Number of options outstanding, including both vested and non-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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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Preferred and Common Stock - Schedule of Shares Outstanding and Weighted-Average Remaining Contractual Life by Exercise Range (Details) - $ / shares	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor	$ 20.68
Exercise price range ceiling	$ 44.39
Number of shares	401,800
20.68 - 24.11
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor	$ 20.68
Exercise price range ceiling	24.11
25.26 - 26.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor	25.26
Exercise price range ceiling	26.92
44.39
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor	44.39
Exercise price range ceiling	$ 44.39
Stock Options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	401,800	712,024	854,809	1,053,509
Weighted average exercise price	$ 36.55	$ 36.73	$ 34.64	$ 32.59
Weighted average remaining contractual life (years)	5 years 1 month 17 days
Stock Options \| 20.68 - 24.11
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	7,000
Weighted average exercise price	$ 22.62
Weighted average remaining contractual life (years)	1 year 2 months 12 days
Stock Options \| 25.26 - 26.92
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	159,600
Weighted average exercise price	$ 25.61
Weighted average remaining contractual life (years)	3 years 9 months 18 days
Stock Options \| 44.39
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	235,200
Weighted average exercise price	$ 44.39
Weighted average remaining contractual life (years)	6 years 2 months 12 days