Income Taxes (Components of Income Tax Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Current:
U.S. federal	$ 197	$ 160	$ 171
Foreign	41	24	41
State and local	10	10	18
Current income tax expense	248	194	230
Deferred:
U.S. federal	23	48	46
Foreign	1	0	(1)
State and local	2	5	(18)
Deferred income taxes expense	26	53	27
Total income tax expense	$ 274	$ 247	$ 257