CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Jan. 31, 2020
Schedule of Available-for-sale Securities
Maturities and sales of investments	$ 15,648	$ 2,965
Bank time deposits
Schedule of Available-for-sale Securities
Cost basis	19,741		$ 20,215
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Estimated Fair Value	19,741		20,215
Total short-term investments
Schedule of Available-for-sale Securities
Cost basis	19,741		20,215
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Estimated Fair Value	19,741		20,215
Cash and bank time deposits
Schedule of Available-for-sale Securities
Cost basis	411,926		379,057
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Estimated Fair Value	411,926		379,057
Money market funds
Schedule of Available-for-sale Securities
Cost basis	144,745		89
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Estimated Fair Value	144,745		89
Total cash and cash equivalents
Schedule of Available-for-sale Securities
Cost basis	556,671		379,146
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Estimated Fair Value	$ 556,671		$ 379,146