Note 9 - Postretirement and Postemployment Benefits - Net Period Postretirement Cost (Benefit) Components for Postretirement Plans (Details) - Postemployment Retirement Benefits [Member] - USD ($)	12 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 29, 2019
Service cost for benefits earned during the year	$ 207,000	$ 500,000	$ 0
Interest cost on projected benefit obligation	429,000	869,000	412,000
Expected return on plan assets	(1,007,000)	(1,060,000)	(1,082,000)
Amortization of net loss	(685,000)	(743,000)	(976,000)
Amortization of prior service benefit	(647,000)	(647,000)	(723,000)
Curtailment gains	(23,830,000)	0	0
Net periodic postretirement benefit	$ (25,533,000)	$ (1,081,000)	$ (2,369,000)