XML 22 R1.htm IDEA: XBRL DOCUMENT v3.19.2
Document And Entity Information - USD ($)
12 Months Ended
Apr. 30, 2019
Jul. 12, 2019
Oct. 31, 2018
Document Information [Line Items]      
Entity Registrant Name BUTLER NATIONAL CORP    
Entity Central Index Key 0000015847    
Trading Symbol buks    
Current Fiscal Year End Date --04-30    
Entity Filer Category Non-accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Emerging Growth Company false    
Entity Small Business true    
Entity Common Stock, Shares Outstanding (in shares)   68,281,071  
Entity Public Float     $ 16,039,527
Entity Shell Company false    
Document Type 10-K    
Document Period End Date Apr. 30, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false