Note 14 - Copyright Fees (Details Textual) - USD ($)	12 Months Ended
Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Revenue from Contract with Customer, Including Assessed Tax	$ 36,257,000	$ 35,868,000	$ 34,574,000
Percentage of Copyright Data Fees	16.80%	44.50%
Third Party Sponsored Assets for Copyright Data	$ 6,100,000,000	$ 4,200,000,000
License [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 7,437,000	$ 6,365,000	$ 4,406,000

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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Balance Type:	credit
Period Type:	duration