Reportable Segments (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended				12 Months Ended
	Oct. 31, 2014		Oct. 31, 2013		Oct. 31, 2014 Segment Industry		Oct. 31, 2013		Apr. 30, 2014
Reportable Segments (Textual) [Abstract]
Number of Reportable Segments					3
Number of industries in which Company operates					1
Net mark-to-market valuation of certain derivative positions recognized in unallocated derivative gains (losses)	$ 7.6	[1]	$ (1.5)	[1]	$ (13.8)	[1]	$ 3.1	[1]	$ 4.1
Cumulative net mark-to-market valuation of certain derivative positions recognized in unallocated derivative gains (losses)					$ (9.7)

[1] As of October 31, 2014, the cumulative amount of net derivative losses from economic hedges that has not yet been allocated to segment profit was $9.7, including net gains of $4.1 incurred prior to 2015. For additional information, see Note 11: Derivative Financial Instruments.