CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - Held-to-maturity Securities - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 30, 2018	Jan. 31, 2018
Cash and Cash Equivalents
Maturity period	329 days	293 days
Accrued interest on held-to-maturity securities	$ 2.1	$ 1.9
Weighted average annual interest rates on short-term investment CDs (as a percent)	1.60%	1.50%