Impairment Of Long-Lived Assets And Other Lease Charges (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 29, 2019 USD ($)	Sep. 30, 2018 USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 500	$ 164	$ 1,777	$ 3,354
Gain on sale-leaseback transactions		100	289	700
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	2
Closed Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges				1,900
Asset impairment charges, number of restaurants			1
Initial Impairment Charge [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 300
Initial Impairment Charge [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges			$ 1,100
Previously Impairment Restaurants [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges		$ 100	300	$ 620
Other Lease Charges [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 200
Other Lease Charges [Member] | De-Imaging [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges			$ 400