Declaration of Special Cash Dividend (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Declaration of Special Cash Dividend [Abstract]
Cash dividend declared per common share	$ 0.60	$ 0.50	$ 0.60	$ 0.50
Dividend payment date			Nov. 07, 2012
Dividend record date			Oct. 11, 2012