Document and Entity Information - shares
 3 Months Ended
Jan. 04, 2020
Feb. 07, 2020
Document and Entity Information [Abstract]    
Entity Registrant Name Blue Bird Corp  
Entity Central Index Key 0001589526  
Current Fiscal Year End Date --10-03  
Entity Filer Category Accelerated Filer  
Document Type 10-Q  
Document Period End Date Jan. 04, 2020  
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   26,839,825
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Shell Company false  
Entity Current Reporting Status Yes