Income Taxes - Valuation Allowances and Elections (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2017	Apr. 30, 2016
Income tax examinations
Liability for uncertain tax position	$ 0	$ 0
State \| Minimum
Income tax examinations
Statute of limitation period	3 years
State \| Maximum
Income tax examinations
Statute of limitation period	4 years

Amount of unrecognized tax benefits.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

Name:	us-gaap_UnrecognizedTaxBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant