Summary of Stock Option Activity (Detail) (2008 Plan, USD $)	12 Months Ended
Apr. 30, 2012	Apr. 30, 2011
2008 Plan
Number of options
Outstanding, beginning of period	29,829,585	38,956,549
Granted
Forfeited	(1,780,871)	(9,126,964)
Exchanged options	(5,676,525)
Outstanding, end of period	22,372,189	29,829,585
Exercisable, end of year	20,702,623	19,533,926
Weighted average exercise price
Outstanding, beginning of period	$ 1.00	$ 1.00
Granted
Forfeited	$ 1	$ 1
Exchanged options	$ 1
Outstanding, end of period	$ 1.00	$ 1.00
Weighted remaining contractual life
Outstanding, end of year	6 years 4 months 24 days	7 years 4 months 24 days

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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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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.

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

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The addition or reduction in the number of reserved shares that could potentially be issued under the option plan attributable to reasons other than grants, exercises, forfeitures, and expirations during the reporting period.

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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.

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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 grantees could have acquired the underlying shares with respect to stock options that were terminated.

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

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Weighted average price at which grantees could acquire or could have acquired the underlying shares with respect to any other type of change in shares reserved for issuance.

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