Derivative Financial Instruments - Summary of Gain (Loss) Recognized in Income on Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Apr. 01, 2012	Mar. 31, 2013	Apr. 01, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	$ (37.0)	$ 27.4	$ 36.0	$ 38.7
Equity conversion feature of preferred stock [Member] | Gain from the change in the fair value of the equity conversion feature of preferred stock [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(39.6)	(26.4)	29.3	1.5
Commodity contracts [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(8.8)	0	(8.8)	0
Foreign exchange contracts [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	1.8	(3.5)	(2.3)	3.8
Call options [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	118.5	73.4	97.6	93.3
Futures contracts [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	13.7	25.6	9.0	40.5
FIA embedded derivatives [Member] | Benefits and other changes in policy reserves [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	$ (122.6)	$ (41.7)	$ (88.8)	$ (100.4)