Income Taxes (Textual) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Income Tax Disclosure [Abstract]
Deferred Income, Tax Benefit of Intercompany Transfer of Assets, Before Amortization		$ 95
Other Income Tax Expense (Benefit), Continuing Operations	15	5
Deferred Tax Assets, Valuation Allowance	27	34
Gross unrecognized tax benefits	13	11	11	13
Reduction in effective income tax rate if recognized	8
Estimated increase in unrecognized tax benefits in next 12 months as a result of net tax positions taken	0
Deferred benefit – tax (Note 11)	$ 75	$ 90