Fair Value of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Oct. 31, 2013	Apr. 30, 2013	Oct. 31, 2012	Apr. 30, 2012
Assets:
Cash and cash equivalents, Carrying Amount	$ 192	$ 204	$ 369	$ 338
Cash and cash equivalents, Fair Value	192	204
Liabilities:
Short-term borrowings, Carrying Amount	6	3
Short-term borrowings, Fair Value	6	3
Current portion of long-term debt, Carrying Amount	1	2
Current portion of long-term debt, Fair Value	1	2
Long-term debt, Carrying Amount	997	997
Long-term debt, Fair Value	954	1,011
Currency derivatives [Member]
Assets:
Currency derivatives, Fair Value	2	5
Liabilities:
Currency derivatives, Fair Value	10	4
Carrying Amount [Member]
Assets:
Cash and cash equivalents, Carrying Amount	192	204
Liabilities:
Short-term borrowings, Carrying Amount	6	3
Current portion of long-term debt, Carrying Amount	1	2
Long-term debt, Carrying Amount	997	997
Carrying Amount [Member] | Currency derivatives [Member]
Assets:
Currency derivatives, Carrying Amount	2	5
Liabilities:
Currency derivatives, Carrying Amount	$ 10	$ 4