Share repurchases (Details) (USD $)	0 Months Ended			6 Months Ended
	Feb. 17, 2015	Sep. 04, 2014	Dec. 17, 2013	Apr. 30, 2015	Dec. 04, 2013
Share repurchases [Abstract]
Number of shares authorized to repurchase	100,000	100,572			24,400
Number of shares repurchased	94,302		20,400	94,302
Stock repurchased price (per share)	$ 23.00	$ 18.45	$ 17.50
Shares repurchased, value	$ 2,168,946	$ 1,855,553	$ 357,000	$ 2,169,000