Stock option plan (Details) (Employee Stock Option [Member], USD $)	0 Months Ended	3 Months Ended
	Sep. 04, 2014	Jan. 31, 2015
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan term	10 years
Vesting term	5 years
Vesting rate	20.00%
No. of Options Outstanding
Options outstanding beginning of period		246,000
Options granted during period	246,000
Options outstanding end of period		246,000
Options expected to vest		238,620
Options exercisable at end of period
Exercise Price
Options outstanding beginning of period		$ 18.45
Options granted during period	$ 18.45
Options outstanding end of period		$ 18.45
Compensation expense related to stock options		$ 23,000
Unrecognized compensation cost		431,000
Unrecognized compensation cost, recognition period		5 years
Aggregate intrinsic value of options outstanding		$ 147,600