SCHEDULE I: CONDENSED FINANCIAL INFORMATION OF REGISTRANT - BALANCE SHEET (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 30, 2020	Dec. 25, 2019	Dec. 26, 2018	Dec. 27, 2017
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Current assets:
Accounts receivable	$ 9,464	$ 9,970
Total current assets	203,186	87,675
TOTAL ASSETS	1,145,348	968,268
Current liabilities:
Accounts payable	23,487	14,300
Accrued expenses	25,920	24,140
Current portion of liabilities under tax receivable agreement	0	7,777
Total current liabilities	109,705	99,392
Liabilities under tax receivable agreement, net of current portion	232,954	226,649
Total liabilities	710,855	646,283
Commitments and contingencies
Stockholders' equity:
Preferred stock, no par value—10,000,000 shares authorized; none issued and outstanding as of December 30, 2020 and December 25, 2019, respectively.	0	0
Additional paid-in capital	395,067	244,410
Retained earnings	12,209	54,367
Total stockholders' equity	434,493	321,985	$ 273,455	$ 224,479
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,145,348	$ 968,268
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Deferred Income Tax Assets, Net	$ 287,007	$ 279,817
Class A Common Stock
Stockholders' equity:
Common stock	$ 39	$ 35
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares, issued (in shares)	38,717,790	34,417,302
Common stock, shares, outstanding (in shares)	38,717,790	34,417,302
Class B Common Stock
Stockholders' equity:
Common stock	$ 3	$ 3
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	35,000,000	35,000,000
Common stock, shares, issued (in shares)	2,951,188	3,145,197
Common stock, shares, outstanding (in shares)	2,951,188	3,145,197
Parent Company
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Current assets:
Cash	$ 9,469	$ 9,223
Accounts receivable	0	1
Prepaid expenses	45	206
Total current assets	9,514	9,430
Due from SSE Holdings	2,103	7,124
Investment in subsidiaries	356,497	247,372
TOTAL ASSETS	653,691	542,938
Current liabilities:
Accounts payable	3	1
Accrued expenses	125	44
Due to SSE Holdings	13,288	9,652
Current portion of liabilities under tax receivable agreement	0	7,777
Total current liabilities	13,416	17,474
Liabilities under tax receivable agreement, net of current portion	232,954	226,649
Total liabilities	246,370	244,123
Commitments and contingencies
Stockholders' equity:
Preferred stock, no par value—10,000,000 shares authorized; none issued and outstanding as of December 30, 2020 and December 25, 2019, respectively.	0	0
Additional paid-in capital	395,067	244,410
Retained earnings	12,209	54,367
Total stockholders' equity	407,321	298,815
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 653,691	$ 542,938
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Deferred Income Tax Assets, Net	$ 285,577	$ 279,012
Parent Company | Class A Common Stock
Stockholders' equity:
Common stock	$ 39	$ 35
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares, issued (in shares)	34,417,302	29,520,833
Common stock, shares, outstanding (in shares)	34,417,302	29,520,833
Parent Company | Class B Common Stock
Stockholders' equity:
Common stock	$ 3	$ 3
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	35,000,000	35,000,000
Common stock, shares, issued (in shares)	3,145,197	7,557,347
Common stock, shares, outstanding (in shares)	3,145,197	7,557,347