Stock-Based Compensation - Summary of Activity under Option and Stock Plans (Detail) (USD $)	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding, Beginning balance	926,224	817,186	675,724
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 14.34	$ 12.10	$ 11.29
Shares, Granted	303,000	293,000	212,500
Shares, Exercised	(309,074)	(153,962)	(55,038)
Shares, Forfeited	(4,000)	(30,000)	(16,000)
Shares, Outstanding, Ending balance	916,150	926,224	817,186	675,724
Shares, Exercisable	613,150
Weighted Average Exercise Price, Granted	$ 21.32	$ 17.36	$ 13.92
Weighted Average Exercise Price, Exercised	$ 12.20	$ 9.33	$ 9.36
Weighted Average Exercise Price, Forfeited	$ 17.33	$ 8.66	$ 11.36
Weighted Average Exercise Price, Outstanding, Ending balance	$ 17.36	$ 14.34	$ 12.10	$ 11.29
Weighted Average Exercise Price, Exercisable	$ 15.40
Weighted Average Remaining Term, Outstanding	6 years 15 days	5 years 4 months 21 days	4 years 11 months 9 days	5 years 9 months 11 days
Weighted Average Remaining Term, Exercisable	5 years 1 month 2 days
Weighted Average Fair Value, Outstanding, Beginning balance	$ 5.58	$ 5.93	$ 5.68	$ 5.79
Weighted Average Fair Value, Exercisable	$ 6.15