Document And Entity Information - USD ($)
$ in Billions
12 Months Ended
Oct. 01, 2017
Nov. 24, 2017
Apr. 13, 2017
Document And Entity Information [Abstract]      
Entity Registrant Name JACK IN THE BOX INC /NEW/    
Entity Central Index Key 0000807882    
Document Type 10-K    
Document Period End Date Oct. 01, 2017    
Amendment Flag false    
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Current Fiscal Year End Date --10-01    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   29,433,478  
Entity Public Float     $ 2.9
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes