Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Apr. 30, 2019
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 179.2	$ 204.5	$ 185.1
Gross unrecognized tax benefits increase (decrease)	(5.9)	18.4
Change in tax benefits that are reasonably possible	24.3
Decrease in Unrecognized Tax Benefits is Reasonably Possible	6.5
Effective Income Tax Rate Reconciliation, Discrete Adjustments, Amount	$ 8.3	$ 0.5
Effective tax rate	29.60%	25.10%
Increase in effective tax rate from discrete item, percent	4.00%	0.20%