Amounts Reclassified Out of Accumulated Other Comprehensive Income - Reclassification out of accumulated other comprehensive (loss) income (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 24, 2016	Sep. 26, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		$ (45,832)	$ (48,883)	$ (45,905)
Other comprehensive income before reclassifications		5,893	(4,569)	(10,202)
Recognition in earnings of net actuarial loss for pension settlement		6,100	2,000	2,000
Reclassifications to earnings		5,027	5,620	5,224
Other comprehensive income (loss)		17,020	3,051	(2,978)
Balance ending		(28,812)	(45,832)	(48,883)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		(205)	(1,311)	(1,540)
Other comprehensive income before reclassifications		(10)	6	(1,159)
Reclassifications to earnings	[1]	215	1,100	1,388
Other comprehensive income (loss)		205	1,106	229
Balance ending		0	(205)	(1,311)
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		(51,391)	(52,836)	(49,034)
Funded status benefit plan obligation		2,779	(5,773)	(10,324)
Recognition in earnings of net actuarial loss for pension settlement	[2]	6,100	2,000	2,000
Other comprehensive income (loss)		14,080	1,445	(3,802)
Balance ending		(37,311)	(51,391)	(52,836)
Amortization of Net Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	5,201	5,218	4,522
Post-Retirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning		5,764	5,264	4,669
Prior service credits		3,246	0	0
Funded status benefit plan obligation		(122)	1,198	1,281
Other comprehensive income (loss)		2,735	500	595
Balance ending		8,499	5,764	5,264
Amortization of Prior Service Credits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	0	(399)	(490)
Amortization of Net (Gain) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications to earnings	[2]	$ (389)	$ (299)	$ (196)

[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 10, “Employee Benefit Plans”.