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Associate Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions | 4 Months Ended
--- | ---
Apr. 18, 2020 | Apr. 20, 2019
Defined Benefit Plan Disclosure [Line Items] |  |
Pension contributions during last plan year | $ 4.6 | $ 4.8
Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net periodic benefit (income) expense |  | 0.4
Retiree Medical Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Expected Company contribution for remainder of fiscal year | 0.5 |
Standard pension funding carryover | 0.1 |
SpartanNash Retiree Medical Plan Plan [Member] | Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net periodic benefit (income) expense | 0.2 | 0.1
SpartanNash Retiree Medical Plan [Member] | Retiree Medical Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Net periodic benefit (income) expense | $ 1.0 | $ 0.1

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