Derivative Financial Instruments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2015	Nov. 30, 2018	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amortization of deferred gain on early termination agreement	$ 8.1	$ 8.0	$ 7.8
Cash margin accounts related to derivative instruments recognized	43.2	40.7
Cumulative net mark to market valuation of certain derivative positions recognized in unallocated derivative gains (losses)	(32.9)	(52.5)
Debt Instrument [Line Items]
Interest expense – net	$ (189.2)	(207.9)	(174.1)
Commodity contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instrument maturity	1 year
Gross notional amount	$ 890.1	544.8
Foreign currency exchange contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instrument maturity	1 year
Gross notional amount	$ 65.6	144.9
Treasury Lock [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Deferred gain (loss) on termination of cash flow hedge			$ 2.7
Interest rate contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gross notional amount	0.0	800.0			$ 300.0	$ 500.0
Deferred gain (loss) on termination of cash flow hedge	(239.8)
Deferred pre-tax net gain (loss) included in accumulated other comprehensive loss	(241.1)	(52.5)
Tax impact related to deferred losses and gains on cash flow hedges included in accumulated other comprehensive loss	55.5	$ 12.1
Effective portion of the hedge loss reclassified to interest expense over the next twelve months	(13.9)
Total Through Q4 2020 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amortization of deferred gain on early termination agreement	41.1
2021 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amortization of deferred gain on early termination agreement	8.4
2022 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amortization of deferred gain on early termination agreement	$ 4.0
Interest rate swap [Member] | Fair Value Hedging [Member] | Cash [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Contract Termination				$ 58.1
Interest rate swap [Member] | Fair Value Hedging [Member] | AccruedandPrepaidInterestNet [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Contract Termination				$ 4.6
3.50% Senior Notes due October 15, 2021
Debt Instrument [Line Items]
Interest rate on notes	3.50%