Derivative Financial Instruments (Details 3) (USD $) In Millions, unless otherwise specified	Jul. 31, 2013	Apr. 30, 2013
[CommodityContractMember]
Outstanding derivative contracts
Gross contract notional amount	$ 315.6	$ 347.6
[ForeignExchangeContractMember]
Outstanding derivative contracts
Gross contract notional amount	$ 68.3	$ 56.8