Interest rate, stated (as a percent) Investment Interest Rate, Stated Investment Interest Rate, Stated Percentage of portfolio investments containing limited consultation with financial advisory services firm (as a percent) Investment Company, Portfolio Investments, Limited Consultation With Financial Advisory Services Firm, Percentage Investment Company, Portfolio Investments, Limited Consultation With Financial Advisory Services Firm, Percentage Portfolio Investment Classification and Valuation of the Investment Portfolio Investment, Policy [Policy Text Block] Non‑Control/Non‑Affiliate investments Investment, Unaffiliated Issuer [Member] Deferred Compensation Plan Postemployment Benefit Plans, Policy [Policy Text Block] Award Timing Predetermined Award Timing Predetermined [Flag] Number of portfolio investments in entities Investment Company, Number Of Portfolio Investments, Entities Investment Company, Number Of Portfolio Investments, Entities Securities Act File Number Additional Paid-In Capital Additional Paid-in Capital [Member] Tabular List, Table Tabular List [Table Text Block] Freeport Financial Funds Freeport Financial Funds [Member] Freeport Financial Funds State and other Investment Income, Operating, Deferred State And Other Tax Expense (Benefit) Investment Income, Operating, Deferred State And Other Tax Expense (Benefit) Recently Issued or Adopted Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] SOFR Secured Overnight Financing Rate (SOFR) [Member] Share repurchase program, expired amount Share Repurchase Program, Remaining Authorized, Expired Amount Share Repurchase Program, Remaining Authorized, Expired Amount Debt Debt investments Debt Securities [Member] 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] Interest and dividend receivable and other assets Increase (Decrease) In Interest And Dividend Receivable And Other Assets Increase (Decrease) In Interest And Dividend Receivable And Other Assets Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] ZRG Partners, LLC ZRG Partners, LLC [Member] ZRG Partners, LLC Investment Company, Nonconsolidated Subsidiary [Axis] Investment Company, Nonconsolidated Subsidiary [Axis] Issuance of restricted stock, net of forfeited shares (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Adjustment to Compensation, Amount Adjustment to Compensation Amount O 2026 Q1 Regular Dividends O 2026 Q1 Regular Dividends [Member] O 2026 Q1 Regular Dividends Concentration risk (as a percent) Concentration Risk, Percentage Unamortized Debt Issuance Costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Federal Investment Income, Operating, Deferred Federal Tax Expense (Benefit) Investment Income, Operating, Deferred Federal Tax Expense (Benefit) Principles of Consolidation Consolidation, Policy [Policy Text Block] Share-based compensation expense Share-Based Payment Arrangement, Noncash Expense Employee Stock Option Share-Based Payment Arrangement, Option [Member] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Total net realized gain (loss) Net realized (gain) loss Amount of Realized Gain/(Loss) Debt and Equity Securities, Realized Gain (Loss) Machinery Machinery [Member] Machinery Taxes paid Income Taxes Paid Total net assets Balance as of beginning of period Balance as of ending of period Equity NAV as of the end of the period Equity, Attributable to Parent Measurement Frequency [Axis] Measurement Frequency [Axis] Insider Trading Policies and Procedures [Line Items] Accretive effect of DRIP issuance (issuing shares above NAV per share) (in dollars per share) Investment Company, Effect Of Dividend Reinvestment Plan, Per Share Investment Company, Effect Of Dividend Reinvestment Plan, Per Share Career Team Holdings, LLC Career Team Holdings, LLC [Member] Career Team Holdings, LLC Common stock, shares authorized (in shares) Common Stock, Shares Authorized Income tax provision Investment Company, Tax Basis, Income Tax Provision Investment Company, Tax Basis, Income Tax Provision Public offering of common stock, net of offering costs (in shares) Stock Issued During Period, Shares, New Issues Fair Value, Recurring Fair Value, Recurring [Member] OMi Topco, LLC OMi Topco, LLC [Member] OMi Topco, LLC LIABILITIES and NET ASSETS Liabilities and Equity [Abstract] First lien debt Debt Securities, First Lien [Member] Debt Securities, First Lien Unfunded commitments Accounts Payable, Other Cash and cash equivalents, Fair Value Cash and Cash Equivalents, Fair Value Disclosure Maximum Maximum [Member] AVEX Aviation Holdings, LLC AVEX Aviation Holdings, LLC [Member] AVEX Aviation Holdings, LLC Specialty Retail Specialty Retail [Member] Specialty Retail JorVet Holdings, LLC JorVet Holdings, LLC [Member] JorVet Holdings, LLC Restricted Stock Restricted Stock [Member] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Rabbi Trust Rabbi Trust [Member] Rabbi Trust Annualized total return on investments (as a percent) Investment Company, Annualized Total Return Investment Company, Annualized Total Return Schedule of Summarized Restricted Stock Awards Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block] Investment, Identifier [Axis] Investment, Identifier [Axis] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Investments at fair value: Fair value Total Level 3 investments 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 Control investments Investment, Affiliated Issuer, Controlled [Member] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Net income before taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Southeast US Southeast Region [Member] Schedule of Investment Holdings Summary Investment Holdings [Table Text Block] Weighted-average borrowings outstanding Average outstanding debt Long-Term Debt, Average Amount Outstanding Southwest US Southwest Region [Member] Accounts payable and other liabilities Accounts payable and other liabilities to affiliates Accounts Payable and Other Accrued Liabilities Schedule of Long-Term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] SPV Facility SPV Facility [Member] SPV Facility Statement of Stockholders' Equity [Abstract] CompareNetworks Topco, LLC CompareNetworks Topco, LLC [Member] CompareNetworks Topco, LLC Variable Rate Component One Variable Rate Component One [Member] Variable Rate Component One Unsecured Revolving Promissory Note Unsecured Revolving Promissory Note [Member] Unsecured Revolving Promissory Note Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Line of Credit Facility [Table] Line of Credit Facility [Table] Interest Interest Interest Expense, Operating Debt Instrument, interest rate, yield-to-worst Debt Instrument, Interest Rate, Yield-To-Worst Debt Instrument, Interest Rate, Yield-To-Worst Contractual obligation, number of additional investments, investment period expired with remaining commitments restricted for fund expenses Investment Company, Number Of Additional Investments, Investment Period Expired With Remaining Commitments Restricted For Fund Expenses Investment Company, Number Of Additional Investments, Investment Period Expired With Remaining Commitments Restricted For Fund Expenses Joerns Healthcare, LLC Joerns Healthcare, LLC [Member] Joerns Healthcare, LLC 2015 Deferred Compensation Plan The 2015 Deferred Compensation Plan [Member] The 2015 Deferred Compensation Plan Accounts receivable from MSCC and its subsidiaries Other Receivables Management fee to MSCC Management Fee Expense Federal Investment Income, Operating, Federal Tax Expense (Benefit), Current Investment Income, Operating, Federal Tax Expense (Benefit), Current Document Fiscal Period Focus Investment company, number of portfolio companies with annual third-party appraisal was obtained, reviewed and certified Investment Company, Number Of Portfolio Companies With Annual Third-Party Appraisal Was Obtained, Reviewed and Certified Investment Company, Number Of Portfolio Companies With Annual Third-Party Appraisal Was Obtained, Reviewed and Certified Award Timing Method Award Timing Method [Text Block] Award Type [Axis] Award Type [Axis] Share-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Trading Symbol Aggregate intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested Entity Address, City or Town Insight Borrower Corporation Insight Borrower Corporation [Member] Insight Borrower Corporation ITA Holdings Group, LLC ITA Holdings Group, LLC [Member] ITA Holdings Group, LLC Federal and state income and other tax expenses Investment Company, Federal And State Income And Other Tax Expense Investment Company, Federal And State Income And Other Tax Expense GS HVAM