Stock and Stock Option Plans - Options Outstanding (Detail) (USD $)			9 Months Ended
	Oct. 31, 2013	Jan. 31, 2013	Oct. 31, 2013 Grant Date June 2004 [Member] Group One [Member]	Oct. 31, 2013 Grant Date June 2004 [Member] Group Two [Member]	Oct. 31, 2013 Grant Date June 2005 [Member]	Oct. 31, 2013 Grant Date September 2005 [Member]	Oct. 31, 2013 Grant Date January 2006 [Member]	Oct. 31, 2013 Grant Date June 2006 [Member]	Oct. 31, 2013 Grant Date June 2007 [Member]	Oct. 31, 2013 Grant Date July 2007 [Member]	Oct. 31, 2013 Grant Date February 2008 [Member]	Oct. 31, 2013 Grant Date January 2009 [Member]	Oct. 31, 2013 Grant Date February 2009 [Member] Group One [Member]	Oct. 31, 2013 Grant Date February 2009 [Member] Group Two [Member]	Oct. 31, 2013 Grant Date June 2009 [Member] Group One [Member]	Oct. 31, 2013 Grant Date June 2009 [Member] Group Two [Member]	Oct. 31, 2013 Grant Date February 2010 [Member] Group One [Member]	Oct. 31, 2013 Grant Date February 2010 [Member] Group Two [Member]	Oct. 31, 2013 Grant Date February 2011 [Member]	Oct. 31, 2013 Grant Date March 2011 [Member]	Oct. 31, 2013 Grant Date June 2011 [Member]	Oct. 31, 2013 Grant Date July 2011 [Member]	Oct. 31, 2013 Grant Date February 2012 [Member]	Oct. 31, 2013 Grant Date April 2012 [Member]	Oct. 31, 2013 Grant Date July 2012 [Member]	Oct. 31, 2013 Grant Date August 2012 [Member]	Oct. 31, 2013 Grant Date April 2013 [Member]	Oct. 31, 2013 Grant Date May 2013 [Member]	Oct. 31, 2013 Grant Date September 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding	1,305,071	1,285,303	20,000	38,076	10,000	90,957	118,750	80,000	65,625	15,500	62,463	6,000	105,141	4,580	87,784	2,472	66,440	2,721	83,100	1,312	2,096	17,893	168,930	27,135	4,708	9,554	190,234	14,952	8,648
Options Exercisable	989,165	965,750	20,000	38,076	10,000	90,957	118,750	80,000	65,625	15,500	62,463	6,000	105,138	4,580	87,784	2,472	66,440	2,721	59,342	874	1,397	11,927	79,771	9,030	1,553	3,152	45,613
Exercise Price	$ 25.43	$ 25.97	$ 16.60	$ 16.65	$ 17.54	$ 23.05	$ 27.87	$ 29.29	$ 42.26	$ 42.76	$ 35.71	$ 24.01	$ 15.78	$ 15.78	$ 21.99	$ 21.99	$ 27.79	$ 25.44	$ 33.10	$ 34.50	$ 28.71	$ 29.31	$ 24.32	$ 21.77	$ 20.89	$ 20.56	$ 21.08	$ 20.40	$ 19.49
Remaining Contractual Term (Months)			8 months	8 months	20 months	23 months	27 months	32 months	44 months	45 months	51 months	62 months	63 months	63 months	67 months	67 months	75 months	75 months	87 months	89 months	91 months	93 months	99 months	101 months	104 months	105 months	113 months	114 months	118 months