Stock-Based Compensation - Schedule of Share Based Compensation Stock Options Activity (Detail) (USD $)	3 Months Ended
Nov. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options outstanding, beginning of period, Shares	1,429,000
Shares, Granted	0
Shares, Exercised	(136,875)
Shares, Cancelled	0
Options outstanding, end of period, Shares	1,292,125
Options exercisable, end of period, Shares	946,460
Weighted-Average Exercise Price, Options Outstanding beginning of period, Per Share	$ 10.42
Weighted-Average Exercise Price, Granted, Per Share	$ 0
Weighted-Average Exercise Price, Exercised, Per Share	$ 16.40
Weighted-Average Exercise Price, Cancelled, Per Share	$ 0
Weighted-Average Exercise Price, Options Outstanding end of period, Per Share	$ 9.78
Weighted-Average Exercise Price, Options exercisable, end of period, Per Share	$ 10.46
Weighted Average Remaining Term, Outstanding, Ending balance (in years)	3 years 2 months 19 days
Weighted Average Remaining Term, Options exercisable (in years)	2 years 7 months 21 days
Aggregate Intrinsic value, Outstanding, Ending balance	$ 11,860,900
Aggregate Intrinsic value, Options exercisable	$ 8,052,000

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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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.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

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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.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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