3.26.1 html 1138 271 1 true 180 0 false 6 false false R1.htm 75000 - Document - Cover Sheet http://ofs.com/20260331/taxonomy/role/Cover Cover Cover 1 false false R2.htm 75020 - Statement - Consolidated Statements of Assets and Liabilities (unaudited) Sheet http://ofs.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfAssetsAndLiabilitiesUnaudited Consolidated Statements of Assets and Liabilities (unaudited) Statements 2 false false R3.htm 75030 - Statement - Consolidated Statements of Assets and Liabilities (Parenthetical) Sheet http://ofs.com/20260331/taxonomy/role/ConsolidatedStatementsofAssetsandLiabilitiesParenthetical Consolidated Statements of Assets and Liabilities (Parenthetical) Statements 3 false false R4.htm 75040 - Statement - Consolidated Statements of Operations (unaudited) Sheet http://ofs.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfOperationsUnaudited Consolidated Statements of Operations (unaudited) Statements 4 false false R5.htm 75050 - Statement - Consolidated Statements of Changes in Net Assets (unaudited) Sheet http://ofs.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited Consolidated Statements of Changes in Net Assets (unaudited) Statements 5 false false R6.htm 75060 - Statement - Consolidated Statements of Cash Flows (unaudited) Sheet http://ofs.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited Consolidated Statements of Cash Flows (unaudited) Statements 6 false false R7.htm 75070 - Statement - Consolidated Schedule of Investments Sheet http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestments Consolidated Schedule of Investments Statements 7 false false R8.htm 75080 - Statement - Consolidated Schedule of Investments (Parenthetical) Sheet http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestmentsParenthetical Consolidated Schedule of Investments (Parenthetical) Statements 8 false false R9.htm 75090 - Statement - Consolidated Schedule of Investments (PIK Investment) Sheet http://ofs.com/20260331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsPikInvestment Consolidated Schedule of Investments (PIK Investment) Statements 9 false false R10.htm 995410 - Disclosure - Pay vs Performance Disclosure Sheet http://xbrl.sec.gov/ecd/role/PvpDisclosure Pay vs Performance Disclosure Notes 10 false false R11.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 11 false false R12.htm 995470 - Disclosure - N-2 Sheet http://xbrl.sec.gov/cef/role/N2 N-2 Notes 12 false false R13.htm 995480 - Disclosure - Organization Sheet http://ofs.com/20260331/taxonomy/role/Organization Organization Notes 13 false false R14.htm 995490 - Disclosure - Summary of Significant Accounting Policies Sheet http://ofs.com/20260331/taxonomy/role/SummaryofSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 14 false false R15.htm 995500 - Disclosure - Related Party Transactions Sheet http://ofs.com/20260331/taxonomy/role/RelatedPartyTransactions Related Party Transactions Notes 15 false false R16.htm 995510 - Disclosure - Investments Sheet http://ofs.com/20260331/taxonomy/role/Investments Investments Notes 16 false false R17.htm 995520 - Disclosure - Fair Value of Financial Instruments Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstruments Fair Value of Financial Instruments Notes 17 false false R18.htm 995530 - Disclosure - Commitments and Contingencies Sheet http://ofs.com/20260331/taxonomy/role/CommitmentsandContingencies Commitments and Contingencies Notes 18 false false R19.htm 995540 - Disclosure - Borrowings Sheet http://ofs.com/20260331/taxonomy/role/Borrowings Borrowings Notes 19 false false R20.htm 995560 - Disclosure - Financial Highlights Sheet http://ofs.com/20260331/taxonomy/role/FinancialHighlights Financial Highlights Notes 20 false false R21.htm 995570 - Disclosure - Capital Transactions Sheet http://ofs.com/20260331/taxonomy/role/CapitalTransactions Capital Transactions Notes 21 false false R22.htm 995580 - Disclosure - Consolidated Schedule of Investments In and Advances To Affiliates Sheet http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestmentsInandAdvancesToAffiliates Consolidated Schedule of Investments In and Advances To Affiliates Notes 22 false false R23.htm 995590 - Disclosure - Subsequent Events Sheet http://ofs.com/20260331/taxonomy/role/DisclosureSubsequentEvents Subsequent