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Nature Of Operations And Summary Of Significant Accounting Policies (Summary Of Number Of Restaurants) (Details) - restaurant | 12 Months Ended |  |
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Sep. 30, 2018 | Oct. 01, 2017 | Oct. 02, 2016
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items] |  |  |
Document Fiscal Year Focus | 2018 |  |
Number of Restaurants | 10 |  |
Jack in the box brand restaurant operations [Member] |  |  |
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items] |  |  |
Number of Restaurants | 2,237 | 2,251 | 2,255
Entity Operated Units [Member] |  |  |
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items] |  |  |
Number of Restaurants | 137 | 276 |
Entity Operated Units [Member] | Jack in the box brand restaurant operations [Member] |  |  |
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items] |  |  |
Number of Restaurants |  |  | 417
Franchised Units [Member] |  |  |
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items] |  |  |
Number of Restaurants | 2,100 | 1,975 |
Franchised Units [Member] | Jack in the box brand restaurant operations [Member] |  |  |
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items] |  |  |
Number of Restaurants |  |  | 1,838

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- Definition This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006. + References No definition available. + Details
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