STOCK-BASED COMPENSATION - Summary of Activity under Company's Stock Option Plans (Details) - $ / shares	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
STOCK-BASED COMPENSATION
Shares, Outstanding, Beginning balance	876,350	916,150	926,224
Shares, Granted	300,000	305,500	303,000
Shares, Exercised	(106,450)	(345,300)	(309,074)
Shares, Forfeited	(6,000)		(4,000)
Shares, Outstanding, Ending balance	1,063,900	876,350	916,150	926,224
Shares, Exercisable	763,900
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 22.34	$ 17.36	$ 14.34
Weighted Average Exercise Price, Granted	34.70	21.09	21.32
Weighted Average Exercise Price, Exercised	17.10	15.61	12.20
Weighted Average Exercise Price, Forfeited	17.33		17.33
Weighted Average Exercise Price, Outstanding, Ending balance	26.38	$ 22.34	$ 17.36	$ 14.34
Weighted Average Exercise Price, Exercisable	$ 23.11
Weighted Average Remaining Term, Outstanding	6 years 4 months 10 days	7 years 29 days	6 years 15 days	5 years 4 months 21 days
Weighted Average Remaining Term, Exercisable	6 years 4 months 28 days
Weighted Average Fair Value, Outstanding	$ 6.91	$ 6.01	$ 5.58	$ 5.93
Weighted Average Fair Value, Exercisable	$ 6.10