Summary of Total Cost and Employer Contributions (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 17, 2021	Jul. 11, 2020	Jul. 17, 2021	Jul. 11, 2020
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan, Plan Name [Extensible List]	flo:FourZeroOneKRetirementSavingsPlanMember	flo:FourZeroOneKRetirementSavingsPlanMember	flo:FourZeroOneKRetirementSavingsPlanMember	flo:FourZeroOneKRetirementSavingsPlanMember
Total cost and employer contributions	$ 6,219	$ 6,593	$ 15,355	$ 15,222