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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Unrecognized cost of unvested share-based compensation awards.

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- Definition

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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No definition available.

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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 ($)	9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Apr. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant (in shares)	2,988,104
Allocated share-based compensation expense	$ 15,458,000	$ 7,356,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Number of options outstanding (in shares)	197,515		222,050
Aggregate intrinsic value for outstanding options	$ 16,171,000
Weighted average remaining contractual life (in years)	2 years 10 months 10 days
Aggregate intrinsic value for exercised options	$ 1,980,000
Unrecognized compensation costs related to plan	0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation costs related to plan	$ 11,298,000