CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Class A Common Stock	Class B Common Stock	Common Stock [Member] Class A Common Stock	Common Stock [Member] Class B Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income	Non- Controlling Interest
Beginning balance (shares) at Dec. 26, 2018				29,520,833	7,557,347
Beginning balance at Dec. 26, 2018	$ 273,455			$ 30	$ 8	$ 195,633	$ 30,404	$ 0	$ 47,380
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	3,607						2,546		1,061
Other comprehensive income:
Net change in foreign currency translation adjustment	0
Equity-based compensation	1,747					1,747
Activity under stock compensation plans (in shares)				73,563
Activity under stock compensation plans	1,477					975			502
Redemption of LLC Interests (in shares)				(103,832)	(103,832)
Redemption of LLC Interests	0			$ (1)	$ (1)	(594)			(594)
Establishment of liabilities under tax receivable agreement and related changes to deferred tax assets associated with increases in tax basis	366					366
Distributions paid to non-controlling interest holders	(109)								(109)
Ending balance (shares) at Mar. 27, 2019				29,698,228	7,453,515
Ending balance at Mar. 27, 2019	285,738			$ 31	$ 7	199,315	37,086	0	49,299
Beginning balance (shares) at Dec. 25, 2019		34,417,302	3,145,197	34,417,302	3,145,197
Beginning balance at Dec. 25, 2019	321,985			$ 35	$ 3	244,410	54,367	2	23,168
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(1,079)						(960)		(119)
Other comprehensive income:
Net change in foreign currency translation adjustment	1							1
Equity-based compensation	1,313					1,313
Activity under stock compensation plans (in shares)				77,903
Activity under stock compensation plans	63					424			(361)
Redemption of LLC Interests (in shares)				(28,195)	(28,195)
Redemption of LLC Interests	0			$ 0	$ 0	(195)			(195)
Establishment of liabilities under tax receivable agreement and related changes to deferred tax assets associated with increases in tax basis	628					628
Distributions paid to non-controlling interest holders	(305)								(305)
Ending balance (shares) at Mar. 25, 2020		34,523,400	3,117,002	34,523,400	3,117,002
Ending balance at Mar. 25, 2020	$ 322,606			$ 35	$ 3	$ 246,970	$ 53,407	$ 3	$ 22,188