] Consolidated Statement of Assets and Liabilities Data: Statement of Assets and Liabilities Data [Abstract] Statement of Assets and Liabilities Data Sale of stock, weighted-average net price per share after deducting commissions and offering costs (in USD per share) Sale Of Stock, Weighted-Average Net Price Per Share After Deducting Commissions And Offering Costs Sale Of Stock, Weighted-Average Net Price Per Share After Deducting Commissions And Offering Costs Industry Concentration Risk Industry Concentration Risk [Member] Industry Concentration Risk Diversified/Conglomerate Services Diversified/Conglomerate Services [Member] Diversified/Conglomerate Services Investment, Affiliate And Control Investment, Affiliate And Control [Member] Investment, Affiliate And Control (Overdistributed) underdistributed net investment income Retained Earnings [Member] J.R. Hobbs J.R. Hobbs [Member] J.R. Hobbs Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities O 2025 M10 Dividends O 2025 M10 Dividends [Member] O 2025 M10 Dividends Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Amount of Investment Income Interest and Dividend Income, Securities, Operating CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF YEAR CASH, CASH EQUIVALENTS AND RESTRICTED CASH, END OF YEAR Total cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income tax expense (benefit) Income Tax Expense (Benefit) Debt Covenants [Domain] Debt Covenants [Domain] Debt Covenants Credits to fees from Adviser - other Investment Company, Voluntary Fee Waived Debt instrument, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate TOTAL INCREASE IN NET ASSETS Stockholders' Equity, Period Increase (Decrease) Sale of Stock [Domain] Sale of Stock [Domain] Other assets, net Other Assets Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Investments at fair value Investments, Fair Value Disclosure Increase in interest payable Increase (Decrease) in Interest Payable, Net Document Information [Line Items] Purchase of investments Purchase of investments Payment for Purchase, Investment, Operating Activity Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Pre-incentive fee net investment income exceeds the hurdle rate Investment Company, Percent of Pre-Incentive Fee Net Investment Income That Exceeds Net Assets Threshold Investment Company, Percent of Pre-Incentive Fee Net Investment Income That Exceeds Net Assets Threshold Customer Concentration Risk Customer Concentration Risk [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Cumulative gross unrealized depreciation Investment, Tax Basis, Unrealized Loss Net increase in net assets resulting from operations, diluted (in USD per share) Diluted net increase in net assets resulting from operations per weighted-average common share (in USD per share) Income (Loss) from Continuing Operations, Per Diluted Share NET INVESTMENT (LOSS) INCOME Net Investment Income Net increase in net assets from operations Net increase in net assets resulting from operations Numerator: net increase in net assets resulting from operations Net Income (Loss), Including Portion Attributable to Noncontrolling Interest O 2026 M2 Dividends O 2026 M2 Dividends [Member] O 2026 M2 Dividends Net investment income (loss) (in USD per share) Cash distributions to common stockholders from net investment income (in USD per share) Investment Company, Distribution to Shareholders from Net Investment Income, Per Share Investment Company, Distribution to Shareholders from Net Investment Income, Per Share Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Risks Related to Our Investments [Member] Risks Related to Our Investments 2030 Principal Repayment And Maturity Of Investments, Year Four Principal Repayment And Maturity Of Investments, Year Four Notes Payable Notes Payable, Other Payables [Member] Net decrease in net assets from distributions Investment Company, Dividend Distribution Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Distribution paid subsequent to fiscal year-end, classified in prior year, capital gains Investment Company, Distribution Paid Subsequent to Fiscal Year-End, Classified in Prior Year, Capital Gains Investment Company, Distribution Paid Subsequent to Fiscal Year-End, Classified in Prior Year, Capital Gains City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Unused line of credit commitments Unused lines of Credit [Member] INVESTMENTS Investment [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Investment, interest rate, paid in cash Investment, Interest Rate, Paid in Cash Undistributed capital (loss) gain Investment Company, Distributable Earnings (Loss), Accumulated Long-Term Capital Gain (Loss) O 2024 M6 Dividends O 2024 M6 Dividends [Member] O 2024 M6 Dividends Debt instrument, variable rate floor Debt Instrument, Variable Rate Floor Debt Instrument, Variable Rate Floor Commitments and Contingencies Disclosure [Abstract] Pyrotek Special Effects, Inc. And Gladstone Alternative Pyrotek Special Effects, Inc. And Gladstone Alternative Income Fund [Member] Pyrotek Special Effects, Inc. And Gladstone Alternative Income Fund REALIZED AND UNREALIZED GAIN (LOSS) Net Realized Gains (Losses) [Abstract] Net Realized Gains (Losses) Deferred Financing and Offering Costs Financing Receivable, Fee and Interest Income [Policy Text Block] Adviser The Adviser [Member] The Adviser Total expenses, net of credits to fees Investment Company, Expense, after Reduction of Fee Waiver and Reimbursement Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash (used in) provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Maximum