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Share-Based Payments - Weighted Average for Key Assumptions Used in Determining Fair Value of Options Granted and Related Share-Based Compensation Expense (Detail)
3 Months Ended
Nov. 18, 2017
Nov. 19, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Expected price volatility 20.00% 18.00%
Risk-free interest rate 1.90% 1.20%
Weighted average expected lives (in years) 5 years 1 month 6 days 5 years 1 month 6 days
Forfeiture rate 10.00% 10.00%
Dividend yield 0.00% 0.00%