Revenues Disaggregation of Revenues (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
Revenue from contract with customer, excluding assessed tax	$ 159,549	[1]	$ 158,023	[1]	$ 157,334	[1]	$ 155,273	[1]	$ 135,499	$ 132,384	$ 133,376	$ 127,910	$ 630,179	$ 529,169	[2]	$ 506,948	[2]
Franchisor Owned Outlet [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax	104,389		103,609		102,741		101,193		100,303	97,915	98,355	93,779	411,932	390,352	[2]	367,310	[2]
Royalty [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax													101,557	100,631	[2]	98,416	[2]
Advertising [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax													78,308	0	[2]	0	[2]
Initial and other fees [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax													6,422	2,466	[2]	2,717	[2]
Occupancy [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax													31,960	35,720	[2]	38,505	[2]
Franchise [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax	$ 55,160	[1]	$ 54,414	[1]	$ 54,593	[1]	$ 54,080	[1]	$ 35,196	$ 34,469	$ 35,021	$ 34,131	218,247	138,817		139,638
Franchise [Member] | Sales Channel, Through Intermediary [Member]
Disaggregation of Revenue
Revenue from contract with customer, excluding assessed tax													$ 218,247	$ 138,817	[2]	$ 139,638	[2]

[1] During 2018, we adopted ASU 2014-09, which clarifies the principles used to recognize revenue. We elected to apply the modified retrospective method of adoption; therefore, results for reporting periods after December 28, 2017 are presented under the new guidance and prior period amounts have not been adjusted. The increase in operating revenue was primarily the result of recognizing advertising revenue on a gross basis versus recording it on a net basis as previously reported. See Note 3 to our Consolidated Financial Statements for details.

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