CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS - Additional Information (Details) - USD ($)	9 Months Ended
	Oct. 31, 2015	Jan. 31, 2015	Oct. 31, 2014	Jan. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents	$ 176,838,000	$ 333,691,000	$ 361,021,000	$ 272,209,000
Joint Venture [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents	45,700,000
Short-term investments	21,000,000
Held-to-maturity Securities [Member]
Cash and Cash Equivalents [Line Items]
Accrued interest on held-to-maturity securities	$ 97,000
Held-to-maturity Securities [Member] | Minimum [Member]
Cash and Cash Equivalents [Line Items]
Maturity period	3 months
Held-to-maturity Securities [Member] | Maximum [Member]
Cash and Cash Equivalents [Line Items]
Maturity period	1 year