Events Notes 23 false false R24.htm 995600 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://ofs.com/20260331/taxonomy/role/SummaryofSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://ofs.com/20260331/taxonomy/role/SummaryofSignificantAccountingPolicies 24 false false R25.htm 995610 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://ofs.com/20260331/taxonomy/role/SummaryofSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) Tables http://ofs.com/20260331/taxonomy/role/SummaryofSignificantAccountingPolicies 25 false false R26.htm 995620 - Disclosure - Related Party Transactions (Tables) Sheet http://ofs.com/20260331/taxonomy/role/RelatedPartyTransactionsTables Related Party Transactions (Tables) Tables http://ofs.com/20260331/taxonomy/role/RelatedPartyTransactions 26 false false R27.htm 995630 - Disclosure - Investments (Tables) Sheet http://ofs.com/20260331/taxonomy/role/InvestmentsTables Investments (Tables) Tables http://ofs.com/20260331/taxonomy/role/Investments 27 false false R28.htm 995640 - Disclosure - Fair Value of Financial Instruments (Tables) Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstrumentsTables Fair Value of Financial Instruments (Tables) Tables http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstruments 28 false false R29.htm 995650 - Disclosure - Commitments and Contingencies (Tables) Sheet http://ofs.com/20260331/taxonomy/role/CommitmentsandContingenciesTables Commitments and Contingencies (Tables) Tables http://ofs.com/20260331/taxonomy/role/CommitmentsandContingencies 29 false false R30.htm 995660 - Disclosure - Borrowings (Tables) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsTables Borrowings (Tables) Tables http://ofs.com/20260331/taxonomy/role/Borrowings 30 false false R31.htm 995680 - Disclosure - Financial Highlights (Tables) Sheet http://ofs.com/20260331/taxonomy/role/FinancialHighlightsTables Financial Highlights (Tables) Tables http://ofs.com/20260331/taxonomy/role/FinancialHighlights 31 false false R32.htm 995690 - Disclosure - Capital Transactions (Tables) Sheet http://ofs.com/20260331/taxonomy/role/CapitalTransactionsTables Capital Transactions (Tables) Tables http://ofs.com/20260331/taxonomy/role/CapitalTransactions 32 false false R33.htm 995700 - Disclosure - Consolidated Schedule of Investments In and Advances To Affiliates (Tables) Sheet http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestmentsInandAdvancesToAffiliatesTables Consolidated Schedule of Investments In and Advances To Affiliates (Tables) Tables http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestmentsInandAdvancesToAffiliates 33 false false R34.htm 995710 - Disclosure - Organization (Additional Information) (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureOrganizationAdditionalInformationDetails Organization (Additional Information) (Details) Details http://ofs.com/20260331/taxonomy/role/Organization 34 false false R35.htm 995730 - Disclosure - Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details) Sheet http://ofs.com/20260331/taxonomy/role/SummaryofSignificantAccountingPoliciesCashandCashEquivalentsDetails Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details) Details 35 false false R36.htm 995760 - Disclosure - Related Party Transactions - Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/RelatedPartyTransactionsNarrativeDetails Related Party Transactions - Narrative (Details) Details 36 false false R37.htm 995770 - Disclosure - Related Party Transactions - Expenses and Distributions (Details) Sheet http://ofs.com/20260331/taxonomy/role/RelatedPartyTransactionsExpensesandDistributionsDetails Related Party Transactions - Expenses and Distributions (Details) Details 37 false false R38.htm 995780 - Disclosure - Related Party Transactions - Schedule Of Related Party Transactions (Parenthetical) (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureRelatedPartyTransactionsScheduleOfRelatedPartyTransactionsParentheticalDetails Related Party Transactions - Schedule Of Related Party Transactions (Parenthetical) (Details) Details 38 false false R39.htm 995790 - Disclosure - Investments - Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/InvestmentsNarrativeDetails Investments - Narrative (Details) Details 39 false false R40.htm 995800 - Disclosure - Investments - By