Deferred fee plan (Details) - USD ($)	6 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Oct. 31, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	$ 423,000
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	410,200	359,700
Deferred trustee fees	$ 423,200	$ 392,500
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	21,037	20,803
Dividends payable	$ 13,000	$ 32,700