Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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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 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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Disclosure of Compensation Related Costs, Share Based Payments (Details) - 2009 Stock Incentive Plan - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Apr. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant	3,573,186
Allocated share-based compensation expense	$ 3,373	$ 2,667
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Number of options outstanding	342,050		401,800
Aggregate intrinsic value for outstanding options	$ 23,735
Weighted average remaining contractual life (in years)	4 years 8 months 10 days
Aggregate intrinsic value for exercised options	$ 3,770
Unrecognized compensation costs related to Plan	0
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation costs related to Plan	$ 11,475