REVENUE - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 23, 2020	Sep. 25, 2019	Sep. 23, 2020	Sep. 25, 2019
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 130,401	$ 157,762	$ 365,357	$ 443,084
Shack Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	126,288	152,366	353,855	428,811
Sales-Based Royalties [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	3,867	5,293	10,943	13,938
Initial territory and opening fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 246	$ 103	$ 559	$ 335

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration