Name:	jack_AcceleratedDepreciation
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Business Combination, Gain (Loss) On Acquisition Of Restaurants

No definition available.

Name:	jack_BusinessCombinationGainLossOnAcquisitionOfRestaurants
Namespace Prefix:	jack_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Impairment And Other Costs Net

No definition available.

Name:	jack_ImpairmentAndOtherCostsNet
Namespace Prefix:	jack_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482130/360-10-45-4

Name:	us-gaap_AssetImpairmentCharges
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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes, but is not limited to, one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and termination benefits associated with an ongoing benefit arrangement. Excludes expenses associated with special or contractual termination benefits, a discontinued operation or an asset retirement obligation.

Name:	us-gaap_BusinessExitCosts1
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ImpairedLongLivedAssetsHeldAndUsedLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.