base management fee paid cannot exceed a percentage of total assets Management and Service Fees, Maximum As A Percentage Of Total Assets Management and Service Fees, Maximum As A Percentage Of Total Assets Interest receivable Interest Receivable Total incentive fee Incentive Fee Expense Related Party Transactions [Abstract] Investments in and Advances to Affiliates, at Fair Value [Roll Forward] Investments in and Advances to Affiliates, at Fair Value [Roll Forward] Risks Related to Our Regulation and Structure [Member] Risks Related to Our Regulation and Structure Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Subsequent Event Subsequent Event [Member] O 2024 M5 Dividends O 2024 M5 Dividends [Member] O 2024 M5 Dividends Incentive fee – income-based Incentive Fee Expense, Income-Based Other liabilities Other Liabilities Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Long-Term Debt, Type [Axis] Long-Term Debt, Type [Axis] O 2026 M1 Dividends O 2026 M1 Dividends [Member] O 2026 M1 Dividends Schedule of Investments [Abstract] General Risk Factors [Member] General Risk Factors Equity Components [Axis] Equity Components [Axis] Secured First Lien Debt Secured first lien debt Debt Securities, Secured First Lien Debt [Member] Debt Securities, Secured First Lien Debt Net investment (loss) income, diluted (in USD per share) Investment Company, Investment Income (Loss), Per Share, Diluted Base management and loan servicing fee due to Adviser, net of credits Base Management Fee And Loan Servicing Fee Due To Adviser [Member] Base Management Fee And Loan Servicing Fee Due To Adviser Auditor Name Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Investment company, cash distributions paid to common stockholders from ordinary income Investment Company, Cash Distributions Paid To Common Stockholders From Ordinary Income, Percent Investment Company, Cash Distributions Paid To Common Stockholders From Ordinary Income, Percent Notes Outstanding Number Of Notes Outstanding Number Of Notes Outstanding Number of reportable segments Number of Reportable Segments Schedule of Investment Company, Financial Highlights Investment Company, Financial Highlights [Table Text Block] Secured Second Lien Debt Secured second lien debt Debt Securities, Secured Second Lien Debt [Member] Debt Securities, Secured Second Lien Debt Net loan servicing fee Net Loan Servicing Fee Net Loan Servicing Fee Other Performance Measure, Amount Other Performance Measure, Amount Schedule of Restricted Cash Restrictions on Cash and Cash Equivalents [Table Text Block] Entity Address, State or Province Cash distributions to common stockholders Dividends, Common Stock Based on a tax cost Investment, Tax Basis, Cost Cumulative unrealized appreciation of investments Cumulative Unrealized Appreciation Of Investments Cumulative Unrealized Appreciation Of Investments UNCONSOLIDATED SIGNIFICANT SUBSIDIARIES Unconsolidated Significant Subsidiaries [Text Block] Unconsolidated Significant Subsidiaries Related Party [Domain] Related and Nonrelated Parties [Domain] Secured Overnight Financing Rate (SOFR), Adjustment Secured Overnight Financing Rate (SOFR), Adjustment [Member] Secured Overnight Financing Rate (SOFR), Adjustment Affiliate investments Investment, Affiliated Issuer, Noncontrolled [Member] Investment Company, Net Assets [Roll Forward] Investment Company, Net Assets [Roll Forward] O 2026 M8 Dividends O 2026 M8 Dividends [Member] O 2026 M8 Dividends Individual: Individual [Axis] Total contractual repayments Principal Repayment And Maturity Of Investments Principal Repayment And Maturity Of Investments, Restricted cash Restricted cash Restricted Cash O 2024 M10 Dividends O 2024 M10 Dividends [Member] O 2024 M10 Dividends Distributions paid to common stockholders Payments of Ordinary Dividends, Common Stock Document Annual Report 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] CASH PAID FOR INTEREST Interest Paid, Excluding Capitalized Interest, Operating Activity Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Distributions Investment Company, Distribution [Policy Text Block] Entity Interactive Data Current Ratio of net expenses to average net assets Investment Company, Expense Ratio after Incentive Allocation 5.00% Notes Due 2026 5.00% Notes Due 2026 [Member] 5.00% Notes Due 2026 Investment company, percentage of ordinary income distribution Investment Company, Percentage Of Ordinary Income Distribution Investment Company, Percentage Of Ordinary Income Distribution Capital loss carryforwards Investment Company, Distributable Earnings (Loss), Accumulated Capital Loss Carryforward Equity [Abstract] Common Stock ATM Program 2024 Common Stock ATM Program 2024 [Member] Common Stock ATM Program 2024 Related Party Fees Related Party Fees [Policy Text Block] Related Party Fees Greater than 50% but Less than or Equal to 65% of Commitment Greater Than 50% But Less Than Or Equal To 65% Of Commitment [Member] Greater Than 50% But Less Than Or Equal To 65% Of Commitment West US West Region [Member] Cost Total cost basis of investments held as of March 31, 2026: Investment Owned, Cost 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] Investment portfolio, equity investments, actual percent Investment Portfolio, Equity Investments, Actual Percent Investment Portfolio, Equity Investments, Actual Percent Other Commitments [Line Items] Other Commitments [Line Items] O 2024 M7 Dividends O 2024 M7 Dividends [Member] O 2024 M7 Dividends Ownership [Domain] Ownership [Domain] New investments, repayments and settlements: Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Weighted Average Weighted Average [Member] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Risks Related to an Investment in Our Securities [Member] Risks Related to an Investment in Our Securities 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) Customer [Domain] Customer [Domain] Entity Central Index Key PEO Name PEO Name Notes 2026 Five Point Zero [Member] Notes 2026 Five Point Zero Consideration received on transaction Sale of Stock, Consideration Received on Transaction Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Senior Securities Data: Senior Securities Data [Abstract] Senior Securities Data Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Schedule of Components Of Our Net Assets On A Tax Basis Schedule of Stockholders Equity [Table Text Block] Credit Facility Revolving Credit Facility [Member] Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Midwest US Midwest Region [Member] Debt and Equity Securities, Unrealized Gain (Loss) Debt and Equity Securities, Unrealized Gain (Loss) [Member] Debt and Equity Securities, Unrealized Gain (Loss) Arrangement Duration Trading Arrangement Duration Number of states which have invested in the company location Number Of States Where Portfolio Company Investments Are Located Number Of States Where Portfolio Company Investments Are Located Investment Company, Changes in Net Assets [Table] Investment Company, Change in Net Assets [Table] 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 Exercise Price Award Exercise Price Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Entity Filer Category Local Phone Number Class of Stock [Domain] Class of Stock [Domain] Debt and Equity Securities, Realized Gain (Loss) Debt and Equity Securities, Realized Gain (Loss) [Member] Debt and Equity Securities, Realized Gain (Loss) Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] ASSETS Assets [Abstract] 6.875% Notes Due 2028 6.875% Notes Due 2028 [Member] 6.875% Notes Due 2028 Credit Facility [Axis] Credit Facility [Axis] Gross Additions Investments in and Advances to Affiliates, at Fair Value, Gross Additions Underlying Security Market Price Change Underlying Security Market Price Change, Percent Debt Instrument [Axis] O 2026 M9 Dividends O 2026 M9 Dividends [Member] O 2026 M9 Dividends Loss on extinguishment of debt Gain (Loss) on Extinguishment of Debt Credit Facility [Domain] Credit Facility [Domain] Net unrealized appreciation (depreciation): Net unrealized (appreciation) depreciation of investments and other Debt and Equity Securities, Unrealized Gain (Loss) ANALYSIS OF NET ASSETS Equity, Attributable to Parent [Abstract] 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 Schedule of Investments in and Advances to Affiliates Schedule of Investments in and Advances to Affiliates, Schedule of Investments [Table Text Block] 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] Senior security, indebtedness, asset coverage amount Investment Company, Senior Security, Indebtedness, Asset Coverage Amount Investment Company, Senior Security, Indebtedness, Asset Coverage Amount Investment owned, percent of net assets Investment Owned, Net Assets, Percentage Entity Address, Address Line One Edge Adhesives Holdings, Inc., J.R. Hobbs Co. and The Mountain B+T, Diligent, Edge and J.R. Hobbs Co. – Atlanta, LLC (“J.R. Hobbs”) [Member] B+T, Diligent, Edge and J.R. Hobbs Co. – Atlanta, LLC (“J.R. Hobbs”) Entity Address, Address Line Two Interest Rate Debt Instrument, Interest Rate, Stated Percentage Investment, Name [Axis] Investment, Name [Axis] Cumulative net unrealized appreciation Investment, Tax Basis, Unrealized Gain Investments [Domain] Investments [Domain] Entity Voluntary Filers 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 Realization Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Asset, Reversal Of Previously Recorded (Appreciation) Depreciation Upon Realization Base management fee (as a percent) Management and Service Fees, Base Rate Ownership [Axis] Ownership [Axis] Cash equivalents Money Market Funds, Fair Value Disclosure Money Market Funds, Fair Value Disclosure Industry Sector [Axis] Industry Sector [Axis] Investment Company [Abstract] FINANCIAL HIGHLIGHTS Investment Company, Financial Highlights [Text Block] Fair Value as of Grant Date Award Grant Date Fair Value Investments in equity securities Equity Securities, FV-NI, Cost Entity Registrant Name Common stock, dividends, paid, ordinary (in USD per share) Common Stock, Dividends, Per Share, Paid, Ordinary Common Stock, Dividends, Per Share, Paid, Ordinary Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Incentive fee due to Adviser Incentive Fee Due To Adviser [Member] Incentive Fee Due To Adviser EBITDA Measurement Input, EBITDA [Member] Measurement Input, EBITDA O 2025 M4 Dividends O 2025 M4 Dividends [Member] O 2025 M4 Dividends Common Stock ATM Program 2022 Common Stock ATM Program 2022 [Member] Common Stock ATM Program 2022 Fair Value Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Old World Christmas, Inc. Old World Christmas, Inc. [Member] Old World Christmas, Inc. Healthcare, Education, and Childcare Healthcare, Education, and Childcare [Member] Healthcare, Education, and Childcare Title and Position [Domain] Title and Position [Domain] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Aerospace and Defense Aerospace and Defense [Member] Aerospace and Defense Discounts, commissions, and offering costs for issuance of common stock Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Gross