XML 17 R1.htm IDEA: XBRL DOCUMENT v3.10.0.1
Document And Entity Information - USD ($)
$ in Billions
 12 Months Ended
Sep. 30, 2018
Nov. 16, 2018
Apr. 13, 2017
Entity Information [Line Items]      
Entity Registrant Name JACK IN THE BOX INC /NEW/    
Entity Central Index Key 0000807882    
Document Type 10-K    
Document Period End Date Sep. 30, 2018    
Amendment Flag false    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Current Fiscal Year End Date --09-30    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   25,742,587  
Entity Public Float     $ 2.4
Entity Well-known Seasoned Issuer Yes    
Entity Shell Company false    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes