REVENUE - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 01, 2026	Jun. 25, 2025	Jul. 01, 2026	Jun. 25, 2025
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 417,618	$ 356,466	$ 784,355	$ 677,364
Shack sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	403,437	343,224	757,484	653,062
Sales-based royalties
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	13,561	12,613	25,714	23,252
Initial territory, opening, and termination fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 620	$ 629	$ 1,157	$ 1,050

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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