Document and Entity Information [Abstract] Document Information [Table] Class of Stock [Axis] Class of Stock [Domain] Common Stock [Member] Common Stock Represents the information pertaining to 7.875% 2028 Notes. 7.875% 2028 Notes 7.875% 2028 Notes Document Information [Line Items] Document Information Document Type Document Annual Report Document Period End Date Document Transition Report Document Fiscal Year Focus Current Fiscal Year End Date Entity File Number Entity Registrant Name Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, City or Town Entity Address State Or Province Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Trading Symbol Security Exchange Name Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company ICFR Auditor Attestation Flag Document Financial Statement Error Correction [Flag] Entity Shell Company Entity Public Float Entity Common Stock, Shares Outstanding Entity Central Index Key Document Fiscal Period Focus Amendment Flag Auditor Name Auditor Location Auditor Firm ID Consolidated Statements of Assets and Liabilities Statement [Table] Investment, Issuer Affiliation [Axis] Investment, Issuer Affiliation [Domain] Non-controlled/non-affiliate company investments Non-controlled/non-affiliate company investments Non-controlled affiliate company investments Non-controlled affiliate company investments Controlled affiliate company investments Controlled affiliate company investments Statement [Line Items] Statement [Line Items] Assets [Abstract] Assets Investment Owned, at Fair Value Ending Fair Value Beginning Fair Value Investments, fair value Total investments, at fair value (amortized cost $607,574 and $695,240, respectively) Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Restricted Cash and Cash Equivalents, Noncurrent Restricted cash and cash equivalents Cash, Held in Foreign Currency Restricted foreign currency (cost of $405 and $894, respectively) Restricted foreign currency Interest And Dividend Receivable Interest And Dividend Receivable Interest and dividend receivable Receivable from Broker-Dealer and Clearing Organization Amounts receivable on unsettled investment transactions Prepaid Expenses And Other Receivables Prepaid Expenses And Other Receivables Prepaid expenses and other receivables The amount of unrealized appreciation on derivative instruments. Derivative Instruments, Unrealized Appreciation Unrealized appreciation Unrealized appreciation on foreign currency forward contracts Assets Total assets Liabilities [Abstract] Liabilities Long-Term Debt Amortized Cost Debt (net of unamortized debt issuance costs of $4,666 and $2,876, respectively) Distribution Payable Distributions payable Management Fee Payable Management fees payable Incentive Fee Payable Incentive fees payable Payable, Investment, Purchase Amounts payable on unsettled investment transactions Interest Payable Interest payable on credit facility Interest payable Accounts Payable and Accrued Liabilities Accounts payable and accrued expenses Advances Received From Unfunded Credit Facilities Advances Received From Unfunded Credit Facilities Advances received from unfunded credit facilities Derivative Liability Net Amount of Derivative Liabilities Unrealized depreciation on foreign currency forward contracts Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies (See Note 8) Stockholders' Equity Attributable to Parent [Abstract] Net assets Common Stock, Value, Issued Common stock, 22,234,045 and 23,243,088 shares issued and outstanding, par value $0.001 per share, respectively, and 100,000,000 shares authorized Additional Paid in Capital Paid-in capital in excess of par Retained Earnings (Accumulated Deficit) Accumulated earnings (losses) Stockholders' Equity Attributable to Parent Total net assets Liabilities and Equity Total liabilities and total net assets Common Stock, Shares, Outstanding Shares outstanding end of period Number of shares outstanding Common stock, share outstanding Net Asset Value Per Share Net asset value, end of period Net asset value, beginning of period Net asset value per share Investment Owned, at Cost Investments, amortized cost Cost of investment Cash, Held in Foreign Currency, Acquisition Cost Restricted foreign currency, cost Debt Issuance Costs, Net Unamortized debt issuance costs Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, Shares, Issued Ending Balance (in shares) Beginning Balance (in shares) Common stock, shares issued Consolidated Statements of Operations Revenues [Abstract] Investment income Interest Income, Operating, Paid in Cash Interest income Interest Income, Operating, Paid in Kind Payment-in-kind income Investment Fee Income Investment Fee Income Fee income Dividend Income, Operating, Paid in Cash Dividend income Gross Investment Income, Operating Total investment income Investment Company, Expense, after Reduction of Fee Waiver and Reimbursement [Abstract] Expenses Interest Expense Interest expense Management Fee Expense Total management fees Base management fees Incentive Fee Expense Performance-based incentive fees Administrative Fees Expense Administrative service fees General and Administrative Expense General and administrative expenses Investment Income, Investment Expense Total expenses, before fees waived Amount of incentive fees waived by investment company. Investment Company, Incentive Fees Waived Performance-based incentive fees waived Investment Company, Expense, after Reduction of Fee Waiver and Reimbursement Total expenses Investment Income Operating Before Expense And Tax Investment Income Operating Before Expense And Tax Net investment income before excise tax Investment Excise Tax Investment Excise Tax Excise tax Net Investment Income Net investment income after excise tax Realized Investment Gains (Losses) [Abstract] Realized and unrealized gains (losses) on investments and foreign currency transactions Gain (Loss) on Sale of Investments Net realized (gains) losses on investments Net realized losses on investments Net realized gains (losses) Foreign Currency Transaction Gain (Loss), Realized Realized gain (loss) on forward currency contracts Foreign currency transactions Gain (Loss) on Sale of Derivatives Foreign currency forward contracts The amount of Gain (Loss) on investments, derivatives and foreign currency translation before tax. Realized Gain (Loss) on Investment, Derivative and Foreign Currency Transaction and Other Before Tax Net realized gains (losses) Debt and Equity Securities, Unrealized Gain (Loss) Net unrealized (appreciation) depreciation on investments Net Change in Unrealized Appreciation (Depreciation) Net change in unrealized appreciation (depreciation) Foreign Currency Transaction Gain (Loss), Unrealized, Excluding Investment Price Change, before Tax Translation of assets and liabilities in foreign currencies Unrealized Gain (Loss) on Derivatives Net unrealized (appreciation) depreciation on foreign currency forward contracts Forward currency contracts Foreign currency forward contracts The amount of unrealized gain loss on investment, derivative and foreign currency translation before tax. Unrealized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction, Operating, Before Tax Net change in unrealized appreciation (depreciation) Realized and Unrealized Gain (Loss), Investment, Derivative, and Foreign Currency Transaction Price Change, Operating, before Tax Net realized and unrealized gains (losses) on investments and foreign currency transactions Net increase in net assets resulting from operations Net increase (decrease) in net assets resulting from operations Net increase (decrease) in net assets resulting from operations CHANGE IN NET ASSETS RESULTING FROM OPERATIONS PER COMMON SHARE Per Common Share Data Earnings Per Share, Basic Basic per share net increase (decrease) in net assets resulting from operations Basic earnings (losses) per common share Earnings Per Share, Diluted Diluted per share net increase (decrease) in net assets resulting from operations Diluted earnings (losses) per common share Common Stock, Dividends, Per Share, Cash Paid Dividends and distributions declared per common share Weighted Average Number of Shares Outstanding, Basic Weighted average shares outstanding, basic Basic weighted average common shares outstanding Weighted Average Number of Shares Outstanding, Diluted Weighted average shares outstanding, diluted Diluted weighted average common shares outstanding Consolidated Statements of Changes in Net Assets Equity Components [Axis] Equity Component [Domain] Additional Paid-in Capital [Member] Paid-in Capital in Excess of Par Retained Earnings [Member] Accumulated Earnings (Losses) Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Ending Balance Beginning Balance Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest [Abstract] Net increase (decrease) in net assets resulting from operations: Stock Repurchased and Retired During Period, Value Purchases of common stock, net of offering costs Stock Repurchased and Retired During Period, Shares Purchases of common stock, net of offering costs (in shares) Investment Income, Operating, after Expense and Tax Net investment income after excise tax Realized Gain (Loss), Investment and Derivative, Operating, after Tax Net realized gains (losses) on investments and foreign currency transactions Unrealized Gain (Loss), Investment and Derivative, Operating, after Tax Net change in unrealized appreciation (depreciation) on investments and foreign currency transactions Investment Company, Dividend Distribution Distributions declared Total distributions Distributions declared Amount of increase (decrease) from reclassification to paid-in capital of permanent difference for distribution to ownership interest holder by investment company. Investment Company, Tax Reclassification Of Increase (Decrease) Tax reclassification of stockholders' equity Consolidated Statements of Cash Flows Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net increase (decrease) in net assets resulting from operations to net cash provided by / (used in) operating activities: Amount of interest income from investment paid in kind, classified as operating including accrued income from prior periods. Interest Income Operating Paid In Kind