Deferred fee plan (Details) - USD ($)	9 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Oct. 31, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	$ 620,000
Dividends payable		$ 2,018,000	$ 2,022,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	607,800	521,500
Deferred trustee fees	$ 620,800	$ 574,600
Basis spread on any deferred fee (percentage)	150.00%
Term of distribution to participants	10 years
Shares issued	32,136	29,473
Dividends payable	$ 13,000	$ 53,100