Impairment Of Long-Lived Assets And Other Lease Charges (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jul. 01, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jul. 01, 2018 USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 367	$ 2,881	$ 1,277	$ 3,190
Gain on sale-leaseback transactions	$ 100	600	105
Cambridge Holdings, LLC [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges			$ 500
Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges, number of restaurants	1		3
Closed Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges				$ 100
Asset impairment charges, number of restaurants			6	2
Defective Product Holding Unit Kitchen Equipment [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges		1,873
Initial Impairment Charge [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 153		$ 863
Previously Impairment Restaurants [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	100	$ 394	249
Other Lease Charges [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 115
Other Lease Charges [Member] | De-Imaging [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges			$ 166