Stock options - Summary of status of options granted under stock option plans and changes in options outstanding (Detail) - Stock Option	3 Months Ended
	Jan. 31, 2020 $ / shares shares
Shares
Outstanding at beginning of year | shares	890,147
Options granted | shares	130,241
Options exercised | shares	(215,943)
Options outstanding at end of year | shares	804,445
Options exercisable at January 31, 2019 | shares	417,279
Options vested and expected to vest at end of year | shares	803,409
Weighted Average Exercise Price
Outstanding at beginning of year | $ / shares	$ 3.62
Options granted | $ / shares	6.53
Options exercised | $ / shares	1.81
Options outstanding at end of year | $ / shares	4.58
Options exercisable at end of year | $ / shares	4.24
Options vested and expected to vest at end of year | $ / shares	$ 4.59