Derivative Financial Instruments (Details 3) - USD ($) $ in Millions	12 Months Ended
Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net gains (losses) on mark-to-market valuation of unallocated derivative positions	$ 0.6	$ (35.4)	$ (29.6)
Less: Net gains (losses) on derivative positions reclassified to segment operating profit	(36.7)	(8.2)	(41.6)
Unallocated derivative gains (losses)	$ 37.3	$ (27.2)	$ 12.0

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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Data Type:	xbrli:monetaryItemType
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