Intangible Assets and Goodwill - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 5,569.1	$ 5,562.5
Accumulated Amortization	2,887.8	2,790.2
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,528.8	4,528.7
Accumulated Amortization	2,266.7	2,186.8
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	46.0	46.0
Accumulated Amortization	0.0	0.0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	556.7	552.8
Accumulated Amortization	402.8	393.8
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	310.3	310.3
Accumulated Amortization	161.1	156.4
Distribution agreement
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	42.0	42.0
Accumulated Amortization	4.1	2.8
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1.5	1.5
Accumulated Amortization	0.1	0.1
Business licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	2.5	2.4
Accumulated Amortization	2.2	2.2
Acquired intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	5,487.8	5,483.7
Accumulated Amortization	2,837.0	2,742.1
Internal-use software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	65.8	64.5
Accumulated Amortization	48.2	46.1
Capitalized software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	15.5	14.3
Accumulated Amortization	$ 2.6	$ 2.0