Deferred fee plan (Details) - USD ($)	3 Months Ended		12 Months Ended
	Jan. 31, 2022	Jan. 31, 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]
Term of distribution to participants	10 years
Basis spread on any deferred fee (percentage)	1.50%
Trustee fee expense	$ 61,600	118,100
Deferred trustee fees	$ 43,800	$ 110,200
Shares issued	2,496	6,919
Dividends payable	$ 17,000	$ 7,900
Cumulative fees	1,454,000		1,454,000
Deferred accrued interest	$ 1,021,000		$ 1,021,000