Deferred fee plan (Details) - USD ($)	3 Months Ended		12 Months Ended
	Jan. 31, 2021	Jan. 31, 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	118,100	203,000
Deferred trustee fees	110,200	$ 203,000
Deferred accrued interest	$ 1,091,000		1,091,000
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	6,919	9,230
Dividends payable	$ 7,900	$ 0
Cumulative fees	$ 1,542,000		$ 1,542,000