Intermediate, LLC GS HVAM Intermediate, LLC [Member] GS HVAM Intermediate, LLC Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Expected principal recovery percentage Measurement Input, Expected Principal Recovery Percentage [Member] Measurement Input, Expected Principal Recovery Percentage Cybermedia Technologies, LLC Cybermedia Technologies, LLC [Member] Cybermedia Technologies, LLC December 2025 Series A Notes December 2025 Series A Notes [Member] December 2025 Series A Notes Other (in dollars per share) Investment Company, Other, Per Share Investment Company, Other, Per Share Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Total income tax provision Investment Company, Income Tax Expense (Benefit) Investment Company, Income Tax Expense (Benefit) Entity Emerging Growth Company Repayments on Credit Facilities 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] Investment Company, Nonconsolidated Subsidiary [Line Items] Investment Company, Nonconsolidated Subsidiary [Line Items] NET REALIZED GAIN (LOSS): Net Realized Gains (Losses) [Abstract] Net Realized Gains (Losses) Deferred financing costs (net of accumulated amortization of $18,351 and $17,601 as of March 31, 2026 and December 31, 2025, respectively) Deferred financing costs (net of accumulated amortization of $3,684 and $3,314 as of March 31, 2026 and December 31, 2025, respectively) Debt Issuance Costs, Net Risk adjusted discount rate Measurement Input, Risk Adjusted Discount Rate [Member] Measurement Input, Risk Adjusted Discount Rate Doral Holdings, LLC Doral Holdings, LLC [Member] Doral Holdings, LLC Common stock, shares outstanding (in shares) Balance as of beginning of period (in shares) Balance as of ending of period (in shares) Common Stock, Shares, Outstanding SI East, LLC SI East, LLC [Member] SI East, LLC Other Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Other Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Other CoreStack, Inc. CoreStack, Inc. [Member] CoreStack, Inc. MoneyThumb Acquisition, LLC MoneyThumb Acquisition, LLC [Member] MoneyThumb Acquisition, LLC Net realized gain (loss) (in dollars per share) Investment Company, Net Realized Gain (Loss) On Investment, Per Share Investment Company, Net Realized Gain (Loss) On Investment, Per Share 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] Number of Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Interest rate (as a percent) Debt Instrument, Interest Rate, Effective Percentage Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Tax expense Income Tax Expense (Benefit) Estimated taxable income Investment Company, Tax Basis, Net Income (Loss) Attributable To Parent, Estimated Investment Company, Tax Basis, Net Income (Loss) Attributable To Parent, Estimated Debt instrument, basis spread on variable rate (as a percent) Debt Instrument, Basis Spread on Variable Rate Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Health Care Providers & Services Health Care Providers & Services [Member] Health Care Providers & Services Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Boccella Precast Products LLC Connect Telecommunications Solutions Holdings, Inc. [Member] Connect Telecommunications Solutions Holdings, Inc. O 2026 M1 Dividends O 2026 M1 Dividends [Member] O 2026 M1 Dividends Equity Offering Costs Stockholders' Equity, Policy [Policy Text Block] Secured Revolving Promissory Note Secured Revolving Promissory Note [Member] Secured Revolving Promissory Note NuStep, LLC NuStep, LLC [Member] NuStep, LLC Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Schedule of Summarized Dividend Reinvestment Plan Information Schedule of Summarized Dividend Reinvestment Plan Information [Table Text Block] Schedule of Summarized Dividend Reinvestment Plan Information DTE Enterprises, LLC DTE Enterprises, LLC [Member] DTE Enterprises, LLC 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] Nonvested beginning balance (in shares) Nonvested ending balance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Commitments and Contingencies Disclosure [Abstract] Middle Market portfolio investments Middle Market Portfolio [Member] Middle Market Portfolio Waiver of incentive fees Investment Company, Expense, after Reduction of Fee Waiver and Reimbursement Student Resource Center, LLC Student Resource Center, LLC [Member] Student Resource Center, LLC Net cash used in operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation O 2025 Q1 Regular Dividends O 2025 Q1 Regular Dividends [Member] O 2025 Q1 Regular Dividends Book income and tax income differences, including debt origination, structuring fees, dividends, realized gains and changes in estimates Investment Company, Tax Basis, Book Income and Tax Income Differences, Increase (Decrease) In Taxable Income Investment Company, Tax Basis, Book Income and Tax Income Differences, Increase (Decrease) In Taxable Income Debt instrument, term (in years) Debt Instrument, Term Investments in and Advances to Affiliates, at Fair Value [Roll Forward] Investments in and Advances to Affiliates, at Fair Value [Roll Forward] Subsequent Event Subsequent Event [Member] Management fee income Management Service, Base [Member] 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] Money Market Funds Money Market Funds [Member] Datacom, LLC Datacom, LLC [Member] Datacom, LLC PIK Rate Investment, Interest Rate, Paid in Kind Schedule of Investments [Abstract] Schedule of Investments [Abstract] Amount of debt outstanding Related Party Transaction, Amount of Debt Outstanding Related Party Transaction, Amount of Debt Outstanding Equity Components [Axis] Equity Components [Axis] Containers & Packaging Containers & Packaging [Member] Containers & Packaging Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Brewer Crane Holdings, LLC Brewer Crane Holdings, LLC [Member] Brewer Crane Holdings, LLC Number of reportable segments Number of Reportable Segments Dividends paid Payments of Ordinary Dividends Electrical Equipment Electrical Equipment [Member] Electrical Equipment Margin Effective Period Two Margin Effective Period Two [Member] Margin Effective Period Two Entity Address, State or Province Food & Staples Retailing Food & Staples Retailing [Member] Food & Staples Retailing December 2025 Notes December 2025 Notes [Member] December 2025 Notes Dividends to stockholders Dividends, Common Stock Affiliate investments Investment, Affiliated Issuer, Noncontrolled [Member] Individual: Individual [Axis] Total dividends Payments of Ordinary Dividends, Common Stock Trantech Radiator Topco, LLC VVS Holdco, LLC [Member] VVS Holdco, LLC Internet & Catalog Retail Internet & Catalog Retail [Member] Internet & Catalog Retail June 2027 Notes June 2027 Notes [Member] June 2027 Notes Current tax expense: Investment Tax Expense (Income), Current [Abstract] Investment Tax Expense (Income), Current BDB Holdings, LLC BDB Holdings, LLC [Member] BDB Holdings, LLC HEADLANDS OP-CO LLC HEADLANDS OP-CO LLC [Member] HEADLANDS OP-CO LLC Hotels, Restaurants & Leisure Hotels, Restaurants & Leisure [Member] Hotels, Restaurants & Leisure Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Entity Interactive Data Current U.S. TelePacific Corp. U.S. TelePacific Corp. [Member] U.S. TelePacific Corp. Condensed Income Statement [Table] Condensed Income Statement [Table] Taxable income earned in prior year and carried forward for distribution in current year Investment Company, Tax Basis, Taxable Income Earned in Prior Year and Carried Forward for Distribution in Current Year Investment Company, Tax Basis Reconciliation, Taxable Income Earned in Prior Year and Carried Forward for Distribution in Current Year Third-party quote Measurement Input, Third-Party Quote [Member] Measurement Input, Third-Party Quote Channel Partners Intermediateco, LLC Channel Partners Intermediateco, LLC [Member] Channel Partners Intermediateco, LLC Jensen Jewelers of Idaho, LLC Jensen Jewelers of Idaho, LLC [Member] Jensen Jewelers of Idaho, LLC Schedule of Restricted Stock Issued Disclosure of Share-Based Compensation Arrangements by Share-Based Payment Award [Table Text Block] Investment, cost Cost Investment Owned, Cost DMA Industries, LLC Gulf Manufacturing, LLC [Member] Gulf Manufacturing, LLC Sale of stock, shares not yet settled (in shares) Sale Of Stock, Shares Not Yet Settled Sale Of Stock, Shares Not Yet Settled CenterPeak Holdings, LLC CenterPeak Holdings, LLC [Member] CenterPeak Holdings, LLC MSMF Main Street Mezzanine Fund, LP [Member] Main Street Mezzanine Fund, LP Airo Purchaser, Inc. Airo Purchaser, Inc. [Member] Airo Purchaser, Inc. Roof Opco, LLC Roof Opco, LLC [Member] Roof Opco, LLC NET ASSET VALUE PER SHARE (in dollars per share) NAV as of the beginning of the period (in dollars per share) NAV as of the end of the period (in dollars per share) Entity Central Index Key Ziegler’s NYPD, LLC Ziegler’s NYPD, LLC [Member] Ziegler’s NYPD, LLC PEO Name PEO Name Total revenues before waivers Revenues 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] Shares outstanding as of the end of the period (in shares) Investment Company, Common Stock, Shares Outstanding Investment Company, Common Stock, Shares Outstanding Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Variable Rate Component [Domain] Variable Rate Component [Domain] Variable Rate Component [Domain] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount MSC Income Fund, Inc. MSC Income Fund, Inc. [Member] MSC Income Fund, Inc. Midwest US Midwest Region [Member] Specialized Aviation Holdings, LLC Specialized Aviation Holdings, LLC [Member] Specialized Aviation Holdings, LLC Exercise Price Award Exercise Price PPL RVs, Inc. Robbins Bros. Jewelry, Inc. [Member] Robbins Bros. Jewelry, Inc. Entity Filer Category LKCM Headwater Investments LKCM Headwater Investments [Member] LKCM Headwater Investments Share-based payment arrangement, nonvested award, excluding option, cost not yet recognized, amount Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Subsequent Event Type [Axis] Subsequent Event Type [Axis] O 2026 Q2 Including Supplemental Dividends O 2026 Q2 Including Supplemental Dividends [Member] O 2026 Q2 Including Supplemental Dividends Accretion of unearned income Accretion of Unearned Income Accretion of Unearned Income Schedule of Investments in and Advances to Affiliates, Schedule of Investments 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] Brainworks Software, LLC Brainworks Software, LLC [Member] Brainworks Software, LLC Entity Address, Address Line One Entity Address, Address Line Two Bridge Capital Solutions Corporation Bridge Capital Solutions Corporation [Member] Bridge Capital Solutions Corporation Shares withheld for payroll taxes paid (in shares) Share-Based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Investments [Domain] Investments [Domain] Mills Fleet Farm Group, LLC Mills Fleet Farm Group, LLC [Member] Mills Fleet Farm Group, LLC Share purchase program, period in force Share Purchase Program, Period in Force Share Purchase Program, Period in Force Value of shares issued pursuant to the dividend reinvestment plan Stock Issued Incentive fee payable, capital-gain-based Incentive Fee Payable, Capital-Gain-Based Management and service fees (as a percent) Management and Service Fees, Base Rate Annual revenues Investments, Annual Revenues Per Company Investments, Annual Revenues Per Company Industry Sector [Axis] Industry Sector [Axis] Interest rate (as a percent) Investment, Index Based Floating Interest Rate Investment, Index Based Floating Interest Rate Direct Marketing Solutions, Inc. Direct Marketing Solutions, Inc. [Member] Direct Marketing Solutions, Inc. Digital Products Holdings LLC Digital Products Holdings LLC [Member] Digital Products Holdings LLC Fair Value as of Grant Date Award Grant Date Fair Value JTI Electrical & Mechanical, LLC JTI Electrical & Mechanical, LLC [Member] JTI Electrical & Mechanical, LLC Debt instrument, issuance price (as a percent) Debt Instrument, Issuance Price, Percentage Debt Instrument, Issuance Price, Percentage August 2028 Notes August 2028 Notes [Member] August 2028 Notes Salaries, share-based compensation and other personnel costs Labor and Related Expense Less net restricted stock granted (in shares) Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Title of Individual [Domain] Title and Position [Domain] Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Related Party Transaction [Line Items] Related Party Transaction [Line Items] Document Quarterly Report Gross Reductions Investments in and Advances to Affiliates, at Fair Value, Gross Reductions 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] Federal Realized Gain (Loss), Investment And Derivative, Operating, Federal Tax Expense (Benefit), Current Realized Gain (Loss), Investment And Derivative, Operating, Federal Tax Expense (Benefit), Current Financial Instrument Performance Status [Axis] Financial Instrument Performance Status [Axis] Counterparty Name [Domain] Counterparty Name [Domain] HDC/HW Intermediate Holdings HDC/HW Intermediate Holdings [Member] HDC/HW Intermediate Holdings Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Auria Space, LLC Auria Space, LLC [Member] Auria Space, LLC Nello Industries Investco, LLC Nello Industries Investco, LLC [Member] Nello Industries Investco, LLC Investment Type [Axis] Investment Type [Axis] Increase in borrowing capacity Line of Credit Facility, Increase (Decrease), Net Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Non-PEO NEO Non-PEO NEO [Member] Communications Equipment Communications Equipment [Member] Communications Equipment Fee income Fee Income Sale of Stock [Axis] Sale of Stock [Axis] Federal Realized Gain (Loss), Investment And Derivative, Operating, Deferred Federal Tax Expense (Benefit) Realized Gain (Loss), Investment And Derivative, Operating, Deferred Federal Tax Expense (Benefit) Award Type [Domain] Award Type [Domain] Amortization of directors’ deferred compensation Adjustments To Additional Paid In Capital, Amortization Of Directors’ Deferred Compensation Adjustments To Additional Paid In Capital, Amortization Of Directors’ Deferred Compensation Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Kickhaefer Manufacturing Company, LLC Kickhaefer Manufacturing Company, LLC [Member] Kickhaefer Manufacturing Company, LLC Second lien debt Debt Securities, Second Lien [Member] Debt Securities, Second Lien Canada CANADA Bettercloud, Inc. Bettercloud, Inc. [Member] Bettercloud, Inc. Compensation Amount Outstanding Recovery Compensation Amount Computer Data Source, LLC Computer Data Source, LLC [Member] Computer Data Source, LLC Software Software [Member] Software 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] South Coast Terminals Holdings, LLC South Coast Terminals Holdings, LLC [Member] South Coast Terminals Holdings, LLC Total revenues before waivers Investment Company, Contractual and Voluntary Fees Waived Victory Energy Operations, LLC AAC Holdings, Inc. [Member] AAC Holdings, Inc. Financial Instruments [Domain] Financial Instruments [Domain] New Investments Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Textiles, Apparel & Luxury Goods Textiles, Apparel & Luxury Goods [Member] Textiles, Apparel & Luxury Goods NAPCO Precast, LLC NAPCO Precast, LLC [Member] NAPCO Precast, LLC Minimum Minimum [Member] Net unrealized appreciation (depreciation) (in dollars per share) Investment Company, Unrealized Gain (Loss) on Investment, Per Share Company Selected Measure Name Company Selected Measure Name DEBT Debt Disclosure [Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Portfolio turnover ratio Investment Company, Portfolio Turnover Revenue Recovery Holdings, LLC Revenue Recovery Holdings, LLC [Member] Revenue Recovery Holdings, LLC Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Dividend payable Dividend payable to MSCC and its subsidiaries Dividends Payable COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] WEIGHTED-AVERAGE SHARES OUTSTANDING—DILUTED (in shares) Weighted Average Number of Shares Outstanding, Diluted Segments Segment Reporting, Policy [Policy Text Block] BP Loenbro Holdings Inc. BP Loenbro Holdings Inc. [Member] BP Loenbro Holdings Inc. OnAsset Intelligence, Inc. OnAsset Intelligence, Inc. [Member] OnAsset Intelligence, Inc. Number of portfolio companies Investment Company, Number Of Portfolio Companies Investment Company, Number Of Portfolio Companies Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Northeast Region and Canada Northeast Region and Canada [Member] Northeast Region and Canada Entity Small Business Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Document Transition Report Summary of Investment Holdings [Line Items] Summary of Investment Holdings [Line Items] Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Document Period End Date Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Trading Companies & Distributors Trading Companies & Distributors [Member] Trading Companies & Distributors Proceeds from Credit Facilities Proceeds from Lines of Credit ATS Operating, LLC ATS Operating, LLC [Member] ATS Operating, LLC Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] State and other Realized Gain (Loss), Investment And Derivative, Operating, Deferred State And Other Tax Expense (Benefit) Realized Gain (Loss), Investment And Derivative, Operating, Deferred State And Other Tax Expense (Benefit) Kennedy Fab HoldCo, LLC Kennedy Fab HoldCo, LLC [Member] Kennedy Fab HoldCo, LLC Schedule of Investments [Table] Schedule of Investments [Table] Cash exceeded federal deposit insurance corporation insurance protection levels Cash, Uninsured Amount Contractual obligation, number of additional investments, investment period expired with remaining commitments restricted for fund expenses or follow on investments in existing portfolio companies Investment Company, Number Of Additional Investments, Commitments Restricted For Fund Expenses Or Follow On Investments In Existing Portfolio Investment Company, Number Of Additional Investments, Commitments Restricted For Fund Expenses Or Follow On Investments In Existing Portfolio Net Realized Gains or Losses and Net Unrealized Appreciation or Depreciation Net Realized Gains or Losses And Net Unrealized Appreciation or Depreciation [Policy Text Block] Net Realized Gains or Losses And Net Unrealized Appreciation or Depreciation SPAU Holdings, LLC SPAU Holdings, LLC [Member] SPAU Holdings, LLC RFG AcquireCo, LLC RFG AcquireCo, LLC [Member] RFG AcquireCo, LLC Document Type Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Name Outstanding Recovery, Individual Name Additional paid‑in capital Contributed capital Additional Paid in Capital Product and Service [Axis] Product and Service [Axis] Schedule of Taxable Income and to Total Distributions Declared to Common Stock Reconciliation Federal Income Tax Note [Table Text Block] Percentage of total investment come, attributable to noncash cumulative dividend income (as a percent) Investment Company, Percentage Of Total Investment Income, Attributable To Noncash Cumulative Dividend Income Investment Company, Percentage Of Total Investment Income, Attributable To Noncash Cumulative Dividend Income Xenon Arc, Inc. Xenon Arc, Inc. [Member] Xenon Arc, Inc. Statistical Measurement [Axis] Statistical Measurement [Axis] American Health Staffing Group, Inc. American Health Staffing Group, Inc. [Member] American Health Staffing Group, Inc. Investment Company, Nonconsolidated Subsidiary [Domain] Investment Company, Nonconsolidated Subsidiary [Domain] Share repurchase program, authorized, amount Share Repurchase Program, Authorized, Amount Line of credit facility, unused capacity, commitment fee (as a percent) Line of Credit Facility, Unused Capacity, Commitment Fee Percentage SBIC debentures SBIC debentures SBIC Debentures [Member] SBIC Debentures WACC Measurement Input, Weighted-Average Cost Of Capital [Member] Measurement Input, Weighted-Average Cost Of Capital 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 Connect Telecommunications Solutions Holdings, Inc. GFG Group, LLC. [Member] GFG Group, LLC. Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] GradeEight Corp. GradeEight Corp. [Member] GradeEight Corp. Total allocated expenses Total expenses Operating Expenses MSCC Funding I, LLC MSCC Funding I, LLC [Member] MSCC Funding I, LLC Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Media Media [Member] Media Dividends Declared But Not Yet Paid Dividends Declared But Not Yet Paid [Member] Dividends Declared But Not Yet Paid Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Table] NET INVESTMENT INCOME PER SHARE— DILUTED (in dollars per share) Earnings Per Share, Diluted EnCap Energy Fund Investments EnCap Energy Fund Investments [Member] EnCap Energy Fund Investments Sale of stock, number of shares issued in transaction (in shares) Sale of Stock, Number of Shares Issued in Transaction Dividends [Axis] Dividends [Axis] Dividend reinvestment DRIP participation Stock Issued During Period, Value, Dividend Reinvestment Plan Air Freight & Logistics Air Freight & Logistics [Member] Air Freight & Logistics Boccella Precast Products LLC Boccella Precast Products LLC [Member] Boccella Precast Products LLC O 2026 Q3 Dividends O 2026 Q3 Dividends [Member] O 2026 Q3 Dividends Investment Company, Nonconsolidated Subsidiary [Table] Investment Company, Nonconsolidated Subsidiary [Table] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Jackmont Hospitality, Inc. Jackmont Hospitality, Inc. [Member] Jackmont Hospitality, Inc. KMS, LLC KMS, LLC [Member] KMS, LLC External Investment Manager External Investment Manager [Member] External Investment Manager Cash equivalents Money Market Funds, at Carrying Value Investment Company, Financial Highlights [Table] Investment Company, Financial Highlights [Table] Net investment income taxes Net Investment Income Tax Expense (Benefit) [Abstract] Net Investment Income Tax Expense (Benefit) Outstanding Balance Debt instrument, outstanding balance Long-Term Debt, Gross Hawk Ridge Systems, LLC Hawk Ridge Systems, LLC [Member] Hawk Ridge Systems, LLC O 2026 Q2 Supplemental Dividends O 2026 Q2 Supplemental Dividends [Member] O 2026 Q2 Supplemental Dividends IT Services IT Services [Member] IT Services CGMS Parent LLC FCC Intermediate Holdco, LLC [Member] FCC Intermediate Holdco, LLC Spread (as a percent) Spread Investment, Basis Spread, Variable Rate Amount of Interest, Fees or Dividends Credited to Income Interest, Fees and Dividend Income, Securities, Operating Interest, Fees and Dividend Income, Securities, Operating CQ Fluency, LLC CQ Fluency, LLC [Member] CQ Fluency, LLC Investment Owned, At Fair Value Investment Owned, At Fair Value [Member] Investment Owned, At Fair Value Units (in shares) Investment Owned, Balance, Shares ASC Interests, LLC ASC Interests, LLC [Member] ASC Interests, LLC Dividends [Domain] Dividends [Domain] Expiration Date Trading Arrangement Expiration Date Net investment income (in dollars per share) Investment Company, Investment Income (Loss), Per Share, Basic Amounts of transaction Related Party Transaction, Amounts of Transaction Dos Rios Partners Harris Preston Fund Investments Two [Member] Harris Preston Fund Investments Two Investments Investments [Member] Geographic Concentration Risk Geographic Concentration Risk [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Investments in and Advances to Affiliates, Schedule of Investments [Abstract] Batjer TopCo, LLC Batjer TopCo, LLC [Member] Batjer TopCo, LLC Obra Capital, Inc. Obra Capital, Inc. [Member] Obra Capital, Inc. Principle Environmental, LLC Principle Environmental, LLC [Member] Principle Environmental, LLC Entity Current Reporting Status Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Ignite Visibility LLC Ignite Visibility LLC [Member] Ignite Visibility LLC Financial Instrument [Axis] Financial Instrument [Axis] Consolidated Schedule of Investments in and Advances to Affiliates Investments in and Advances to Affiliates, Schedule of Investments [Text Block] Statement of Financial Position [Abstract] Executive Category: Executive Category [Axis] Accounts payable and other liabilities Increase (Decrease) in Accounts Payable and Other Operating Liabilities Debt instrument, number of lenders Debt Instrument, Number Of Lenders Debt Instrument, Number Of Lenders Market approach Valuation, Market Approach [Member] Current Fiscal Year End Date At-The-Market Offerings At-The-Market Offerings [Member] At-The-Market Offerings Weighted-Average Grant-Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Restricted stock available for issuance (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Ratio of operating expenses to average NAV Investment Company, Operating Expenses Ratio Investment Company, Operating Expenses Ratio Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Charps, LLC Charps, LLC [Member] Charps, LLC Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent) Investment Company, Percentage of Portfolio With Annual Third-Party Appraisal Was Obtained, Reviewed and Certified Investment Company, Percentage of Portfolio With Annual Third-Party Appraisal Was Obtained, Reviewed and Certified Income tax provision on net realized gain (loss) and net unrealized appreciation (in dollars per share) Investment​ Company, Income Tax Benefit (Provision) On Net Realized Gain And Net Unrealized Appreciation, ​​Per​ Share Investment​ Company, Income Tax Benefit (Provision) On Net Realized Gain And Net Unrealized Appreciation, ​​Per​ Share NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS PER SHARE—DILUTED (in dollars per share) Investment Company, Investment Income (Loss) from Operations, Per Share, Per Diluted Share Investment Company, Investment Income (Loss) from Operations, Per Share, Per