Note 7 - Federal, State and Local Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	30.33%	35.00%
Effective Income Tax Rate Reconciliation, Percent, Total	26.81%	(23.87%)	33.05%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent		(54.51%)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	6.02%	0.70%	(0.88%)
Open Tax Year	2016 2017 2018
Former Employee [Member]
Deferred Tax Assets, Deferred Non Cash Postemployment Compensation, Noncurrent	$ 1,770,000
Asset Management and Mutual Fund Distribution Subsidiaries [Member]
Deconsolidation, Gain (Loss), Amount	$ 50,805,000