STOCK-BASED COMPENSATION - Summary of Activity under Company's Stock Option Plans (Details) - $ / shares shares in Thousands	3 Months Ended		12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Jan. 31, 2016	Jan. 31, 2015
STOCK-BASED COMPENSATION
Shares, Outstanding, Beginning balance	1,064	876	876
Shares, Granted	75	100
Shares, Exercised	(22)	(38)
Shares, Forfeited		(6)
Shares, Outstanding, Ending balance	1,117	932	1,064	876
Shares, Exercisable	842	707
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 26.38	$ 22.34	$ 22.34
Weighted Average Exercise Price, Granted	33.85	32.68
Weighted Average Exercise Price, Exercised	18.80	11.48
Weighted Average Exercise Price, Forfeited		17.33
Weighted Average Exercise Price, Outstanding, Ending balance	27.03	23.92	$ 26.38	$ 22.34
Weighted Average Exercise Price, Exercisable	$ 24.36	$ 21.01
Weighted Average Remaining Term, Outstanding	6 years 11 months 1 day	7 years 3 months 26 days	6 years 4 months 10 days	7 years 29 days
Weighted Average Remaining Term, Exercisable	6 years 5 months 5 days	6 years 9 months 26 days
Weighted Average Fair Value, Outstanding	$ 7.08	$ 6.38	$ 6.91	$ 6.01
Weighted Average Fair Value, Exercisable	$ 6.41	$ 5.72