Capital Gains Based Incentive Fees, Rate

No definition available.

Name:	bxsl_CapitalGainsBasedIncentiveFeesRate
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Income Based Incentive Fees, Cap, Percentage Of Cumulative Net Return

+ References

No definition available.

+ Details

Name:	bxsl_IncomeBasedIncentiveFeesCapPercentageOfCumulativeNetReturn
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Income Based Incentive Fees, Catch-Up Amount, Annualized Percentage

+ References

No definition available.

+ Details

Name:	bxsl_IncomeBasedIncentiveFeesCatchUpAmountAnnualizedPercentage
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Income Based Incentive Fees, Catch-Up Amount, Percentage

+ References

No definition available.

+ Details

Name:	bxsl_IncomeBasedIncentiveFeesCatchUpAmountPercentage
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Income Based Incentive Fees, Percentage Of Pre-Incentive Fee Net Investment Income

+ References

No definition available.

+ Details

Name:	bxsl_IncomeBasedIncentiveFeesPercentageOfPreIncentiveFeeNetInvestmentIncome
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Income Based Incentive Fees, Rate

+ References

No definition available.

+ Details

Name:	bxsl_IncomeBasedIncentiveFeesRate
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Investment Company, Agreement, Number Of Components

+ References

No definition available.

+ Details

Name:	bxsl_InvestmentCompanyAgreementNumberOfComponents
Namespace Prefix:	bxsl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Management And Service Fees, Income Based Incentive Rate, Catch up, Percentage

+ References

No definition available.

+ Details

Name:	bxsl_ManagementAndServiceFeesIncomeBasedIncentiveRateCatchUpPercentage
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Related Party Transaction, Income Based Incentive Fee, Quarterly Hurdle Rate

+ References

No definition available.

+ Details

Name:	bxsl_RelatedPartyTransactionIncomeBasedIncentiveFeeQuarterlyHurdleRate
Namespace Prefix:	bxsl_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for capital-gain-based incentive fee for performance under arrangement to manage operation, including, but not limited to, managing investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

+ Details

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

- Definition

Amount of expense for income-based incentive fee for performance under arrangement to manage operation, including, but not limited to, managing investment.

+ References

+ Details

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

- Definition

Amount of capital-gain-based incentive fee payable for performance under arrangement to manage operation, including, but not limited to, managing investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(12)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1

+ Details

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

- Definition

Amount of income-based incentive fee payable for performance under arrangement to manage operation, including, but not limited to, managing investment.

+ References

+ Details

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

- Definition

Rate based on performance for management and service fees under arrangement to manage operations, including, but not limited to, investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

+ Details

Name:	us-gaap_ManagementAndServiceFeesIncentiveRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-3

Reference 4: 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 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=bxsl_InvestmentManagementAgreementIncentiveRateQuarterlyHurdleRateMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=bxsl_InvestmentManagementAgreementIncentiveRateAnnualizedHurdleRateMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=bxsl_InvestmentAdvisoryAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	bxsl_VoluntaryWaiverScenarioAxis=bxsl_VoluntaryWaiverNotInPlaceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	bxsl_IncomeBasedIncentiveFeesScenarioAxis=bxsl_PreIncentiveFeeNetInvestmentIncomeForTrailingTwelveQuartersLessThanOrEqualToCatchUpAmountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	bxsl_IncomeBasedIncentiveFeesScenarioAxis=bxsl_PreIncentiveFeeNetInvestmentIncomeForTrailingTwelveQuartersGreaterThanCatchUpAmountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Agreements and Related Party Transactions - Incentive Fees (Details)			3 Months Ended		6 Months Ended		29 Months Ended
	Oct. 28, 2021	Oct. 18, 2021	Jun. 30, 2025 USD ($) component	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) component	Jun. 30, 2024 USD ($)	Mar. 31, 2024	Dec. 31, 2024 USD ($)
Related Party Transaction [Line Items]
Income based incentive fees (Note 3)			$ 34,718,000	$ 37,380,000	$ 69,019,000	$ 73,225,000
Income based incentive fees payable (Note 3)			34,718,000		34,718,000			$ 38,708,000
Capital gains based incentive fees (Note 3)			0	$ 3,122,000	0	$ 6,256,000
Capital gains based incentive fees payable (Note 3)			$ 0		$ 0			$ 0
Investment Management Agreement - Incentive Rate, Quarterly Hurdle Rate \| Affiliated Entity
Related Party Transaction [Line Items]
Incentive fees rate					1.50%
Investment Management Agreement - Incentive Rate, Annualized Hurdle Rate \| Affiliated Entity
Related Party Transaction [Line Items]
Incentive fees rate					6.00%
Investment Advisory Agreement
Related Party Transaction [Line Items]
Number of components \| component			1		1
Income based incentive rate	17.50%
Quarterly hurdle rate	1.50%
Incentive rate, catch up, percentage	100.00%
Capital gains based incentive rate							17.50%
Investment Advisory Agreement \| Affiliated Entity
Related Party Transaction [Line Items]
Number of components \| component			2		2
Quarterly hurdle rate		1.50%
Investment Advisory Agreement \| Voluntary Waiver Not In Place
Related Party Transaction [Line Items]
Pre incentive fee cap percentage	17.50%
Investment Advisory Agreement \| Pre-Incentive Fee Net Investment Income For Trailing Twelve Quarters Less Than Or Equal To Catch-Up Amount
Related Party Transaction [Line Items]
Payment of pre incentive rate investment income, percentage	100.00%
Investment Advisory Agreement \| Pre-Incentive Fee Net Investment Income For Trailing Twelve Quarters Less Than Or Equal To Catch-Up Amount \| Voluntary Waiver Not In Place
Related Party Transaction [Line Items]
Catch-up amount prior to the waiver period	1.82%
Annual catch up amount prior to the waiver period	7.27%
Investment Advisory Agreement \| Pre-Incentive Fee Net Investment Income For Trailing Twelve Quarters Greater Than Catch-Up Amount \| Voluntary Waiver Not In Place
Related Party Transaction [Line Items]
Payment of pre incentive rate investment income, percentage	17.50%