Basis Of Presentation Narrative (Details)	3 Months Ended						12 Months Ended
	Dec. 31, 2017 USD ($)	Jul. 02, 2017	Apr. 02, 2017	Oct. 02, 2016	Jul. 03, 2016	Jan. 03, 2016	Dec. 31, 2017 USD ($)	Jan. 01, 2017 USD ($)	Jan. 03, 2016 USD ($)	Dec. 30, 2012	Oct. 01, 2017	Apr. 03, 2016
Entity Information [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 27,600,000						$ 27,600,000
Restaurants Acquired	4	17	43	11	6	27	64	56	55	278
Number of Restaurants	807	799	788	734	723		807	753			798	717
Number of states	17						17
Weeks In fiscal period							52		53
Franchise Term Renewal Period							20 years
Franchise Agreement, Term							20 years
Long-term Debt, Fair Value	$ 290,500,000						$ 290,500,000	$ 216,500,000
Asset Impairment Charges							1,700,000	$ 1,000,000	$ 1,500,000
Cash, FDIC Insured Amount	$ 250,000						$ 250,000
Number of Reportable Segments							1
Right of First Refusal, Number of States	20						20
Cumulative-effect adjustment from adoption of ASU 2016-09	$ 3,734,000						$ 3,734,000
Minimum [Member]
Entity Information [Line Items]
Weeks In fiscal period							52
Maximum [Member]
Entity Information [Line Items]
Weeks In fiscal period							53
Retained Earnings [Member]
Entity Information [Line Items]
Cumulative-effect adjustment from adoption of ASU 2016-09	$ 3,734,000						$ 3,734,000