REVENUE - Schedule of Respective Liability Balances (Details) - USD ($) $ in Thousands	Jun. 24, 2020	Dec. 25, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gift card liability	$ 2,188	$ 2,258
Deferred revenue, current	552	511
Deferred revenue, long-term	11,221	11,310
Shack Sales [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer, asset, net	3,713	4,265
Licensing receivables
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer, asset, net	$ 2,664	$ 4,510