Derivative Financial Instruments - Fair Value of Outstanding Derivative Contracts in Condensed Consolidated Balance Sheets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013
Derivatives, Fair Value [Line Items]
Document Period End Date	Dec. 31, 2013
Total asset derivatives	$ 294.5	$ 221.8
Call options [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	294.1	221.8
Derivatives designated as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	4.6	2.1
Total liability derivatives	5.5	5.2
Derivatives designated as hedging instruments [Member] | Commodity swap and option agreements [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	1.3	0.4
Derivatives designated as hedging instruments [Member] | Commodity swap and option agreements [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0.3	0
Derivatives designated as hedging instruments [Member] | Foreign exchange forward agreements [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	3.0	1.7
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	5.2	4.6
Derivatives designated as hedging instruments [Member] | Foreign exchange contracts [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	0.3	0.1
Derivatives designated as hedging instruments [Member] | Commodity contracts [Member] | Accounts payable and other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	0	0.5
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	299.7	227.7
Total liability derivatives	2,034.0	1,888.6
Not Designated as Hedging Instrument [Member] | Equity conversion feature of preferred stock [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	378.0	330.8
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		5.3
Not Designated as Hedging Instrument [Member] | Foreign exchange forward agreements [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	3.6
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0.2	0.1
Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Receivables, net [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives		3.7
Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Derivatives For Trading And Investment [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0.4
Not Designated as Hedging Instrument [Member] | Commodity contracts [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	2.2	1.9
Not Designated as Hedging Instrument [Member] | Call options [Member] | Derivatives For Trading And Investment [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	294.1	221.8
Not Designated as Hedging Instrument [Member] | FIA embedded derivatives [Member] | Contractholder funds [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives	1,644.7	1,544.4
Not Designated as Hedging Instrument [Member] | Futures contracts [Member] | Derivatives For Trading And Investment [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	0.4	0
Not Designated as Hedging Instrument [Member] | Futures contracts [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Total liability derivatives		$ 1.0