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. 29, 2018	18,754,000
Balance at Sep. 29, 2018	$ 27,340	$ (11,994)	$ 743,745	$ 759,091
Issuance of common stock upon exercise of stock options (in shares)	20,000
Issuance of common stock upon exercise of stock options	$ 1,704	0	0	1,704
Foreign currency translation adjustment	0	(1,359)	0	(1,359)
Dividends declared	0	0	(9,389)	(9,389)
Share-based compensation	972	0	0	972
Net earnings	0	0	17,526	17,526
Reclass from accumulated other comprehensive gain	$ 0	(85)	85	0
Balance (in shares) at Dec. 29, 2018	18,774,000
Balance at Dec. 29, 2018	$ 30,016	(13,438)	751,967	768,545
Balance (in shares) at Sep. 29, 2018	18,754,000
Balance at Sep. 29, 2018	$ 27,340	(11,994)	743,745	759,091
Foreign currency translation adjustment				(469)
Net earnings				68,752
Balance (in shares) at Jun. 29, 2019	18,830,000
Balance at Jun. 29, 2019	$ 37,840	(12,548)	784,375	809,667
Balance (in shares) at Dec. 29, 2018	18,774,000
Balance at Dec. 29, 2018	$ 30,016	(13,438)	751,967	768,545
Issuance of common stock upon exercise of stock options (in shares)	34,000
Issuance of common stock upon exercise of stock options	$ 3,451	0	0	3,451
Foreign currency translation adjustment	0	394	0	394
Dividends declared	0	0	(9,405)	(9,405)
Share-based compensation	914	0	0	914
Net earnings	$ 0	0	20,354	20,354
Issuance of common stock for employee stock purchase plan (in shares)	6,000
Issuance of common stock for employee stock purchase plan	$ 772	0	0	772
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	0	0	0	0
Repurchase of common stock	$ (0)	(0)	(0)	(0)
Balance (in shares) at Mar. 30, 2019	18,815,000
Balance at Mar. 30, 2019	$ 35,243	(13,044)	762,916	785,115
Issuance of common stock upon exercise of stock options (in shares)	15,000
Issuance of common stock upon exercise of stock options	$ 1,499	0	0	1,499
Foreign currency translation adjustment	0	496	0	496
Dividends declared	0	0	(9,413)	(9,413)
Share-based compensation	1,098	0	0	1,098
Net earnings	0	0	30,872	30,872
Repurchase of common stock	0	0	0	0
Repurchase of common stock	$ 0	0	0	0
Balance (in shares) at Jun. 29, 2019	18,830,000
Balance at Jun. 29, 2019	$ 37,840	(12,548)	784,375	$ 809,667
Balance (in shares) at Sep. 28, 2019	18,895,000			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			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			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
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)
Repurchase of common stock	$ 8,972	(0)	(0)	8,972
Balance (in shares) at Mar. 28, 2020	18,888,000
Balance at Mar. 28, 2020	$ 45,549	(16,099)	803,618	833,068
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			18,888,000
Balance at Jun. 27, 2020	$ 46,560	$ (16,058)	$ 780,098	$ 810,600