Derivative Financial Instruments - Summary of Gain (Loss) Recognized in Income on Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Document Period End Date	Dec. 31, 2013
Gain (Loss) Recognized in Income on Derivatives	$ 177.8	$ 73.0
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	(47.2)	68.9
Commodity contracts [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(3.4)	0
Bronze Commodity Contract [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives		0
Bronze Commodity Contract [Member] | Consumer products cost of goods sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(0.1)
Foreign exchange contracts [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	0.8	(4.1)
Call options [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	114.3	(20.9)
Futures contracts [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	13.1	(4.7)
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	$ 100.3	$ 33.8