Note 8 - Federal, State and Local Income Taxes - Effective Income Tax Rate Reconciliation (Details)	3 Months Ended	9 Months Ended
	Jul. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%
State and local income taxes, net of federal income tax benefit		2.08%	6.20%
Effect of dividends received deductions		(0.29%)	(0.20%)
Other, net		0.03%	0.05%
Effective income tax rate		22.82%	27.05%