CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - Held-to-maturity Securities - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jul. 31, 2018	Jan. 31, 2018
Cash and Cash Equivalents
Maturity period	262 days	293 days
Accrued interest on held-to-maturity securities	$ 1.5	$ 1.9
Weighted average annual interest rates of CDs (as a percent)	2.00%	1.50%