Debt instrument percentage of interest retained.

No definition available.

Name:	bcsf_DebtInstrumentPercentageOfInterestRetained
Namespace Prefix:	bcsf_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt that is retained.

+ References

No definition available.

+ Details

Name:	bcsf_DebtInstrumentRetained
Namespace Prefix:	bcsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of investments in equity interests.

+ References

No definition available.

+ Details

Name:	bcsf_EquityMethodInvestmentEquityInterests
Namespace Prefix:	bcsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Equity method investment preferred equity interests.

+ References

No definition available.

+ Details

Name:	bcsf_EquityMethodInvestmentPreferredEquityInterests
Namespace Prefix:	bcsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of investments in subordinated notes.

+ References

No definition available.

+ Details

Name:	bcsf_EquityMethodInvestmentSubordinatedNotes
Namespace Prefix:	bcsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Investment membership interest amount

+ References

No definition available.

+ Details

Name:	bcsf_InvestmentMembershipInterestAmount
Namespace Prefix:	bcsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of voting equity interest acquired in business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-8

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 38
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479303/805-10-55-38

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of outstanding long-term debt or borrowing associated with any securities or credit agreement for which there has been a default in principal, interest, sinking fund, or redemption provisions, or any breach of covenant that existed at the end of the period and subsequently has not been cured.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

Name:	us-gaap_DebtDefaultLongtermDebtAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of the entity's equity method investment which has been sold.

+ References

No definition available.

+ Details

Name:	us-gaap_EquityMethodInvestmentSoldCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

+ Details

Name:	us-gaap_GainLossOnSaleOfInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481303/470-50-40-2

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481303/470-50-40-4

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

Name:	us-gaap_InvestmentCompanyNonconsolidatedSubsidiaryLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates type of variable interest rate of investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-12A(Column A)(Footnote 3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12(Column A)(Footnote 4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-12B(Column A)(Footnote 3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(Column A)(Footnote 3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6

+ Details

Name:	us-gaap_InvestmentVariableInterestRateTypeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482987/272-10-50-3

+ Details

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Total contributions made by each class of partners (i.e., general, limited and preferred partners).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 4.F)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

+ Details

Name:	us-gaap_PartnersCapitalAccountContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

Name:	us-gaap_PaymentsToAcquireInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash inflow from sale of investment, classified as operating activity. Includes, but is not limited to, repayment, principal payment, paydown, and maturity of investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 230
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477867/946-230-45-1

+ Details

Name:	us-gaap_ProceedsFromDispositionOfInvestmentOperatingActivity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_Notes2018OneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_Notes2023OneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_Notes2024OneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_Notes2025OneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassATwoRTwoZeroOneEightOneNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassbRSeniorDeferrableFloatingRateNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClasscRSeniorDeferrableFloatingRateNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=bcsf_BccMiddleMarketClo2018LlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=bcsf_BainCapitalSeniorLoanProgramLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=bcsf_MM222CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=bcsf_MM233CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=bcsf_MMCLOWH3CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_PreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherOwnershipInterestsByNameAxis=bcsf_MembershipInterestsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassAOneRTwoZeroOneEightOneNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassAJRTwoZeroOneEightOneNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassBRTwoZeroOneEightOneNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassCRTwoZeroOneEightOneNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassDRTwoZeroOneEightOneNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassD-RSeniorDeferrableFloatingRateNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassE-RSeniorDeferrableFloatingRateNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bcsf_ClassENotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=bcsf_AmberstoneCo.Ltd.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Investments - SLP (Details) - USD ($)												3 Months Ended
Investments - SLP (Details) - USD ($)	Aug. 13, 2025	Jul. 08, 2025	Dec. 09, 2024	Jul. 10, 2024	Mar. 13, 2024	Sep. 27, 2023	Jun. 15, 2023	Aug. 24, 2022	Mar. 07, 2022	Feb. 09, 2022	Nov. 30, 2021	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	May 20, 2024	Aug. 09, 2023
Investment Company, Nonconsolidated Subsidiary [Line Items]
Investments sold												$ 2,486,100,000
Investments purchased												102,500,000
Proceeds from principal payments and sales of investments												245,867,000	$ 251,317,000
Maximum borrowing capacity															$ 1,500,000,000
Total aggregate principal amount committed												$ 2,127,000,000		$ 2,077,000,000
Weighted average interest rate of debt (as a percent)												4.60%		4.80%
2018-1 Notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Net realized loss on extinguishment of debt					$ (1,300,000)
2023-1 Notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Term Debt Secuiritisation																$ 400,000,000
2024-1 Notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Term Debt Secuiritisation				$ 450,400,000
2025-1 Notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Term Debt Secuiritisation		$ 349,100,000
Class A-2-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)					2.90%
Total aggregate principal amount committed					$ 30,000,000
Class BR senior deferrable floating rate notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Debt instrument retained											$ 32,500,000
Total aggregate principal amount committed											47,500,000
Class CR senior deferrable floating rate notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Debt instrument retained											25,000,000
Total aggregate principal amount committed											$ 25,000,000
BCC Middle Market CLO 20181 LLC \| 2018-1 Notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)							0.26%
Investment, Variable Interest Rate, Type [Extensible Enumeration]							us-gaap:SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Bain Capital Senior Loan Program, LLC
Investment Company, Nonconsolidated Subsidiary [Line Items]
Subordinated notes												$ 166,900,000		$ 157,900,000
Total aggregate principal amount committed	$ 331,600,000				500,000,000
Weighted average interest rate of debt (as a percent)												6.10%		6.90%
Bain Capital Senior Loan Program, LLC \| M M 22 2 Credit Facility [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Maximum borrowing capacity								$ 225,000,000
Spread rate (as a percent)								2.10%
Investment, Variable Interest Rate, Type [Extensible Enumeration]								us-gaap:SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Bain Capital Senior Loan Program, LLC \| M M 23 3 Credit Facility [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Maximum borrowing capacity						$ 140,000,000
Spread rate (as a percent)						2.85%
Investment, Variable Interest Rate, Type [Extensible Enumeration]						us-gaap:SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Bain Capital Senior Loan Program, LLC \| MM CLO WH 3 Credit Facility [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Maximum borrowing capacity			$ 300,000,000
Spread rate (as a percent)			200.00%
Investment, Variable Interest Rate, Type [Extensible Enumeration]			us-gaap:SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
Bain Capital Senior Loan Program, LLC \| Preferred Stock [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Investments at fair value												$ 1,800,000		$ 1,800,000
Bain Capital Senior Loan Program, LLC \| Common Stock [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Equity interests												$ 3,600,000		$ 5,000,000
Bain Capital Senior Loan Program, LLC \| 2018-1 Notes \| Membership Interests [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Total aggregate principal amount committed					22,400,000
Investment membership interest					$ 60,000,000
Bain Capital Senior Loan Program, LLC \| 2023-1 Notes \| Membership Interests [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Investment membership interest	$ 45,600,000
Debt instrument percentage of interest retained	100.00%
Bain Capital Senior Loan Program, LLC \| 2024-1 Notes \| Membership Interests [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Investment membership interest				$ 76,400,000
Debt instrument percentage of interest retained				100.00%
Bain Capital Senior Loan Program, LLC \| 2025-1 Notes \| Membership Interests [Member]
Investment Company, Nonconsolidated Subsidiary [Line Items]
Investment membership interest		$ 53,400,000
Debt instrument percentage of interest retained		100.00%
Bain Capital Senior Loan Program, LLC \| Class A-1-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)	1.58%				2.25%
Total aggregate principal amount committed	$ 188,500,000				$ 290,000,000
Bain Capital Senior Loan Program, LLC \| Class A-J-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)					2.70%
Total aggregate principal amount committed					$ 20,000,000
Bain Capital Senior Loan Program, LLC \| Class A-2-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)	1.80%
Total aggregate principal amount committed	$ 9,800,000
Bain Capital Senior Loan Program, LLC \| Class B-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)					3.90%
Total aggregate principal amount committed					$ 40,000,000
Bain Capital Senior Loan Program, LLC \| Class C-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)					5.90%
Total aggregate principal amount committed					$ 30,000,000
Bain Capital Senior Loan Program, LLC \| Class D-R
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)					8.32%
Total aggregate principal amount committed					$ 30,000,000
Bain Capital Senior Loan Program, LLC \| Class BR senior deferrable floating rate notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)	1.90%
Total aggregate principal amount committed	$ 22,800,000
Bain Capital Senior Loan Program, LLC \| Class CR senior deferrable floating rate notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)	2.25%
Debt instrument retained	$ 27,600,000
Total aggregate principal amount committed	$ 27,600,000
Bain Capital Senior Loan Program, LLC \| Class DR senior deferrable floating rate notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)	3.25%
Debt instrument retained	$ 17,900,000
Total aggregate principal amount committed	$ 17,900,000
Bain Capital Senior Loan Program, LLC \| Class ER senior deferrable floating rate notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Spread rate (as a percent)	6.50%
Debt instrument retained	$ 19,500,000
Total aggregate principal amount committed	$ 19,500,000
Bain Capital Senior Loan Program, LLC \| Class E notes
Investment Company, Nonconsolidated Subsidiary [Line Items]
Debt instrument retained				$ 25,500,000
Bain Capital Senior Loan Program, LLC \| BCC Middle Market CLO 20181 LLC
Investment Company, Nonconsolidated Subsidiary [Line Items]
Membership equity interest acquired									70.00%	70.00%
Membership interests (as a percent)									30.00%	30.00%
Proceeds from principal payments and sales of investments									$ 56,100,000
Net realized gain from sale of investment									$ 1,200,000
Amberstone Co., Ltd. \| Bain Capital Senior Loan Program, LLC
Investment Company, Nonconsolidated Subsidiary [Line Items]
Economic ownership interest										50.00%
Initial capital contributions										$ 179,000,000