CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - Held-to-maturity Securities - USD ($) $ in Millions		3 Months Ended
Jan. 31, 2019	Apr. 30, 2019
Cash and Cash Equivalents
Maturity period	250 days	250 days
Accrued interest on held-to-maturity securities	$ 1.2	$ 1.4
Weighted average annual interest rates of CDs (as a percent)	2.60%	2.70%

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