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Financial Instruments and Risk Management - Additional Information (Details) - USD ($)
3 Months Ended 12 Months Ended
Dec. 30, 2017
Sep. 30, 2017
Derivatives, Fair Value [Line Items]    
Maximum maturity period of highly liquid investment considered as cash equivalents 3 months  
Margin over basis rate (in hundredths) 1.00%  
Cash collateral $ 0 $ 0
Commodity Contract [Member]    
Derivatives, Fair Value [Line Items]    
Weighted average maturity of outstanding commodity-related derivatives 4 months 5 months