Income Taxes (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Apr. 30, 2016
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 97.1	$ 75.2	$ 111.5
Unrecognized Tax Benefits, Period Increase (Decrease)	(14.4)	(11.0)
Effect of anticipated settlements of audit issues and expiring statutes of limitations	7.7
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	12.8
Net Discreet Tax Expense (Benefit)	$ 8.9	$ 36.2
Effective Income Tax Rate Reconciliation, Percent	37.20%	44.40%
Effective tax rate, impact of discrete tax items	(1.50%)	(6.30%)