Derivative Financial Instruments - Fair Value of Outstanding Derivative Contracts in Condensed Consolidated Balance Sheets (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014 Call options	Sep. 30, 2013 Call options	Sep. 30, 2014 Derivatives designated as hedging instruments	Sep. 30, 2013 Derivatives designated as hedging instruments	Sep. 30, 2014 Derivatives designated as hedging instruments Interest rate contracts Accounts payable and other current liabilities	Sep. 30, 2013 Derivatives designated as hedging instruments Interest rate contracts Accounts payable and other current liabilities	Sep. 30, 2014 Derivatives designated as hedging instruments Commodity swap and option agreements Receivables, net	Sep. 30, 2013 Derivatives designated as hedging instruments Commodity swap and option agreements Receivables, net	Sep. 30, 2014 Derivatives designated as hedging instruments Commodity swap and option agreements Other assets	Sep. 30, 2013 Derivatives designated as hedging instruments Commodity swap and option agreements Other assets	Sep. 30, 2014 Derivatives designated as hedging instruments Foreign exchange forward agreements Receivables, net	Sep. 30, 2013 Derivatives designated as hedging instruments Foreign exchange forward agreements Receivables, net	Sep. 30, 2014 Derivatives designated as hedging instruments Foreign exchange forward agreements Accounts payable and other current liabilities	Sep. 30, 2013 Derivatives designated as hedging instruments Foreign exchange forward agreements Accounts payable and other current liabilities	Sep. 30, 2014 Derivatives designated as hedging instruments Foreign exchange contracts Other assets	Sep. 30, 2012 Derivatives designated as hedging instruments Foreign exchange contracts Other assets	Sep. 30, 2014 Derivatives designated as hedging instruments Foreign exchange contracts Other liabilities	Sep. 30, 2013 Derivatives designated as hedging instruments Foreign exchange contracts Other liabilities	Sep. 30, 2014 Derivatives designated as hedging instruments Commodity contracts Accounts payable and other current liabilities	Sep. 30, 2013 Derivatives designated as hedging instruments Commodity contracts Accounts payable and other current liabilities	Sep. 30, 2014 Derivatives not designated as hedging instrument	Sep. 30, 2013 Derivatives not designated as hedging instrument	Sep. 30, 2014 Derivatives not designated as hedging instrument Equity conversion feature of preferred stock	Sep. 30, 2013 Derivatives not designated as hedging instrument Equity conversion feature of preferred stock	Sep. 30, 2013 Derivatives not designated as hedging instrument Foreign exchange forward agreements Accounts payable and other current liabilities	Sep. 30, 2014 Derivatives not designated as hedging instrument Foreign exchange forward agreements Other liabilities	Sep. 30, 2014 Derivatives not designated as hedging instrument Foreign exchange contracts Receivables, net	Sep. 30, 2013 Derivatives not designated as hedging instrument Foreign exchange contracts Receivables, net	Sep. 30, 2013 Derivatives not designated as hedging instrument Commodity contracts Receivables, net	Sep. 30, 2014 Derivatives not designated as hedging instrument Commodity contracts Derivatives	Sep. 30, 2014 Derivatives not designated as hedging instrument Commodity contracts Other liabilities	Sep. 30, 2013 Derivatives not designated as hedging instrument Commodity contracts Other liabilities	Sep. 30, 2014 Derivatives not designated as hedging instrument Call options Derivatives	Sep. 30, 2013 Derivatives not designated as hedging instrument Call options Derivatives	Sep. 30, 2013 Derivatives not designated as hedging instrument FIA embedded derivatives Contractholder funds	Sep. 30, 2014 Derivatives not designated as hedging instrument Futures contracts Derivatives	Sep. 30, 2013 Derivatives not designated as hedging instrument Futures contracts Derivatives	Sep. 30, 2014 Derivatives not designated as hedging instrument Futures contracts Contractholder funds	Sep. 30, 2014 Derivatives not designated as hedging instrument Futures contracts Other liabilities	Sep. 30, 2013 Derivatives not designated as hedging instrument Futures contracts Other liabilities
Derivatives, Fair Value [Line Items]
Total asset derivatives	$ 296.3	$ 221.8	$ 14.2	$ 2.1			$ 0.6	$ 0	$ 1.3	$ 0.4	$ 0.3	$ 0			$ 12.0	$ 1.7					$ 324.1	$ 227.7					$ 0.5	$ 0.1	$ 3.7	$ 1.9			$ 296.3	$ 221.8		$ 11.2	$ 0
Total liability derivatives			$ 1.9	$ 5.2	$ 1.8	$ 0							$ 0	$ 4.6			$ 0	$ 0.1	$ 0.1	$ 0.5	$ 1,910.9	$ 1,888.6	$ 0	$ 330.8	$ 5.3	$ 0.1					$ 0.3	$ 1.9			$ 1,544.4			$ 1,908.1	$ 0.5	$ 1.0