Derivative Financial Instruments - Summary of Gain (Loss) Recognized in Income on Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Document Period End Date			Jun. 30, 2014
Gain (Loss) Recognized in Income on Derivatives	$ 283.4	$ 136.2	$ 547.2	$ 172.2
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net	0.3	0	0.3	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	38.0	52.6	(12.7)	81.9
Commodity contracts [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(2.2)	9.6	(12.4)	0.8
Bronze Commodity Contract [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives		(0.2)
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		0	(0.2)
Foreign exchange contracts [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(0.2)	0.5	0.4	(1.8)
Call options [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	91.1	16.5	226.6	114.1
Futures contracts [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivatives	10.5	3.5	24.9	12.5
Embedded Derivative Financial Instruments [Member] | Net investment gains [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net	0.3	0	0.3	0
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	$ 145.8	$ 53.7	$ 320.1	$ (35.1)