Document And Entity Information - shares
4 Months Ended
Jan. 20, 2019
Feb. 15, 2019
Document And Entity Information [Abstract]    
Entity Common Stock, Shares Outstanding   25,806,804
Entity Registrant Name JACK IN THE BOX INC /NEW/  
Entity Central Index Key 0000807882  
Current Fiscal Year End Date --09-29  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Jan. 20, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Emerging Growth Company false  
Entity Small Business false