Debt Instrument, Credit Spread Adjustment

No definition available.

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- Definition

Debt Instrument, Ownership Percentage For Immediate Conversion

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Debt Instrument, Variable Interest Rate, Floor

+ References

No definition available.

+ Details

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Namespace Prefix:	bbdc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, accordion feature, increase limit, subject to certain conditions by obtaining additional commitments from existing and/or new lenders.

+ References

No definition available.

+ Details

Name:	bbdc_LineOfCreditFacilityAccordionFeatureAggregateLimit
Namespace Prefix:	bbdc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility, Unused Capacity, Less Than Two-Thirds Of Commitment Fee Percentage

+ References

No definition available.

+ Details

Name:	bbdc_LineOfCreditFacilityUnusedCapacityLessThanTwoThirdsOfCommitmentFeePercentage
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Interest Rate Increase

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Line Of Credit, Interest Rate Step Up To Increase Pursuant To Debt To Total Assets Threshold

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Line Of Credit, Repayment Period After Maturity

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
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+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
-Paragraph 6
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-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
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+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount, before accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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+ Details

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

- 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

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Details

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- Details

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- Details

Name:	bbdc_InterestPeriodAxis=bbdc_InterestPeriodOfOneMonthMember
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- Details

Name:	bbdc_InterestPeriodAxis=bbdc_InterestPeriodOfThreeMonthMember
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Name:	bbdc_InterestPeriodAxis=bbdc_InterestPeriodOfSixMonthMember
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Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
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- Details

Name:	us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingInvestmentGradeMember
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- Details

Name:	us-gaap_VariableRateAxis=bbdc_SecuredOvernightFinancingRateSOFRMember
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Name:	us-gaap_VariableRateAxis=bbdc_ApplicableRateMember
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Name:	us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingNonInvestmentGradeMember
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Name:	us-gaap_VariableRateAxis=bbdc_ScreenRateMember
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Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsPurchasedMember
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Name:	us-gaap_DebtInstrumentAxis=bbdc_BorrowingsDenominatedInUSDollarsUnderFebruary2019CreditFacilityMember
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Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Name:	us-gaap_VariableRateAxis=bbdc_StockholmInterbankOfferedRateSTIBORMember
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Name:	us-gaap_VariableRateAxis=bbdc_EuroInterbankOfferedRateEURIBORMember
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- Details

