Deferred fee plan (Details) - USD ($)	9 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Oct. 31, 2018
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Dividends payable	$ 848,000	$ 338,000	$ 338,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	745,500	623,000
Deferred trustee fees	$ 677,300	$ 609,000
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	46,070	39,835
Dividends payable	$ 68,200	$ 14,000