CASH, CASH EQUIVALENTS, AND SHORT-TERM INVESTMENTS CASH, CASH EQUIVALENTS, AND SHORT-TERM INVESTMENTS (Details) - USD ($)	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Gains (losses) on sales of available-for-sale securities	$ 0	$ 0	$ 0
Proceeds from sales and maturities of available-for-sale securities	8,700,000	52,800,000	$ 71,500,000
Commercial paper and corporate debt securities (available-for-sale)
Schedule of Available-for-sale Securities [Line Items]
Marketable debt securities	2,002,000
Gross unrealized gains	0
Gross unrealized losses	0
Estimated Fair Value	2,002,000
Bank time deposits
Schedule of Available-for-sale Securities [Line Items]
Marketable debt securities	4,564,000	3,184,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated Fair Value	4,564,000	3,184,000
Total short-term investments
Schedule of Available-for-sale Securities [Line Items]
Marketable debt securities	6,566,000	3,184,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated Fair Value	6,566,000	3,184,000
Cash and bank time deposits
Schedule of Available-for-sale Securities [Line Items]
Marketable debt securities	337,756,000	307,188,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated Fair Value	337,756,000	307,188,000
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Marketable debt securities	186,000	175,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated Fair Value	186,000	175,000
Total cash and cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Marketable debt securities	337,942,000	307,363,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated Fair Value	$ 337,942,000	$ 307,363,000