Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive (loss) income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2018	Jun. 24, 2017	Jun. 30, 2018	Jun. 24, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		$ (27,298)	$ (43,221)	$ (28,812)	$ (45,832)
Other comprehensive income before reclassifications		0	0	0	(10)
Reclassifications to earnings		757	1,203	2,271	3,824
Other comprehensive income		757	1,203	2,271	3,814
Balance ending		(26,541)	(42,018)	(26,541)	(42,018)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		0	0	0	(205)
Other comprehensive income before reclassifications		0	0	0	(10)
Reclassifications to earnings	[1]	0	0	0	215
Other comprehensive income		0	0	0	205
Balance ending		0	0	0	0
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		(35,469)	(48,791)	(37,311)	(51,391)
Other comprehensive income		920	1,301	2,762	3,901
Balance ending		(34,549)	(47,490)	(34,549)	(47,490)
Amortization of Net Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	920	1,301	2,762	3,901
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		8,171	5,570	8,499	5,764
Other comprehensive income		(163)	(98)	(491)	(292)
Balance ending		8,008	5,472	8,008	5,472
Amortization of Net (Gain) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	$ (163)	$ (98)	$ (491)	$ (292)

[1] Reclassification of realized losses on cash flow hedges are recognized in interest expense.

[2] These amounts are included in the computation of net periodic benefit cost. See Note 13, “Pension Plans and Other Postretirement Benefits.”