Fair Value Measurements - Changes in Fair Value of Recurring Fair Value Measurements Using Significant Unobservable Inputs (Level 3), Consisting of Contingent Consideration Liabilities (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 28, 2013
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 0.0	$ 3.8	$ 86.4
Contingent consideration recorded at acquisition		0.0	0.5
Fair value adjustments	$ 0.0	0.0	11.3
Payments / Accruals		(3.8)	(94.4)
Balance at end of period		$ 0.0	$ 3.8