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Retirement Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Sep. 28, 2018 USD ($) plan	Sep. 29, 2017 USD ($)	Sep. 30, 2016 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total retirement, post-retirement benefit plan and defined benefit plan expense	$ 30.2	$ 30.1	$ 29.8
Accumulated benefit obligation for defined benefit pension plans	$ 203.3	$ 199.0
Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target percentage allocation	18.00%
Debt and fixed income assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target percentage allocation	78.00%
Real Estate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target percentage allocation	4.00%
U.K. Savings Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of plans \| plan	5
Defined Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	1.69%	1.40%
Rate of projected compensation increase (as a percent)	2.37%	2.40%
Contributions by employer	$ 9.0	$ 8.2	$ 8.0
Expected total contribution to the defined benefit plans for the next year	$ 8.0
Defined Benefit Plans \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	0.70%
Rate of projected compensation increase (as a percent)	1.75%
Defined Benefit Plans \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	2.90%
Rate of projected compensation increase (as a percent)	3.70%
Defined Benefit Plans \| Domestic Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Maximum eligible participant compensation that company matches under defined contribution plan (as a percent)	6.00%
Defined Benefit Plans \| Domestic Plan \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, annual contributions per employee (percent)	1.00%
Defined Benefit Plans \| Domestic Plan \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, annual contributions per employee (percent)	25.00%
Contribution as percentage on after-tax basis (as a percent)	15.00%
Defined Benefit Plans \| U.K. Savings Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Maximum eligible participant compensation that company matches under defined contribution plan (as a percent)	6.00%
Defined Benefit Plans \| U.K. Savings Plan \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, annual contributions per employee (percent)	4.00%
Defined Benefit Plans \| U.K. Savings Plan \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, annual contributions per employee (percent)	100.00%
Other Postretirement Benefits Plan \| Domestic Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Years of service for 100% vesting	1 year