Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Common Class B Units	Retained Earnings	Non-controlling Interests	Non-controlling Interests Common Class B Units
Balances at Dec. 31, 2017	$ 113,861	$ 15	$ 95,151		$ 13,495	$ 5,200
Balance, shares at Dec. 31, 2017		14,695,176
Cumulative effect of change in accounting policy (Note 10 and Note 9)	34				34
Share-based compensation	2,140		233			1,907
Net income (loss)	1,593				1,593
Balances at Apr. 01, 2018	117,628	$ 15	95,384		15,122	7,107
Balance, shares at Apr. 01, 2018		14,695,176
Balances at Dec. 31, 2017	113,861	$ 15	95,151		13,495	5,200
Balance, shares at Dec. 31, 2017		14,695,176
Net income (loss)	3,065
Balances at Sep. 30, 2018	120,879	$ 15	95,976		16,594	8,294
Balance, shares at Sep. 30, 2018		14,695,176
Balances at Apr. 01, 2018	117,628	$ 15	95,384		15,122	7,107
Balance, shares at Apr. 01, 2018		14,695,176
Share-based compensation	243		296			(53)
Net income (loss)	2,105				2,105
Balances at Jul. 01, 2018	119,976	$ 15	95,680		17,227	7,054
Balance, shares at Jul. 01, 2018		14,695,176
Share-based compensation	1,536		296			1,240
Net income (loss)	(633)				(633)
Balances at Sep. 30, 2018	120,879	$ 15	95,976		16,594	8,294
Balance, shares at Sep. 30, 2018		14,695,176
Balances at Dec. 30, 2018	121,659	$ 15	96,272		17,528	7,844
Balance, shares at Dec. 30, 2018		14,695,176
Cumulative effect of change in accounting policy (Note 10 and Note 9)	(1,257)				(1,257)
Share-based compensation	296		296
Cancellation of subsidiary Class B Units (Note 2 (g))				$ 6,286			$ (6,286)
Net income (loss)	3,848				3,848
Balances at Mar. 31, 2019	124,546	$ 15	102,854		20,119	1,558
Balance, shares at Mar. 31, 2019		14,695,176
Balances at Dec. 30, 2018	121,659	$ 15	96,272		17,528	7,844
Balance, shares at Dec. 30, 2018		14,695,176
Net income (loss)	6,787
Balances at Sep. 29, 2019	128,219	$ 15	103,588		23,058	1,558
Balance, shares at Sep. 29, 2019		14,959,176
Balances at Mar. 31, 2019	124,546	$ 15	102,854		20,119	1,558
Balance, shares at Mar. 31, 2019		14,695,176
Share-based compensation	296		296
Net income (loss)	2,168				2,168
Balances at Jun. 30, 2019	127,010	$ 15	103,150		22,287	1,558
Balance, shares at Jun. 30, 2019		14,695,176
Share-based compensation	438	$ 264,000	438
Net income (loss)	771				771
Balances at Sep. 29, 2019	$ 128,219	$ 15	$ 103,588		$ 23,058	$ 1,558
Balance, shares at Sep. 29, 2019		14,959,176