Deferred fee plan (Details) - USD ($)	6 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Oct. 31, 2018
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Dividends payable	$ 848,000	$ 337,000	$ 338,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	471,200	423,300
Deferred trustee fees	$ 517,300	$ 430,000
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	32,753	28,118
Dividends payable	$ 46,100	$ 6,700