Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands		3 Months Ended
		Dec. 26, 2020	Dec. 28, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		$ (25,776)	$ (26,186)
Reclassifications to earnings		593	541
Other comprehensive income		593	541
Balance ending		(25,183)	(25,645)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		(32,286)	(33,733)
Reclassifications to earnings	[1]	898	862
Other comprehensive income		898	862
Balance ending		(31,388)	(32,871)
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		6,510	7,547
Amortization of net gain and prior service credits	[1]	(305)	(321)
Other comprehensive income		(305)	(321)
Balance ending		$ 6,205	$ 7,226

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