Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		$ (25,104)	$ (23,566)	$ (26,186)	$ (24,670)
Recognition in earnings of net actuarial loss for pension settlement		900	0	900	0
Reclassifications to earnings		541	552	1,623	1,656
Other comprehensive income		1,441	552	2,523	1,656
Balance ending		(23,663)	(23,014)	(23,663)	(23,014)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		(32,009)	(31,447)	(33,733)	(33,180)
Recognition in earnings of net actuarial loss for pension settlement	[1]	900	0	900	0
Reclassifications to earnings	[1]	862	867	2,586	2,600
Other comprehensive income		1,762	867	3,486	2,600
Balance ending		(30,247)	(30,580)	(30,247)	(30,580)
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		6,905	7,881	7,547	8,510
Amortization of net gain and prior service credits	[1]	(321)	(315)	(963)	(944)
Other comprehensive income		(321)	(315)	(963)	(944)
Balance ending		$ 6,584	$ 7,566	$ 6,584	$ 7,566

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