Selected Quarterly Financial and Earnings Data (Unaudited) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Oct. 01, 2017 USD ($)	Jul. 02, 2017 USD ($)	Apr. 02, 2017 USD ($)	Oct. 02, 2016 USD ($)	Jul. 03, 2016 USD ($)	Apr. 03, 2016 USD ($)	Jan. 03, 2016 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2017 USD ($)	Jan. 03, 2016 USD ($)	Dec. 30, 2012
Effect of Fourth Quarter Events [Line Items]
Restaurants Acquired	4		17	43	11	6		27	64	56	55	278
Acquisition-related costs	$ 100	$ 500	$ 500	$ 700	$ 500	$ 200	$ 400	$ 800
Impairment and other lease charges	800	$ 1,000	400	$ 500	$ 700	$ 300	$ 200	$ 1,200	$ 2,827	$ 2,355	$ 3,078
Insured Event, Gain (Loss)	$ 700		$ 500							$ 1,200
Number of Restaurants	807	798	799	788	734	723	717		807	753
Litigation Settlement, Expense										$ 1,850
Gain (Loss) on Condemnation							$ 500
Income tax expense, valuation allowance									$ 0	$ (30,374)	$ 2,959
Damage from Fire, Explosion or Other Hazard [Member]
Effect of Fourth Quarter Events [Line Items]
Properties damaged in fire	1		1							2
Unfavorable Regulatory Action [Member]
Effect of Fourth Quarter Events [Line Items]
Number of Restaurants							1			1