Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $)	3 Months Ended			6 Months Ended
	Apr. 15, 2012		Apr. 17, 2011	Apr. 15, 2012		Apr. 17, 2011	Oct. 02, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount of Jack in the Box underperforming or intend to close restaurants	$ 833,605,000			$ 833,605,000			$ 855,426,000
Impairment charges	910,000		878,000	2,109,000		1,167,000
Total liabilities at fair value	(40,711,000)			(40,711,000)			(36,970,000)
Underperforming Jack In The Box Restaurants [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of Jack in the Box restaurants determinted to be underperforming or intend to close				6
Carrying amount of Jack in the Box underperforming or intend to close restaurants	2,100,000			2,100,000
Implied fair value of underperforming or intend to close Jack in the Box restaurants	300,000			300,000
Impairment charges				1,800,000
Fair Value, Measurements, Recurring [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(2,604,000)	[1]		(2,604,000)	[1]		(2,682,000)	[1]
Fair Value, Measurements, Recurring [Member] | Non-Qualified Deferred Compensation Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(38,107,000)	[2]		(38,107,000)	[2]		(34,288,000)	[2]
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(38,107,000)	[3]		(38,107,000)	[3]		(34,288,000)	[3]
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Non-Qualified Deferred Compensation Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(38,107,000)	[2],[3]		(38,107,000)	[2],[3]		(34,288,000)	[2],[3]
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(2,604,000)	[3]		(2,604,000)	[3]		(2,682,000)	[3]
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	$ (2,604,000)	[1],[3]		$ (2,604,000)	[1],[3]		$ (2,682,000)	[1],[3]

[1] We entered into interest rate swaps to reduce our exposure to rising interest rates on our variable debt. The fair values of our interest rate swaps are based upon Level 2 inputs which include valuation models as reported by our counterparties. The key inputs for the valuation models are quoted market prices, interest rates and forward yield curves.

[2] We maintain an unfunded defined contribution plan for key executives and other members of management excluded from participation in our qualified savings plan. The fair value of this obligation is based on the closing market prices of the participants’ elected investments.

[3] We did not have any transfers in or out of Level 1 or Level 2.