| Schedule of Cash, Cash Equivalents and Short-term Investments [Table Text Block] |
The following tables summarize our cash, cash equivalents, and short-term investments as of April 30, 2018 and January 31, 2018: | | | | | | | | | | | | | | | | | | | | April 30, 2018 | (in thousands) | | Cost Basis | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Cash and cash equivalents: | | | | | | | | | Cash and bank time deposits | | $ | 341,974 |
| | $ | — |
| | $ | — |
| | $ | 341,974 |
| Money market funds | | 40,263 |
| | — |
| | — |
| | 40,263 |
| Total cash and cash equivalents | | $ | 382,237 |
| | $ | — |
| | $ | — |
| | $ | 382,237 |
| | | | | | | | | | Short-term investments: | | | | | | | | | Corporate debt securities | | $ | 2,010 |
| | $ | — |
| | $ | — |
| | $ | 2,010 |
| Bank time deposits | | 7,210 |
| | — |
| | — |
| | 7,210 |
| Total short-term investments | | $ | 9,220 |
| | $ | — |
| | $ | — |
| | $ | 9,220 |
|
| | | | | | | | | | | | | | | | | | | | January 31, 2018 | (in thousands) | | Cost Basis | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Cash and cash equivalents: | | | | | | | | | Cash and bank time deposits | | $ | 337,756 |
| | $ | — |
| | $ | — |
| | $ | 337,756 |
| Money market funds | | 186 |
| | — |
| | — |
| | 186 |
| Total cash and cash equivalents | | $ | 337,942 |
| | $ | — |
| | $ | — |
| | $ | 337,942 |
| | | | | | | | | | Short-term investments: | | | | | | | | | Corporate debt securities (available-for-sale) | | $ | 2,002 |
| | $ | — |
| | $ | — |
| | $ | 2,002 |
| Bank time deposits | | 4,564 |
| | — |
| | — |
| | 4,564 |
| Total short-term investments | | $ | 6,566 |
| | $ | — |
| | $ | — |
| | $ | 6,566 |
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