Fair Value of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2014	Apr. 30, 2013	Jan. 31, 2013	Apr. 30, 2012
Assets:
Cash and cash equivalents, Carrying Amount	$ 287	$ 204	$ 387	$ 338
Cash and cash equivalents, Fair Value	287	204
Liabilities:
Short-term borrowings, Carrying Amount	9	3
Short-term borrowings, Fair Value	9	3
Current portion of long-term debt, Carrying Amount	0	2
Current portion of long-term debt, Fair Value	0	2
Long-term debt, Carrying Amount	997	997
Long-term debt, Fair Value	952	1,011
Currency derivatives [Member]
Assets:
Currency derivatives, Fair Value	11	5
Liabilities:
Currency derivatives, Fair Value	2	4
Carrying Amount [Member]
Assets:
Cash and cash equivalents, Carrying Amount	287	204
Liabilities:
Short-term borrowings, Carrying Amount	9	3
Current portion of long-term debt, Carrying Amount	0	2
Long-term debt, Carrying Amount	997	997
Carrying Amount [Member] | Currency derivatives [Member]
Assets:
Currency derivatives, Carrying Amount	11	5
Liabilities:
Currency derivatives, Carrying Amount	$ 2	$ 4