Basis of Presentation and Summary of Significant Accounting Policies - Impact of Adoption of Topic 606 - Consolidated Statements of Comprehensive Income (Details) - USD ($)	3 Months Ended						4 Months Ended		6 Months Ended	12 Months Ended
	Sep. 11, 2018	Jun. 19, 2018	Mar. 27, 2018	Sep. 12, 2017	Jun. 20, 2017	Mar. 28, 2017	Jan. 01, 2019	Jan. 02, 2018	Dec. 29, 2015	Jan. 01, 2019	Jan. 02, 2018	Jan. 03, 2017
Restaurant operating expenses:
Pre-opening costs											$ 1,591,000
Successor
Revenue:
Total revenue	$ 117,830,000	$ 117,813,000	$ 112,554,000	$ 110,988,000	$ 108,581,000	$ 105,345,000	$ 157,293,000	$ 146,542,000		$ 505,490,000	471,456,000	$ 452,083,000
Restaurant operating expenses:
Labor and related expenses										151,954,000	145,012,000	135,725,000
Occupancy and other operating expenses										97,745,000	92,825,000	88,908,000
General and administrative										43,773,000	38,154,000	37,220,000
Franchise advertising expenses										13,300,000	0	0
Depreciation and amortization										25,794,000	23,362,000	23,129,000
Occupancy and other - franchise subleases and other										3,167,000	2,608,000	2,207,000
Pre-opening costs									$ 700,000	1,584,000	1,591,000	731,000
Impairment of long-lived assets										3,861,000	0	0
Restaurant closure charges, net										394,000	191,000	435,000
Loss on disposal of assets, net										1,012,000	1,075,000	312,000
Total operating expenses										471,457,000	430,209,000	408,783,000
Income from operations	9,195,000	7,804,000	6,338,000	9,533,000	10,276,000	8,613,000	10,696,000	12,825,000		34,033,000	41,247,000	43,300,000
Other expense (income), net:
Interest expense										9,075,000	7,200,000	6,327,000
Other income										(660,000)	0	0
Total other expense, net										8,415,000	7,200,000	7,058,000
Income from operations before provision (benefit) for income taxes										25,618,000	34,047,000	36,242,000
Provision (benefit) for income taxes									15,329,000	6,659,000	(15,824,000)	15,329,000
Net income	$ 5,874,000	$ 4,210,000	$ 3,229,000	$ 5,101,000	$ 5,330,000	$ 4,238,000	$ 5,646,000	$ 35,202,000	$ 20,913,000	18,959,000	49,871,000	20,913,000
Other comprehensive income (loss):
Change in fair value of interest rate cap, net of tax										122,000	(162,000)	172,000
Reclassification of interest rate cap amortization included in net income, net of tax										44,000	4,000	0
Total other comprehensive income (loss), net										166,000	(158,000)	172,000
Comprehensive income										$ 19,125,000	$ 49,713,000	$ 21,085,000
Earnings per share:
Basic (in dollars per share)	$ 0.15	$ 0.11	$ 0.08	$ 0.13	$ 0.14	$ 0.11	$ 0.15	$ 0.91	$ 0.54	$ 0.50	$ 1.29	$ 0.54
Diluted (in dollars per share)	$ 0.15	$ 0.11	$ 0.08	$ 0.13	$ 0.13	$ 0.10	$ 0.15	$ 0.89	$ 0.53	$ 0.49	$ 1.25	$ 0.53
Successor | Amounts Under Previous Standards
Revenue:
Total revenue										$ 491,508,000
Restaurant operating expenses:
Labor and related expenses										151,954,000
Occupancy and other operating expenses										97,745,000
General and administrative										43,003,000
Franchise advertising expenses										0
Depreciation and amortization										25,794,000
Occupancy and other - franchise subleases and other										2,855,000
Pre-opening costs										1,584,000
Impairment of long-lived assets										3,861,000
Restaurant closure charges, net										394,000
Loss on disposal of assets, net										1,012,000
Total operating expenses										457,075,000
Income from operations										34,433,000
Other expense (income), net:
Interest expense										9,075,000
Other income										(660,000)
Total other expense, net										8,415,000
Income from operations before provision (benefit) for income taxes										26,018,000
Provision (benefit) for income taxes										6,767,000
Net income										19,251,000
Other comprehensive income (loss):
Change in fair value of interest rate cap, net of tax										122,000
Reclassification of interest rate cap amortization included in net income, net of tax										44,000
Total other comprehensive income (loss), net										166,000
Comprehensive income										$ 19,417,000
Earnings per share:
Basic (in dollars per share)										$ 0.51
Diluted (in dollars per share)										$ 0.50
Successor | Accounting Standards Update 2014-09 | Adjustments for Prior Revenue Recognition Standards
Revenue:
Total revenue										$ (13,982,000)
Restaurant operating expenses:
Labor and related expenses										0
Occupancy and other operating expenses										0
General and administrative										(770,000)
Franchise advertising expenses										(13,300,000)
Depreciation and amortization										0
Occupancy and other - franchise subleases and other										(312,000)
Pre-opening costs										0
Impairment of long-lived assets										0
Restaurant closure charges, net										0
Loss on disposal of assets, net										0
Total operating expenses										(14,382,000)
Income from operations										400,000
Other expense (income), net:
Interest expense										0
Other income										0
Total other expense, net										0
Income from operations before provision (benefit) for income taxes										400,000
Provision (benefit) for income taxes										108,000
Net income										292,000
Other comprehensive income (loss):
Change in fair value of interest rate cap, net of tax										0
Reclassification of interest rate cap amortization included in net income, net of tax										0
Total other comprehensive income (loss), net										0
Comprehensive income										$ 292,000
Earnings per share:
Basic (in dollars per share)										$ 0.01
Diluted (in dollars per share)										$ 0.01
Successor | Company restaurant sales
Revenue:
Revenue										$ 471,193,000	$ 452,148,000	$ 434,064,000
Successor | Company restaurant sales | Amounts Under Previous Standards
Revenue:
Revenue										471,193,000
Successor | Company restaurant sales | Accounting Standards Update 2014-09 | Adjustments for Prior Revenue Recognition Standards
Revenue:
Revenue										0
Successor | Franchise revenue
Revenue:
Revenue										17,569,000	16,464,000	15,676,000
Successor | Franchise revenue | Amounts Under Previous Standards
Revenue:
Revenue										17,199,000
Successor | Franchise revenue | Accounting Standards Update 2014-09 | Adjustments for Prior Revenue Recognition Standards
Revenue:
Revenue										(370,000)
Successor | Franchise advertising contributions
Revenue:
Revenue										13,300,000	0	0
Successor | Franchise advertising contributions | Amounts Under Previous Standards
Revenue:
Revenue										0
Successor | Franchise advertising contributions | Accounting Standards Update 2014-09 | Adjustments for Prior Revenue Recognition Standards
Revenue:
Revenue										(13,300,000)
Successor | Franchise sublease and other income
Revenue:
Revenue										3,428,000	2,844,000	2,343,000
Successor | Franchise sublease and other income | Amounts Under Previous Standards
Revenue:
Revenue										3,116,000
Successor | Franchise sublease and other income | Accounting Standards Update 2014-09 | Adjustments for Prior Revenue Recognition Standards
Revenue:
Revenue										(312,000)
Successor | Food and paper costs
Restaurant operating expenses:
Food and paper costs										128,873,000	$ 125,391,000	$ 120,116,000
Successor | Food and paper costs | Amounts Under Previous Standards
Restaurant operating expenses:
Food and paper costs										128,873,000
Successor | Food and paper costs | Accounting Standards Update 2014-09 | Adjustments for Prior Revenue Recognition Standards
Restaurant operating expenses:
Food and paper costs										$ 0