Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2017	Sep. 28, 2016	Sep. 27, 2017	Sep. 28, 2016
Revenue
Company-operated restaurant revenue	$ 94,982	$ 89,738	$ 287,316	$ 268,984
Franchise revenue	6,173	6,078	19,183	18,660
Total revenue	101,155	95,816	306,499	287,644
Cost of operations
Food and paper cost	27,851	26,960	84,069	80,760
Labor and related expenses	27,514	24,455	80,939	73,323
Occupancy and other operating expenses	22,242	20,071	64,358	58,401
Gain on recovery of insurance proceeds, lost profit	0	(502)	0	(502)
Company restaurant expenses	77,607	70,984	229,366	211,982
General and administrative expenses	8,285	8,252	27,594	25,776
Franchise expenses	709	797	2,532	2,960
Depreciation and amortization	4,697	4,074	13,646	11,796
Loss on disposal of assets	65	58	724	524
Expenses related to fire loss	0	0	0	48
Gain On Business Interruption Insurance Recovery Property Equipment And Expenses	0	(148)	0	741
Recovery of securities lawsuits related legal expenses	(634)	0	(1,145)	0
Asset impairment and closed-store reserves	16,038	2,490	17,293	2,624
Total expenses	106,767	86,803	290,010	254,969
(Loss) gain on disposition of restaurants	0	(5)	0	28
(Loss) income from operations	(5,612)	9,008	16,489	32,703
Interest expense, net of interest income of $6 and $7 for the quarters ended September 27, 2017 and September 28, 2016, respectively and $17 and $22 for year-to-date ended September 27, 2017 and September 28, 2016, respectively.	903	785	2,471	2,441
Income tax receivable agreement (income) expense	(19)	182	107	411
(Loss) income before (benefit) provision for income taxes	(6,496)	8,041	13,911	29,851
(Benefit) provision for income taxes	(2,457)	2,830	5,254	11,930
Net (loss) income	$ (4,039)	$ 5,211	$ 8,657	$ 17,921
Net (loss) income per share
Basic (usd per share)	$ (0.11)	$ 0.14	$ 0.23	$ 0.47
Diluted (usd per share)	$ (0.11)	$ 0.13	$ 0.22	$ 0.46
Weighted-average shares used in computing net (loss) income per share
Basic (shares)	38,462,100	38,415,189	38,449,453	38,331,400
Diluted (shares)	38,462,100	39,083,577	39,101,214	39,020,127