Earnings per share (Details) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2012
Earnings per share [Line Items]
Document Period End Date			Jul. 31, 2013
Basic weighted average common shares outstanding	6,985	6,923	6,958	6,919
Dilutive effect of equity incentive plans	69	0	27	0
Weighted average common shares outstanding assuming full dilution	7,054	6,923	6,985	6,919
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	375	497	375	494
Stock options with an exercise price below the average market price	574	467	574	470