SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 02, 2020	Jun. 26, 2020	Mar. 27, 2020	Dec. 27, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 15,547	$ 12,869	$ 20,387	$ 6,430	$ 3,903	$ 22,066	$ 21,923	$ 3,521	$ 55,233	$ 51,413	$ 40,669
Less: Undistributed earnings reallocated to non-vested shareholders									(220)	(226)	(224)
Dilutive earnings									$ 55,013	$ 51,187	$ 40,445
Dilutive stock options and restricted stock units (shares)									30	27	54
Weighted average common shares - Dilutive (shares)									10,064	10,021	9,996
Class A
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares - Basic (shares)									8,822	8,782	8,730
Net income per common share - Basic (USD per share)	$ 1.56	$ 1.29	$ 2.05	$ 0.65	$ 0.49	$ 2.22	$ 2.21	$ 0.36	$ 5.54	$ 5.18	$ 4.12
Net income per common share - Diluted (USD per share)	1.53	1.27	2.02	0.64	0.49	2.19	2.18	0.35	$ 5.47	$ 5.11	$ 4.05
Class B
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares - Basic (shares)									1,212	1,212	1,212
Net income per common share - Basic (USD per share)	1.42	1.17	1.86	0.59	0.45	2.02	2.01	0.32	$ 5.04	$ 4.71	$ 3.74
Net income per common share - Diluted (USD per share)	$ 1.53	$ 1.27	$ 2.02	$ 0.64	$ 0.49	$ 2.19	$ 2.18	$ 0.35	$ 5.47	$ 5.11	$ 4.05