Reductions Investments in and Advances to Affiliates, at Fair Value, Gross Reductions CAPITAL ACTIVITY Investment Company, Capital Share Transaction, Increase (Decrease) [Abstract] Schedule of Fair Value Measurement Inputs and Valuation Techniques Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Counterparty Name [Domain] Counterparty Name [Domain] O 2024 M2 Dividends O 2024 M2 Dividends [Member] O 2024 M2 Dividends Investment Owned, At Fair Value Investment Owned, At Fair Value [Member] Investment Owned, At Fair Value Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Schedule of Debt Schedule of Debt [Table Text Block] OPERATIONS Net Income (Loss), Including Portion Attributable to Noncontrolling Interest [Abstract] Investment Type [Axis] Investment Type [Axis] Yield Analysis Yield Analysis [Member] Yield Analysis Related Party [Axis] Related and Nonrelated Parties [Axis] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Printing and Publishing Printing and Publishing [Member] Printing and Publishing DISTRIBUTIONS Investment Company, Distribution to Shareholders [Abstract] Restatement Determination Date: Restatement Determination Date [Axis] O 2026 M5 Dividends O 2026 M5 Dividends [Member] O 2026 M5 Dividends Non-PEO NEO Non-PEO NEO [Member] Line of credit at cost Borrowings outstanding at cost Letters of Credit Outstanding, Amount Net realized and unrealized gain Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, after Tax Success fee income: Fee Income Investment Company, Changes in Net Assets [Line Items] Investment Company, Change in Net Assets [Line Items] Investment Type Concentration Risk Investment Type Concentration Risk [Member] Investment Type Concentration Risk Sale of Stock [Axis] Sale of Stock [Axis] Name Trading Arrangement, Individual Name Total Investment Company, Financial Support to Investee Contractually Required, Not Provided, Amount All Award Types Award Type [Domain] Investments in and Advances to Affiliates [Abstract] Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Undistributed 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 Canada CANADA Compensation Amount Outstanding Recovery Compensation Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Schedule of Investments [Line Items] Schedule of Investments [Line Items] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Diversified/Conglomerate Manufacturing Diversified/Conglomerate Manufacturing [Member] Diversified/Conglomerate Manufacturing Investment, Issuer Affiliation [Domain] Investment, Issuer Affiliation [Domain] Name Awards Close in Time to MNPI Disclosures, Individual Name O 2026 M6 Dividends O 2026 M6 Dividends [Member] O 2026 M6 Dividends 7.125% Notes Due 2031 7.125% Notes Due 2031 [Member] 7.125% Notes Due 2031 Escrow holdbacks Escrow Deposit Thereafter Principal Repayment And Maturity Of Investments, After Year Five Principal Repayment And Maturity Of Investments, After Year Five WEIGHTED-AVERAGE SHARES OF COMMON STOCK OUTSTANDING: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Risks Related to the 5.00% 2026 Notes, 4.875% 2028 Notes and 8.00% 2028 Notes (collectively, the "Notes") [Member] Risks Related to the 5.00% 2026 Notes, 4.875% 2028 Notes and 8.00% 2028 Notes (collectively, the "Notes") ICFR Auditor Attestation Flag INVESTMENT INCOME Revenues [Abstract] Documents Incorporated by Reference Leisure, Amusement, Motion Pictures, and Entertainment Leisure, Amusement, Motion Pictures, and Entertainment [Member] Leisure, Amusement, Motion Pictures, and Entertainment Horizon Facilities Services, Inc. Horizon Facilities Services, Inc. [Member] Horizon Facilities Services, Inc. Cargo Transport Cargo Transport [Member] Cargo Transport Financial Instruments [Domain] Financial Instruments [Domain] Liability Class [Axis] Liability Class [Axis] Cost percentage Investment Owned, Percent of Cost Basis Investment Owned, Percent of Cost Basis Auditor Firm ID Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Line of credit facility, available Availability Line of Credit Facility, Remaining Borrowing Capacity Net Unrealized Appreciation (Depreciation) Investments in and Advances to Affiliates, at Fair Value, Period Increase (Decrease) Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Taxes on deemed distributions of long-term capital gains (in USD per share) Investment Company, Taxes On Deemed Distributions Of Long-Term Capital Gains Per Common Share Investment Company, Taxes On Deemed Distributions Of Long-Term Capital Gains Per Common Share Net unrealized appreciation (depreciation) of investments Unrealized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction Price Change, Operating, before Tax Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Ratios/Supplemental Data: Investment Company, Financial Ratios [Abstract] Principal repayments of investments Proceeds from Principal Repayments Of Investments, Operating Activity Proceeds from Principal Repayments Of Investments, Operating Activity Government Assistance [Line Items] Government Assistance [Line Items] Amortization of deferred financing costs and discounts Amortization of Debt Issuance Costs and Discounts Number of investment portfolio company Number Of Investment Portfolio Company Number Of Investment Portfolio Company Minimum Minimum [Member] Investment portfolio, debt investments, intended percent Investment Portfolio, Debt Investments, Intended Percent Investment Portfolio, Debt Investments, Intended Percent Net unrealized appreciation (depreciation) of investments and other (in USD per share) Investment