Schedule of Changes in Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 28, 2012
Income Tax Disclosure [Abstract]
Unrecognized tax benefits balance–beginning of fiscal year	$ 37.0	$ 38.8	$ 37.1
Additions based on tax positions related to a prior year	10.7	2.5	3.8
Reductions based on tax positions related to a prior year	(0.3)	(0.7)	(0.9)
Additions based on tax positions related to the current year	8.2	6.6	6.8
Settlements	(0.4)	(4.2)	(0.4)
Reductions resulting from the expiration of the applicable statute of limitations	(5.6)	(6.0)	(7.6)
Unrecognized tax benefits balance–end of fiscal year	$ 49.6	$ 37.0	$ 38.8