Dividends (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Dividends [Abstract]
Dividends paid	$ 4,745	$ 4,367	$ 13,492	$ 13,094
Cash dividends paid per common share (in dollars per share)	$ 0.13	$ 0.12	$ 0.37	$ 0.36