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Stockholders' equity (Detail) - Stock option plans (USD $)
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12 Months Ended | ||
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Jul. 31, 2012
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Jul. 31, 2011
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Jul. 31, 2010
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| Outstanding at beginning of year | 785,124 | 1,132,450 | 1,191,519 |
| Outstanding at beginning of year (in Dollars per share) | $ 14.53 | $ 14.30 | $ 14.41 |
| Cancelled | (48,634) | (347,326) | (59,069) |
| Cancelled (in Dollars per share) | $ 15.05 | $ 13.78 | $ 16.14 |
| Outstanding at end of year | 736,490 | 785,124 | 1,132,450 |
| Outstanding at end of year (in Dollars per share) | $ 14.50 | $ 14.53 | $ 14.30 |
| Exercisable at end of year | 736,490 | 785,124 | 1,132,450 |
| Exercisable at end of year (in Dollars per share) | $ 14.50 | $ 14.53 | $ 14.30 |
| X | ||||||||||
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- Definition
The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Weighted average price of options that were either forfeited or expired. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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