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. 28, 2020	Mar. 30, 2019	Mar. 28, 2020	Mar. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		$ (25,645)	$ (24,118)	$ (26,186)	$ (24,670)
Reclassifications to earnings		541	552	1,082	1,104
Other comprehensive income		541	552	1,082	1,104
Balance ending		(25,104)	(23,566)	(25,104)	(23,566)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		(32,871)	(32,314)	(33,733)	(33,180)
Reclassifications to earnings	[1]	862	867	1,724	1,733
Other comprehensive income		862	867	1,724	1,733
Balance ending		(32,009)	(31,447)	(32,009)	(31,447)
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		7,226	8,196	7,547	8,510
Amortization of net gain and prior service credits	[1]	(321)	(315)	(642)	(629)
Other comprehensive income		(321)	(315)	(642)	(629)
Balance ending		$ 6,905	$ 7,881	$ 6,905	$ 7,881

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