Basis Of Presentation Narrative (Details)	3 Months Ended			12 Months Ended
	Dec. 30, 2018 USD ($)	Apr. 01, 2018	Jul. 02, 2017	Dec. 30, 2018 USD ($) restaurant	Dec. 31, 2017 USD ($)	Jan. 01, 2017 USD ($)	Dec. 30, 2012	Dec. 31, 2018 USD ($)	Sep. 30, 2018	Jul. 01, 2018	Oct. 01, 2017	Apr. 02, 2017
Entity Information [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 27,600,000			$ 27,600,000
Restaurants Acquired	10	1	17	44		4	278
Number of Restaurants	849	807	799	849	807				838	807	798	788
Number of states	18			18
Weeks In fiscal period				52		52
Franchise Term Renewal Period				20 years
Franchise Agreement, Term				20 years
Long-term Debt, Fair Value	$ 277,100,000			$ 277,100,000	$ 290,500,000
Asset Impairment Charges				2,700,000	1,700,000	$ 1,000,000
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
Deferred income-sale-leaseback of real estate	$ 10,073,000			$ 10,073,000	$ 11,451,000
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
Subsequent Events | Scenario, Forecast | Minimum [Member]
Entity Information [Line Items]
Operating Lease, Liability								$ 500,000,000
Subsequent Events | Scenario, Forecast | Maximum [Member]
Entity Information [Line Items]
Operating Lease, Liability								$ 550,000,000