Revenues Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 26, 2018	Sep. 27, 2017		Sep. 26, 2018	Sep. 27, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	$ 158,023	$ 132,384	[1]	$ 470,630	$ 393,670	[1]
Franchisor Owned Outlet [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	103,609	97,915		307,543	290,049
Franchisor Owned Outlet [Member] | Sales Channel, Directly to Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	103,609	97,915	[1]	307,543	290,049	[1]
Royalties [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	25,518	25,174	[1]	75,875	75,056	[1]
Advertising [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	19,546	0	[1]	58,386	0	[1]
Initial and other fees [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	1,415	507	[1]	4,642	1,579	[1]
Occupancy [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	7,935	8,788	[1]	24,184	26,986	[1]
Franchise [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	54,414	34,469		163,087	103,621
Franchise [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers, excluding assessed tax	$ 54,414	$ 34,469	[1]	$ 163,087	$ 103,621	[1]

[1] As disclosed in Note 2, prior period amounts have not been adjusted under the modified retrospective method of adoption of Topic 606.