Including Accrued Income Payment-in-kind income Foreign Currency Transaction Gain (Loss), before Tax Net realized loss on foreign currency translation Total net realized and unrealized gains (losses) on forward currency contracts Net unrealized appreciation depreciation on translation of assets and liabilities in foreign currencies Net unrealized appreciation depreciation on translation of assets and liabilities in foreign currencies Net unrealized (appreciation) depreciation on translation of assets and liabilities in foreign currencies Amortization of Debt Discount (Premium) Accretion of discount Amortization of Debt Issuance Costs Amortization of deferred financing costs Amortization of debt issuance costs Payments for Purchase of Investment, Operating Activity Acquisition of investments Proceeds from Disposition of Investment, Operating Activity Paydown received under investments Proceeds from principal payments and sales of portfolio investments The amount of proceeds from sale of investments to Joint Venture. Proceeds from Disposition of Investments to Joint venture Proceeds from sales of portfolio investments to STRS JV Increase (Decrease) in Operating Capital [Abstract] Net changes in operating assets and liabilities: Increase (Decrease) in Interest and Dividends Receivable Interest and dividend receivable Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other receivables Increase (Decrease) in Receivable for Investment Sold Amounts receivable on unsettled investment transactions Increase (Decrease) in Payable for Investment Purchased Amounts payable on unsettled investment transactions Increase (Decrease) in Management Fee Payable Management fees payable Increase (Decrease) in Incentive Fee Payable Incentive fees payable Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and accrued expenses Increase (Decrease) in Interest Payable, Net Interest payable Line of Credit Facility, Increase (Decrease), Net Advances received from unfunded credit facilities Increase in credit facility limit Net Cash Provided by (Used in) Operating Activities Net cash provided by / (used in) operating activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities Proceeds from Notes Payable Proceeds from notes issued Payments for Repurchase of Common Stock Purchases of common stock, net of offering costs Proceeds from Issuance of Long-Term Debt Borrowings Repayments of Long-Term Debt Repayments of debt Payments of Loan Costs Deferred financing costs Amount of cash outflow to dividend distribution. Investment Company, Payments of Dividend Distribution Distributions paid to common stockholders, net of distributions reinvested Net Cash Provided by (Used in) Financing Activities Net cash provided by / (used in) financing activities Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations Effect of exchange rate changes on cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net change in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Cash, cash equivalents and restricted cash at end of period Cash, cash equivalents and restricted cash at beginning of period Total cash and cash equivalents, restricted cash and cash equivalents and restricted foreign currency presented in consolidated statements of cash flows Supplemental Cash Flow Information [Abstract] Supplemental and non-cash disclosure of cash flow information: Interest Paid, Excluding Capitalized Interest, Operating Activities Interest paid Income Taxes Paid, Net Taxes, including excise tax, paid during the year Transfer to Investments Non-cash exchanges of investments No definition available. Reconciliation of cash, cash equivalents [Abstract] Reconciliation of cash, cash equivalents Restricted Cash and Cash Equivalents Restricted cash and cash equivalents Consolidated Schedule of Investments Schedule of Investments [Table] Investment, Issuer Name [Axis] Investment, Issuer Name [Domain] Represents the information pertaining to MSI Information Services, Inc. MSI Information Services, Inc [Member] MSI Information Services, Inc. Alvaria Holdco. Alvaria Holdco [Member] Alvaria Holdco Honors Holdings, LLC [Member] Honors Holdings, LLC [Member] Honors Holdings, LLC Represents the information pertaining to Telestream Holdings Corporation Telestream Holdings Corporation [Member] Telestream Holdings Corporation Investment Type [Axis] Investments [Domain] Debt Investments First Lien Secured Term Loan [Member] First Lien Secured Term Loan [Member] Subordinated Debt [Member] Subordinated Notes Equity Investments Equity (excluding STRS JV) Warrant [Member] Warrant Money Market Funds [Member] Money Market Funds Represents information about Goldman Sachs Money Market Fund. Goldman Sachs Money Market Fund [Member] Goldman Sachs Money Market Fund (CUSIP: 38141W315) Represents information about Invesco Treasury Money Market Fund. Invesco Treasury Money Market [Member] Invesco Treasury Money Market Fund (CUSIP: 825252406) Represents information about Dreyfus treasury obligations cash management fund. Dreyfus Treasury Obligations Cash Management Fund [Member] Dreyfus Treasury Obligations Cash Management Fund (CUSIP: 261908107)