Income taxes Income taxes (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jul. 31, 2013 Rate	Jul. 31, 2012 Rate	Jan. 31, 2013
Income tax [Abstract]
effective income tax rate from continuing operations	(2.90%)	(1.80%)
Valuation allowance release	$ 0.6
Open tax year	2010
Open tax years up to the amount of research tax credit generated	January 31, 2002 through January 31, 2009
Operating loss carryforwards			$ 7.8
Operating Loss Carryforwards, Expiration Dates	Jan. 31, 2030