For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Credit Concentration (Details)	12 Months Ended
Credit Concentration (Details)	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Accounts Receivable [Member] \| Customer A [Member]
Concentration Risk [Line Items]
Concentration risk percentage	8.20%	12.40%
Accounts Receivable [Member] \| Customer B [Member]
Concentration Risk [Line Items]
Concentration risk percentage	20.70%	21.00%
Sales Revenue, Gross [Member] \| Customer A [Member]
Concentration Risk [Line Items]
Concentration risk percentage	20.70%	23.90%	26.50%
Sales Revenue, Gross [Member] \| Customer B [Member]
Concentration Risk [Line Items]
Concentration risk percentage	16.50%	17.20%	18.60%