Loans Payable and Long-Term Debt (Narrative) (Details) $ in Thousands	6 Months Ended
Oct. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)
Debt Instrument [Line Items]
Ratio of total liabilities to tangible net worth	0.4
Ratio of cash flow to fixed charges	3.6
Proceeds from long-term debt	$ 734	$ 2,003
Maximum [Member]
Debt Instrument [Line Items]
Ratio of total liabilities to tangible net worth	1.4
Minimum [Member]
Debt Instrument [Line Items]
Ratio of cash flow to fixed charges	1.5

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Name:	us-gaap_ProceedsFromIssuanceOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration