Document And Entity Information - shares	4 Months Ended
	Jan. 21, 2018	Feb. 16, 2018
Document And Entity Information [Abstract]
Entity Common Stock, Shares Outstanding		29,532,155
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	Jan. 21, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Amendment Flag	false