Debt and Financing Arrangements (Details Textual)	3 Months Ended		6 Months Ended
	Oct. 31, 2018 USD ($) Bank	Oct. 31, 2017 USD ($)	Oct. 31, 2018 USD ($) Bank	Oct. 31, 2017 USD ($)	Jul. 31, 2018 USD ($)	May 14, 2018 USD ($)	Apr. 30, 2018 USD ($)
Debt and Financing Arrangements (Textual) [Abstract]
Debt instrument face amount	$ 5,900,000,000		$ 5,900,000,000				$ 4,700,000,000
Repayments of long-term debt			$ 300,000,000	$ 150,000,000
Number of banks | Bank	11		11
Outstanding balance under revolving credit facility	$ 0		$ 0				0
Revolving credit facility maximum borrowing capacity	1,800,000,000.0		1,800,000,000.0
Interest paid	84,100,000	$ 78,900,000	107,400,000	$ 83,500,000
Short-term borrowings	$ 390,000,000		$ 390,000,000				144,000,000
Senior Notes [Member]
Debt and Financing Arrangements (Textual) [Abstract]
Percentage of the principal amount thereof which company can prepay	100.00%		100.00%
Term Loan Credit Agreement due May 14, 2021
Debt and Financing Arrangements (Textual) [Abstract]
Debt instrument face amount	$ 1,200,000,000		$ 1,200,000,000			$ 1,500,000,000.0	$ 0
Repayments of long-term debt	$ 300,000,000		$ 300,000,000
Long-term Debt, Weighted Average Interest Rate, at Point in Time	3.42%		3.42%
Debt Issuance Costs, Gross	$ 2,800,000		$ 2,800,000
Payments of Debt Issuance Costs	$ 0		$ 2,000,000
Commercial Paper [Member]
Debt and Financing Arrangements (Textual) [Abstract]
Commercial paper weighted-average interest rate	2.45%		2.45%				2.20%
Commercial paper, borrowing capacity	$ 1,800,000,000.0		$ 1,800,000,000.0
Short-term borrowings	390,000,000		390,000,000				$ 144,000,000
Interest rate contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount	$ 500,000,000		500,000,000		$ 500,000,000		$ 0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax			$ 10,500,000