Equity incentive plan (Schedule of Stock Option Activity) (Details) - Employee Stock Option [Member] - $ / shares					6 Months Ended
	Mar. 04, 2019	May 03, 2018	Nov. 10, 2016	Sep. 04, 2014	Apr. 30, 2021	Apr. 30, 2020
No. of Options Outstanding
Options outstanding at beginning of period					310,740	310,740
Options granted during period	5,000	38,000	38,000	246,000
Options forfeited/cancelled during period
Options outstanding at end of period					310,740	310,740
Options vested and expected to vest					308,310	308,310
Options exercisable at end of period					277,340	261,140
Weighted Average Exercise Price
Options outstanding beginning of period					$ 18.35	$ 18.35
Options granted during period	$ 15.00	$ 15.50	$ 21.00	$ 18.45
Options forfeited/cancelled during period
Options outstanding end of period					$ 18.35	$ 18.35