Deferred fee plan (Details) - USD ($)	6 Months Ended		12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Oct. 31, 2020
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Dividends payable	$ 342,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	230,600	367,000
Deferred trustee fees	214,600	$ 367,000
Deferred accrued interest	$ 1,021,000		1,091,000
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	13,233	18,046
Dividends payable	$ 16,000	$ 0
Cumulative fees	$ 1,454,000		$ 1,542,000