REVENUE FROM CONTRACTS WITH CUSTOMERS - Revenues Disaggregated by Revenue Source and Market (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2023	Jun. 29, 2022	Jun. 28, 2023	Jun. 29, 2022
Disaggregation of Revenue [Line Items]
Total revenue	$ 121,492	$ 124,111	$ 236,018	$ 234,159
Core Market
Disaggregation of Revenue [Line Items]
Total revenue	106,980	109,622	207,643	206,795
Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	14,512	14,489	28,375	27,364
Company-operated restaurant revenue
Disaggregation of Revenue [Line Items]
Total revenue	103,901	106,454	201,774	200,411
Company-operated restaurant revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	98,697	101,440	191,568	191,066
Company-operated restaurant revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	5,204	5,015	10,206	9,345
Franchise revenue
Disaggregation of Revenue [Line Items]
Total revenue	10,119	10,064	19,791	19,319
Franchise revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	4,863	4,708	9,433	9,058
Franchise revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	5,256	5,357	10,358	10,262
Franchise advertising fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	7,472	7,593	14,453	14,429
Franchise advertising fee revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	3,420	3,474	6,642	6,671
Franchise advertising fee revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	$ 4,052	$ 4,117	$ 7,811	$ 7,757