Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive (loss) income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 25, 2017	Mar. 26, 2016	Mar. 25, 2017	Mar. 26, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		$ (44,434)	$ (47,414)	$ (45,832)	$ (48,883)
Other comprehensive income before reclassifications		(5)	(117)	(10)	60
Reclassifications to earnings		1,218	1,560	2,621	2,852
Other comprehensive income		1,213	1,443	2,611	2,912
Balance ending		(43,221)	(45,971)	(43,221)	(45,971)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		(10)	(801)	(205)	(1,311)
Other comprehensive income before reclassifications		(5)	(117)	(10)	60
Reclassifications to earnings	[1]	15	259	215	592
Other comprehensive income		10	142	205	652
Balance ending		0	(659)	0	(659)
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		(50,091)	(51,702)	(51,391)	(52,836)
Other comprehensive income		1,300	1,475	2,600	2,609
Balance ending		(48,791)	(50,227)	(48,791)	(50,227)
Amortization of Net Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	1,300	1,475	2,600	2,609
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		5,667	5,089	5,764	5,264
Other comprehensive income		(97)	(174)	(194)	(349)
Balance ending		5,570	4,915	5,570	4,915
Amortization of Prior Service Credits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	0	(100)	0	(200)
Amortization of Net (Gain) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	$ (97)	$ (74)	$ (194)	$ (149)

[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 12, “Pension Plans and Other Postretirement Benefits.”