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
	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Net income	$ 3,903	$ 22,066	$ 21,923	$ 3,521	$ (4,956)	$ 23,770	$ 21,620	$ 235	$ 51,413	$ 40,669	$ 35,157
Less: Undistributed earnings reallocated to non-vested shareholders									(226)	(224)	(375)
Dilutive earnings									$ 51,187	$ 40,445	$ 34,782
Dilutive stock options and restricted stock units (shares)									27	54	33
Weighted average common shares - Dilutive (shares)									10,021	9,996	9,920
Class A
Weighted average common shares - Basic (shares)									8,782	8,730	8,675
Net income per common share - Basic (USD per share)	$ 0.49	$ 2.22	$ 2.21	$ 0.36	$ (0.50)	$ 2.40	$ 2.19	$ 0.02	$ 5.18	$ 4.12	$ 3.56
Net income per common share - Diluted (USD per share)	0.49	2.19	2.18	0.35	(0.49)	2.37	2.15	0.02	$ 5.11	$ 4.05	$ 3.51
Class B
Weighted average common shares - Basic (shares)									1,212	1,212	1,212
Net income per common share - Basic (USD per share)	0.45	2.02	2.01	0.32	(0.46)	2.19	1.99	0.02	$ 4.71	$ 3.74	$ 3.23
Net income per common share - Diluted (USD per share)	$ 0.49	$ 2.19	$ 2.18	$ 0.35	$ (0.49)	$ 2.37	$ 2.15	$ 0.02	$ 5.11	$ 4.05	$ 3.51