Document And Entity Information	4 Months Ended
	Jan. 18, 2015	Feb. 13, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	JACK IN THE BOX INC /NEW/
Entity Central Index Key	0000807882
Current Fiscal Year End Date	--09-27
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jan. 18, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		38,069,087