Marketable Securities - SERP Investments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Net Investment Income [Line Items]
Investment Income (Loss) and Interest Expense	$ 2,140	$ 3,066	$ 3,752	$ (953)
Supplemental Employee Retirement Plan [Member]
Net Investment Income [Line Items]
Investment Income (Loss) and Interest Expense	$ 1,800	$ 2,600	$ 2,600	$ (58)

Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities plus amount of the cost of borrowed funds accounted for as interest expense.

No definition available.

Name:	wmk_InvestmentIncomeLossAndInterestExpense
Namespace Prefix:	wmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration