Consolidated Statements Of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Total
Balance (in shares) at Dec. 31, 2018	6,981
Balance at Dec. 31, 2018	$ 7,441	$ 10,360	$ 362,709	$ 21	$ (14,408)	$ 366,123
Net earnings			30,496			30,496
Unrealized loss on available-for-sale securities, net of tax				135		135
Other (in shares)	22
Other		838	1		384	1,224
Dividends paid			(42,087)			(42,087)
Balance (in shares) at Sep. 29, 2019	7,003
Balance at Sep. 29, 2019	$ 7,441	11,198	351,119	157	(14,024)	355,891
Balance (in shares) at Jun. 30, 2019	6,997
Balance at Jun. 30, 2019	$ 7,441	10,914	334,730	180	(14,066)	339,199
Net earnings			16,389			16,389
Unrealized loss on available-for-sale securities, net of tax				(23)		(23)
Other (in shares)	6
Other		284			42	326
Balance (in shares) at Sep. 29, 2019	7,003
Balance at Sep. 29, 2019	$ 7,441	11,198	351,119	157	(14,024)	355,891
Balance (in shares) at Dec. 31, 2019	7,006
Balance at Dec. 31, 2019	$ 7,441	11,447	362,842	136	(13,909)	367,957
Net earnings			33,017			33,017
Unrealized loss on available-for-sale securities, net of tax				94		94
Other (in shares)	15
Other		684			467	1,151
Dividends paid			(42,172)			(42,172)
Balance (in shares) at Sep. 27, 2020	7,021
Balance at Sep. 27, 2020	$ 7,441	12,131	353,687	230	(13,442)	360,047
Balance (in shares) at Jun. 28, 2020	7,019
Balance at Jun. 28, 2020	$ 7,441	11,923	341,549	294	(13,512)	347,695
Net earnings			12,138			12,138
Unrealized loss on available-for-sale securities, net of tax				(64)		(64)
Other (in shares)	2
Other		208			70	278
Balance (in shares) at Sep. 27, 2020	7,021
Balance at Sep. 27, 2020	$ 7,441	$ 12,131	$ 353,687	$ 230	$ (13,442)	$ 360,047