XML 51 R65.htm IDEA: XBRL DOCUMENT
v3.20.1

Retirement Plans - Narrative (Details) | 3 Months Ended | 4 Months Ended | 6 Months Ended |
--- | --- | --- | --- | ---
Apr. 12, 2020 USD ($) | Jan. 19, 2020 USD ($) | Apr. 12, 2020 healthcare_plan defined_benefit_plan | Jan. 01, 2019 USD ($)
Retirement Benefits [Abstract] |  |  |  |
Number of sponsored defined benefit pension plans | defined_benefit_plan |  |  | 2 |
Lump sum payments from Qualified Plan |  | $ 122,300,000 |  |
Pension settlement | $ 300,000 | $ 38,600,000 |  |
Number of postretirement health care plans | healthcare_plan |  |  | 2 |
Minimum required contribution for retirement plans |  |  |  | $ 0

X
- Definition Minimum required contribution for retirement plans + References No definition available. + Details
Name: | jack_MinimumRequiredContributionForRetirementPlans
Namespace Prefix: | jack_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number Of Defined Benefit Pension Plans Sponsored + References No definition available. + Details
Name: | jack_NumberOfDefinedBenefitPensionPlansSponsored
Namespace Prefix: | jack_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Postretirement Medical Plan, Number Sponsored + References No definition available. + Details
Name: | jack_PostretirementMedicalPlanNumberSponsored
Namespace Prefix: | jack_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
Name: | us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(8) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanSettlementsPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration