Revenue from Contracts with Customers - Revenues Disaggregated by Revenue Source and Market (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]
Total revenue	$ 110,979	$ 112,067	$ 315,746	$ 334,784
Core Market
Disaggregation of Revenue [Line Items]
Total revenue	96,615	96,782	275,642	284,092
Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	14,364	15,285	40,104	50,692
Company-operated restaurant revenue
Disaggregation of Revenue [Line Items]
Total revenue	97,276	99,052	277,617	296,341
Company-operated restaurant revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	90,207	90,277	257,493	264,391
Company-operated restaurant revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	7,069	8,775	20,124	31,950
Franchise revenue
Disaggregation of Revenue [Line Items]
Total revenue	7,781	7,273	21,562	21,635
Franchise revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	3,660	3,696	10,376	11,369
Franchise revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	4,121	3,577	11,186	10,266
Franchise advertising fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	5,922	5,742	16,567	16,808
Franchise advertising fee revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	2,748	2,809	7,773	8,332
Franchise advertising fee revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,174	$ 2,933	$ 8,794	$ 8,476