Impairment Of Long-Lived Assets And Other Lease Charges (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)	Apr. 01, 2018 USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 910	$ 309
Gain on sale-leaseback transactions	$ 93	$ 100
Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges, number of restaurants	2
Closed Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges, number of restaurants	6	2
Previously Impaired [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges		$ 141
Changes in Future Costs [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges		$ 116
Initial Impairment Charge [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 710
Previously Impairment Restaurants [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	149
Other Lease Charges [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 51