Income taxes Income taxes (Details) (USD $)	3 Months Ended
	Apr. 30, 2013 Rate	Apr. 30, 2012 Rate	Jan. 31, 2013
Income tax [Abstract]
effective income tax rate from continuing operations	2.90%	10.90%
Open Tax Year	2010
Income tax expense from discontinued operations	$ 2,356,000	$ 37,000
Open tax years up to the amount of research tax credit generated	January 31, 2002 through January 31, 2009
Operating loss carryforwards			$ 7,800,000
Operating Loss Carryforwards, Expiration Dates	January 31, 2030