Diluted Share Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Other Commitments [Table] Other Commitments [Table] Net cash provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Televerde, LLC Televerde, LLC [Member] Televerde, LLC Measure: Measure [Axis] Spring Engineering Holdings, LLC Spring Engineering Holdings, LLC [Member] Spring Engineering Holdings, LLC Island Pump and Tank, LLC Island Pump and Tank, LLC [Member] Island Pump and Tank, LLC Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Net Unrealized Appreciation (Depreciation) Debt and Equity Securities, Unrealized Gain (Loss) [Member] Debt and Equity Securities, Unrealized Gain (Loss) Approximate dollar value of shares that may yet be purchased under the plans or programs Share Repurchase Program, Remaining Authorized, Amount Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Amortization of deferred financing costs Amortization of Debt Issuance Costs Total expenses Investment Income, Investment Expense Entity Tax Identification Number SOFR Adjustment Spread SOFR Adjustment Spread [Member] SOFR Adjustment Spread Discounted cash flow Valuation Technique, Discounted Cash Flow [Member] Investment valuation related taxes Investment Tax Expense (Income) [Abstract] Investment Tax Expense (Income) Common stock, shares issued (in shares) Common Stock, Shares, Issued UniTek Global Services, Inc. UniTek Global Services, Inc. [Member] UniTek Global Services, Inc. O 2026 Q1 Supplemental Dividends O 2026 Q1 Supplemental Dividends [Member] O 2026 Q1 Supplemental Dividends Nearshore AcquireCo, LLC Nearshore AcquireCo, LLC [Member] Nearshore AcquireCo, LLC Titan Meter Midco Corp. Titan Meter Midco Corp. [Member] Titan Meter Midco Corp. Current tax expense: Current Federal, State and Local, Tax Expense (Benefit) [Abstract] Investments Investments, Per Company Investments, Per Company Moffitt Holdings, LLC Moffitt Holdings, LLC [Member] Moffitt Holdings, LLC Trading Arrangement: Trading Arrangement [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Deferred tax expense (benefit): Deferred Tax Expense (Income) [Abstract] Deferred Tax Expense (Income) Security Exchange Name Deferred financing costs, accumulated amortization Accumulated Amortization, Debt Issuance Costs Accretive effect of stock offerings (issuing shares above NAV per share) (in dollars per share) Investment Company, Effect of Stock Offerings, Per Share Investment Company, Effect of Stock Offerings, Per Share Line of credit facility Line of Credit Facility, Maximum Borrowing Capacity Trantech Radiator Topco, LLC Trantech Radiator Topco, LLC [Member] Trantech Radiator Topco, LLC MSC Income MSC Income [Member] MSC Income Dividend reinvestment (in shares) Shares issued for DRIP (in shares) Stock Issued During Period, Shares, Dividend Reinvestment Plan MonitorUS Holding, LLC MonitorUS Holding, LLC [Member] MonitorUS Holding, LLC Market value as of the end of the period (in dollars per share) Investment Company, Market Value, Per Share Total number of shares purchased (in shares) Stock Repurchased During Period, Shares O 2026 Q2 Dividends O 2026 Q2 Dividends [Member] O 2026 Q2 Dividends Phantom Stock Units Phantom Share Units (PSUs) [Member] Asset Class [Domain] Asset Class [Domain] Increase (decrease) in incentive fee payable Increase (Decrease) in Incentive Fee Payable Gain (loss) included in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings KBK Industries, LLC KBK Industries, LLC [Member] KBK Industries, LLC June 2027 Notes, Additional June 2027 Notes, Additional [Member] June 2027 Notes, Additional Statement [Line Items] Statement [Line Items] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] External Investment Manager External Investment Manager Investments [Member] External Investment Manager Investments Cash and cash equivalents Cash and cash equivalent, Cost Cash and cash equivalents Cash and Cash Equivalent Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Proceeds from sales and return of capital of equity investments in portfolio companies Proceeds From Sales And Return Of Capital Of Equity Investments In Portfolio Companies Proceeds From Sales And Return Of Capital Of Equity Investments In Portfolio Companies Subsequent Event [Line Items] Subsequent Event [Line Items] Other direct G&A expenses Other General and Administrative Expense, Direct Other General and Administrative Expense, Direct California Splendor Holdings LLC California Splendor Holdings LLC [Member] California Splendor Holdings LLC Common Stock Common Stock [Member] Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Distributors Distributors [Member] Distributors Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] MCT Purchaserco Holding Inc. MCT Purchaserco Holding Inc. [Member] MCT Purchaserco Holding Inc. Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Dividends paid, per share (in dollars 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] CGMS Parent LLC CGMS Parent LLC [Member] CGMS Parent LLC Related Party Transaction [Axis] Related Party Transaction [Axis] Asset Class [Axis] Asset Class [Axis] Share purchase (repurchase) program, number of active plans Share Purchase (Repurchase) Program, Number Of Active Plans Share Purchase (Repurchase) Program, Number Of Active Plans State and other Investment Income, Operating, State And Other Tax Expense (Benefit), Current Investment Income, Operating, State And Other Tax Expense (Benefit), Current Valuation Approach and 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Assets [Abstract] Investment Company, Ratio To Average Net Assets EBITDA multiple Measurement Input, EBITDA Multiple [Member] Measurement Input Type [Domain] Measurement Input Type [Domain] EXPENSES: EXPENSES: Interest and Debt Expense [Abstract] Affiliated Entity Affiliated Entity [Member] Private Loan Fund II Private Loan Fund II [Member] Private Loan Fund II Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Other G&A expenses Other General and Administrative Expense Creative Foam Corporation Creative Foam Corporation [Member] Creative Foam Corporation Average NAV Investment Company, Average Net Assets Share‑based compensation Share‑based compensation Share-Based Payment Arrangement, Expense Net increase in net assets resulting from operations (in dollars per share) Investment Company, Investment Income (Loss) from Operations, Per Share Total liabilities and net assets Liabilities and Equity OnPoint Industrial Services, LLC OnPoint Industrial Services, LLC [Member] OnPoint Industrial Services, LLC Infinity X1 Holdings, LLC Infinity X1 Holdings, LLC [Member] Infinity X1 Holdings, LLC Victory Energy Operations, LLC Victory Energy Operations, LLC [Member] Victory Energy Operations, LLC Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Dynamic Communities, LLC Dynamic Communities, LLC [Member] Dynamic Communities, LLC Advisory Agreement, Previous Advisory Agreement, Previous [Member] Advisory Agreement, Previous Fuse, LLC Fuse, LLC [Member] Fuse, LLC Accounting Policies [Abstract] Equity Warrant Equity warrants Equity Warrant [Member] Equity Warrant Concentration Risk Type [Domain] Concentration Risk Type [Domain] Mini Melts of America, LLC Mini Melts of America, LLC [Member] Mini Melts of America, LLC Percentage of total commitments (as a percent) Related Party Transaction, Percentage of Total Commitments Related Party Transaction, Percentage of Total Commitments MS Private Loan Fund I, LP MS Private Loan Fund I, LP [Member] MS Private Loan Fund I, LP Dividends Payable [Line Items] Dividends Payable [Line Items] Pay vs Performance Disclosure [Line Items] Ratio of operating expenses, excluding interest expense, to average NAV Investment Company, Operating Expense Ratio Excluding Interest Expense Investment Company, Operating Expense Ratio Excluding Interest Expense LIABILITIES LIABILITIES Liabilities [Abstract] Summary of Investment Holdings [Table] Investment Holdings [Table] Bond Brand Loyalty ULC Bond Brand Loyalty ULC [Member] Bond Brand Loyalty ULC 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] Leisure Equipment & Products Leisure Equipment & Products [Member] Leisure Equipment & Products Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Debt instrument, unamortized debt 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Rug Doctor, LLC. [Member] Rug Doctor, LLC. 