Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2021	Sep. 29, 2020	Sep. 28, 2021	Sep. 29, 2020
Revenue:
Total revenue	$ 125,126	$ 105,982	$ 360,352	$ 286,487
Restaurant operating costs (exclusive of depreciation and amortization shown separately below):
Other restaurant operating costs	21,529	19,383	62,816	51,861
General and administrative	12,187	10,827	36,094	31,415
Depreciation and amortization	5,571	5,541	16,734	16,273
Pre-opening	125	239	346	383
Restaurant impairments, closure costs and asset disposals	1,126	369	2,747	3,983
Total costs and expenses	119,806	105,260	350,187	303,144
Income (loss) from operations	5,320	722	10,165	(16,657)
Interest expense, net	594	822	1,714	2,710
Income (loss) before taxes	4,726	(100)	8,451	(19,367)
Provision for income taxes	29	27	48	73
Net income (loss)	$ 4,697	$ (127)	$ 8,403	$ (19,440)
Earnings (loss) per Class A and Class B common stock, combined
Basic (USD per share)	$ 0.10	$ 0	$ 0.19	$ (0.44)
Diluted (USD per share)	$ 0.10	$ 0	$ 0.18	$ (0.44)
Weighted average shares of Class A and Class B common stock outstanding, combined:
Basic (in shares)	45,635,455	44,358,763	45,414,332	44,238,400
Diluted (in shares)	46,382,509	44,358,763	46,134,994	44,238,400
Restaurant revenue
Revenue:
Total revenue	$ 123,094	$ 104,413	$ 354,553	$ 283,150
Restaurant operating costs (exclusive of depreciation and amortization shown separately below):
Restaurant operating costs	30,946	25,900	88,728	71,124
Franchising royalties and fees, and other
Revenue:
Total revenue	2,032	1,569	5,799	3,337
Labor
Restaurant operating costs (exclusive of depreciation and amortization shown separately below):
Restaurant operating costs	36,896	31,264	108,128	92,632
Occupancy
Restaurant operating costs (exclusive of depreciation and amortization shown separately below):
Restaurant operating costs	$ 11,426	$ 11,737	$ 34,594	$ 35,473