Document and Entity Information	Nov. 30, 2023
Cover [Abstract]
Document Type	424B2
Entity Registrant Name	GOLUB CAPITAL BDC, INC.
Entity Central Index Key	0001476765
Amendment Flag	false

Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

No definition available.

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- Definition

Cover page.

+ References

No definition available.

+ Details

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- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

+ References

No definition available.

+ Details

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Namespace Prefix:	dei_
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- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

+ Details

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- Definition

The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

+ Details

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