Name:	us-gaap_DebtInstrumentAxis=bbdc_SeriesASeniorUnsecuredNotesDueAugust2025Member
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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
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BORROWINGS - Additional information (Details) € in Millions, £ in Millions, kr in Millions		1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 23, 2021 USD ($)	Feb. 28, 2019 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Mar. 31, 2023 SEK (kr)	Mar. 31, 2023 GBP (£)	Mar. 31, 2023 EUR (€)	Dec. 31, 2022 SEK (kr)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Apr. 30, 2022 USD ($)	Apr. 01, 2022 USD ($)	Feb. 25, 2022 USD ($)	Nov. 04, 2021 USD ($)	Feb. 25, 2021 USD ($)	Nov. 04, 2020 USD ($)	Sep. 29, 2020 USD ($)	Sep. 24, 2020 USD ($)	Aug. 03, 2020 USD ($)
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 769,112,000	$ 729,144,000
February 21, 2019 \| Line of Credit
Debt Instrument [Line Items]
Commitment aggregate amount		$ 800,000,000	$ 1,100,000,000	1,100,000,000								$ 1,100,000,000	$ 965,000,000	$ 875,000,000
Line of credit facility commitment aggregate value		$ 1,200,000,000										$ 1,500,000,000	$ 1,500,000,000
Debt instrument, basis spread on variable floor rate (as percent)		1.00%
Percentage of unused portion of credit facility, greater than two-third of commitments (as percent)		0.50%
Percentage of unused portion of credit facility, less than two-third of commitments (as percent)		0.375%
Debt issuance costs, financing fees		$ 6,400,000									$ 1,700,000
Effective interest rate			6.277%		6.277%	6.277%	6.277%
Line Of Credit, Repayment Period After Maturity			1 year
February 21, 2019 \| Line of Credit \| Interest Period Of One Month
Debt Instrument [Line Items]
Debt instrument, credit spread adjustment		0.0010
February 21, 2019 \| Line of Credit \| Interest Period Of Three Month
Debt Instrument [Line Items]
Debt instrument, credit spread adjustment		0.0015
February 21, 2019 \| Line of Credit \| Interest Period Of Six Month
Debt Instrument [Line Items]
Debt instrument, credit spread adjustment		0.0025
February 21, 2019 \| Fair Value, Inputs, Level 3 \| Line of Credit
Debt Instrument [Line Items]
Fair value of long-term debt			$ 769,100,000	729,100,000
February 21, 2019 \| Base Rate \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.25%
February 21, 2019 \| Base Rate \| Line of Credit \| External Credit Rating, Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
February 21, 2019 \| SOFR \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.25%
February 21, 2019 \| SOFR \| Line of Credit \| External Credit Rating, Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.00%
February 21, 2019 \| Applicable Rate \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.00%
February 21, 2019 \| Applicable Rate \| Line of Credit \| External Credit Rating, Non Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.25%
February 21, 2019 \| Screen Rate \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.20%
February 21, 2019 \| Screen Rate \| Line of Credit \| External Credit Rating, Non Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.45%
February 21, 2019 \| Federal Funds Purchased \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
February 21, 2019 \| Overnight Bank Funding Rate \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
February 21, 2019 \| One-Month Secured Overnight Financing Rate (SOFR) \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Debt instrument, credit spread adjustment		0.0010
Debt Denominated In U.S Dollars \| Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 532,500,000	$ 497,500,000
Effective interest rate			6.798%	6.324%	6.798%	6.798%	6.798%	6.324%	6.324%	6.324%
Debt Denominated In U.S Dollars \| One-Month Secured Overnight Financing Rate (SOFR) \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			4.698%
Debt Denominated In U.S Dollars \| LIBOR \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				4.224%
Debt Denominated In Swedish Kronas \| Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 1,200,000	$ 1,200,000	kr 12.8			kr 12.8
Effective interest rate			5.00%	4.375%	5.00%	5.00%	5.00%	4.375%	4.375%	4.375%
Debt Denominated In Swedish Kronas \| Stockholm Interbank Offered Rate (STIBOR) \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			3.00%	2.375%
Debt Denominated In British Pounds \| Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 84,800,000	$ 82,500,000		£ 68.6			£ 68.6
Effective interest rate			5.96%	4.96%	5.96%	5.96%	5.96%	4.96%	4.96%	4.96%
Debt Denominated In British Pounds \| Sterling Overnight Index Average (SONIA) \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			3.96%	2.96%
Debt Denominated In Euro \| Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 150,600,000	$ 147,900,000			€ 138.6			€ 138.6
Effective interest rate			4.625%	3.625%	4.625%	4.625%	4.625%	3.625%	3.625%	3.625%
Debt Denominated In Euro \| Euro Interbank Offered Rate (EURIBOR) \| Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			2.625%	1.625%
September 24, 2020 - August 2025 Notes \| Notes
Debt Instrument [Line Items]
Aggregate principal amount																	$ 25,000,000	$ 25,000,000	$ 50,000,000
Fixed interest rate			4.66%		4.66%	4.66%	4.66%												4.66%
Debt Instrument, Ownership Percentage For Immediate Conversion			66.67%		66.67%	66.67%	66.67%
September 24, 2020 - August 2025 Notes \| Fair Value, Inputs, Level 3 \| Notes
Debt Instrument [Line Items]
Fair value of long-term debt			$ 46,600,000	$ 46,100,000
November 5, 2020 - Series B Notes \| Notes
Debt Instrument [Line Items]
Aggregate principal amount																$ 62,500,000
Fixed interest rate			4.25%		4.25%	4.25%	4.25%									4.25%
November 5, 2020 - Series B Notes \| Fair Value, Inputs, Level 3 \| Notes
Debt Instrument [Line Items]
Fair value of long-term debt			$ 56,800,000	56,800,000
November 5, 2020 - Series C Notes \| Notes
Debt Instrument [Line Items]
Aggregate principal amount																$ 112,500,000
Fixed interest rate			4.75%		4.75%	4.75%	4.75%									4.75%
November 5, 2020 - Series C Notes \| Fair Value, Inputs, Level 3 \| Notes
Debt Instrument [Line Items]
Fair value of long-term debt			$ 98,300,000	97,700,000
Series B And Series C Senior Unsecured Notes Due November \| Notes
Debt Instrument [Line Items]
Interest rate extended																0.0075
Investment grade conditions																0.0150
February 25, 2021 Series D Notes \| Notes
Debt Instrument [Line Items]
Aggregate principal amount															$ 80,000,000
Fixed interest rate			3.41%		3.41%	3.41%	3.41%								3.41%
February 25, 2021 Series D Notes \| Fair Value, Inputs, Level 3 \| Notes
Debt Instrument [Line Items]
Fair value of long-term debt			$ 70,900,000	69,600,000
February 25, 2021 Series E Notes \| Notes
Debt Instrument [Line Items]
Aggregate principal amount															$ 70,000,000
Fixed interest rate			4.06%		4.06%	4.06%	4.06%								4.06%
February 25, 2021 Series E Notes \| Fair Value, Inputs, Level 3 \| Notes
Debt Instrument [Line Items]
Fair value of long-term debt			$ 59,100,000	57,800,000
Series D And Series E Senior Unsecured Notes Due February \| Notes
Debt Instrument [Line Items]
Interest rate extended															0.0075
Investment grade conditions															0.0150
Debt Instrument, Ownership Percentage For Immediate Conversion			66.67%		66.67%	66.67%	66.67%
November 23, 2021 - November 2026 Notes \| Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 350,000,000
Fixed interest rate	3.30%		3.30%		3.30%	3.30%	3.30%
Redemption percentage on purchase price (as percent)	100.00%
Debt Instrument, Ownership Percentage For Immediate Conversion			66.67%		66.67%	66.67%	66.67%
November 23, 2021 - November 2026 Notes \| Fair Value, Inputs, Level 3 \| Notes
Debt Instrument [Line Items]
Fair value of long-term debt			$ 296,500,000	$ 294,600,000