Income Taxes (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
Oct. 31, 2019	Oct. 31, 2018	Apr. 30, 2019
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 156.7	$ 189.6	$ 185.1
Gross unrecognized tax benefits increase (decrease)	(28.4)	3.5
Change in tax benefits that are reasonably possible	14.1
Discrete income tax benefit	$ 25.2	$ 7.4
Effective tax rate	29.70%	25.80%
Increase in effective tax rate from discrete item, percent	5.40%	1.70%

Effective Income Tax Rate Reconciliation, Discrete Adjustments, Amount

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Effective Income Tax Rate Reconciliation, Effect of Discrete Items, Percent

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

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The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date.

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Amount of unrecognized tax benefits.

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Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

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