Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Oct. 31, 2014	Apr. 30, 2014
Other Current Assets [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	$ 28.8	$ 54.4
Other Current Assets [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	16.5	41.4
Other Current Assets [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	12.3	13.0
Other Current Assets [Member] | Commodity contracts [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	0	23.4
Other Current Assets [Member] | Commodity contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	9.2	11.6
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	3.1	1.4
Other Current Assets [Member] | Interest rate contract [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	16.5	18.0
Other Current Liabilities [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	11.0	17.4
Other Current Liabilities [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	0	10.9
Other Current Liabilities [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	11.0	6.5
Other Current Liabilities [Member] | Commodity contracts [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	0	10.9
Other Current Liabilities [Member] | Commodity contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities	11.0	5.8
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	0.7
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
Other Noncurrent Assets [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	11.1
Other Noncurrent Assets [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	10.9
Other Noncurrent Assets [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	0.2
Other Noncurrent Assets [Member] | Commodity contracts [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	0
Other Noncurrent Assets [Member] | Commodity contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	0.2
Other Noncurrent Assets [Member] | Foreign currency exchange contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	0
Other Noncurrent Assets [Member] | Interest rate contract [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Assets	10.9
Other Noncurrent Liabilities [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		3.1
Other Noncurrent Liabilities [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		3.1
Other Noncurrent Liabilities [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		0
Other Noncurrent Liabilities [Member] | Commodity contracts [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		0
Other Noncurrent Liabilities [Member] | Commodity contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		0
Other Noncurrent Liabilities [Member] | Foreign currency exchange contracts [Member] | Not designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		0
Other Noncurrent Liabilities [Member] | Interest rate contract [Member] | Designated as hedging instruments [Member]
Fair value of derivative instruments [Line Items]
Derivatives Instruments, Liabilities		$ 3.1