| 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, 2016 and January 31, 2016: | | | | | | | | | | | | | | | | | | | | April 30, 2016 | (in thousands) | | Cost Basis | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Cash and cash equivalents: | | | | | | | | | Cash and bank time deposits | | $ | 306,252 |
| | $ | — |
| | $ | — |
| | $ | 306,252 |
| Money market funds | | 170 |
| | — |
| | — |
| | 170 |
| Commercial paper and corporate debt securities | | 17,483 |
| | — |
| | — |
| | 17,483 |
| Total cash and cash equivalents | | $ | 323,905 |
| | $ | — |
| | $ | — |
| | $ | 323,905 |
| | | | | | | | | | Short-term investments: | | | | | | | | | Commercial paper and corporate debt securities (available-for-sale) | | $ | 41,036 |
| | $ | — |
| | $ | (5 | ) | | $ | 41,031 |
| Bank time deposits | | 7,056 |
| | — |
| | — |
| | 7,056 |
| Total short-term investments | | $ | 48,092 |
| | $ | — |
| | $ | (5 | ) | | $ | 48,087 |
|
| | | | | | | | | | | | | | | | | | | | January 31, 2016 | (in thousands) | | Cost Basis | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Cash and cash equivalents: | | | | | | | | | Cash and bank time deposits | | $ | 334,938 |
| | $ | — |
| | $ | — |
| | $ | 334,938 |
| Money market funds | | 12,137 |
| | — |
| | — |
| | 12,137 |
| Commercial paper and corporate debt securities | | 5,054 |
| | — |
| | (24 | ) | | 5,030 |
| Total cash and cash equivalents | | $ | 352,129 |
| | $ | — |
| | $ | (24 | ) | | $ | 352,105 |
| | | | | | | | | | Short-term investments: | | | | | | | | | Commercial paper and corporate debt securities (available-for-sale) | | $ | 53,018 |
| | $ | — |
| | $ | (86 | ) | | $ | 52,932 |
| Bank time deposits | | 3,050 |
| | — |
| | — |
| | 3,050 |
| Total short-term investments | | $ | 56,068 |
| | $ | — |
| | $ | (86 | ) | | $ | 55,982 |
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