Dividends and Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2015	Jul. 31, 2014
Stockholders' Equity Note [Abstract]
Dividends paid	$ 4,894	$ 4,376	$ 9,834	$ 8,747
Cash dividends paid per common share (in dollars per share)	$ 0.13	$ 0.12	$ 0.26	$ 0.24
Stock Repurchase Program, Authorized Amount	$ 40,000		$ 40,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 29,175		$ 29,175