Impairment, Disposition Of Property And Equipment, And Restaurant Closing Costs (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		3 Months Ended	12 Months Ended
	Sep. 30, 2012 restaurant	Oct. 02, 2011 restaurant	Oct. 03, 2010 40 Closed Restaurants In 2010 [Member] Jack In The Box [Member] restaurant	Oct. 03, 2010 40 Closed Restaurants In 2010 [Member] Jack In The Box [Member]
Impairment, Disposition of Property and Equipment, and Restaurant Closing Costs [Line Items]
Number of restaurants closed	1	3	40
Property and equipment impairment charges				$ 8.4