Note 9 - Postretirement and Postemployment Benefits - Fair Value Hierarchy of Benefit Plan Assets (Details) - USD ($) $ in Thousands	Sep. 26, 2021	Sep. 27, 2020
Fair Value Measured at Net Asset Value Per Share [Member]
Hedge fund investment	$ 18,758	$ 15,977
Fair Value, Inputs, Level 1 [Member]
Hedge fund investment	0	0
Fair Value, Inputs, Level 2 [Member]
Hedge fund investment	0	0
Fair Value, Inputs, Level 3 [Member]
Hedge fund investment	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Cash and cash equivalents	0	0
Debt securities	0	0
Hedge fund investment	3,235	2,754
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI, Current	904	590
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI, Current	0	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI, Current	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	25	59
Debt securities	18,363	18,229
Hedge fund investment	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI, Current	2,643	2,868
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI, Current	603	539
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI, Current	747	579
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Debt securities	0	0
Hedge fund investment	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI, Current	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI, Current	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI, Current	660	759
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0	0
Debt securities	0	0
Hedge fund investment	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI, Current	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI, Current	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI, Current	$ 0	$ 0