Derivative Instruments and Hedging Activities - Effective Portion of Foreign Currency Forward Contracts Designated as Cash Flow Hedges (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016
Derivative [Line Items]
Revenues	$ 801.6	$ 709.1	$ 729.9	$ 678.5	$ 721.8	$ 632.8	$ 663.2	$ 601.5	$ 2,919.1	$ 2,619.3	$ 2,593.7
Revenues
Derivative [Line Items]
Revenues									2,919.1	2,619.3	2,593.7
Revenues | Designated as Hedging Instrument
Derivative [Line Items]
Amount loss reclassified from other comprehensive earnings into earnings									(0.9)	0.0	(1.0)
Foreign currency forward contracts
Derivative [Line Items]
Foreign currency forward contracts									$ (0.9)	$ 0.0	$ (1.0)