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v3.20.2

Revenue (Narrative) (Details) | 12 Months Ended
--- | ---
Sep. 27, 2020 USD ($)
Revenue from Contract with Customer [Abstract] |
Initial franchise fee | $ 50,000
Royalty and marketing fee, percent of gross sales | 5.00%

X
- Definition Franchise Fees - Current Standard + References No definition available. + Details
Name: | jack_FranchiseFeesCurrentStandard
Namespace Prefix: | jack_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Royalty And Marketing Fee, Percent Of Gross Sales + References No definition available. + Details
Name: | jack_RoyaltyAndMarketingFeePercentOfGrossSales
Namespace Prefix: | jack_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration