Revenue from Contracts with Customers - Revenues Disaggregated by Revenue Source and Market (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 25, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 107,721	$ 105,163
Core Market
Disaggregation of Revenue [Line Items]
Total revenue	93,687	92,065
Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	14,034	13,098
Company-operated restaurant revenue
Disaggregation of Revenue [Line Items]
Total revenue	94,161	92,634
Company-operated restaurant revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	87,224	85,915
Company-operated restaurant revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	6,937	6,719
Franchise revenue
Disaggregation of Revenue [Line Items]
Total revenue	7,612	7,062
Franchise revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	3,687	3,508
Franchise revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	3,925	3,554
Franchise advertising fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	5,948	5,467
Franchise advertising fee revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	2,776	2,642
Franchise advertising fee revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,172	$ 2,825