Deferred fee plan (Details) - USD ($)	6 Months Ended		12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Oct. 31, 2021
Deferred Compensation Arrangement with Individual, Excluding Share-Based Payments and Postretirement Benefits [Line Items]
Dividends payable	$ 686,000	$ 342,000	$ 686,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-Based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	100,500	230,600
Deferred trustee fees	65,200	$ 214,600
Deferred accrued interest	$ 951,000		1,021,000
Basis spread on any deferred fee (percentage)	150.00%
Term of distribution to participants	10 years
Shares issued	4,080	13,233
Dividends payable	$ 35,300	$ 16,000
Cumulative fees	$ 1,366,000		$ 1,454,000