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. 26, 2021	Jun. 27, 2020	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		$ (24,020)		$ (25,104)	$ (25,776)	$ (26,186)
Recognition of net actuarial loss for pension settlement		142	$ 900	900	712	900
Reclassifications to earnings		593		541	1,779	1,623
Other comprehensive income		735		1,441	2,491	2,523
Balance ending		(23,285)	(23,663)	(23,663)	(23,285)	(23,663)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		(29,920)		(32,009)	(32,286)	(33,733)
Recognition of net actuarial loss for pension settlement	[1]	142		900	712	900
Reclassifications to earnings	[1]	899		862	2,695	2,586
Other comprehensive income		1,041		1,762	3,407	3,486
Balance ending		(28,879)	(30,247)	(30,247)	(28,879)	(30,247)
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		5,900		6,905	6,510	7,547
Amortization of net gain and prior service credits	[1]	(306)		(321)	(916)	(963)
Other comprehensive income		(306)		(321)	(916)	(963)
Balance ending		$ 5,594	$ 6,584	$ 6,584	$ 5,594	$ 6,584

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