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Associate Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2020	Oct. 05, 2019	Oct. 03, 2020	Oct. 05, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension contributions during last plan year	$ 2.5	$ 2.4	$ 10.6	$ 10.6
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income) expense		10.1	1.0	19.3
Retiree Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Company contribution for remainder of fiscal year	0.5		0.5
Standard pension funding carryover			0.3
SpartanNash Retiree Medical Plan Plan [Member] \| Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income) expense	$ 0.1		$ 0.5
SpartanNash Retiree Medical Plan [Member] \| Retiree Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income) expense		$ 0.1		$ 0.3