Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 27, 2014	Mar. 29, 2014	Dec. 28, 2013	Sep. 26, 2015	Sep. 27, 2014	Sep. 28, 2013	Aug. 01, 2012
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Investments, Fair Value Disclosure	$ 39.8			$ 27.7	$ 39.8
Impairment of goodwill				0.0	0.0	$ 1,117.4
Impairment charge		$ 28.6				3.7
Impairment charge allocated to intangible assets		27.1
Non-cash impairment charges				0.0	38.4	9.4
Asset impairment charge			$ 3.1			5.0
Cost-method equity investments in non-publicly traded securities	5.2			4.2	5.2
Other-than-temporary impairment charges					6.9	$ 6.4
Borrowed principal under credit agreement				1,000.0
Property, Plant and Equipment [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Non-cash impairment charges		$ 1.5
Credit Agreement [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Borrowed principal under credit agreement				1,660.0			$ 2,500.0
Senior Notes [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value of debt instrument				1,030.0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Investments, Fair Value Disclosure	0.0			$ 0.0	0.0
Diagnostics [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Non-cash impairment charges	$ 5.1
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Impairment charge allocated to intangible assets					$ 32.2