Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2014	Apr. 30, 2013
Other Current Assets [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	$ 27.9	$ 6.4
Other Current Assets [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	18.3	2.1
Other Current Assets [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	9.6	4.3
Other Current Assets [Member] | Commodity contracts [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	4.6	2.1
Other Current Assets [Member] | Commodity contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	6.1	3.6
Other Current Assets [Member] | Foreign currency exchange contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	3.5	0.7
Other Current Assets [Member] | Interest Rate Contract [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	13.7	0
Other Current Liabilities [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	4.7	4.5
Other Current Liabilities [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	0.9	2.0
Other Current Liabilities [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	3.8	2.5
Other Current Liabilities [Member] | Commodity contracts [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	0.9	2.0
Other Current Liabilities [Member] | Commodity contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	3.7	2.3
Other Current Liabilities [Member] | Foreign currency exchange contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	0.1	0.2
Other Current Liabilities [Member] | Interest Rate Contract [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	$ 0	$ 0