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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The ceiling 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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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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Preferred and Common Stock - Schedule of Shares Outstanding and Weighted-Average Remaining Contractual Life by Exercise Range (Details) - $ / shares	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Exercise price range floor (in Dollars per share)	$ 25.26
Exercise price range ceiling (in Dollars per share)	$ 44.39
Number of shares	181,673
Stock Options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	181,673	222,050	291,200	401,800
Weighted average exercise price (in Dollars per share)	$ 39.48	$ 38.51	$ 37.46	$ 36.55
Weighted average remaining contractual life (years)	2 years 7 months 24 days
Stock Options \| Exercise price range one
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	1,500
Weighted average exercise price (in Dollars per share)	$ 25.49
Weighted average remaining contractual life (years)	1 year
Stock Options \| Exercise price range two
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	45,100
Weighted average exercise price (in Dollars per share)	$ 25.26
Weighted average remaining contractual life (years)	1 year 2 months
Stock Options \| Exercise price range three
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Number of shares	135,073
Weighted average exercise price (in Dollars per share)	$ 44.39
Weighted average remaining contractual life (years)	3 years 2 months