Income Taxes (Details) - USD ($) $ in Millions	Apr. 30, 2018	Apr. 30, 2017
Income Taxes
Unrecognized tax benefits that would affect effective tax rate, if recognized	$ 9.6	$ 8.5
Liability for unrecognized tax benefits for interest and penalties	$ 1.4	$ 1.2

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant