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

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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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) - USD ($)	3 Months Ended				6 Months Ended
	Oct. 31, 2016	Jul. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Oct. 31, 2016	Oct. 31, 2015	Apr. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Net cash provided by operating activities					$ 240,084,000	$ 250,276,000
Net cash used in financing activities					69,586,000	(25,830,000)
Income tax expense	$ 32,299,000		$ 44,163,000		66,179,000	80,534,000
Accounting Standards Update 2016-09 \| New Accounting Pronouncement, Early Adoption, Effect
Share-based Compensation Arrangement by Share-based Payment Award
Net cash provided by operating activities					$ 3,900,000
Net cash used in financing activities				$ 3,900,000
Income tax expense		$ 3,046,000
2009 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant (in shares)	3,245,262				3,245,262
Allocated share-based compensation expense					$ 4,948,000	$ 3,373,000
2009 Stock Incentive Plan \| Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Number of options outstanding (in shares)	240,500				240,500		291,200
Aggregate intrinsic value for outstanding options	$ 17,985,000				$ 17,985,000
Weighted average remaining contractual life (in years)					3 years 10 months 28 days
Aggregate intrinsic value for exercised options					$ 4,675,000
Unrecognized compensation costs related to plan	0				0
2009 Stock Incentive Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation costs related to plan	$ 17,606,000				$ 17,606,000