Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2018	Sep. 27, 2017	Sep. 26, 2018	Sep. 27, 2017
Revenue
Total revenue	$ 112,178	$ 101,155	$ 329,567	$ 306,499
Cost of operations
Food and paper cost	28,349	27,851	84,265	84,069
Labor and related expenses	29,164	27,514	84,682	80,939
Occupancy and other operating expenses	24,187	22,242	69,019	64,358
Company restaurant expenses	81,700	77,607	237,966	229,366
General and administrative expenses	12,186	8,285	37,862	27,594
Franchise expenses	6,342	709	18,424	2,532
Depreciation and amortization	4,507	4,697	13,063	13,646
Loss on disposal of assets	140	65	193	724
Recovery of securities lawsuits related legal expenses	(2,036)	(634)	(6,099)	(1,145)
Asset impairment and closed-store reserves	(153)	16,038	6,629	17,293
Total expenses	102,686	106,767	308,038	290,010
Income (loss) from operations	9,492	(5,612)	21,529	16,489
Interest expense, net of interest income of $14 and $6 for the quarters ended September 26, 2018 and September 27, 2017, respectively, and $29 and $17 for year-to-date ended September 26, 2018 and September 27, 2017, respectively.	840	903	2,688	2,471
Income tax receivable agreement (income) expense	(571)	(19)	(777)	107
Income (loss) before provision (benefit) for income taxes	9,223	(6,496)	19,618	13,911
Provision (benefit) for income taxes	2,388	(2,457)	5,202	5,254
Net income (loss)	$ 6,835	$ (4,039)	$ 14,416	$ 8,657
Net income (loss) per share
Basic (usd per share)	$ 0.18	$ (0.11)	$ 0.37	$ 0.23
Diluted (usd per share)	$ 0.17	$ (0.11)	$ 0.37	$ 0.22
Weighted-average shares used in computing net income per share
Basic (shares)	38,602,658	38,462,100	38,516,792	38,449,453
Diluted (shares)	39,205,090	38,462,100	39,102,130	39,101,214
Company-operated restaurant revenue
Revenue
Total revenue	$ 100,024	$ 94,982	$ 294,204	$ 287,316
Franchise revenue
Revenue
Total revenue	6,665	6,173	19,324	19,183
Franchise advertising fee revenue
Revenue
Total revenue	$ 5,489	$ 0	$ 16,039	$ 0