Stock-Based Compensation and Stockholders equity Dividends (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended		0 Months Ended
	Jul. 31, 2013	Apr. 30, 2013	Jul. 31, 2012	Jul. 31, 2010	Jul. 31, 2013	Jul. 31, 2012	Aug. 23, 2013 Subsequent Event
Dividends Declared [Line Items]
Dividends payable, date declared	May 23, 2013	Mar. 07, 2013					Aug. 22, 2013
Dividends payable, date to be paid	Jul. 01, 2013	Apr. 10, 2013					Sep. 30, 2013
Dividends payable, date of record	Jun. 10, 2013	Mar. 22, 2013		Jul. 06, 2010			Sep. 10, 2013
Common stock dividend per share annual amount		$ 0.18
Cash dividends declared per common share	$ 0.045	$ 0.045	$ 0.000		$ 0.090	$ 0.000	$ 0.045
Dividends paid	$ (5,079)	$ (5,064)			$ (10,143)	$ 0