Document And Entity Information	6 Months Ended
	Apr. 15, 2012	May 11, 2012
Document And Entity Information [Abstract]
Entity Registrant Name	JACK IN THE BOX INC /NEW/
Entity Central Index Key	0000807882
Document Type	10-Q
Document Period End Date	Apr. 15, 2012
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		44,219,044