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Employee Stock Plans - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
9 Months Ended
Jun. 29, 2018
Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation $ 9,424 $ 7,549
Shares issued under share-based compensation plans 60,479 532,491
Restricted Stock Units    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Granted 45,985 37,100
Weighted Average Grant Date Fair Value $ 86.26 $ 76.83
Performance Share Plan Shares    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Granted 33,700 43,650
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 20,981 11,338
Weighted-average grant date fair value of options granted $ 22.67 $ 24.61
Equity Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of options granted 239,680 237,200
Weighted-average grant date fair value of options granted $ 30.80 $ 32.66
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%