Revenue from Contracts with Customers - Revenues Disaggregated by Revenue Source and Market (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 26, 2018	Sep. 26, 2018	Jun. 27, 2018	Mar. 28, 2018	Dec. 27, 2017	Sep. 27, 2017	Jun. 28, 2017	Mar. 29, 2017	Dec. 26, 2018	Dec. 27, 2017	Dec. 28, 2016
Disaggregation of Revenue [Line Items]
Total revenue	$ 106,261	$ 112,178	$ 111,633	$ 105,756	$ 95,202	$ 101,155	$ 105,573	$ 99,771	$ 435,828	$ 401,701	$ 380,123
Core Market
Disaggregation of Revenue [Line Items]
Total revenue									365,396
Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									70,432
Company-operated restaurant revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue									340,421
Company-operated restaurant revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									48,414
Franchise revenue
Disaggregation of Revenue [Line Items]
Total revenue									25,771	25,086	24,655
Franchise revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue									14,144
Franchise revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									11,627
Franchise advertising fee revenue
Disaggregation of Revenue [Line Items]
Total revenue									21,222	$ 0	$ 0
Franchise advertising fee revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue									10,831
Franchise advertising fee revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue									$ 10,391