Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jan. 31, 2016	Apr. 30, 2015	Jan. 31, 2015	Apr. 30, 2014
Assets:
Cash and cash equivalents, Carrying Amount	$ 317	$ 370	$ 250	$ 437
Cash and cash equivalents, Fair Value	317	370
Liabilities:
Short-term borrowings, Carrying Amount	509	190
Short-term borrowings, Fair Value	509	190
Current portion of long-term debt, Carrying Amount	0	250
Current portion of long-term debt, Fair Value	0	253
Long-term debt, Carrying Amount	1,229	743
Long-term debt, Fair Value	1,256	735
Currency derivatives [Member]
Assets:
Currency derivatives, Fair Value	77	59
Liabilities:
Currency derivatives, Fair Value	1	18
Reported Value Measurement [Member]
Assets:
Cash and cash equivalents, Carrying Amount	317	370
Liabilities:
Short-term borrowings, Carrying Amount	509	190
Current portion of long-term debt, Carrying Amount	0	250
Long-term debt, Carrying Amount	1,229	743
Reported Value Measurement [Member] | Currency derivatives [Member]
Assets:
Currency derivatives, Carrying Amount	77	59
Liabilities:
Currency derivatives, Carrying Amount	$ 1	$ 18