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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- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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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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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) - USD ($)	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Apr. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Income tax expense	$ 33,880,000	$ 36,371,000
New Accounting Pronouncement, Early Adoption, Effect
Share-based Compensation Arrangement by Share-based Payment Award
Income tax expense	$ 3,046
2009 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant	3,263,144
Allocated share-based compensation expense	$ 2,471,000	$ 1,737,000
2009 Stock Incentive Plan \| Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Number of options outstanding	243,450		291,200
Aggregate intrinsic value for outstanding options	$ 23,201,000
Weighted average remaining contractual life (in years)	4 years 1 month 22 days
Aggregate intrinsic value for exercised options	$ 4,435,000
Unrecognized compensation costs related to Plan	0
2009 Stock Incentive Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation costs related to Plan	$ 20,082,000