Stock-based compensation (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Apr. 30, 2014	Jan. 31, 2014
Option activity [Line Items]
Unrecognized compensation expense	$ 800,000
Stock-based compensation (benefit) expense	2 years 2 months 20 days
Restricted Stock [Member]
Option activity [Line Items]
Unrecognized compensation expense	100,000
Stock-based compensation (benefit) expense	1 year 2 months 20 days
Stock Option [Member]
Option activity [Line Items]
Outstanding at beginning of year		776
Weighted Average Exercise Price Per Share		$ 11.69
Weighted Average Remaining Contractual Term		6 years 1 month 24 days
Options Outstanding Aggregate Intrinsic Value	1,697,000	3,859,000
Exercised	(22)
Exercised Weighted Average Exercise Price Per Share	$ 7.40
Exercised Aggregate Intrinsic Value	1,082,000
Expired or forfeited	(47)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 20.64
Outstanding end of period	707
Outstanding Weighted Average Exercise Price Per Share	$ 11.23
Outstanding Weighted Average Remaining Contractual Term	5 years 10 months 30 days
Exercisable end of period	449
Exercisable Weighted Average Remaining Contractual Term	4 years 6 months 24 days
Exercisable Weighted Average Exercise Price Per Share	$ 12.91
Exercisable Aggregate Intrinsic Value	1,023,000
unvested option [Member]
Option activity [Line Items]
Outstanding at beginning of year	258	263
Weighted Average Exercise Price Per Share	$ 8.31	$ 8.31
Options Outstanding Aggregate Intrinsic Value	$ 673,000	$ 1,633,000
Expired or forfeited	(5)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 8.24