Per Share Amounts and Common Shares Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Equity [Abstract]
Net income (loss)	$ 173	$ (493)
Weighted-average shares outstanding, basic	23,187,000	22,910,000
Weighted-average shares, partially-paid share subscriptions	0	162,000
Basic weighted average shares	23,187,000	23,072,000
Incremental shares from assumed exercise of stock subscription purchase rights	0	119,000
Incremental shares from assumed exercise of stock options and awards	984,000	827,000
Diluted weighted-average shares	24,171,000	24,018,000
Net income per share basic	$ 0.01	$ (0.02)
Net income per share diluted	$ 0.01	$ (0.02)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at January 1, 2020	23,176,803
Shares purchased	(333,302)
Shares sold	207,304
Options and awards exercised	15,669
Shares outstanding at March 28, 2020	23,066,474
Employee options exercisable	936,457
Common shares, net of treasury shares [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at January 1, 2020	18,029,921
Shares purchased	(215,384)
Shares sold	110
Options and awards exercised	15,669
Shares outstanding at March 28, 2020	17,830,316
Redeemable shares [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at January 1, 2020	5,146,882
Shares purchased	(117,918)
Shares sold	207,194
Options and awards exercised	0
Shares outstanding at March 28, 2020	5,236,158