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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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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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