Stock-based compensation (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jul. 31, 2014	Jan. 31, 2014
Option activity [Line Items]
Granted	97
Granted, Weighted Average Exercise Price	$ 12.41
Unrecognized compensation expense	$ 1,000,000
Unrecognized compensation expense recognized period	2 years 9 months 40 days
Restricted Stock [Member]
Option activity [Line Items]
Unrecognized compensation expense	600,000
Unrecognized compensation expense recognized period	2 years 3 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	1,687,000	3,859,000
Granted	97
Granted, Weighted Average Exercise Price	$ 12.41
Exercised	(38)
Exercised Weighted Average Exercise Price Per Share	$ 7.20
Exercised Aggregate Intrinsic Value	155,000
Expired or forfeited	(53)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 19.91
Outstanding end of period	782
Outstanding Weighted Average Exercise Price Per Share	$ 11.45
Outstanding Weighted Average Remaining Contractual Term	6 years 2 months 30 days
Exercisable end of period	530
Exercisable Weighted Average Exercise Price Per Share	$ 12.09
Exercisable Weighted Average Remaining Contractual Term	4 years 9 months 40 days
Exercisable Aggregate Intrinsic Value	1,314,000
unvested option [Member]
Option activity [Line Items]
Outstanding at beginning of year	252	263
Weighted Average Exercise Price Per Share	$ 10.08	$ 8.31
Options Outstanding Aggregate Intrinsic Value	$ 373,000	$ 1,633,000
Vested	(100)
Expired or forfeited	(8)
Expired or Forfeited Weighted Average Exercise Price Per Share	$ 8.30