Employee Stock Plans - Additional Information (Detail) $ in Millions	12 Months Ended
	Sep. 29, 2017 USD ($) performance_period shares	Sep. 30, 2016 USD ($) performance_period shares	Oct. 02, 2015 USD ($) shares	Sep. 26, 2014 shares	Feb. 28, 2005 shares
Employee Stock Plans [Line Items]
Total pre-tax intrinsic value of options exercised | $	$ 25.6	$ 23.8	$ 51.1
Fair value | $	9.7	10.2	10.0
Grant date fair value | $	31.4	38.4	38.1
Shares vested during the year, fair value | $	$ 29.8	31.7	44.5
Shares withheld for employees minimum withholding taxes at vesting (in shares)	(100,000)
Shares repurchased for tax withholdings on vesting of restricted stock and restricted stock units | $	$ (10.7)	$ (11.0)	$ (16.3)
Purchase period (in months)	6 months
Maximum number of shares purchased (in shares)	7,000,000
Number of shares issued (in shares)	200,000	300,000
Shares issued, value | $	$ 16.2	$ 17.2
Number of shares available for issuance (in shares)	2,500,000	4,600,000	6,700,000	8,200,000
Employee Stock Option Plans
Employee Stock Plans [Line Items]
Unrecognized compensation expense related to outstanding stock awards | $	$ 9.8
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	1 year 9 months 11 days
Restricted Stock Restricted Stock Units Deferred Stock Units And Performance Units
Employee Stock Plans [Line Items]
Unrecognized compensation expense related to outstanding stock awards | $	$ 30.6
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	1 year 8 months 27 days
Employee Stock Purchase Plans
Employee Stock Plans [Line Items]
Common stock employee purchase price percentage lower than fair market value	85.00%
Fourth Amended 2005 Plan
Employee Stock Plans [Line Items]
Number of shares authorized (in shares)					25,000,000
Award vesting percentage	33.33%
Fourth Amended 2005 Plan | Employee Stock Option Plans
Employee Stock Plans [Line Items]
Award expiration period	7 years
Shares counted against the available for grant (in shares)	1
Fourth Amended 2005 Plan | Restricted Stock Units (RSUs)
Employee Stock Plans [Line Items]
Period between grant date and retirement date (in years)	1 year
Fourth Amended 2005 Plan | Performance Shares
Employee Stock Plans [Line Items]
Service period	3 years
Fourth Amended 2005 Plan | Performance Units
Employee Stock Plans [Line Items]
Performance period	3 years
Fourth Amended 2005 Plan | After February 9, 2012
Employee Stock Plans [Line Items]
Counted against available for grant limit (in shares)	2.6
Fourth Amended 2005 Plan | Beginning In Fiscal 2016
Employee Stock Plans [Line Items]
Maximum payout of shares that could be issued for each performance unit granted (in shares)	1.75
Fourth Amended 2005 Plan | Beginning In Fiscal 2015
Employee Stock Plans [Line Items]
Maximum payout of shares that could be issued for each performance unit granted (in shares)	2.0
Fourth Amended 2005 Plan | Maximum | Restricted Stock And Restricted Stock Unit
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Fourth Amended 2005 Plan | Minimum | Restricted Stock And Restricted Stock Unit
Employee Stock Plans [Line Items]
Award vesting period (in years)	1 year
Fourth Amended 2005 Plan | Minimum | Deferred Stock Units
Employee Stock Plans [Line Items]
Award vesting period (in years)	1 year
Common stock equivalent (in shares)	1
Fourth Amended 2005 Plan | Tranche One
Employee Stock Plans [Line Items]
Award vesting period (in years)	1 year
Period between grant date and retirement date (in years)	1 year
Fourth Amended 2005 Plan | Tranche Two
Employee Stock Plans [Line Items]
Award vesting period (in years)	2 years
Fourth Amended 2005 Plan | Before Fiscal Year 2015
Employee Stock Plans [Line Items]
Maximum payout of shares that could be issued for each performance unit granted (in shares)	1.5
Fourth Amended 2005 Plan | Before Fiscal Year 2015 | Performance Shares
Employee Stock Plans [Line Items]
Performance period		3 years
Fourth Amended 2005 Plan | Before Fiscal Year 2015 | Performance Shares, Company Performance
Employee Stock Plans [Line Items]
Number of performance periods | performance_period		1
Fourth Amended 2005 Plan | Beginning Fiscal Year 2015 | Performance Shares, Company Performance
Employee Stock Plans [Line Items]
Performance period		1 year
Fourth Amended 2005 Plan | Beginning Fiscal Year 2015 | Performance Units
Employee Stock Plans [Line Items]
Performance period		3 years
Fourth Amended 2005 Plan | Beginning Fiscal Year 2016 | Performance Shares, Company Performance
Employee Stock Plans [Line Items]
Number of performance periods | performance_period	3
Performance period	1 year
Employee Stock Purchase Plans
Employee Stock Plans [Line Items]
Number of shares available for issuance (in shares)	5,400,000