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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. 17, 2018
Nov. 18, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Expected price volatility 21.00% 20.00%
Risk-free interest rate 3.10% 1.90%
Weighted average expected lives (in years) 5 years 7 months 6 days 5 years 1 month 6 days
Forfeiture rate 10.00% 10.00%
Dividend yield 0.00% 0.00%