Company, Unrealized Gain (Loss) on Investment, Per Share Repayment of notes payable Repayments of Notes Payable Investment portfolio, equity investments, intended percent Investment Portfolio, Equity Investments, Intended Percent Investment Portfolio, Equity Investments, Intended Percent Company Selected Measure Name Company Selected Measure Name Revenue Recognition Revenue [Policy Text Block] Ratio of expenses to average net assets - annualized Investment Company, Expense Ratio before Incentive Allocation BORROWINGS Debt Disclosure [Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates [Table] Portfolio turnover ratio Investment Company, Portfolio Turnover Revolving Line of Credit Revolving Line of Credit [Member] Revolving Line of Credit Interest payable Interest Payable Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] All Executive Categories All Executive Categories [Member] Collateral Held [Domain] Collateral Held [Domain] Common stock, $0.001 par value per share, 100,000,000 shares authorized; 39,821,967 and 36,837,381 shares issued and outstanding, respectively Common stock Common Stock, Value, Issued Cumulative unrealized depreciation of other Investment Company, Distributable Earnings (Loss), Accumulated Depreciation, Other Investment Company, Distributable Earnings (Loss), Accumulated Depreciation, Other COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Title and Position [Axis] Title and Position [Axis] Diluted (in shares) Diluted weighted-average common shares (in shares) Weighted-average shares of common stock outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Segment Reporting Segment Reporting, Policy [Policy Text Block] Commitments and contingencies Commitments and Contingencies Changes in assets and liabilities: Increase (Decrease) in Operating Liabilities [Abstract] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Indebtedness asset coverage on our senior securities Investment Company, Senior Security, Indebtedness, Asset Coverage Ratio 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) Fair Value Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] 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 O 2024 M4 Dividends O 2024 M4 Dividends [Member] O 2024 M4 Dividends 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) Entity Small Business SFEG Holdings, Inc SFEG Holdings, Inc [Member] SFEG Holdings, Inc Fair value, measurement input Investment Company, Investment Owned, Measurement Input Ratio of net investment (loss) income to average net assets Investment Company, Investment Income (Loss) Ratio, after Incentive Allocation Commitment (unused) fees incurred Line of Credit Facility, Commitment Fee Amount Document Transition Report Summary of Investment Holdings [Line Items] Summary of Investment Holdings [Line Items] Number of industries that have made investments Number Of Industries Invested In Number Of Industries Invested In Long-Term Debt Long-Term Debt [Member] Allowance for uncollectible receivables Investment Company, Allowance For Uncollectible Receivables Investment Company, Allowance For Uncollectible Receivables Administrator The Administrator [Member] The Administrator Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Bad debt expense, net of recoveries Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery Document Period End Date O 2025 M9 Dividends O 2025 M9 Dividends [Member] O 2025 M9 Dividends Risks Related to Our External Management [Member] Risks Related to Our External Management PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount O 2026 M4 Dividends O 2026 M4 Dividends [Member] O 2026 M4 Dividends 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 O 2026 M12 Dividends O 2026 M12 Dividends [Member] O 2026 M12 Dividends Investment Owned, At Cost Investment Owned, At Cost [Member] Investment Owned, At Cost FEDERAL AND STATE INCOME TAXES Income Tax Disclosure [Text Block] Incentive fee - capital gains-based Incentive Fee Expense, Capital-Gain-Based Proceeds from line of credit Proceeds from Lines of Credit 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 Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Schedule of Investments [Table] Schedule of Investments [Table] Investment, Unaffiliated and Affiliated Issuer, Excluding Other Investment, Unaffiliated and Affiliated Issuer, Excluding Other [Member] Investment, Unaffiliated and Affiliated Issuer, Excluding Other O 2026 M3 Dividends O 2026 M3 Dividends [Member] O 2026 M3 Dividends Document Type Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] NET INCREASE (DECREASE) IN NET ASSETS RESULTING FROM OPERATIONS PER WEIGHTED-AVERAGE COMMON SHARE Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Capital in excess of par value Capital in excess of par value Additional Paid in Capital Excise tax Investment Company, Excise Tax Investment Company, Excise Tax Proceeds from issuance of common stock, net of discounts, commissions and offering costs Proceeds from Issuance of Common Stock Notes payable, net of unamortized deferred financing costs of $8,460 and $8,029, respectively Notes Payable Transfers Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net All Individuals All Individuals [Member] Electronics Electronics [Member] Electronics Long-Term Debt, Type [Domain] Long-Term Debt, Type [Domain] 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  Name Forgone Recovery, Individual Name Total from equity capital activity (in USD per share) Investment Company, Distribution to Shareholders, Per Share Net accretive (dilutive) effect of equity offering (in USD per share) Net Accretive (Dilutive) Effect of Equity Offering Per Share Net Accretive (Dilutive) Effect of Equity Offering Per Share Cumulative gross unrealized appreciation for federal income tax purposes Investment, Tax Basis, Unrealized Gain (Loss) Risks Related to Interest Rates [Member] Risks Related to Interest Rates Statistical Measurement [Axis] Statistical Measurement [Axis] 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] Distribution per common share (in USD per share) Common Stock, Dividends, Per Share, Declared, Ordinary Common Stock, Dividends, Per Share, Declared, Ordinary O 2027 M1 Dividends O 2027 M1 Dividends [Member] O 2027 M1 Dividends Unused fee percentage Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Co-investment expense Other Receivables, Net, Current 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 Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Net realized loss on other Realized Gain (Loss), Other, Operating, Before Tax Realized Gain (Loss), Other, Operating, Before Tax Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Proceeds from issuance of notes payable, net of deferred offering costs Proceeds from Notes Payable Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] B+T Group Acquisition, Inc., Edge Adhesives Holdings Inc., And J.R. Hobbs Co B+T Group Acquisition, Inc., Edge Adhesives Holdings Inc., And J.R. Hobbs Co [Member] B+T Group Acquisition, Inc., Edge Adhesives Holdings Inc., And J.R. Hobbs Co Geographical [Axis] Geographical [Axis] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Discounts, commissions, and offering costs par share (in USD per share) Investment Company, Discounts, Commissions, And Offering Costs, Per Share Investment Company, Discounts, Commissions, And Offering Costs, Per Share Common stock, dividends, paid, supplemental (in USD per share) Common Stock, Dividends, Per Share, Paid, Supplemental Common Stock, Dividends, Per Share, Paid, Supplemental Schedule of Distributions to Common Stockholders Schedule of Subsequent Events [Table Text Block] O 2026 M7 Dividends O 2026 M7 Dividends [Member] O 2026 M7 Dividends Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Line of credit at fair value (Cost of $23,900 and $0, respectively) Long-Term Line of Credit 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 Related Party Transaction [Table] Related Party Transaction [Table] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Title of 12(b) Security 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 Greater Than 65% Of Commitment Greater Than 65% Of Commitment [Member] Greater Than 65% Of Commitment O 2024 M1 Dividends O 2024 M1 Dividends [Member] O 2024 M1 Dividends Debt Covenants [Axis] Debt Covenants [Axis] Debt Covenants Sale of stock, number of shares sold (in shares) Sale of Stock, Number of Shares Issued in Transaction Dividends [Axis] Dividends [Axis] O 2025 M7 Dividends O 2025 M7 Dividends [Member] O 2025 M7 Dividends Amortization of deferred financing costs and discounts Amortization Of Deferred Financing Costs And Discounts Amortization Of Deferred Financing Costs And Discounts Net investment (loss) income Investment Income, Operating, after Expense and Tax BASIC AND DILUTED PER COMMON SHARE: Earnings Per Share [Abstract] Noncontrolling interest, ownership percentage by parent Subsidiary, Ownership Percentage, Parent O 2025 M11 Dividends O 2025 M11 Dividends [Member] O 2025 M11 Dividends Investments, Debt and Equity Securities [Abstract] Auditor Location Average total assets subject to base management fee Assets under Management, Average Balance Ratio of net expenses to average net assets Investment Company, Ratio of Net Expenses to Average Net Assets Investment Company, Ratio of Net Expenses to Average Net Assets Government Assistance [Abstract] Audit Information [Abstract] Audit Information Cash equivalents, net assets, percentage Money Market Funds, Net Assets, Percentage Money Market Funds, Net Assets, Percentage Ratio of net investment income (loss) to average net assets – annualized Ratio of net investment (loss) income to average net assets – annualized Investment Company, Investment Income (Loss) Ratio, before Incentive Allocation 6.25% Series D Cumulative Term Preferred Stock due 2023 [Member] 6.25% Series D Cumulative Term Preferred Stock due 2023 Gladstone Alternative Income Fund ("GALT") Gladstone Alternative Income Fund ("GALT") [Member] Gladstone Alternative Income Fund ("GALT") Interest income: Interest Income, Operating, Paid in Cash The Mountain The Mountain [Member] The Mountain 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 Investment company, capital gains-based incentive fees payable (reversal) Investment Company, Capital Gains-based Incentive Fees Payable Investment Company, Capital Gains-based Incentive Fees Payable Administration fee Administrative Fees Expense Credit Facility Lines of Credit, Fair Value Disclosure Multiplied by annual base management fee of 2.0% Management and Service Fees, Rate Principal Amount per Note Debt Instrument, Principal Amount Per Note Debt Instrument, Principal Amount Per Note 2028 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 Cash equivalents Cash equivalents Money Market Funds, at Carrying Value O 2026 M11 Dividends O 2026 M11 Dividends [Member] O 2026 M11 Dividends Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] 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 Award Timing Disclosures [Line Items] Total borrowings, at cost Aggregate Principal Amount Long-Term Debt, Gross Fair value percentage Investment