Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock Including Additional Paid in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Sep. 28, 2019	18,895,000
Balance at Sep. 28, 2019	$ 45,744	$ (12,988)	$ 800,995	$ 833,751
Issuance of common stock upon exercise of stock options (in shares)	5,000
Issuance of common stock upon exercise of stock options	$ 468	0	0	468
Foreign currency translation adjustment	0	810	0	810
Dividends declared	0	0	(10,867)	(10,867)
Share-based compensation	1,299	0	0	1,299
Net earnings	$ 0	0	17,059	17,059
Balance (in shares) at Dec. 28, 2019	18,900,000
Balance at Dec. 28, 2019	$ 47,511	(12,178)	807,187	842,520
Balance (in shares) at Sep. 28, 2019	18,895,000
Balance at Sep. 28, 2019	$ 45,744	(12,988)	800,995	833,751
Foreign currency translation adjustment				(3,070)
Net earnings				11,721
Balance (in shares) at Jun. 27, 2020	18,888,000
Balance at Jun. 27, 2020	$ 46,560	(16,058)	780,098	810,600
Balance (in shares) at Dec. 28, 2019	18,900,000
Balance at Dec. 28, 2019	$ 47,511	(12,178)	807,187	842,520
Issuance of common stock upon exercise of stock options (in shares)	47,000
Issuance of common stock upon exercise of stock options	$ 5,049	0	0	5,049
Foreign currency translation adjustment	0	(3,921)	0	(3,921)
Dividends declared	0	0	(10,878)	(10,878)
Share-based compensation	1,088	0	0	1,088
Net earnings	$ 0	0	7,309	7,309
Issuance of common stock for employee stock purchase plan (in shares)	6,000
Issuance of common stock for employee stock purchase plan	$ 783	0	0	783
Balance (in shares) at Mar. 28, 2020	18,888,000
Balance at Mar. 28, 2020	$ 45,549	(16,099)	803,618	833,068
Issuance of common stock under deferred stock plan (in shares)	1,000
Issuance of common stock under deferred stock plan	$ 90	0	0	90
Repurchase of common stock (in shares)	(66,000)
Repurchase of common stock	$ (8,972)	0	0	(8,972)
Foreign currency translation adjustment	0	41	0	41
Dividends declared	0	0	(10,873)	(10,873)
Share-based compensation	1,011	0	0	1,011
Net earnings	$ 0	0	(12,647)	(12,647)
Balance (in shares) at Jun. 27, 2020	18,888,000
Balance at Jun. 27, 2020	$ 46,560	(16,058)	780,098	$ 810,600
Balance (in shares) at Sep. 26, 2020	18,915,000			18,915,000
Balance at Sep. 26, 2020	$ 49,268	(15,587)	775,817	$ 809,498
Issuance of common stock upon exercise of stock options (in shares)	41,000
Issuance of common stock upon exercise of stock options	$ 4,390	0	0	4,390
Foreign currency translation adjustment	0	2,279	0	2,279
Dividends declared	0	0	(10,900)	(10,900)
Share-based compensation	1,244	0		1,244
Net earnings	$ 0	0	1,778	1,778
Balance (in shares) at Dec. 26, 2020	18,956,000
Balance at Dec. 26, 2020	$ 54,902	(13,308)	766,695	$ 808,289
Balance (in shares) at Sep. 26, 2020	18,915,000			18,915,000
Balance at Sep. 26, 2020	$ 49,268	(15,587)	775,817	$ 809,498
Foreign currency translation adjustment				2,405
Net earnings				$ 36,732
Balance (in shares) at Jun. 26, 2021	19,061,000			19,061,000
Balance at Jun. 26, 2021	$ 69,572	(13,182)	778,640	$ 835,030
Balance (in shares) at Dec. 26, 2020	18,956,000
Balance at Dec. 26, 2020	$ 54,902	(13,308)	766,695	808,289
Issuance of common stock upon exercise of stock options (in shares)	72,000
Issuance of common stock upon exercise of stock options	$ 8,384	0	0	8,384
Foreign currency translation adjustment	0	(531)	0	(531)
Dividends declared	0	0	(10,943)	(10,943)
Share-based compensation	1,026	0		1,026
Net earnings	$ 0	0	6,061	6,061
Issuance of common stock for employee stock purchase plan (in shares)	6,000
Issuance of common stock for employee stock purchase plan	$ 714	0	0	714
Balance (in shares) at Mar. 27, 2021	19,034,000
Balance at Mar. 27, 2021	$ 65,026	(13,839)	761,813	813,000
Issuance of common stock upon exercise of stock options (in shares)	27,000
Foreign currency translation adjustment	$ 0	657	0	657
Dividends declared	0	0	(12,066)	(12,066)
Share-based compensation	982	0	0	982
Net earnings	0	0	28,893	28,893
Issuance of common stock for employee stock purchase plan	$ 3,564	0	0	$ 3,564
Balance (in shares) at Jun. 26, 2021	19,061,000			19,061,000
Balance at Jun. 26, 2021	$ 69,572	$ (13,182)	$ 778,640	$ 835,030