Deferred fee plan (Details) - USD ($)	3 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Oct. 31, 2017
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	$ 201,000
Dividends payable		$ 1,011,000
Deferred Fee Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Trustee fee expense	201,000	198,400
Deferred trustee fees	$ 201,000	$ 211,400
Basis spread on any deferred fee (percentage)	1.50%
Term of distribution to participants	10 years
Shares issued	13,289	10,058
Dividends payable	$ 0	$ 13,000