Deferred fee plan (Details) - USD ($)	3 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Oct. 31, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	$ 211,000
Dividends payable	1,011,000	$ 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	198,400	167,500
Deferred trustee fees	$ 211,400	$ 182,200
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	10,058	10,334
Dividends payable	$ 13,000	$ 14,700