Cover Page - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Dec. 07, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2023
Current Fiscal Year End Date	--09-30
Document Transition Report	false
Entity File Number	001-36267
Entity Registrant Name	BLUE BIRD CORPORATION
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Central Index Key	0001589526
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-3891989
Entity Address, Address Line One	3920 Arkwright Road
Entity Address, Address Line Two	2nd Floor
Entity Address, City or Town	Macon
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	31210
City Area Code	478
Local Phone Number	822-2801
Title of 12(b) Security	Common stock, $0.0001 par value
Trading Symbol	BLBD
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float	$ 354.7
Entity Common Stock, Shares Outstanding		32,165,225
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement to be delivered to stockholders in connection with the Registrant’s 2024 Annual Meeting of Stockholders are incorporated by reference in response to Part III of this report.
Document Financial Statement Error Correction [Flag]	false