Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 26, 2022	Mar. 27, 2021	Mar. 26, 2022	Mar. 27, 2021
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		$ (17,290)	$ (25,183)	$ (17,584)	$ (25,776)
Recognition in earnings of net actuarial loss for pension settlement		0	570	0	570
Reclassifications to earnings		294	593	588	1,186
Other comprehensive income		294	1,163	588	1,756
Balance ending		(16,996)	(24,020)	(16,996)	(24,020)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		(22,704)	(31,388)	(23,303)	(32,286)
Recognition in earnings of net actuarial loss for pension settlement	[1]	0	570	0	570
Reclassifications to earnings	[1]	600	898	1,199	1,796
Other comprehensive income		600	1,468	1,199	2,366
Balance ending		(22,104)	(29,920)	(22,104)	(29,920)
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		5,414	6,205	5,719	6,510
Amortization of net gain and prior service credits	[1]	(306)	(305)	(611)	(610)
Other comprehensive income		(306)	(305)	(611)	(610)
Balance ending		$ 5,108	$ 5,900	$ 5,108	$ 5,900

[1] These amounts are included in the computation of net periodic benefit cost.  See Note 15, “Pension Plans and Other Postretirement Benefits.