Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive (loss) income (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 25, 2021	Sep. 26, 2020	Sep. 28, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		$ (25,776)	$ (26,186)	$ (24,670)
Other comprehensive income before reclassifications		5,166	(2,805)	(3,723)
Recognition in earnings of net actuarial loss for pension settlement		958	1,051	0
Reclassifications to earnings		2,068	2,164	2,207
Other comprehensive income (loss)		8,192	410	(1,516)
Balance ending		(17,584)	(25,776)	(26,186)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		(32,286)	(33,733)	(33,180)
Funded status benefit plan obligation		4,736	(3,052)	(4,019)
Recognition in earnings of net actuarial loss for pension settlement	[1]	958	1,051	0
Reclassifications to earnings	[1]	3,289	3,448	3,466
Other comprehensive income (loss)		8,983	1,447	(553)
Balance ending		(23,303)	(32,286)	(33,733)
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance beginning		6,510	7,547	8,510
Funded status benefit plan obligation		430	247	296
Other comprehensive income (loss)		(791)	(1,037)	(963)
Balance ending		5,719	6,510	7,547
Amortization of Prior Service Credits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassifications to earnings	[1]	(498)	(498)	(498)
Amortization of Net (Gain) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassifications to earnings	[1]	$ (723)	$ (786)	$ (761)

[1] These amounts are included in the computation of net periodic benefit cost.  See Note 12, “Employee Benefit Plans”.