0000001 - Document - Cover link:presentationLink link:calculationLink link:definitionLink 0000002 - Statement - Consolidated Balance Sheets link:presentationLink link:calculationLink link:definitionLink 0000003 - Statement - Consolidated Balance Sheets (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000004 - Statement - Consolidated Statements of Operations link:presentationLink link:calculationLink link:definitionLink 0000005 - Statement - Consolidated Statements of Changes in Net Assets link:presentationLink link:calculationLink link:definitionLink 0000006 - Statement - Consolidated Statements of Cash Flows link:presentationLink link:calculationLink link:definitionLink 0000007 - Statement - Consolidated Schedule of Investments link:presentationLink link:calculationLink link:definitionLink 0000007 - Statement - Consolidated Schedule of Investments link:presentationLink link:calculationLink link:definitionLink 0000008 - Statement - Consolidated Schedule of Investments (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000008 - Statement - Consolidated Schedule of Investments (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000009 - Disclosure - ORGANIZATION AND BASIS OF PRESENTATION link:presentationLink link:calculationLink link:definitionLink 0000010 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES link:presentationLink link:calculationLink link:definitionLink 0000011 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION link:presentationLink link:calculationLink link:definitionLink 0000012 - Disclosure - EXTERNAL INVESTMENT MANAGER link:presentationLink link:calculationLink link:definitionLink 0000013 - Disclosure - DEBT link:presentationLink link:calculationLink link:definitionLink 0000014 - Disclosure - FINANCIAL HIGHLIGHTS link:presentationLink link:calculationLink link:definitionLink 0000015 - Disclosure - DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME link:presentationLink link:calculationLink link:definitionLink 0000016 - Disclosure - COMMON STOCK link:presentationLink link:calculationLink link:definitionLink 0000017 - Disclosure - DIVIDEND REINVESTMENT PLAN link:presentationLink link:calculationLink link:definitionLink 0000018 - Disclosure - SHARE-BASED COMPENSATION link:presentationLink link:calculationLink link:definitionLink 0000019 - Disclosure - COMMITMENTS AND CONTINGENCIES link:presentationLink link:calculationLink link:definitionLink 0000020 - Disclosure - RELATED PARTY TRANSACTIONS link:presentationLink link:calculationLink link:definitionLink 0000021 - Disclosure - SUBSEQUENT EVENTS link:presentationLink link:calculationLink link:definitionLink 0000022 - Disclosure - Consolidated Schedule of Investments in and Advances to Affiliates link:presentationLink link:calculationLink link:definitionLink 9955511 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) link:presentationLink link:calculationLink link:definitionLink 9955512 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9955513 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION (Tables) link:presentationLink link:calculationLink link:definitionLink 9955514 - Disclosure - EXTERNAL INVESTMENT MANAGER (Tables) link:presentationLink link:calculationLink link:definitionLink 9955515 - Disclosure - DEBT (Tables) link:presentationLink link:calculationLink link:definitionLink 9955516 - Disclosure - FINANCIAL HIGHLIGHTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955517 - Disclosure - DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME (Tables) link:presentationLink link:calculationLink link:definitionLink 9955518 - Disclosure - DIVIDEND REINVESTMENT PLAN (Tables) link:presentationLink link:calculationLink link:definitionLink 9955519 - Disclosure - SHARE-BASED COMPENSATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9955520 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9955521 - Disclosure - RELATED PARTY TRANSACTIONS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955522 - Disclosure - Consolidated Schedule of Investments in and Advances to Affiliates (Tables) link:presentationLink link:calculationLink link:definitionLink 9955523 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955524 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Investment Income (Details) link:presentationLink link:calculationLink link:definitionLink 9955525 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955526 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Level 3 Portfolio Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9955527 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Changes in Fair Value of Level 3 Portfolio Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9955528 