Owned, Percent of Fair Value Investment Owned, Percent of Fair Value Entity Well-known Seasoned Issuer Measurement Frequency [Domain] Measurement Frequency [Domain] 6.375% Series E Cumulative Term Preferred Stock due 2025 [Member] 6.375% Series E Cumulative Term Preferred Stock due 2025 (Loss) income from investment operations Investment Company, Investment Income (Loss) from Operations, Per Share [Abstract] Investment, reference rate and spread Investment, Basis Spread, Variable Rate DISTRIBUTIONS TO COMMON STOCKHOLDERS Equity [Text Block] Sale of stock, aggregate offering price authorized Sale of Stock, Aggregate Offering Price Authorized Sale of Stock, Aggregate Offering Price Authorized Adjusted availability Line of Credit Facility, Current Borrowing Capacity Advisory Agreement Advisory Agreement [Member] Advisory Agreement 2027 Principal Repayment And Maturity Of Investments, Year One Principal Repayment And Maturity Of Investments, Year One Shares Principal Shares Investment Owned, Balance, Shares NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS Net Income (Loss) Attributable to Parent Subsequent Event [Table] Subsequent Event [Table] Dividends [Domain] Dividends [Domain] Distribution paid subsequent to fiscal year-end, classified in prior year, capital loss Investment Company, Distribution Paid Subsequent to Fiscal Year-End, Classified in Prior Year, Capital Loss Investment Company, Distribution Paid Subsequent to Fiscal Year-End, Classified in Prior Year, Capital Loss Expiration Date Trading Arrangement Expiration Date Net investment (loss) income, basic (in USD per share) Investment Company, Investment Income (Loss), Per Share, Basic Increase in other liabilities Increase (Decrease) in Other Operating Liabilities Units Principal Units Investment Owned, Percentage Investment Owned, Percentage Total Investments [Member] Securities, aggregate value authorized Sale of Stock, Aggregate Value of Securities Authorized Sale of Stock, Aggregate Value of Securities Authorized Adoption Date Trading Arrangement Adoption Date O 2024 M12 Dividends O 2024 M12 Dividends [Member] O 2024 M12 Dividends O 2025 M1 Dividends O 2025 M1 Dividends [Member] O 2025 M1 Dividends Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Gladstone Securities, LLC Gladstone Securities, LLC [Member] Gladstone Securities, LLC Entity Current Reporting Status 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 Customer [Axis] Customer [Axis] Investment interest rate Investment Interest Rate Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] O 2026 M10 Dividends O 2026 M10 Dividends [Member] O 2026 M10 Dividends Collateral Held [Axis] Collateral Held [Axis] Line of Credit Line of Credit [Member] Total distributable earnings Retained Earnings (Accumulated Deficit) Gain (loss) on investment (in USD per share) Cash distributions to common stockholders from net realized gains (in USD per share) Investment Company, Distribution To Shareholders From Realized Gains, Per Share Investment Company, Distribution To Shareholders From Realized Gains, Per Share Financial Instrument [Axis] Financial Instrument [Axis] INVESTMENTS IN AND ADVANCES TO AFFILIATES Investments in and Advances to Affiliates, Schedule of Investments [Text Block] Statement of Financial Position [Abstract] 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] Executive Category: Executive Category [Axis] Net increase in net assets from capital activity Investment Company, Capital Activity, Increase (Decrease) Investment Company, Capital Activity, Increase (Decrease) Capital gains-based incentive fee Capital Gains-based Incentive Fee Capital Gains-based Incentive Fee Proceeds from issuance of long-term debt Proceeds from Issuance of Long-Term Debt 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] 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 Current Fiscal Year End Date Class of Stock [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Increase (decrease) in fees due to related party Increase (Decrease) in Due to Related Parties 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 Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] 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 Loan servicing fee Loan Processing Fee Professional fees Professional Fees Statement [Table] Statement [Table] CASH FLOWS FROM FINANCING ACTIVITIES Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Board of Directors Chairman Board of Directors Chairman [Member] Adjustments to reconcile net increase in net assets resulting from operations to net cash (used in) provided by 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 Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] 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 REGISTRATION STATEMENT AND COMMON EQUITY OFFERINGS Registration Statement And Common Equity Offerings [Text Block] Registration Statement And Common Equity Offerings Variable Rate [Domain] Variable Rate [Domain] Total Enterprise Value Total Enterprise Value [Member] Total Enterprise Value ORGANIZATION Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Schedule of Changes in Level 3 Fair Value Measurements of Investments Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] All Adjustments to Compensation All Adjustments to Compensation [Member] 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 Amendment Flag Collateral Pledged Collateral Pledged [Member] 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 Other Commitments [Table] Other Commitments [Table] Termination Date Trading Arrangement Termination Date