Deferred fee plan (Details) - USD ($)	6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2017
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	$ 434,000
Dividends payable	337,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	423,300	410,200
Deferred trustee fees	$ 430,000	$ 423,200
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	28,118	21,037
Dividends payable	$ 6,700	$ 13,000