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	3 Months Ended
	Dec. 24, 2016	Dec. 26, 2015
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	0	(820)
Contracts purchased during the period	48	223
Change in the fair value of outstanding contracts	332	(38)
Ending balance of over-the-counter options	1,189	2,146
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	(21)
Contracts purchased during the period	0	0
Change in the fair value of outstanding contracts	0	(103)
Ending balance of over-the-counter options	$ 0	$ 223