Net cash provided by (used in) financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation 2031 Principal Repayment And Maturity Of Investments, Year Five Principal Repayment And Maturity Of Investments, Year Five Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Net realized (loss) gain on investments and other (in USD per share) Investment Company, Realized Gain (Loss) on Investment, Per Share 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 NET ASSETS Net assets at end of year Net Assets Geographic Regions Risk Geographic Regions Concentration Risk [Member] Geographic Regions Concentration Risk Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Risks Related to the Economy [Member] Risks Related to the Economy Five Largest Portfolio Investments Five Largest Portfolio Investments [Member] Five Largest Portfolio Investments Schedule of Investments by Security Type at Fair Value and Investments Valued Using Level 3 Inputs Fair Value, Assets Measured on Recurring Basis [Table Text Block] Decrease in due from administrative agent Increase (Decrease) in Due from Related Parties Basic (in shares) Basic weighted-average common shares (in shares) Weighted-average shares of common stock outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Investment Company, Financial Highlights [Roll Forward] Investment Company, Financial Highlights [Roll Forward] Buildings and Real Estate Buildings and Real Estate [Member] Buildings and Real Estate Schedule of Computation of Basic and Diluted Net Increase in Net Assets Resulting from Operations Per Weighted-Average Common Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Related Party Transaction [Domain] Related Party Transaction [Domain] Net base management fee Net Base Management Fee Net Base Management Fee Subsequent Events [Abstract] 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 Schedule of Investment Company, Changes in Net Assets Investment Company, Change in Net Assets [Table Text Block] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Debt Disclosure [Abstract] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Expenses before credits from Adviser Investment Income, Investment Expense Entity Tax Identification Number Investment owned, percent of voting securities Investment Owned, Percent of Voting Securities Investment Owned, Percent of Voting Securities O 2025 M8 Dividends O 2025 M8 Dividends [Member] O 2025 M8 Dividends 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 Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Common stock, par value (in USD per share) Common Stock, Par or Stated Value Per Share Common stock, shares, issued (In shares) Common Stock, Shares, Issued 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 O 2024 M3 Dividends O 2024 M3 Dividends [Member] O 2024 M3 Dividends Realized gain on equity Equity Securities, FV-NI, Realized Gain (Loss) Other temporary differences Investment Company, Distributable Earnings (Loss), Accumulated Other Temporary Differences Investment Company, Distributable Earnings (Loss), Accumulated Other Temporary Differences Other due to Adviser Other Due To Adviser [Member] Other Due To Adviser Use of Estimates Use of Estimates, Policy [Policy Text Block] Settlements / repayments Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Entity Public Float Trading Arrangement: Trading Arrangement [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Northeast US Northeast Region [Member] Debt instrument, measurement input Debt Instrument, Measurement Input SUBSEQUENT EVENT Subsequent Events [Text Block] Insider Trading Arrangements [Line Items] Security Exchange Name Total equity/equivalents Equity Securities [Member] TOTAL LIABILITIES Liabilities 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 O 2025 M12 Dividends O 2025 M12 Dividends [Member] O 2025 M12 Dividends Commitment amount Line of Credit Facility, Maximum Borrowing Capacity Credits to fees from Adviser - other Investment Company, Credits To Incentive Fees From Adviser, Other Investment Company, Credits To Incentive Fees From Adviser, Other Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Per common share market value at beginning of period (in USD per share) Per common share market value at end of period (in USD per share) Investment Company, Market Value, Per Share 2029 Principal Repayment And Maturity Of Investments, Year Three Principal Repayment And Maturity Of Investments, Year Three EXPENSES Operating Expenses [Abstract] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Asset Class [Domain] Asset Class [Domain] O 2027 M3 Dividends O 2027 M3 Dividends [Member] O 2027 M3 Dividends Effective interest rate Line of Credit Facility, Interest Rate During Period Total gain (loss) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Issuance of common stock Stock Issued During Period, Value, New Issues Statement [Line Items] Statement [Line Items] Variable Rate [Axis] Variable Rate [Axis] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] PSI Molded Plastics, Inc PSI Molded Plastics, Inc [Member] PSI Molded Plastics, Inc Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Counterparty Name [Axis] Counterparty Name [Axis] Subsequent Event [Line Items] Subsequent Event [Line Items] Total investment income Gross Investment Income, Operating Common Stock, $0.001 par value per share Common Stock [Member] Entity Incorporation, State or Country Code 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 Non-NEOs Non-NEOs [Member] NET (DECREASE) INCREASE 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