Income taxes Income taxes (Details)	6 Months Ended
	Jul. 31, 2014 Rate	Jul. 31, 2013 Rate
Income tax [Abstract]
effective income tax rate from continuing operations	21.40%	(2.70%)
Open tax year	2011
Open tax years up to the amount of research tax credit generated	January 31, 2002 through January 31, 2011
Operating loss carryforwards, expiration dates beginning	Jan. 31, 2030