CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017
Cash and Cash Equivalents
Weighted average annual interest rate on short-term investment CDs (as a percent)	1.17%	1.13%
Held-to-maturity Securities
Cash and Cash Equivalents
Maturity period	198 days	185 days
Accrued interest on held-to-maturity securities	$ 1.1	$ 0.8