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. 26, 2015	Dec. 27, 2014
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	$ 2,781	$ 1,512
Beginning balance realized during the period	(820)	(304)
Contracts purchased during the period	223	589
Change in the fair value of outstanding contracts	(38)	3,500
Ending balance of over-the-counter options	2,146	5,297
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	347	0
Beginning balance realized during the period	(21)	0
Contracts purchased during the period	0	12
Change in the fair value of outstanding contracts	(103)	0
Ending balance of over-the-counter options	$ 223	$ 12