CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - Held-to-maturity Securities - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 31, 2018	Jan. 31, 2018
Cash and Cash Equivalents
Maturity period	230 days	293 days
Accrued interest on held-to-maturity securities	$ 1.0	$ 1.9
Weighted average annual interest rates of CDs (as a percent)	2.50%	1.50%