Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Apr. 30, 2013	Sep. 04, 2013 Subsequent Event [Member]
Operating Loss Carryforwards [Line Items]
Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority				$ 100
Unrecognized tax benefits that would impact effective tax rate	145.3	208.0	146.4
Unrecognized Tax Benefits, Period Increase (Decrease)	(1.1)	1.6
Effect of anticipated settlements of audit issues and expiring statutes of limitations	33
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	15.5
Effective Income Tax Rate, Continuing Operations	38.60%	37.60%
Net Discreet Tax Expense (Benefit)	0.2	2.7
Discreet Tax Reconciliation, Difference in Income Tax Reserve Compared to Prior Period	4.4
Discreet Tax Reconciliation, Decrease in State Interest Receivable as Compared to Prior Period	$ 1.9
Effective Income Tax Rate, Continuing Operations, Change in Rate	1.00%