Stock Options Outstanding (Detail) - $ / shares	12 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Exercisable, Shares	707,725	594,863	918,706
$41.00 - $55.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	$ 41.00
Range of Exercise Prices, upper limit	$ 55.00
Options Outstanding, Shares	102,250
Options Outstanding Weighted Average Remaining Life (years)	2 years 4 months 24 days
Options Outstanding, Weighted Average Price	$ 48.08
Options Exercisable, Shares	102,250
Options Exercisable, Weighted Average Price	$ 48.08
$55.01 - $65.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	55.01
Range of Exercise Prices, upper limit	$ 65.00
Options Outstanding, Shares	131,875
Options Outstanding Weighted Average Remaining Life (years)	2 years 3 months 18 days
Options Outstanding, Weighted Average Price	$ 62.69
Options Exercisable, Shares	131,875
Options Exercisable, Weighted Average Price	$ 62.69
$65.01 - $75.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	65.01
Range of Exercise Prices, upper limit	$ 75.00
Options Outstanding, Shares	260,405
Options Outstanding Weighted Average Remaining Life (years)	7 years 9 months 18 days
Options Outstanding, Weighted Average Price	$ 70.22
Options Exercisable, Shares	62,675
Options Exercisable, Weighted Average Price	$ 68.20
$75.01 - $85.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	75.01
Range of Exercise Prices, upper limit	$ 85.00
Options Outstanding, Shares	237,475
Options Outstanding Weighted Average Remaining Life (years)	7 years 2 months 12 days
Options Outstanding, Weighted Average Price	$ 82.10
Options Exercisable, Shares	98,075
Options Exercisable, Weighted Average Price	$ 81.04
$85.01 - $100.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	85.01
Range of Exercise Prices, upper limit	$ 100.00
Options Outstanding, Shares	324,800
Options Outstanding Weighted Average Remaining Life (years)	6 years 6 months
Options Outstanding, Weighted Average Price	$ 94.50
Options Exercisable, Shares	197,350
Options Exercisable, Weighted Average Price	$ 95.15
$100.01 - $117.53
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	100.01
Range of Exercise Prices, upper limit	$ 117.53
Options Outstanding, Shares	147,525
Options Outstanding Weighted Average Remaining Life (years)	5 years 9 months 18 days
Options Outstanding, Weighted Average Price	$ 110.40
Options Exercisable, Shares	115,500
Options Exercisable, Weighted Average Price	$ 110.45