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BEFORE TAXES Net investment income Net Investment Income Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Corporate Facility Corporate Facility [Member] Corporate Facility April 2031 Notes April 2031 Notes [Member] April 2031 Notes Organization, Consolidation and Presentation of Financial Statements [Abstract] Adams Publishing Group, LLC Adams Publishing Group, LLC [Member] Adams Publishing Group, LLC City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Pinnacle TopCo, LLC Pinnacle TopCo, LLC [Member] Pinnacle TopCo, LLC Bolder Panther Group, LLC Bolder Panther Group, LLC [Member] Bolder Panther Group, LLC Debt instrument, credit spread adjustment (as a percent) Debt Instrument, Credit Spread Adjustment Debt Instrument, Credit Spread Adjustment Net deferred tax liability Deferred Tax Liabilities, Net EXTERNAL INVESTMENT MANAGER External Investment Manager [Text Block] External Investment Manager General 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IG Investor, LLC [Member] IG Investor, LLC Other Non-U.S. Non-US [Member] O 2026 M2 Dividends O 2026 M2 Dividends [Member] O 2026 M2 Dividends Schedule of Financial Highlights Investment Company, Financial Highlights [Table Text Block] Iron-Main Investments, LLC Iron-Main Investments, LLC [Member] Iron-Main Investments, LLC Expenses allocated to the External Investment Manager Expenses allocated Investment Company, Expense Offset Arrangement Investments in portfolio companies Payments To Investments In Portfolio Companies Payments To Investments In Portfolio Companies Supplemental cash flow disclosures: Supplemental Cash Flow Information [Abstract] Other Performance Measure, Amount Other Performance Measure, Amount Trinity Medical Holdings, LLC Trinity Medical Holdings, LLC [Member] Trinity Medical Holdings, LLC Gamber-Johnson Holdings, LLC GRT Rubber Technologies LLC [Member] GRT Rubber Technologies LLC Ratio of net investment income to average NAV Investment Company, Investment 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[Member] Metalforming Holdings, LLC 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] Investment Owned, At Cost Investment Owned, At Cost [Member] Investment Owned, At Cost Net Changes from Unrealized to Realized Debt and Equity Securities, Realized Gain (Loss) [Member] Debt and Equity Securities, Realized Gain (Loss) Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activity Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Vitesse Systems Vitesse Systems [Member] Vitesse Systems Investment company, number of companies within portfolio excluded from EBITDA calculation Investment Company, Number of Companies Within Portfolio Excluded From EBITDA Calculation Investment Company, Number of Companies Within Portfolio Excluded From EBITDA Calculation Plan Name [Domain] Plan Name [Domain] Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition (in years) Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Tax credit carryforward Investment Company, Distributable Earnings (Loss), Accumulated Capital Loss Carryforward Equity [Abstract] Share purchase program, authorized, amount Share Purchase Program, Authorized, Amount Share Purchase Program, Authorized, Amount DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME Dividend, Distributions, Income Tax Disclosure [Text Block] Dividend, Distributions, Income Tax Disclosure NET UNREALIZED APPRECIATION (DEPRECIATION): NET UNREALIZED APPRECIATION (DEPRECIATION): Investment Owned, Recognized Unrealized Appreciation (Depreciation), Net [Abstract] Investment Owned, Recognized Unrealized Appreciation (Depreciation), Net West US West Region [Member] Fair Value, Assets and Liabilities Measured on 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transaction, net Sale of Stock, Consideration Received on Transaction Event Holdco, LLC Event Holdco, LLC [Member] Event Holdco, LLC IG Parent Corporation IG Parent Corporation [Member] IG Parent Corporation Revolving Credit Facility Credit Facility Revolving Credit Facility [Member] Chemicals Chemicals [Member] Chemicals Arrangement Duration Trading Arrangement Duration Investment, Issuer Name [Domain] Investment, Issuer Name [Domain] PrimeFlight Aviation Services PrimeFlight Aviation Services [Member] PrimeFlight Aviation Services Clad-Rex Steel, LLC Clad-Rex Steel, LLC [Member] Clad-Rex Steel, LLC Local Phone Number Implus Footcare, LLC Implus Footcare, LLC [Member] Implus Footcare, LLC Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Diluted equity ownership (as a percent) Investment Company, Average Fully Diluted Equity Ownership, Percentage Investment Company, Average Fully Diluted Equity Ownership, Percentage Share price (in dollars per share) SHARE-BASED 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Bluestem Brands, Inc. [Member] Bluestem Brands, Inc. Berry Aviation, Inc. Berry Aviation, Inc. [Member] Berry Aviation, Inc. MVI MSO, LLC NRP Jones, LLC [Member] NRP Jones, LLC GULF PACIFIC ACQUISITION, LLC GULF PACIFIC ACQUISITION, LLC [Member] GULF PACIFIC ACQUISITION, LLC Investment Company [Abstract] FINANCIAL HIGHLIGHTS Investment Company, Financial Highlights [Text Block] Accounts receivable - advisory clients (1) Accounts Receivable, after Allowance for Credit Loss Entity Registrant Name Investment Company, Financial Highlights [Line Items] Investment Company, Financial Highlights [Line Items] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Private Loan portfolio investments Private Loan Portfolio [Member] Private Loan Portfolio Margin Effective Period One Margin Effective Period One [Member] Margin Effective Period One Strike price (in dollars per share) Option Indexed to Issuer's Equity, Strike Price Tedder Industries, LLC Tedder Industries, LLC [Member] Tedder Industries, LLC Unused capacity, commitment fee (as a percent) Related Party Transaction, Unused 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[Axis] O 2026 M4 Dividends O 2026 M4 Dividends [Member] O 2026 M4 Dividends Total Interest Expense Interest Expense, Debt Main Street Capital Corporation 2022 Non-Employee Director Restricted Stock Plan Main Street Capital Corporation 2022 Non-Employee Director Restricted Stock Plan [Member] Main Street Capital Corporation 2022 Non-Employee Director Restricted Stock Plan Payment-in-kind interest Payment-in-Kind Interest Payment-in-Kind Interest Name Trading Arrangement, Individual Name Committed capital Investment Company, Financial Support to Investee Contractually Required, Not Provided, Amount Elgin AcquireCo, LLC Elgin AcquireCo, LLC [Member] Elgin AcquireCo, LLC Beverages Beverages [Member] Beverages Dividend payable as of period end and paid in the following period Investment Company, Tax Basis, Dividends Paid Or Payable Investment Company, Tax Basis, Dividends Paid Or Payable Debt instrument, par value Face amount Debt Instrument, Face Amount Main Street Capital Corporation 2022 Equity and Incentive Plan Main Street Capital Corporation 2022 Equity and Incentive Plan [Member] Main Street Capital Corporation 2022 Equity and Incentive Plan Total deferred tax expense Investment Income, Operating, Deferred Tax Expense (Benefit) Investment Income, Operating, Deferred Tax Expense (Benefit) Units (as a percent) Investment Owned, Balance, Percent Of Shares Investment Owned, Balance, Percent Of Shares Market comparable / Enterprise value Valuation, Market And Enterprise Value Approach [Member] Valuation, Market And Enterprise Value Approach Investment, Issuer Affiliation [Domain] Investment, Issuer Affiliation [Domain] Name Awards Close in Time to MNPI Disclosures, Individual Name Hornblower Sub, LLC Hornblower Sub, LLC [Member] Hornblower Sub, LLC Nonvested beginning balance (in dollars per share) Nonvested ending balance (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Variable Rate Component [Axis] Variable Rate Component [Axis] Variable Rate Component Share‑based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Richardson Sales Solutions Richardson Sales Solutions [Member] Richardson Sales Solutions MVI MSO, LLC MVI MSO, LLC [Member] MVI MSO, LLC Average EBITDA Investment Company, Average Earnings Before Interest, Taxes, Depreciation, And Amortization Investment Company, Average Earnings Before Interest, Taxes, Depreciation, And Amortization Debt instrument, remaining term (in years) Debt Instrument, Remaining Term Debt Instrument, Remaining Term Taxable income earned prior to period end and carried forward for distribution next period Investment Company, Tax Basis, Taxable Income Earned Prior To Period End and Carried Forward For Distribution Next Period Investment Company, Tax Basis, Taxable Income Earned Prior To Period End and Carried Forward For Distribution Next Period Computers & Peripherals Computers & Peripherals [Member] Computers & Peripherals Income Statement Location [Axis] Statement of Income Location, Balance [Axis] Interface Security Systems, L.L.C Interface Security Systems, L.L.C [Member] Interface Security Systems, L.L.C O 2026 M5 Dividends O 2026 M5 Dividends [Member] O 2026 M5 Dividends Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Garyline, LLC Garyline, LLC [Member] Garyline, LLC UserZoom Technologies, Inc. UserZoom Technologies, Inc. [Member] UserZoom Technologies, Inc. Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Harris Preston Fund Investments Harris Preston Fund Investments [Member] Harris Preston Fund Investments Consultation period subsequent to initial investment (in months) Investment Company, Consultation Period Subsequent To Initial Investment Investment Company, Consultation Period Subsequent To Initial Investment Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates [Table] LMM portfolio investments Lower Middle Market Portfolio [Member] Lower Middle Market Portfolio Interest payable Interest payable Interest Payable RA Outdoors LLC RA Outdoors LLC [Member] RA Outdoors LLC All Executive Categories All Executive Categories [Member] Common stock, $0.01 par value per share (150,000,000 shares authorized; 92,454,655 and 89,834,849 shares issued and outstanding as of March 31, 2026 and December 31, 2025, respectively) Common Stock, Value, Issued Interest and dividend receivable and other assets Interest and dividend receivable and other assets Interest And Dividend Receivable And Other Assets Interest And Dividend Receivable And Other Assets Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Title of Individual [Axis] Title and Position [Axis] Commitments and contingencies (Note K) Commitments and Contingencies O 2026 M6 Dividends O 2026 M6 Dividends [Member] O 2026 M6 Dividends Advisory Agreement, Active Advisory Agreement, Active [Member] Advisory Agreement, Active Coregistics Buyer LLC Coregistics Buyer LLC [Member] Coregistics Buyer LLC Measurement input Investment Company, Investment Owned, Measurement Input Schedule of Investment Income Investment Income [Table Text Block] Short-term portfolio investments Short-Term Investments [Member] Houston Plating and Coatings, LLC Houston Plating and Coatings, LLC [Member] Houston Plating and Coatings, LLC B-O-F Corporation B-O-F Corporation [Member] B-O-F Corporation Percentage of total investment income, attributable to noncash paid-in-kind interest income (as a percent) Investment Company, Percentage Of Total Investment Income, Attributable To Noncash Paid-in-Kind Interest Income Investment Company, Percentage Of Total Investment Income, Attributable To Noncash Paid-in-Kind Interest Income PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Variable Rate Component Two Variable Rate Component Two [Member] Variable Rate Component Two Adjustments to reconcile net increase in net assets resulting from operations to net cash 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 Estimated Fair Value Debt Instrument, Fair Value Disclosure Scenario [Axis] Scenario [Axis] Oil, Gas & Consumable Fuels Oil, Gas & Consumable Fuels [Member] Oil, Gas & Consumable Fuels O 2026 M3 Dividends O 2026 M3 Dividends [Member] O 2026 M3 Dividends Fee multiple Measurement Input, Fee Multiple [Member] Measurement Input, Fee Multiple Proceeds from public offering of common stock, net of offering costs Proceeds from Issuance of Common Stock Transfers Into (Out of) Level 3 Hierarchy Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Colonial Electric Company LLC Colonial Electric Company LLC [Member] Colonial Electric Company LLC Inspire Aesthetics Management, LLC Inspire Aesthetics Management, LLC [Member] Inspire Aesthetics Management, LLC All Individuals All Individuals [Member] Long-Term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Schedule of Information from External Investment Manager Investment Company, Nonconsolidated Subsidiary, Summarized Financial Information [Table Text Block] Name Forgone Recovery, Individual Name Dividends paid (in dollars per share) Investment Company, Distribution to Shareholders, Per Share Royal Cup Inc. Royal Cup Inc. [Member] Royal Cup Inc. Invincible Boat Company, LLC. Invincible Boat Company, LLC. [Member] Invincible Boat Company, LLC. TEC Services, LLC TEC Services, LLC [Member] TEC Services, LLC 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] Schedule of Outstanding Commitments Investment Company, Outstanding Capital Commitments [Table Text Block] Investment Company, Outstanding Capital Commitments Electro Technical Industries, LLC Electro Technical Industries, LLC [Member] Electro Technical Industries, LLC Total deferred tax expense Realized Gain (Loss), Investment And Derivative, Operating, Deferred Tax Expense (Benefit) Realized Gain (Loss), Investment And Derivative, Operating, Deferred Tax Expense (Benefit) Integral Energy Services Integral Energy Services [Member] Integral Energy Services Debt instrument, weighted-average annual interest rate (as a percent) Debt, Weighted Average Interest Rate CRC Evans USA Bidco, Inc. CRC Evans USA Bidco, Inc. [Member] CRC Evans USA Bidco, Inc. Debt issuance premiums, net Proceeds From Debt Issuance Premiums, Net Proceeds From Debt Issuance Premiums, Net Per Share Data: Investment Company, Per Share Data [Abstract] Investment Company, Per Share Data Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] PavCon LLC PavCon LLC [Member] PavCon LLC July 2026 Notes July 2026 Notes [Member] July 2026 Notes Investment Management Agreement Investment Management Agreement [Member] Investment Management Agreement Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Geographical [Axis] Geographical [Axis] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Increase in common stock, dividends, per share, declared, monthly (as a percent) Increase (Decrease) In Common Stock, Dividends, Declared, Monthly Increase (Decrease) In Common Stock, Dividends, Declared, Monthly UnionRock Energy Fund Investments UnionRock Energy Fund Investments [Member] UnionRock Energy Fund Investments Forecast Forecast [Member] Interest rate (as a percent) Related Party Transaction, Rate Buca C, LLC DMA Industries, LLC [Member] DMA Industries, LLC Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Title of 12(b) Security Achieved total return on investments (as a percent) Investment Company, Achieved Total Return Investment Company, Achieved Total Return Accounts payable to MSCC and its subsidiaries Accounts Payable Unearned Income—Debt Origination Fees and Original Issue Discount and Discounts / Premiums to Par Value Unearned Income [Policy Text Block] Unearned Income NET INVESTMENT INCOME Investment Income, Operating, after Expense and Tax Sale of stock, shares authorized under agreement (in shares) Sale Of Stock, Shares Authorized Under Agreement Sale Of Stock, Shares Authorized Under Agreement Book-tax difference from share-based compensation expense Investment Company, Tax Basis, Book-tax Difference From Share-based Compensation Expense, Increase (Decrease) In Taxable Income Investment Company, Tax Basis, Book-tax Difference From Share-based Compensation Expense, Increase (Decrease) In Taxable Income Percentage of total investment income, attributable to interest income, debt investments, net (as a percent) Investment Company, Percentage Of Total Investment Income, Attributable To Interest Income, Debt Investments, Net Investment Company, Percentage Of Total Investment Income, Attributable To Interest Income, Debt Investments, Net Legacy Swim Group MS Private Loan Fund II, LP [Member] MS Private Loan Fund II, LP Schedule of Interest Expense Interest Income and Interest Expense Disclosure [Table Text Block] BLI Acquisition, LLC BLI Acquisition, LLC [Member] BLI Acquisition, LLC Brightwood Capital Fund Investments Brightwood Capital Fund Investments Brightwood Capital Fund Investments [Member] Brightwood Capital Fund Investments Management and service fees, catch up feature rate (as a percent) Management and Service Fees, Rate Weighted-average annual effective yield (as a percent) Debt Securities, Available-for-Sale, Weighted Average Yield Deferred compensation (in shares) Related Party Transaction, Transaction Amount, Shares Related Party Transaction, Transaction Amount, Shares Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Total net investment income tax provision Investment Income, Operating, Tax Expense (Benefit) Award Timing Disclosures [Line Items] Pre-tax book income not consolidated for tax purposes Investment Company, Tax Basis, Pre-tax Book (Income) Loss Not Consolidated For Tax