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Stock-Based Compensation - Schedule of Assumptions Used to Determine Grant Date Fair Value of Market Based Restricted Common Shares (Detail) - Market-Based Restricted Common Shares
12 Months Ended
Sep. 28, 2018
May 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dividend yield 2.16% 1.60%
Expected volatility 33.60% 44.00%
Risk-free interest rate 2.96% 1.70%