Composition and Domicile (Details) Sheet http://ofs.com/20260331/taxonomy/role/InvestmentsByCompositionandDomicileDetails Investments - By Composition and Domicile (Details) Details 40 false false R41.htm 995810 - Disclosure - Investments - By Composition and Domicile (Parenthetical) (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureInvestmentsByCompositionAndDomicileParentheticalDetails Investments - By Composition and Domicile (Parenthetical) (Details) Details 41 false false R42.htm 995820 - Disclosure - Investments - By Industry (Details) Sheet http://ofs.com/20260331/taxonomy/role/InvestmentsByIndustryDetails Investments - By Industry (Details) Details 42 false false R43.htm 995830 - Disclosure - Investments - By Portfolio Concentration (Details) Sheet http://ofs.com/20260331/taxonomy/role/InvestmentsByPortfolioConcentrationDetails Investments - By Portfolio Concentration (Details) Details 43 false false R44.htm 995840 - Disclosure - Investments - By Portfolio Concentration (Parenthetical) (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureInvestmentsByPortfolioConcentrationParentheticalDetails Investments - By Portfolio Concentration (Parenthetical) (Details) Details 44 false false R45.htm 995860 - Disclosure - Fair Value of Financial Instruments - Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstrumentsNarrativeDetails Fair Value of Financial Instruments - Narrative (Details) Details 45 false false R46.htm 995870 - Disclosure - Fair Value of Financial Instruments - Investment Portfolio Measured at Fair Value on a Recurring Basis (Details) Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstrumentsInvestmentPortfolioMeasuredatFairValueonaRecurringBasisDetails Fair Value of Financial Instruments - Investment Portfolio Measured at Fair Value on a Recurring Basis (Details) Details 46 false false R47.htm 995880 - Disclosure - Fair Value of Financial Instruments - Significant Level 3 Inputs (Details) Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstrumentsSignificantLevel3InputsDetails Fair Value of Financial Instruments - Significant Level 3 Inputs (Details) Details 47 false false R48.htm 995890 - Disclosure - Fair Value of Financial Instruments - Level 3 Rollforward (Details) Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstrumentsLevel3RollforwardDetails Fair Value of Financial Instruments - Level 3 Rollforward (Details) Details 48 false false R49.htm 995900 - Disclosure - Fair Value of Financial Instruments - Carrying Values and Fair Values of Debt (Details) Sheet http://ofs.com/20260331/taxonomy/role/FairValueofFinancialInstrumentsCarryingValuesandFairValuesofDebtDetails Fair Value of Financial Instruments - Carrying Values and Fair Values of Debt (Details) Details 49 false false R50.htm 995910 - Disclosure - Commitments and Contingencies (Details) Sheet http://ofs.com/20260331/taxonomy/role/CommitmentsandContingenciesDetails Commitments and Contingencies (Details) Details http://ofs.com/20260331/taxonomy/role/CommitmentsandContingenciesTables 50 false false R51.htm 995920 - Disclosure - Commitments and Contingencies (Additional Information) (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetails Commitments and Contingencies (Additional Information) (Details) Details http://ofs.com/20260331/taxonomy/role/CommitmentsandContingenciesTables 51 false false R52.htm 995930 - Disclosure - Borrowings - Unsecured Notes Narrative (Details) Notes http://ofs.com/20260331/taxonomy/role/BorrowingsUnsecuredNotesNarrativeDetails Borrowings - Unsecured Notes Narrative (Details) Details 52 false false R53.htm 995940 - Disclosure - Borrowings - Natixis Facility Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureBorrowingsNatixisFacilityNarrativeDetails Borrowings - Natixis Facility Narrative (Details) Details 53 false false R54.htm 995950 - Disclosure - Borrowings - Unsecured Notes Interest Expense and Average Outstanding Balance (Details) Notes http://ofs.com/20260331/taxonomy/role/BorrowingsUnsecuredNotesInterestExpenseandAverageOutstandingBalanceDetails Borrowings - Unsecured Notes Interest Expense and Average Outstanding Balance (Details) Details 54 false false R55.htm 995960 - Disclosure - Borrowings - Banc of California Credit Facility Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsBancofCaliforniaCreditFacilityNarrativeDetails