Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Items	Noncontrolling Interest	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings
Beginning balance (in shares) at Dec. 29, 2018		14,624,159			3,514,163
Beginning balance at Dec. 29, 2018	$ 374,571	$ 146	$ 104,731	$ 393,578	$ (86,111)	$ (39,376)	$ 1,603	$ (17)	$ (17)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	43,679			43,319			360
Dividends declared – Common Stock	(7,753)			(7,753)
Activity under stock plans	4,461		488		$ 3,973
Activity under stock plans (in shares)					(162,129)
Other comprehensive items	(8,068)					(7,984)	(84)
Ending balance (in shares) at Sep. 28, 2019		14,624,159			3,352,034
Ending balance at Sep. 28, 2019	406,873	$ 146	105,219	429,127	$ (82,138)	(47,360)	1,879
Beginning balance (in shares) at Jun. 29, 2019		14,624,159			3,369,304
Beginning balance at Jun. 29, 2019	400,560	$ 146	103,767	415,605	$ (82,562)	(38,251)	1,855
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	16,213			16,115			98
Dividends declared – Common Stock	(2,593)			(2,593)
Activity under stock plans	1,876		1,452		$ 424
Activity under stock plans (in shares)					(17,270)
Other comprehensive items	(9,183)					(9,109)	(74)
Ending balance (in shares) at Sep. 28, 2019		14,624,159			3,352,034
Ending balance at Sep. 28, 2019	406,873	$ 146	105,219	429,127	$ (82,138)	(47,360)	1,879
Beginning balance (in shares) at Dec. 28, 2019		14,624,159			3,214,888
Beginning balance at Dec. 28, 2019	427,079	$ 146	106,698	435,249	$ (78,778)	(37,620)	1,384
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	39,358			38,989			369
Dividends declared – Common Stock	(8,275)			(8,275)
Dividend paid to noncontrolling interest	(525)						(525)
Activity under stock plans	4,144		1,686		$ 2,458
Activity under stock plans (in shares)					(100,289)
Other comprehensive items	464					388	76
Ending balance (in shares) at Sep. 26, 2020		14,624,159			3,114,599
Ending balance at Sep. 26, 2020	462,245	$ 146	108,384	465,963	$ (76,320)	(37,232)	1,304
Beginning balance (in shares) at Jun. 27, 2020		14,624,159			3,127,565
Beginning balance at Jun. 27, 2020	440,359	$ 146	107,202	453,874	$ (76,638)	(45,863)	1,638
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	14,980			14,851			129
Dividends declared – Common Stock	(2,762)			(2,762)
Dividend paid to noncontrolling interest	(525)						(525)
Activity under stock plans	1,500		1,182		$ 318
Activity under stock plans (in shares)					(12,966)
Other comprehensive items	8,693					8,631	62
Ending balance (in shares) at Sep. 26, 2020		14,624,159			3,114,599
Ending balance at Sep. 26, 2020	$ 462,245	$ 146	$ 108,384	$ 465,963	$ (76,320)	$ (37,232)	$ 1,304