Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Oct. 31, 2016	Apr. 30, 2016	Oct. 31, 2015	Apr. 30, 2015
Assets:
Cash and cash equivalents, Carrying Amount	$ 211	$ 263	$ 195	$ 370
Cash and cash equivalents, Fair Value	211	263
Liabilities:
Short-term borrowings, Carrying Amount	337	271
Short-term borrowings, Fair Value	337	271
Long-term debt, Carrying Amount	1,917	1,230
Long-term debt, Fair Value	2,011	1,293
Currency derivatives [Member]
Assets:
Currency derivatives, Fair Value	50	19
Liabilities:
Currency derivatives, Fair Value	6	10
Reported Value Measurement [Member]
Assets:
Cash and cash equivalents, Carrying Amount	211	263
Liabilities:
Short-term borrowings, Carrying Amount	337	271
Long-term debt, Carrying Amount	1,917	1,230
Reported Value Measurement [Member] | Currency derivatives [Member]
Assets:
Currency derivatives, Carrying Amount	50	19
Liabilities:
Currency derivatives, Carrying Amount	$ 6	$ 10