Borrowings - Banc of California Credit Facility Narrative (Details) Details 55 false false R56.htm 995970 - Disclosure - Borrowings - Banc of California Credit Facility Interest Expense and Average Outstanding Balance (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsBancofCaliforniaCreditFacilityInterestExpenseandAverageOutstandingBalanceDetails Borrowings - Banc of California Credit Facility Interest Expense and Average Outstanding Balance (Details) Details 56 false false R57.htm 995990 - Disclosure - Borrowings - BNP Facility Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsBNPFacilityNarrativeDetails Borrowings - BNP Facility Narrative (Details) Details 57 false false R58.htm 996000 - Disclosure - Borrowings - BNP Facility Interest Expense and Average Outstanding Balance (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsBNPFacilityInterestExpenseandAverageOutstandingBalanceDetails Borrowings - BNP Facility Interest Expense and Average Outstanding Balance (Details) Details 58 false false R59.htm 996010 - Disclosure - Borrowings - SBA Debentures Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsSBADebenturesNarrativeDetails Borrowings - SBA Debentures Narrative (Details) Details 59 false false R60.htm 996020 - Disclosure - Borrowings - Natixis Facility Interest Expense and Average Outstanding Balance (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureBorrowingsNatixisFacilityInterestExpenseAndAverageOutstandingBalanceDetails Borrowings - Natixis Facility Interest Expense and Average Outstanding Balance (Details) Details 60 false false R61.htm 996030 - Disclosure - Borrowings - Average Dollar Borrowings and Weighted Average Effective Interest Rate (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsAverageDollarBorrowingsandWeightedAverageEffectiveInterestRateDetails Borrowings - Average Dollar Borrowings and Weighted Average Effective Interest Rate (Details) Details 61 false false R62.htm 996040 - Disclosure - Borrowings - Maturity (Details) Sheet http://ofs.com/20260331/taxonomy/role/BorrowingsMaturityDetails Borrowings - Maturity (Details) Details 62 false false R63.htm 996080 - Disclosure - Federal Income Tax - Cost of Investments and Associated Gross Unrealized Appreciation (Depreciation) (Details) Sheet http://ofs.com/20260331/taxonomy/role/FederalIncomeTaxCostofInvestmentsandAssociatedGrossUnrealizedAppreciationDepreciationDetails Federal Income Tax - Cost of Investments and Associated Gross Unrealized Appreciation (Depreciation) (Details) Details 63 false false R64.htm 996120 - Disclosure - Financial Highlights (Details) Sheet http://ofs.com/20260331/taxonomy/role/FinancialHighlightsDetails Financial Highlights (Details) Details http://ofs.com/20260331/taxonomy/role/FinancialHighlightsTables 64 false false R65.htm 996130 - Disclosure - Capital Transactions - Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/CapitalTransactionsNarrativeDetails Capital Transactions - Narrative (Details) Details 65 false false R66.htm 996140 - Disclosure - Capital Transactions - Distributions (Details) Sheet http://ofs.com/20260331/taxonomy/role/CapitalTransactionsDistributionsDetails Capital Transactions - Distributions (Details) Details 66 false false R67.htm 996150 - Disclosure - Capital Transactions - DRIP Participation (Details) Sheet http://ofs.com/20260331/taxonomy/role/CapitalTransactionsDRIPParticipationDetails Capital Transactions - DRIP Participation (Details) Details 67 false false R68.htm 996160 - Disclosure - Consolidated Schedule of Investments In and Advances To Affiliates (Details) Sheet http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestmentsInandAdvancesToAffiliatesDetails Consolidated Schedule of Investments In and Advances To Affiliates (Details) Details http://ofs.com/20260331/taxonomy/role/ConsolidatedScheduleofInvestmentsInandAdvancesToAffiliatesTables 68 false false R69.htm 996170 - Disclosure - Subsequent Events Narrative (Details) Sheet http://ofs.com/20260331/taxonomy/role/DisclosureSubsequentEventsNarrativeDetails Subsequent Events Narrative (Details) Details 69 false false All Reports Book All Reports ofs-20260331.htm ofs-20260331.xsd http://fasb.org/srt/2025 http://fasb.org/us-gaap/2025 http://xbrl.sec.gov/cef/2025 http://xbrl.sec.gov/dei/2025 http://xbrl.sec.gov/ecd/2025 false false