Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2018	Jun. 28, 2017	Jun. 27, 2018	Jun. 28, 2017
Revenue
Total revenue	$ 111,633	$ 105,573	$ 217,389	$ 205,344
Cost of operations
Food and paper cost	28,681	29,146	55,916	56,218
Labor and related expenses	27,856	26,592	55,518	53,425
Occupancy and other operating expenses	22,913	21,574	44,832	42,116
Company restaurant expenses	79,450	77,312	156,266	151,759
General and administrative expenses	12,474	9,576	25,676	19,309
Franchise expenses	6,250	1,006	12,082	1,823
Depreciation and amortization	4,344	4,632	8,556	8,949
(Gain) loss on disposal of assets	(8)	434	53	659
Recovery of securities lawsuits related legal expenses	(2,429)	(511)	(4,063)	(511)
Asset impairment and closed-store reserves	3,963	384	6,782	1,255
Total expenses	104,044	92,833	205,352	183,243
Income from operations	7,589	12,740	12,037	22,101
Interest expense, net of interest income of $7 and $6 for the quarters ended June 27, 2018 and June 28, 2017, respectively, and $15 and $11 for year-to-date ended June 27, 2018 and June 28, 2017, respectively.	960	778	1,848	1,568
Income tax receivable agreement expense (income)	712	(101)	(206)	126
Income before provision for income taxes	5,917	12,063	10,395	20,407
Provision for income taxes	865	4,244	2,814	7,711
Net income	$ 5,052	$ 7,819	$ 7,581	$ 12,696
Net income per share
Basic (usd per share)	$ 0.13	$ 0.20	$ 0.20	$ 0.33
Diluted (usd per share)	$ 0.13	$ 0.20	$ 0.19	$ 0.32
Weighted-average shares used in computing net income per share
Basic (shares)	38,482,074	38,449,240	38,473,641	38,443,130
Diluted (shares)	39,043,434	39,123,961	39,015,259	39,102,501
Company-operated restaurant revenue
Revenue
Total revenue	$ 99,627	$ 98,885	$ 194,180	$ 192,334
Franchise revenue
Revenue
Total revenue	6,553	6,688	12,659	13,010
Franchise advertising fee revenue
Revenue
Total revenue	$ 5,453	$ 0	$ 10,550	$ 0