Stockholders' Equity (Summary of Stock Option Activity) (Detail) (USD $)	9 Months Ended
Jan. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, April 30, 2012	1,661
Stock Options, Granted	285
Stock Options, Exercised
Stock Options, Forfeited	(589)
Stock Options, Outstanding, January 31, 2013	1,357
Exercisable, January 31, 2013	981
Weighted Average Exercise Price, Outstanding, April 30, 2012	$ 10.55
Weighted Average Exercise Price, Granted	$ 4.03
Weighted Average Exercise Price, Exercised
Weighted Average Exercise Price, Forfeited	$ 11.43
Weighted Average Exercise Price, Outstanding, January 31, 2013	$ 8.81
Weighted Average Exercise Price, Exercisable, January 31, 2013	$ 10.64

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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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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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.

+ References

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

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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.

+ References

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- Definition

Weighted average price of options that were either forfeited or expired.

+ References

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- Definition

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

+ References

No definition available.

+ Details

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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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph A240

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

+ References

No definition available.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

+ References

No definition available.

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

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

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