Minimum period the individual is required to perform services to be fully vested under the deferred compensation arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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The interest rate used to adjust for the time value of money for the plan.

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Expected rate of compensation increases (for pay-related plans).

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Amount of contributions made by the employer to defined benefit plans.

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Target allocation of investments of this type to total plan assets presented on a weighted average basis.

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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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Percentage employer matches of the employee's percentage contribution matched.

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Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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Additional participant contribution percentage on an after tax basis of eligible base pay.

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Retirement Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2016 USD ($) plan	Oct. 02, 2015 USD ($)	Sep. 26, 2014 USD ($)
Retirement Plans [Line Items]
Total retirement, post-retirement benefit plan and defined benefit plan expense	$ 33.3	$ 32.1	$ 28.6
Accumulated benefit obligation for defined benefit pension plans	$ 193.4	$ 175.6
Equity Securities
Retirement Plans [Line Items]
Target percentage allocation	25.00%
Debt and fixed income assets
Retirement Plans [Line Items]
Target percentage allocation	64.00%
Real Estate
Retirement Plans [Line Items]
Target percentage allocation	3.00%
Other
Retirement Plans [Line Items]
Target percentage allocation	8.00%
U.K. Savings Plan
Retirement Plans [Line Items]
Number of plans \| plan	7
Defined Benefit Plans
Retirement Plans [Line Items]
Discount rate	1.03%	2.09%
Rate of projected compensation increase (as a percent)	2.33%	2.50%
Contributions by employer	$ 8.1	$ 6.9	$ 7.2
Expected total contribution to the defined benefit plans for the next year	$ 7.2
Minimum \| Defined Benefit Plans
Retirement Plans [Line Items]
Discount rate	0.30%
Rate of projected compensation increase (as a percent)	1.75%
Maximum \| Defined Benefit Plans
Retirement Plans [Line Items]
Discount rate	4.75%
Rate of projected compensation increase (as a percent)	5.00%
United States Retirement Plan \| Minimum
Retirement Plans [Line Items]
Participant contribution for eligible base compensation (as a percent)	1.00%
United States Retirement Plan \| Maximum
Retirement Plans [Line Items]
Contribution as percentage on after-tax basis (as a percent)	15.00%
Participant contribution for eligible base compensation (as a percent)	25.00%
US 401(K) Plan
Retirement Plans [Line Items]
Years of service	1 year
Maximum eligible participant compensation that company matches under defined contribution plan (as a percent)	6.00%
U.K. Savings Plan
Retirement Plans [Line Items]
Maximum eligible participant compensation that company matches under defined contribution plan (as a percent)	6.00%
U.K. Savings Plan \| Minimum
Retirement Plans [Line Items]
Participant contribution for eligible base compensation (as a percent)	4.00%
U.K. Savings Plan \| Maximum
Retirement Plans [Line Items]
Participant contribution for eligible base compensation (as a percent)	100.00%