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Stockholders' equity (Detail) (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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Jul. 31, 2012
Treasury Stock [Member]
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Jul. 31, 2011
Treasury Stock [Member]
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Jul. 31, 2010
Treasury Stock [Member]
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Jul. 31, 2012
Additional Paid-in Capital [Member]
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Jul. 31, 2011
Additional Paid-in Capital [Member]
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Jul. 31, 2010
Additional Paid-in Capital [Member]
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Jul. 31, 2012
1999 Plan [Member]
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Jul. 31, 2012
2005 Plan [Member]
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Jul. 31, 2012
2011 Plan [Member]
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Jan. 14, 2012
2011 Plan [Member]
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| Stock Issued During Period Shares Acquisition Earn Out (in Shares) | 275,000 | ||||||||||||
| Fair Value Of Stock Issued For Acquisition Earn Out | $ 500,000 | ||||||||||||
| Stock Issued During Period, Shares, Employee Benefit Plan (in Shares) | (233,458) | (173,834) | (111,706) | ||||||||||
| Payments of Stock Issuance Costs | 649,000 | 690,000 | 697,000 | ||||||||||
| Stock Issued During Period, Value, Employee Benefit Plan | $ 649,000 | $ 690,000 | $ 697,000 | $ 3,313,000 | $ 2,467,000 | $ 1,586,000 | $ (2,664,000) | $ (1,777,000) | $ (889,000) | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares) | 2,312,356 | 1,000,000 | |||||||||||
| Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Units (in Shares) | 3,000,000 | ||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in Shares) | 2,686,000 | ||||||||||||
| Description Of Stock Options Exercisable | Stock options generally become exercisable at 25% per year after one year and expire ten years after the date of grant. | ||||||||||||