Income Taxes (Deferred Tax Liabilities Not Recognized) (Details) - USD ($) $ in Millions	Apr. 30, 2017	Apr. 30, 2016
Income Tax Disclosure [Abstract]
Undistributed earnings of foreign subsidiaries	$ 1,053	$ 1,005
Deferred Tax Liability Not Recognized, Amount of Unrecognized Deferred Tax Liability, Undistributed Earnings of Foreign Subsidiaries	$ 222	$ 222