Revenue from Contracts with Customers - Revenues Disaggregated by Revenue Source and Market (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2018	Jun. 28, 2017	Jun. 27, 2018	Jun. 28, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 111,633	$ 105,573	$ 217,389	$ 205,344
Core Market
Disaggregation of Revenue [Line Items]
Total revenue	93,220		182,167
Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	18,413		35,222
Company-operated restaurant revenue
Disaggregation of Revenue [Line Items]
Total revenue	99,627	98,885	194,180	192,334
Company-operated restaurant revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	86,842		169,804
Company-operated restaurant revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	12,785		24,376
Franchise revenue
Disaggregation of Revenue [Line Items]
Total revenue	6,553	6,688	12,659	13,010
Franchise revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	3,609		6,985
Franchise revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	2,944		5,674
Franchise advertising fee revenue
Disaggregation of Revenue [Line Items]
Total revenue	5,453	$ 0	10,550	$ 0
Franchise advertising fee revenue | Core Market
Disaggregation of Revenue [Line Items]
Total revenue	2,769		5,378
Franchise advertising fee revenue | Non-Core Market
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,684		$ 5,172