Impairment Of Long-Lived Assets And Other Lease Charges (Details) $ in Thousands	3 Months Ended
	Mar. 29, 2020 USD ($)	Mar. 31, 2019 USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 2,881	$ 910
Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges, number of restaurants	3	2
Closed Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges, number of restaurants	9	6
Initial Impairment Charge [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 1,500	$ 700
Previously Impairment Restaurants [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	200	100
Other Lease Charges [Member] | Underperforming Restaurants [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment and other lease charges	$ 1,200	$ 100