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Fair Value Hierarchy (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9955530 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Percentage of Portfolio Investments by Type of Investment (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Percentage of Portfolio Investments by Geographical Regions (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Percentage of Portfolio Investments by Industry Sector (Details) link:presentationLink link:calculationLink link:definitionLink 9955533 - Disclosure - EXTERNAL INVESTMENT MANAGER - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955534 - Disclosure - EXTERNAL INVESTMENT MANAGER - Schedule of Balance Sheet (Details) link:presentationLink link:calculationLink link:definitionLink 9955535 - Disclosure - EXTERNAL INVESTMENT MANAGER - Schedule of Statement of Operations (Details) link:presentationLink link:calculationLink link:definitionLink 9955536 - Disclosure - DEBT - Schedule of Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9955537 - Disclosure - DEBT - Schedule of Interest Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955538 - Disclosure - DEBT - Schedule of Average Amount of Total Borrowings Outstanding and Overall Weighted-Average Effective Interest Rate (Details) link:presentationLink link:calculationLink link:definitionLink 9955539 - Disclosure - DEBT - Corporate Facility (Details) link:presentationLink link:calculationLink link:definitionLink 9955540 - Disclosure - DEBT - SPV Facility (Details) link:presentationLink link:calculationLink link:definitionLink 9955541 - Disclosure - DEBT - Schedule of MSCC Funding Balance Sheet (Details) link:presentationLink link:calculationLink link:definitionLink 9955542 - Disclosure - DEBT - Schedule of MSCC Funding Statement of Operations (Details) link:presentationLink link:calculationLink link:definitionLink 9955543 - Disclosure - DEBT - Notes Due and SBIC Debentures (Details) link:presentationLink link:calculationLink link:definitionLink 9955544 - Disclosure - FINANCIAL HIGHLIGHTS (Details) link:presentationLink link:calculationLink link:definitionLink 9955545 - Disclosure - DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME - Schedule of Dividend Information (Details) link:presentationLink link:calculationLink link:definitionLink 9955546 - Disclosure - DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME - Schedule of Reconciliation to Taxable Income and to Total Distributions Declared to Common Stockholders (Details) link:presentationLink link:calculationLink link:definitionLink 9955547 - Disclosure - DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME - Schedule of Net Investment Income Related Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 9955548 - Disclosure - DIVIDENDS, DISTRIBUTIONS AND TAXABLE INCOME - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955549 - Disclosure - COMMON STOCK (Details) link:presentationLink link:calculationLink link:definitionLink 9955550 - Disclosure - DIVIDEND REINVESTMENT PLAN (Details) link:presentationLink link:calculationLink link:definitionLink 9955551 - Disclosure - SHARE-BASED COMPENSATION - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955552 - Disclosure - SHARE-BASED COMPENSATION - Schedule of Restricted Stock Authorized and Available for Issuance (Details) link:presentationLink link:calculationLink link:definitionLink 9955553 - Disclosure - SHARE-BASED COMPENSATION - Schedule of Restricted Share Awards (Details) link:presentationLink link:calculationLink link:definitionLink 9955554 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details) link:presentationLink link:calculationLink link:definitionLink 9955554 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details) link:presentationLink link:calculationLink link:definitionLink 9955555 - Disclosure - RELATED PARTY TRANSACTIONS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955556 - Disclosure - RELATED PARTY TRANSACTIONS - Summarizes of Main Street’s Purchases of Shares (Details) link:presentationLink link:calculationLink link:definitionLink 9955557 - Disclosure - SUBSEQUENT EVENTS (Details) link:presentationLink link:calculationLink link:definitionLink 9955558 - Disclosure - Consolidated Schedule of Investments in and Advances to Affiliates (Details) link:presentationLink link:calculationLink link:definitionLink 9955558 - Disclosure - Consolidated Schedule of Investments in and Advances to Affiliates (Details) link:presentationLink link:calculationLink link:definitionLink 9955559 - Disclosure - Consolidated Schedule of Investments in and Advances to Affiliates - Footnotes (Details) link:presentationLink link:calculationLink link:definitionLink