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. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Derivative [Line Items]
Revenues	$ 878.9	$ 825.8	$ 779.4	$ 741.0	$ 801.6	$ 709.1	$ 729.9	$ 678.5	$ 3,225.1	$ 2,919.1	$ 2,619.3
Amount gain (loss) reclassified from other comprehensive earnings (loss) into earnings									0.2	(0.6)	0.0
Revenues
Derivative [Line Items]
Revenues									3,225.1	2,919.1	2,619.3
Amount gain (loss) reclassified from other comprehensive earnings (loss) into earnings									0.2	(0.9)	0.0
Foreign currency forward contracts
Derivative [Line Items]
Foreign currency forward contracts									$ 3.0	$ (0.9)	$ 0.0