Revenue from Contracts with Customers - Revenues Disaggregated by Revenue Source and Market (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 25, 2019	Sep. 25, 2019	Jun. 26, 2019	Mar. 27, 2019	Dec. 26, 2018	Sep. 26, 2018	Jun. 27, 2018	Mar. 28, 2018	Dec. 25, 2019	Dec. 26, 2018	Dec. 27, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 107,546	$ 112,067	$ 113,740	$ 108,977	$ 106,261	$ 112,178	$ 111,633	$ 105,756	$ 442,330	$ 435,828	$ 401,701
Core Market
Disaggregation of Revenue [Line Items]
Total revenue									377,591	365,396
Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									64,739	70,432
Company-operated restaurant revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue									351,624	340,421
Company-operated restaurant revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									39,488	48,414
Franchise revenue
Disaggregation of Revenue [Line Items]
Total revenue									28,819	25,771	25,086
Franchise revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue									14,918	14,144
Franchise revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									13,901	11,627
Franchise advertising fee revenue
Disaggregation of Revenue [Line Items]
Total revenue									22,399	21,222	$ 0
Franchise advertising fee revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue									11,049	10,831
Franchise advertising fee revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									$ 11,350	$ 10,391