STOCK-BASED COMPENSATION - Summary of Activity under Company's Stock Option Plans (Details) - $ / shares shares in Thousands	6 Months Ended		12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
STOCK-BASED COMPENSATION
Shares, Outstanding, Beginning balance	1,064	876	876
Shares, Granted	105	135
Shares, Exercised	(195)	(59)
Shares, Forfeited		(6)
Shares, Outstanding, Ending balance	974	946	1,064	876
Shares, Exercisable	704	686
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 26.38	$ 22.34	$ 22.34
Weighted Average Exercise Price, Granted	36.09	33.62
Weighted Average Exercise Price, Exercised	21.59	16.82
Weighted Average Exercise Price, Forfeited		17.33
Weighted Average Exercise Price, Outstanding, Ending balance	28.39	24.33	$ 26.38	$ 22.34
Weighted Average Exercise Price, Exercisable	$ 25.55	$ 20.85
Weighted Average Remaining Term, Outstanding	7 years 11 days	7 years 2 months 12 days	6 years 4 months 10 days	7 years 29 days
Weighted Average Remaining Term, Exercisable	6 years 6 months 18 days	6 years 7 months 6 days
Weighted Average Fair Value, Outstanding	$ 7.51	$ 6.53	$ 6.91	$ 6.01
Weighted Average Fair Value, Exercisable	$ 6.85	$ 5.71