Fair Value Measurements (Details) - USD ($) $ in Millions	Jul. 31, 2017	Apr. 30, 2017
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term borrowings	$ 258	$ 211
Long-term debt	1,792	1,752
Currency derivatives [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Currency derivatives	28	10
Fair Value, Measurements, Recurring [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term borrowings	258	211
Current portion of long-term debt	250	249
Long-term debt	1,792	1,752
Fair Value, Measurements, Recurring [Member] | Currency derivatives [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Currency derivatives	9	25
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Currency derivatives	28	10
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term borrowings	0	0
Current portion of long-term debt	0	0
Long-term debt	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Currency derivatives [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Currency derivatives	0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Currency derivatives	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term borrowings	258	211
Current portion of long-term debt	250	249
Long-term debt	1,792	1,752
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Currency derivatives [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Currency derivatives	9	25
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Currency derivatives	28	10
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term borrowings	0	0
Current portion of long-term debt	0	0
Long-term debt	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Currency derivatives [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Currency derivatives	0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Currency derivatives	$ 0	$ 0