Basis Of Presentation (Policy)	6 Months Ended
Basis Of Presentation (Policy)	Apr. 10, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations [Text Block]	Nature of operations — Founded in 1951, Jack in the Box Inc. (the “Company”) operates and franchises Jack in the Box^® quick-service restaurants and Qdoba Mexican Eats^® (“Qdoba”) fast-casual restaurants.
New Accounting Pronouncement, Early Adoption [Table Text Block]	Effect of new accounting pronouncements — In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue Recognition - Revenue from Contracts with Customers (Topic 606), which provides a comprehensive new revenue recognition model that requires an entity to recognize revenue in an amount that reflects the consideration the entity expects to receive for the transfer of promised goods or services to its customers. The standard also requires additional disclosure regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Further, in March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), which clarifies the guidance in ASU No. 2014-09 when evaluating when another party, along with the entity, is involved in providing a good or service to a customer. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, which clarifies the guidance in ASU No. 2014-09 regarding assessing whether promises to transfer goods or services are distinct, and whether an entity's promise to grant a license provides a customer with a right to use, or right to access the entity's intellectual property. All standards are effective for annual periods beginning after December 15, 2017, and interim periods within that reporting period. As such, we will be required to adopt these standards in the first quarter of fiscal 2019. These standards are to be applied retrospectively or using a cumulative effect transition method, and early adoption is not permitted. We are currently evaluating which transition method to use and the effect that these standards will have on our consolidated financial statements and related disclosures. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes, which simplifies the presentation of deferred income taxes. This standard requires deferred tax liabilities and assets to be classified as noncurrent in a classified statement of financial position. This standard is effective prospectively or retrospectively for all periods presented for annual and interim periods beginning after December 15, 2017, with early adoption permitted. We early adopted this standard in the first quarter of 2016 and the prior period was retrospectively adjusted, resulting in a $40.0 million reclassification of current deferred income taxes to other assets, net on our September 27, 2015 condensed consolidated balance sheet. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires a lessee to recognize assets and liabilities on the balance sheet for those leases classified as operating leases under previous guidance. This standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. This standard requires adoption based upon a modified retrospective transition approach, with early adoption permitted. We are currently evaluating the impact this standard will have on our consolidated financial statements and related disclosures. In March 2016, the FASB issued ASU No. 2016-04, Liabilities-Extinguishment of Liabilities (Subtopic 405-20): Recognition of Breakage for Certain Prepaid Stored-Value Products, which is designed to provide guidance and eliminate diversity in the accounting for the derecognition of financial liabilities related to certain prepaid stored-value products using a revenue-like breakage model. This standard is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted. This standard is to be applied retrospectively or using a cumulative effect transition method as of the date of adoption. We are currently evaluating which transition method to use, but believe the impact this standard will have on our consolidated financial statements and related disclosures will be immaterial upon adoption. In March 2016, the FASB issued ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. This standard is intended to simplify various aspects of accounting for share-based compensation arrangements, including the income tax impact, classification on the statement of cash flows and forfeitures. This standard is effective for annual reporting periods beginning after December 15, 2016, and interim periods within that reporting period, with early adoption permitted. We are currently evaluating the impact of the standard on our consolidated financial statements and related disclosures.
Basis of presentation	Basis of presentation — The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles and the rules and regulations of the Securities and Exchange Commission (“SEC”). During fiscal 2012, we entered into an agreement to outsource our Jack in the Box distribution business. In the third quarter of fiscal 2013, we closed 62 Qdoba restaurants (the “2013 Qdoba Closures”) as part of a comprehensive Qdoba market performance review. The results of operations for our distribution business and for the 2013 Qdoba Closures are reported as discontinued operations for all periods presented. Refer to Note 2, Discontinued Operations, for additional information. Unless otherwise noted, amounts and disclosures throughout these Notes to Condensed Consolidated Financial Statements relate to our continuing operations. In our opinion, all adjustments considered necessary for a fair presentation of financial condition and results of operations for these interim periods have been included. Operating results for one interim period are not necessarily indicative of the results for any other interim period or for the full year. These financial statements should be read in conjunction with the consolidated financial statements and related notes contained in our Annual Report on Form 10-K for the fiscal year ended September 27, 2015 (“2015 Form 10-K”). The accounting policies used in preparing these condensed consolidated financial statements are the same as those described in our 2015 Form 10-K with the exception of a new accounting pronouncement adopted in fiscal 2016 which is described below.
Principles of consolidation	Principles of consolidation — The condensed consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries and the accounts of any variable interest entities (“VIEs”) where we are deemed the primary beneficiary. All significant intercompany accounts and transactions are eliminated. The financial results and position of our VIE are immaterial to our condensed consolidated financial statements.
Reclassification, Policy [Policy Text Block]	Reclassifications and adjustments — Certain prior year amounts in the condensed consolidated financial statements have been reclassified to conform to the fiscal 2016 presentation. In our 2015 Form 10-K, on our consolidated statements of earnings, we began to separately state our franchise revenues derived from rentals and those derived from royalties and other. To provide clarity, we additionally have separately stated the associated rental expense, and depreciation and amortization related to the rental income received from franchisees. For comparison purposes, we have reclassified prior year franchise revenue and franchise costs line items to reflect the new method of presentation in our accompanying condensed consolidated statements of earnings.
Fiscal year	Fiscal year — Our fiscal year is 52 or 53 weeks ending the Sunday closest to September 30. Fiscal year 2016 includes 53 weeks, while fiscal year 2015 includes 52 weeks. Our first quarter includes 16 weeks and all other quarters include 12 weeks, with the exception of the fourth quarter of fiscal 2016, which includes 13 weeks. All comparisons between 2016 and 2015 refer to the 12-weeks (“quarter”) and 28-weeks (“year-to-date”) ended April 10, 2016 and April 12, 2015, respectively, unless otherwise indicated.
Use of estimates	Use of estimates — In preparing the condensed consolidated financial statements in conformity with U.S. generally accepted accounting principles, management is required to make certain assumptions and estimates that affect reported amounts of assets, liabilities, revenues, expenses and the disclosure of contingencies. In making these assumptions and estimates, management may from time to time seek advice and consider information provided by actuaries and other experts in a particular area. Actual amounts could differ materially from these estimates.