Stock-based compensation Stock-based compensation expense (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Stock-based compensation expense [Abstract]
Stock-based compensation expense	$ 106,000	$ 173,000	$ 366,000	$ 470,000
unrecognized compensation expense related to unvested stock options	$ 1,000,000		$ 1,000,000
expense is expected to be recognized over a period			2 years 7 months 30 days