Financial Instruments and Risk Management - Reconciliation of the Beginning and Ending Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 24, 2017	Jun. 25, 2016
Reconciliation of beginning and ending balances of assets measured at fair value on recurring basis using significant unobservable inputs [Rollforward]
Beginning balance of over-the-counter options	$ 809	$ 2,781
Beginning balance realized during the period	(589)	(2,546)
Contracts purchased during the period	0	762
Change in the fair value of outstanding contracts	(115)	(234)
Ending balance of over-the-counter options	105	763
Reconciliation of beginning and ending balances of liabilities measured at fair value on recurring basis using significant unobservable inputs [Rollforward]
Beginning balance of over-the-counter options	0	347
Beginning balance realized during the period	0	(275)
Contracts purchased during the period	0	0
Change in the fair value of outstanding contracts	0	(72)
Ending balance of over-the-counter options	$ 0	$ 0