Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Current:
U.S. federal	$ 95	$ 107	$ 265
Foreign	29	34	47
State and local	19	28	17
Current income tax expense	143	169	329
Deferred:
U.S. federal	34	37	(48)
Foreign	7	4	(13)
State and local	(2)	(3)	(8)
Deferred income taxes expense	39	38	(69)
Total income tax expense	$ 182	$ 207	$ 260