Computation of Basic and Diluted Net Loss Per Common Share - Reconciliation of Numerator and Denominator of Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 26, 2020	Sep. 26, 2020	Sep. 28, 2019	Sep. 28, 2019	Sep. 26, 2020	Sep. 26, 2020	Sep. 28, 2019	Sep. 28, 2019
Numerator:
Net loss	$ (1,719)	$ (1,719)	$ (1,785)	$ (1,785)	$ (6,150)	$ (6,150)	$ (7,252)	$ (7,252)
Denominator:
Weighted average shares of common stock (basic)	13,893		13,768		13,824	13,824	13,682	13,682
Weighted average shares of common stock (diluted)	13,893		13,768		13,824	13,824	13,682	13,682
Per share data:
Basic net loss per share	$ (0.12)		$ (0.13)		$ (0.44)	$ (0.44)	$ (0.53)	$ (0.53)
Diluted net loss per share	$ (0.12)		$ (0.13)		$ (0.44)	$ (0.44)	$ (0.53)	$ (0.53)