Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) $ in Thousands		6 Months Ended	12 Months Ended
		Apr. 15, 2018 USD ($)	Sep. 30, 2018 USD ($) restaurant		Oct. 01, 2017 USD ($) restaurant	Oct. 02, 2016 USD ($) restaurant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current Fiscal Year End Date			--09-30
Obligations, Fair Value Disclosure			$ 38,150		$ 60,146
Number of Restaurants | restaurant			10
Asset Impairment Charges	[1]		$ 211		$ 0	$ 0
Impairment of Long-Lived Assets Held-for-use		$ 800
Gain (Loss) on Sale of Assets and Asset Impairment Charges			$ (200)
Jack in the box brand restaurant operations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of Restaurants | restaurant			2,237		2,251	2,255
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	[2]		$ 37,447		$ 37,219
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	[2]		703		22,927
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	[2]		0		0
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	[3]		703		22,927
Interest Rate Swaps [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]
Obligations, Fair Value Disclosure			0	[2]	0
Interest Rate Swaps [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	[2],[3]		703		22,927
Interest Rate Swaps [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure			0	[2]	0
Non Qualified Deferred Compensation Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	[4]		37,447		37,219
Non Qualified Deferred Compensation Plan [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]
Obligations, Fair Value Disclosure	[2],[4]		37,447		37,219
Non Qualified Deferred Compensation Plan [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure			0		0
Non Qualified Deferred Compensation Plan [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure			0		$ 0
change in market value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (Loss) on Sale of Assets and Asset Impairment Charges			$ (400)

[1] (1)In 2018, impairment charges relate to our landlord’s sale of a restaurant property to a franchisee.

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

[3] We entered into interest rate swaps to reduce our exposure to rising interest rates on our variable rate debt. The fair values of our interest rate swaps are based upon Level 2 inputs, which include valuation models as reported by our counterparties. These valuation models use a discounted cash flow analysis on the cash flows of each derivative. The key inputs for the valuation models are quoted market prices, discount rates, and forward yield curves. The Company also considers its own nonperformance risk and the respective counter-party’s nonperformance risk in the fair value measurements.

[4] (1)We maintain an unfunded defined contribution plan for key executives and other members of management. The fair value of this obligation is based on the closing market prices of the participants’ elected investments. The obligation is included in accrued liabilities and other long-term liabilities on our condensed consolidated balance sheets.