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Associate Retirement Plans - Assumed Current Healthcare Cost Trend Rates Used to Determine Net Periodic Benefit Cost (Income) (Detail) | 12 Months Ended
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Jan. 02, 2021 | Dec. 28, 2019 | Dec. 29, 2018
Defined Benefit Plan Assumed Health Care Cost Trend Rates [Abstract] |  |  |
Post-65 | 7.50% | 7.50% | 8.00%

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- Definition Defined benefit plan health care cost trend rate assumed for post sixty five year age. + References No definition available. + Details
Name: | sptn_DefinedBenefitPlanHealthCareCostTrendRateAssumedForPostSixtyFiveYearAge
Namespace Prefix: | sptn_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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