Income Taxes (Components of Income Tax Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Current:
U.S. federal	$ 243	$ 197	$ 160
Foreign	49	41	24
State and local	1	10	10
Current income tax expense	293	248	194
Deferred:
U.S. federal	3	23	48
Foreign	(6)	1	0
State and local	(2)	2	5
Deferred income taxes expense	(5)	26	53
Total income tax expense	$ 288	$ 274	$ 247