Stockholders' Equity - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Jul. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options, Outstanding, April 30, 2013	1,442
Stock Options, Granted
Stock Options, Exercised
Stock Options, Forfeited	(20)
Stock Options, Outstanding, July 31, 2013	1,422
Stock Options, Exercisable, July 31, 2013	1,068
Weighted Average Exercise Price, Outstanding, April 30, 2013	$ 8.48
Weighted Average Exercise Price, Granted
Weighted Average Exercise Price, Exercised
Weighted Average Exercise Price, Forfeited	$ 9.26
Weighted Average Exercise Price, Outstanding, July 31, 2013	$ 8.58
Weighted Average Exercise Price, Exercisable, July 31, 2013	$ 10.07
Weighted Average Remaining Contractual Term Outstanding	5 years 2 months 12 days
Weighted Average Remaining Contractual Term Exercisable	3 years 9 months 18 days
Aggregate Intrinsic Value Outstanding, July 31, 2013	$ 502
Aggregate Intrinsic Value Exercisable, July 31, 2013	$ 257

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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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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Weighted average price of options that were either forfeited or 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 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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