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Short-Term Investments - Additional Information (Detail) (USD $)
|
6 Months Ended | 12 Months Ended |
|---|---|---|
|
Jan. 31, 2015
position
|
Jul. 31, 2014
position
|
|
| Investments, Debt and Equity Securities [Abstract] | ||
| Investments related to credit losses | $ 0 | $ 0 |
| Securities having unrealized loss position for more than one year | 0 | 0 |