Earnings per share (Details) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Earnings per share [Line Items]
Basic weighted average common shares outstanding	7,068	6,924	6,995	6,921
Dilutive effect of equity incentive plans	95	0	46	0
Weighted average common shares outstanding assuming full dilution	7,163	6,924	7,041	6,921
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	216	785	362	494
Stock options with an exercise price below the average market price	665	172	519	463