Computation of Basic and Diluted Net Income (Loss) Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income	$ 9,124us-gaap_NetIncomeLoss	$ 7,790us-gaap_NetIncomeLoss	$ 22,608us-gaap_NetIncomeLoss	$ 23,329us-gaap_NetIncomeLoss
Weighted-average number of common shares outstanding-basic	12,419	12,403	12,401	12,421
Effect of dilutive securities:
Stock options and restricted stock units	184	244	200	258
Weighted-average number of common shares outstanding-diluted	12,603	12,647	12,601	12,679
Basic net income per share	$ 0.73us-gaap_EarningsPerShareBasic	$ 0.63us-gaap_EarningsPerShareBasic	$ 1.82us-gaap_EarningsPerShareBasic	$ 1.88us-gaap_EarningsPerShareBasic
Diluted net income per share	$ 0.72us-gaap_EarningsPerShareDiluted	$ 0.62us-gaap_EarningsPerShareDiluted	$ 1.79us-gaap_EarningsPerShareDiluted	$ 1.84us-gaap_EarningsPerShareDiluted
Anti-dilutive shares related to outstanding stock options and unvested restricted stock	16	123	179	109

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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