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, 2014	Sep. 30, 2013	Jun. 30, 2014 Call options [Member]	Sep. 30, 2013 Call options [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Interest Rate Contract [Member] Accounts payable and other current liabilities [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Interest Rate Contract [Member] Accounts payable and other current liabilities [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Interest Rate Contract [Member] Other liabilities [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Interest Rate Contract [Member] Other liabilities [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Commodity swap and option agreements [Member] Receivables, net [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Commodity swap and option agreements [Member] Receivables, net [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Foreign exchange forward agreements [Member] Receivables, net [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Foreign exchange forward agreements [Member] Receivables, net [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Foreign exchange forward agreements [Member] Accounts payable and other current liabilities [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Foreign exchange forward agreements [Member] Accounts payable and other current liabilities [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Foreign exchange contracts [Member] Other assets [Member]	Sep. 30, 2012 Derivatives designated as hedging instruments [Member] Foreign exchange contracts [Member] Other assets [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Foreign exchange contracts [Member] Other liabilities [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Foreign exchange contracts [Member] Other liabilities [Member]	Jun. 30, 2014 Derivatives designated as hedging instruments [Member] Commodity contracts [Member] Accounts payable and other current liabilities [Member]	Sep. 30, 2013 Derivatives designated as hedging instruments [Member] Commodity contracts [Member] Accounts payable and other current liabilities [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Equity conversion feature of preferred stock [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Equity conversion feature of preferred stock [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Foreign exchange forward agreements [Member] Accounts payable and other current liabilities [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Foreign exchange forward agreements [Member] Other liabilities [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Foreign exchange contracts [Member] Receivables, net [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Foreign exchange contracts [Member] Receivables, net [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Commodity contracts [Member] Receivables, net [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Commodity contracts [Member] Derivatives For Trading And Investment [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Commodity contracts [Member] Other liabilities [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Commodity contracts [Member] Other liabilities [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Call options [Member] Derivatives For Trading And Investment [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Call options [Member] Derivatives For Trading And Investment [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] FIA embedded derivatives [Member] Contractholder funds [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] FIA embedded derivatives [Member] Contractholder funds [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Futures contracts [Member] Derivatives For Trading And Investment [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Futures contracts [Member] Derivatives For Trading And Investment [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Futures contracts [Member] Other liabilities [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Futures contracts [Member] Other liabilities [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Embedded Derivative Financial Instruments [Member] Derivatives For Trading And Investment [Member]	Sep. 30, 2013 Not Designated as Hedging Instrument [Member] Embedded Derivative Financial Instruments [Member] Derivatives For Trading And Investment [Member]	Jun. 30, 2014 Fair Value, Measurements, Recurring [Member] Foreign exchange forward agreements [Member]		Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Foreign exchange forward agreements [Member]		Jun. 30, 2014 Fair Value, Measurements, Recurring [Member] Call options [Member]		Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Call options [Member]		Jun. 30, 2014 Level 2 [Member] Fair Value, Measurements, Recurring [Member] Foreign exchange forward agreements [Member]		Sep. 30, 2013 Level 2 [Member] Fair Value, Measurements, Recurring [Member] Foreign exchange forward agreements [Member]		Jun. 30, 2014 Level 2 [Member] Fair Value, Measurements, Recurring [Member] Call options [Member]		Sep. 30, 2013 Level 2 [Member] Fair Value, Measurements, Recurring [Member] Call options [Member]
Derivatives, Fair Value [Line Items]
Document Period End Date	Jun. 30, 2014
Total asset derivatives			$ 324.6	$ 221.8	$ 2.1	$ 2.1					$ 1.3	$ 0.4	$ 0.7	$ 1.7			$ 0.1	$ 0					$ 338.6	$ 227.7					$ 0.1	$ 0.1	$ 3.7	$ 0.1			$ 324.6	$ 221.8			$ 0.1	$ 0			$ 11.6	$ 0
Derivatives	324.7	221.8																																											0.9	[1]	1.8	[1]	324.7	[1]	221.8	[1]	0.9	[1]	1.8	[1]	324.7	[1]	221.8	[1]
Total liability derivatives					$ 7.2	$ 5.2	$ 1.8	$ 0	$ 0.1	$ 0					$ 5.0	$ 4.6			$ 0.3	$ 0.1	$ 0	$ 0.5	$ 1,876.3	$ 1,888.6	$ 0	$ 330.8	$ 5.3	$ 0.3					$ 4.3	$ 1.9			$ 1,864.5	$ 1,544.4			$ 0	$ 1.0

[1] The carrying amounts of trade receivables, accounts payable, accrued investment income and portions of other insurance liabilities approximate fair value due to their short duration and, accordingly, they are not presented in the tables above.