STOCK-BASED COMPENSATION - Summary of Activity under Company's Stock Option Plans (Details) - $ / shares shares in Thousands	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
STOCK-BASED COMPENSATION
Shares, Outstanding, Beginning balance	889	707	1,064
Shares, Granted	257	302	270
Shares, Exercised	(6)	(110)	(622)
Shares, Forfeited		(10)	(5)
Shares, Outstanding, Ending balance	1,140	889	707	1,064
Shares, Exercisable	765
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 44.83	$ 39.04	$ 26.38
Weighted Average Exercise Price, Granted	40.54	53.49	57.88
Weighted Average Exercise Price, Exercised	17.19	28.81	25.57
Weighted Average Exercise Price, Forfeited		71.75	36.73
Weighted Average Exercise Price, Outstanding, Ending balance	44.01	$ 44.83	$ 39.04	$ 26.38
Weighted Average Exercise Price, Exercisable	$ 44.82
Weighted Average Remaining Term (Years), Outstanding	7 years 6 months 15 days	7 years 10 months 28 days	7 years 9 months 26 days	6 years 4 months 10 days
Weighted Average Remaining Term (Years), Exercisable	5 years 11 months 19 days
Weighted Average Fair Value, Outstanding	$ 11.22	$ 11.74	$ 10.22	$ 6.91
Weighted Average Fair Value, Exercisable	$ 11.79