Derivative Financial Instruments - Fair Value of Outstanding Derivative Contracts in Condensed Consolidated Balance Sheets (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Jun. 30, 2013	Sep. 30, 2012
Derivatives, Fair Value [Line Items]
Document Period End Date	Jun. 30, 2013
Total asset derivatives	$ 227.4	$ 200.7
Call options [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	227.4	200.7
Derivatives designated as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	5.8	3.2
Total liability derivatives	1.4	3.1
Derivatives designated as hedging instruments [Member] | Commodity swap and option agreements [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0	1.0
Derivatives designated as hedging instruments [Member] | Commodity swap and option agreements [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0	1.0
Derivatives designated as hedging instruments [Member] | Foreign exchange forward agreements [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	5.2	1.2
Derivatives designated as hedging instruments [Member] | Foreign exchange forward agreements [Member] | Accounts payable and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	0.1	3.1
Derivatives designated as hedging instruments [Member] | Foreign exchange contracts [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0.6	0
Derivatives designated as hedging instruments [Member] | Commodity contracts [Member] | Accounts payable and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	1.2	0
Derivatives designated as hedging instruments [Member] | Commodity contracts [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	0.1	0
Derivatives Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	237.6	203.9
Total liability derivatives	1,740.6	1,793.7
Derivatives Not Designated as Hedging Instrument [Member] | Equity conversion feature of preferred stock [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	147.3	232.0
Derivatives Not Designated as Hedging Instrument [Member] | Foreign exchange forward agreements [Member] | Accounts payable and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	1.1	2.9
Derivatives Not Designated as Hedging Instrument [Member] | Foreign exchange forward agreements [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	3.3	4.0
Derivatives Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0	0
Derivatives Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives		0
Derivatives Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Derivatives [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	4.4
Derivatives Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Accounts payable and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	0.2
Derivatives Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	1.0	0
Derivatives Not Designated as Hedging Instrument [Member] | Call options [Member] | Derivatives [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	227.4	200.7
Derivatives Not Designated as Hedging Instrument [Member] | FIA embedded derivatives [Member] | Contractholder funds [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	1,585.9	1,550.8
Derivatives Not Designated as Hedging Instrument [Member] | Futures contracts [Member] | Derivatives [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0	0
Derivatives Not Designated as Hedging Instrument [Member] | Futures contracts [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	$ 0.4	$ 0.9