Note 8 - Postretirement and Postemployment Benefits - Fair Value Hierarchy of Benefit Plan Assets (Details) - USD ($) $ in Thousands	Sep. 27, 2020	Sep. 29, 2019
Fair Value Measured at Net Asset Value Per Share [Member]
Hedge fund investments	$ 15,977
Fair Value, Inputs, Level 1 [Member]
Hedge fund investments	0
Fair Value, Inputs, Level 2 [Member]
Hedge fund investments	0
Fair Value, Inputs, Level 3 [Member]
Hedge fund investments	0
Other Postretirement Benefits Plan [Member]
Cash and cash equivalents		$ 0
Debt securities		0
Hedge fund investments		3,587
Other Postretirement Benefits Plan [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI		778
Other Postretirement Benefits Plan [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI		0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Cash and cash equivalents	0
Debt securities	0
Hedge fund investments	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	590
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI	0
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	59	0
Debt securities	18,229	17,707
Hedge fund investments	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI	2,868	2,640
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI	539
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI	579	628
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Debt securities	0	0
Hedge fund investments	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI	759	750
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0	0
Debt securities	0	0
Hedge fund investments	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic Equity Securities [Member]
Equity Securities, FV-NI	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Emerging Equity Securities [Member]
Equity Securities, FV-NI	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Equity Securities [Member]
Equity Securities, FV-NI	$ 0	$ 0