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Fair Value Measurements Fair Value Measurements Not Practicable (Details) - USD ($)
Dec. 24, 2017
Sep. 24, 2017
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]    
Fair Value, Estimate Not Practicable, Investments $ 6,068,000  
Debt, Long-term and Short-term, Combined Amount $ 531,953,000 $ 548,385,000