Document And Entity Information - shares	6 Months Ended
	Apr. 15, 2018	May 11, 2018
Document And Entity Information [Abstract]
Entity Common Stock, Shares Outstanding		28,438,227
Entity Registrant Name	JACK IN THE BOX INC /NEW/
Entity Central Index Key	0000807882
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Apr. 15, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Amendment Flag	false