Note 8 - Federal, State and Local Income Taxes - Effective Income Tax Rate Reconciliation (Details)	3 Months Ended	6 Months Ended
	Jul. 31, 2020	Oct. 31, 2020	Oct. 31, 2019
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		4.22%	6.45%
Effect of dividends received deductions		(0.28%)	(0.20%)
Other, net		(0.01%)	0.04%
Effective income tax rate		24.93%	27.29%