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Short-Term Investments (Tables)
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6 Months Ended |
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Jan. 31, 2015
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| Investments, Debt and Equity Securities [Abstract] |
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| Summary of Short-Term Investments |
The following table summarizes the Company's short-term investments: | | | | | | | | | | | | | | | | | | Cost Basis | | Gross Unrealized Gains | | Gross Unrealized Losses | | Fair Value | | (in thousands) | Balance at January 31, 2015 | | | | | | | | Corporate bonds | $ | 44,254 |
| | $ | 27 |
| | $ | (8 | ) | | $ | 44,273 |
| U.S. government agency securities | 79,514 |
| | 42 |
| | (14 | ) | | 79,542 |
| U.S. treasury bills | 9,834 |
| | 3 |
| | — |
| | 9,837 |
| Commercial paper | 5,395 |
| | 2 |
| | — |
| | 5,397 |
| Total | $ | 138,997 |
| | $ | 74 |
| | $ | (22 | ) | | $ | 139,049 |
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| | | | | | | | | | | | | | | | | | Cost Basis | | Gross Unrealized Gains | | Gross Unrealized Losses | | Fair Value | | (in thousands) | Balance at July 31, 2014 | | | | | | | | Corporate bonds | $ | 54,969 |
| | $ | 79 |
| | $ | (15 | ) | | $ | 55,033 |
| U.S. government agency securities | 90,681 |
| | 17 |
| | (58 | ) | | 90,640 |
| U.S. treasury bills | 14,560 |
| | 17 |
| | — |
| | 14,577 |
| Commercial paper | 4,587 |
| | 4 |
| | — |
| | 4,591 |
| Municipal notes and bonds | 1,518 |
| | — |
| | — |
| | 1,518 |
| Total | $ | 166,315 |
| | $ | 117 |
| | $ | (73 | ) | | $ | 166,359 |
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| Cost Basis and Fair Value of Debt Securities by Contractual Maturity |
The following table summarizes the cost basis and fair value of the short-term investments by contractual maturity: | | | | | | | | | | Cost Basis | | Fair Value | | (in thousands) | Balance at January 31, 2015 | | | | One year or less | $ | 75,684 |
| | $ | 75,709 |
| Over one year and less than two years | 63,313 |
| | 63,340 |
| Total | $ | 138,997 |
| | $ | 139,049 |
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| | | | | | | | | | Cost Basis | | Fair Value | | (in thousands) | Balance at July 31, 2014 | | | | One year or less | $ | 110,184 |
| | $ | 110,280 |
| Over one year and less than two years | 56,131 |
| | 56,079 |
| Total | $ | 166,315 |
| | $ | 166,359 |
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| Fair Value and Gross Unrealized Losses of Company's Investments |
The following table summarizes the fair value and gross unrealized losses of the Company’s investments with unrealized losses aggregated by type of investment instrument and the length of time that individual securities have been in a continuous unrealized loss position: | | | | | | | | | | Less than 12 Months | | Fair Value | | Unrealized Loss | | (in thousands) | Balance at January 31, 2015 | | | | Corporate bonds | $ | 15,396 |
| | $ | (8 | ) | U.S. government agency securities | 30,613 |
| | (14 | ) | Total | $ | 46,009 |
| | $ | (22 | ) |
| | | | | | | | | | Less than 12 Months | | Fair Value | | Unrealized Loss | | (in thousands) | Balance at July 31, 2014 | | | | Corporate bonds | $ | 14,101 |
| | $ | (15 | ) | U.S. government agency securities | 57,566 |
| | (58 | ) | Total | $ | 71,667 |
| | $ | (73 | ) |
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