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CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Jan. 31, 2017 | Jan. 31, 2016 | Jan. 31, 2015 | Jan. 31, 2014
Cash and Cash Equivalents |  |  |  |
Weighted average annual interest rates on short-term investment CDs (as a percent) | 1.13% | 0.63% |  |
Cash, cash equivalents | $ 167,198 | $ 160,909 | $ 333,691 | $ 272,209
Joint Venture |  |  |  |
Cash and Cash Equivalents |  |  |  |
Cash, cash equivalents | $ 12,500 |  |  |
Held-to-maturity Securities |  |  |  |
Cash and Cash Equivalents |  |  |  |
Maturity period | 185 days | 174 days |  |
Accrued interest on held-to-maturity securities | $ 100 | $ 800 |  |

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