Consolidated Statements of Comprehensive Income (Loss) - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Jan. 02, 2018
Revenue:
Total revenue	$ 512,951,000	$ 505,490,000	$ 471,456,000
Restaurant operating expenses:
Labor and related expenses	156,095,000	151,954,000	145,012,000
Occupancy and other operating expenses	105,376,000	97,745,000	92,825,000
General and administrative	43,877,000	43,773,000	38,154,000
Franchise advertising expenses	14,516,000	13,300,000	0
Depreciation and amortization	25,488,000	25,794,000	23,362,000
Occupancy and other - franchise subleases and other	4,463,000	3,167,000	2,608,000
Pre-opening costs	1,650,000	1,584,000	1,591,000
Goodwill, Impaired, Accumulated Impairment Loss	118,250,000
Goodwill, Impairment Loss	118,250,000	0	0
Impairment of long-lived assets	7,159,000	3,861,000	0
Restaurant closure charges, net	2,961,000	394,000	191,000
Loss on disposal of assets and adjustments to assets held for sale, net	9,448,000	1,012,000	1,075,000
Total operating expenses	619,994,000	471,457,000	430,209,000
(Loss) income from operations	(107,043,000)	34,033,000	41,247,000
Other expense (income), net:
Interest expense	7,235,000	9,075,000	7,200,000
Other income	(364,000)	(660,000)	0
Total other expense, net	6,871,000	8,415,000	7,200,000
(Loss) income from operations before provision (benefit) for income taxes	(113,914,000)	25,618,000	34,047,000
Provision (benefit) for income taxes	4,371,000	6,659,000	(15,824,000)
Net (loss) income	(118,285,000)	18,959,000	49,871,000
Other comprehensive (loss) income:
Change in fair value of interest rate cap, net of tax	(364,000)	122,000	(162,000)
Reclassification of interest rate cap amortization included in net income, net of tax	132,000	44,000	4,000
Total other comprehensive (loss) income, net	(232,000)	166,000	(158,000)
Comprehensive (loss) income	$ (118,517,000)	$ 19,125,000	$ 49,713,000
(Loss) earnings per share:
Basic (in dollars per share)	$ (3.20)	$ 0.50	$ 1.29
Diluted (in dollars per share)	$ (3.20)	$ 0.49	$ 1.25
Weighted-average shares outstanding:
Basic (in shares)	37,018,445	38,106,057	38,689,508
Diluted (in shares)	37,018,445	38,683,959	39,949,907
Company restaurant sales
Revenue:
Revenue	$ 473,991,000	$ 471,193,000	$ 452,148,000
Franchise revenue
Revenue:
Revenue	19,002,000	17,569,000	16,464,000
Franchise advertising contributions
Revenue:
Revenue	14,516,000	13,300,000	0
Franchise sublease and other income
Revenue:
Revenue	5,442,000	3,428,000	2,844,000
Food and paper costs
Restaurant operating expenses:
Food and paper costs	$ 130,711,000	$ 128,873,000	$ 125,391,000