Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended
		Jul. 31, 2022	Jul. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance		$ (237.4)
Accumulated Other Comprehensive Income (Loss), Ending Balance		(233.4)
Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance		(21.1)	$ (9.0)
Reclassification adjustments		0.0	0.0
Current period credit (charge)		1.4	(4.0)
Income tax benefit (expense)		0.0	0.0
Accumulated Other Comprehensive Income (Loss), Ending Balance		(19.7)	(13.0)
Net Gains (Losses) on Cash Flow Hedging Derivatives [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	[1]	(163.9)	(174.8)
Reclassification adjustments	[1]	3.3	2.9
Current period credit (charge)	[1]	0.0	0.0
Income tax benefit (expense)	[1]	(0.8)	(0.6)
Accumulated Other Comprehensive Income (Loss), Ending Balance	[1]	(161.4)	(172.5)
Pension and Other Postretirement Liabilities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	[2]	(54.2)	(97.3)
Reclassification adjustments	[2]	0.7	(5.3)
Current period credit (charge)	[2]	0.0	1.8
Income tax benefit (expense)	[2]	(0.3)	0.9
Accumulated Other Comprehensive Income (Loss), Ending Balance	[2]	(53.8)	(99.9)
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance		1.8	3.7
Reclassification adjustments		0.0	0.0
Current period credit (charge)		(0.4)	0.2
Income tax benefit (expense)		0.1	(0.1)
Accumulated Other Comprehensive Income (Loss), Ending Balance		1.5	3.8
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Beginning Balance		(237.4)	(277.4)
Reclassification adjustments		4.0	(2.4)
Current period credit (charge)		1.0	(2.0)
Income tax benefit (expense)		(1.0)	0.2
Accumulated Other Comprehensive Income (Loss), Ending Balance		$ (233.4)	$ (281.6)

[1] The reclassification is composed of deferred gains (losses) related to terminated interest rate contracts. During both 2023 and 2022, the reclassification was primarily from accumulated other comprehensive income (loss) to interest expense. In addition, during the first quarter of 2022, a portion of the reclassification was to other income (expense) – net, which was driven by the prepayment of the Senior Notes due March 15, 2022. For additional information, see Note 9: Derivative Financial Instruments.

[2] The reclassification from accumulated other comprehensive income (loss) to other income (expense) – net is composed of settlement charges and amortization of net losses and prior service costs. For additional information, see Note 8: Pensions and Other Postretirement Benefits.