Consolidated Statements Of Comprehensive Income - USD ($)	3 Months Ended		9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Revenues:
Revenue	$ 407,036,000	$ 402,345,000	$ 1,126,972,000	$ 1,061,693,000
Costs and expenses:
Cost of sales	121,228,000	121,283,000	328,858,000	313,015,000
Restaurant wages and related expenses	126,040,000	131,070,000	362,503,000	352,402,000
Restaurant rent expense	30,536,000	29,300,000	88,974,000	77,906,000
Other restaurant operating expenses	60,486,000	62,710,000	172,774,000	164,623,000
Advertising expense	15,989,000	16,052,000	44,281,000	42,601,000
General and administrative (including stock-based compensation expense of $1,303, $1,707, $3,543 and $4,515 respectively)	20,440,000	21,365,000	59,808,000	61,709,000
Depreciation and amortization	19,620,000	21,200,000	60,947,000	53,613,000
Impairment and other lease charges	1,954,000	500,000	7,776,000	1,777,000
Other expense (income), net (Note 14)		(20,000)
Total operating expenses	396,808,000	403,460,000	1,124,489,000	1,065,873,000
Income (loss) from operations	10,228,000	(1,115,000)	2,483,000	(4,180,000)
Loss on extinguishment of debt	0	0	0	7,443,000
Interest expense	6,649,000	7,578,000	20,159,000	20,425,000
Income (loss) before income taxes	3,579,000	(8,693,000)	(17,676,000)	(32,048,000)
Provision (benefit) for income taxes	48,000	(1,881,000)	(6,840,000)	(10,035,000)
Net income (loss)	$ 3,531,000	$ (6,812,000)	$ (10,836,000)	$ (22,013,000)
Basic and diluted net income (loss) per share	$ 0.06	$ (0.15)	$ (0.21)	$ (0.54)
Weighted average common shares outstanding:
Weighted average common shares outstanding (in shares)	50,923,686	45,947,413	50,887,182	41,014,635
Shares used in computing diluted net income (loss) per share (in shares)	60,542,580	45,947,413	50,887,182	41,014,635
Other comprehensive income (loss), net of tax:
Net income (loss)	$ 3,531,000	$ (6,812,000)	$ (10,836,000)	$ (22,013,000)
Change in valuation of interest rate swap (Note 7)	169,000	0	(7,218,000)	0
Comprehensive income (loss)	3,700,000	(6,812,000)	(18,054,000)	(22,013,000)
Restaurant Sales [Member]
Revenues:
Revenue	407,036,000	398,414,000	1,126,972,000	1,054,877,000
Other Revenue [Member]
Revenues:
Revenue	$ 0	$ 3,931,000	$ 0	$ 6,816,000