purposes, Increase (Decrease) In Taxable Income Investment Company, Tax Basis, Pre-tax Book (Income) Loss Not Consolidated For Tax purposes, Increase (Decrease) In Taxable Income Excise tax expense Excise Investment Company, Excise Tax Expense Analytical Systems Keco Holdings, LLC Analytical Systems Keco Holdings, LLC [Member] Analytical Systems Keco Holdings, LLC Measurement Frequency [Domain] Measurement Frequency [Domain] December 2025 Series B Notes December 2025 Series B Notes [Member] December 2025 Series B Notes COMMON STOCK Equity [Text Block] Net unrealized (appreciation) depreciation Investment Company, Tax Basis, Unrealized (Gain) Loss, Not Currently (Taxable) Deductible Deferred fees and other Increase (Decrease) In Deferred Fees and Other Increase (Decrease) In Deferred Fees and Other O 2026 A2 Life-To-Date Dividends O 2026 A3 Life-To-Date Dividends [Member] O 2026 A3 Life-To-Date Dividends Weighted-average effective interest rate Average interest rate (as a percent) Debt Instrument, Interest Rate During Period NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS Net increase in net assets resulting from operations Net increase in net assets resulting from operations Net Income (Loss) Attributable to Parent Subsequent Event [Table] Subsequent Event [Table] Behavior Development Group Holdings Behavior Development Group Holdings [Member] Behavior Development Group Holdings Private Loan Fund I Private Loan Fund I [Member] Private Loan Fund I Net assets, percentage (as a percent) Investments in and Advances to Affiliates, Percentage Of Net Assets Investments in and Advances to Affiliates, Percentage Of Net Assets Vesting period (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Ratio of total expenses, including income tax expense, to average NAV Investment Company, Expense Ratio, Including Income Tax Expense Investment Company, Expense Ratio, Including Income Tax Expense Adoption Date Trading Arrangement Adoption Date PPL RVs, Inc. PPL RVs, Inc. [Member] PPL RVs, Inc. Management and service fees, incentive rate (as a percent) Management and Service Fees, Incentive Rate Auto Components Auto Components [Member] Auto Components Total Rate Interest rate (as a percent) Investment Interest Rate Core Transformers Core Transformers [Member] Core Transformers Line of Credit Line of Credit [Member] Total undistributed earnings Total undistributed earnings Retained Earnings (Accumulated Deficit) Buca C, LLC Buca C, LLC [Member] Buca C, LLC 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] Volusion, LLC Volusion, LLC [Member] Volusion, LLC Margin Effective Period [Domain] Margin Effective Period [Domain] Margin Effective Period [Domain] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Dividend income Investment Income, Dividend 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] Schedule of Condensed Balance Sheet and Statement of Operations of MSCC Funding Condensed Financial Statements [Table Text Block] Statement [Table] Statement [Table] Deferred taxes Deferred Income Tax Expense (Benefit) CASH FLOWS FROM FINANCING ACTIVITIES Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Share purchase program, percentage of outstanding stock maximum (as a percent) Share Purchase Program, Percentage of Outstanding Stock Maximum Share Purchase Program, Percentage of Outstanding Stock Maximum Fee Income Management and Investment Advisory Fees, Policy [Policy Text Block] Variable Rate [Domain] Variable Rate [Domain] ORGANIZATION AND BASIS OF PRESENTATION Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Schedule of Changes in Fair Value of Main Street’s Level 3 Portfolio Investments Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] All Adjustments to Compensation All Adjustments to Compensation [Member] Amendment Flag Sale of stock, price per share (in dollars per share) Sale of Stock, Price Per Share Compensation Salary and Wage, Excluding Cost of Good and Service Sold Restricted stock authorized under the plan (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Termination Date Trading Arrangement Termination Date Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Diversified Consumer Services Diversified Consumer Services [Member] Diversified Consumer Services Dividend Revenue Recognition, Dividends [Policy Text Block] Dividends Payable [Table] Dividends Payable [Table] ArborWorks, LLC ArborWorks, LLC [Member] ArborWorks, LLC Schedule of Portfolio Investments by Level in the Fair Value Hierarchy Fair Value, Assets Measured on Recurring Basis [Table Text Block] Cody Pools, Inc. Cody Pools, Inc. [Member] Cody Pools, Inc. WEIGHTED-AVERAGE SHARES OUTSTANDING—BASIC (in shares) Weighted Average Number of Shares Outstanding, Basic INVESTMENT INCOME: INVESTMENT INCOME: Investment Income, Net [Abstract] Investment Company, Financial Highlights [Roll Forward] Investment Company, Financial Highlights [Roll Forward] Director Director [Member] Investment, Issuer Name [Axis] Investment, Issuer Name [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Subsequent Events [Abstract] Debt Disclosure [Abstract] Scenario [Domain] Scenario [Domain] O 2025 Q1 Supplemental Dividends O 2025 Q1 Supplemental Dividends [Member] O 2025 Q1 Supplemental Dividends Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Gamber-Johnson Holdings, LLC Gamber-Johnson Holdings, LLC [Member] Gamber-Johnson Holdings, LLC DIVIDEND REINVESTMENT PLAN Stockholders' Equity, Dividend Reinvestment Plan [Text Block] Stockholders' Equity, Dividend Reinvestment Plan Deferred tax expense (benefit): Investment Tax Expense (Income), Deferred [Abstract] Investment Tax Expense (Income), Deferred NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS PER SHARE—BASIC (in dollars per share) Investment Company, Investment Income (Loss) from Operations, Per Share, Per Basic Share Investment Company, Investment Income (Loss) from Operations, Per Share, Per Basic Share March 2029 Notes March 2029 Notes [Member] March 2029 Notes Use of Estimates Use of Estimates, Policy [Policy Text Block] Redemptions/ Repayments Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Total number of shares purchased as part of publicly announced plans or programs (in shares) Sale Of Stock, Total Shares Issued Sale Of Stock, Total Shares Issued Food Products Food Products [Member] Food Products Industry Concentration Risk Industry Concentration Risk [Member] Industry Concentration Risk Northeast US Northeast Region [Member] Winter Services LLC Winter Services LLC [Member] Winter Services LLC SUBSEQUENT EVENTS Subsequent Events [Text Block] Insider Trading Arrangements [Line Items] Funded commitments Related Party Transaction, Purchases from Related Party Other Other [Member] Other Total distributions accrued or paid to common stockholders Investment Company, Tax Basis, Distributions Accrued Or Paid To Common Stockholders Investment Company, Tax Basis, Distributions Accrued Or Paid To Common Stockholders Equity investments Equity Equity Securities [Member] Escalent, Inc. Escalent, Inc. [Member] Escalent, Inc. Total liabilities Liabilities Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] MSC III Main Street Capital III, LP [Member] Main Street Capital III, LP Commitment fee (as a percentage) Line of Credit Facility, Commitment Fee Percentage Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Total current tax expense Realized Gain (Loss), Investment And Derivative, Operating, Tax Expense (Benefit), Current Realized Gain (Loss), Investment And Derivative, Operating, Tax Expense (Benefit), Current Investment Type Concentration Risk Investment Type Concentration Risk [Member] Investment Type Concentration Risk Financial Instrument Performance Status [Domain] Financial Instrument Performance Status [Domain] Total current tax expense Investment Income, Operating, Tax Expense (Benefit), Current Investment Income, Operating, Tax Expense (Benefit), Current Other Portfolio investments Other Other Security Investments [Member] Professional Services Professional Services [Member] Professional Services Public offering of common stock, net of offering costs Stock Issued During Period, Value, New Issues Variable Rate [Axis] Variable Rate [Axis] Chamberlin Holding LLC Chamberlin Holding LLC [Member] Chamberlin Holding LLC American Nuts, LLC American Nuts, LLC [Member] American Nuts, LLC Counterparty Name [Axis] Counterparty Name [Axis] Total investment income Total investment income Gross Investment Income, Operating Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Mission Critical Group Mission Critical Group [Member] Mission Critical Group