Deferred fee plan (Details) - USD ($)	9 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Oct. 31, 2017
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Dividends payable	$ 338,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	623,000	620,800
Deferred trustee fees	$ 609,000	$ 607,800
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	39,835	32,136
Dividends payable	$ 14,000	$ 13,000