Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jul. 31, 2015	Apr. 30, 2015	Jul. 31, 2014	Apr. 30, 2014
Assets:
Cash and cash equivalents, Carrying Amount	$ 494	$ 370	$ 460	$ 437
Cash and cash equivalents, Fair Value	494	370
Liabilities:
Short-term borrowings, Carrying Amount	13	190
Short-term borrowings, Fair Value	13	190
Current portion of long-term debt, Carrying Amount	250	250
Current portion of long-term debt, Fair Value	252	253
Long-term debt, Carrying Amount	1,229	743
Long-term debt, Fair Value	1,219	735
Currency derivatives [Member]
Assets:
Currency derivatives, Fair Value	75	59
Liabilities:
Currency derivatives, Fair Value	11	18
Reported Value Measurement [Member]
Assets:
Cash and cash equivalents, Carrying Amount	494	370
Liabilities:
Short-term borrowings, Carrying Amount	13	190
Current portion of long-term debt, Carrying Amount	250	250
Long-term debt, Carrying Amount	1,229	743
Reported Value Measurement [Member] | Currency derivatives [Member]
Assets:
Currency derivatives, Carrying Amount	75	59
Liabilities:
Currency derivatives, Carrying Amount	$ 11	$ 18