Supplemental Guarantor Condensed Consolidating Financials - Schedule of Supplemental Condensed Consolidating Statements of Comprehensive (Loss) Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 28, 2015	Mar. 29, 2014	Mar. 28, 2015	Mar. 29, 2014
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 47.8	$ (16.8)	$ 77.0	$ (22.1)
Changes in foreign currency translation adjustment	(9.5)	(5.8)	(18.5)	(7.0)
Changes in unrealized holding gain on available-for-sale securities	(8.3)	(1.0)	(3.2)	(2.2)
Changes in pension plans, net of taxes	0	0	0.1	(0.6)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	1.6	0	1.6	0
Comprehensive income (loss)	28.4	(23.6)	53.8	(31.9)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	145.6	13.1	179.3	3.4
Changes in foreign currency translation adjustment	0	0	0	0
Changes in unrealized holding gain on available-for-sale securities	0	0	0	0
Changes in pension plans, net of taxes			0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	0		0
Comprehensive income (loss)	145.6	13.1	179.3	3.4
Parent/Issuer
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	47.8	(16.8)	77.0	(22.1)
Changes in foreign currency translation adjustment	0	0	0	0
Changes in unrealized holding gain on available-for-sale securities	0	0	0	0
Changes in pension plans, net of taxes			0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	(1.6)		(1.6)
Comprehensive income (loss)	46.2	(16.8)	75.4	(22.1)
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(162.6)	20.4	(185.3)	39.5
Changes in foreign currency translation adjustment	(0.2)	0	(0.5)	0.1
Changes in unrealized holding gain on available-for-sale securities	(8.3)	(1.0)	(3.2)	(2.2)
Changes in pension plans, net of taxes			0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	0		0
Comprehensive income (loss)	(171.1)	19.4	(189.0)	37.4
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	17.0	(33.5)	6.0	(42.9)
Changes in foreign currency translation adjustment	(9.3)	(5.8)	(18.0)	(7.1)
Changes in unrealized holding gain on available-for-sale securities	0	0	0	0
Changes in pension plans, net of taxes			0.1	(0.6)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	0		0
Comprehensive income (loss)	$ 7.7	$ (39.3)	$ (11.9)	$ (50.6)