Business, Basis of Presentation and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) $ in Millions	9 Months Ended
Jan. 31, 2018 USD ($)
ASU 2016 09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits	$ 1.2

Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=SL79508275-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration