Borrowings and Credit Arrangements - Convertible Notes and Related Equity Components (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 27, 2014	Sep. 28, 2013
Two Thousand And Seven Notes [Member]
Schedule Of Borrowings [Line Items]
Debt Instrument, Face Amount	$ 0	$ 405.0
Debt Instrument, Unamortized Discount	0	(4.9)
Convertible Notes Payable	0	400.1
Debt Instrument, Convertible, Carrying Amount of Equity Component	0	121.5
Two Thousand And Ten Notes [Member]
Schedule Of Borrowings [Line Items]
Debt Instrument, Face Amount	450.0	450.0
Debt Instrument, Unamortized Discount	(41.5)	(58.3)
Convertible Notes Payable	408.5	391.7
Debt Instrument, Convertible, Carrying Amount of Equity Component	60.1	60.1
Two Thousand And Twelve Notes [Member]
Schedule Of Borrowings [Line Items]
Debt Instrument, Face Amount	500.0	500.0
Debt Instrument, Unamortized Discount	(27.3)	(34.6)
Convertible Notes Payable	472.7	465.4
Debt Instrument, Convertible, Carrying Amount of Equity Component	49.2	49.2
Two Thousand And Thirteen Notes [Member]
Schedule Of Borrowings [Line Items]
Debt Instrument, Face Amount	370.0	370.0
Debt Instrument, Unamortized Discount	(40.1)	(48.3)
Convertible Notes Payable	354.4	330.9
Debt Instrument, Convertible, Carrying Amount of Equity Component	131.5	131.5
Base Principal Amount For Accretion Value	$ 24.5	$ 9.2