Earnings per share (Details) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Earnings per share [Line Items]
Basic weighted average common shares outstanding	7,290	7,068	7,238	6,995
Dilutive effect of equity incentive plans	0	95	99	46
Weighted average common shares outstanding assuming full dilution	7,290	7,163	7,337	7,041
Stock options not included in the computation of diluted earnings per share of common stock because the option exercise prices exceeded the average market prices of the common shares	346	216	257	362
Stock options with an exercise price below the average market price	421	665	510	519