REVENUE - Schedule of Respective Liability Balances (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 30, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gift card liability	$ 2,600	$ 2,637
Deferred revenue, current	612	608
Deferred revenue, long-term	11,965	12,151
Shack Sales [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer, asset, net	5,641	5,373
Licensing receivables, net of allowance for doubtful accounts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer, asset, net	$ 2,420	$ 2,647

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130533-203044

Name:	us-gaap_ContractWithCustomerAssetNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant