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Employee Stock Plans - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
6 Months Ended
Mar. 30, 2018
Mar. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation $ 6,715 $ 7,352
Shares issued under share-based compensation plans 46,888 345,484
Restricted Stock Units    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Granted 42,050 37,100
Weighted Average Grant Date Fair Value $ 87.34 $ 76.83
Performance Share Plan Shares    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Granted 33,700 42,600
Performance period 3 years  
Performance Share Plan Shares | Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Percentage of the target number of shares paid out 0.00%  
Performance Share Plan Shares | Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Percentage of the target number of shares paid out 300.00%  
Employee Share-save Scheme    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Discount rate of market value on purchase date 5.00%  
The term of options, years 3 years  
Number of options granted 0 0
Equity Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of options granted 218,800 234,700
Weighted-average grant date fair value of options granted $ 30.85 $ 32.60
Employee Stock Purchase Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Discount rate of market value on purchase date 5.00%