CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - Held-to-maturity Securities - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 31, 2017	Jan. 31, 2017
Cash and Cash Equivalents
Maturity period	269 days	185 days
Accrued interest	$ 1.5	$ 0.8
Weighted average annual interest rate on short-term investment CDs (as a percent)	1.36%	1.13%