Accounting Policies Advertising expense policy (Details)	12 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Revenue recognition policy [Abstract]
Advertising Cost, Expense Method [Fixed List]	Expensed first time advertising takes place	Expensed first time advertising takes place

Indicates method for expensing advertising cost either as incurred or first time advertising takes place. Acceptable values are "Expensed as incurred" and "Expensed first time advertising takes place".

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 720
-SubTopic 35
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

Name:	us-gaap_AdvertisingCostExpenseMethodFixedList
Namespace Prefix:	us-gaap_
Data Type:	us-types:advertisingExpenseMethodItemType
Balance Type:	na
Period Type:	duration