Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2017
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 141.4	$ 106.0	$ 149.9
Unrecognized Tax Benefits, Period Increase (Decrease)	(8.5)	(5.5)
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	10.4
Effect of anticipated settlements of audit issues and expiring statutes of limitations	4.2
Net Discreet Tax Expense (Benefit)	$ 5.2	$ 6.8
Effective Income Tax Rate Reconciliation, Percent	37.70%	40.50%
Effective tax rate, impact of discrete tax items	2.50%	3.30%