Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Schedule of Earnings Per Share, Two Class Method [Line Items]
Net income	$ 631.7	$ 876.3	$ 779.5
Weighted-average common shares outstanding (in shares)	107.9
Weighted-average common shares outstanding – assuming dilution (in shares)	108.4
Net income per common share (in dollars per share)	$ 5.84	$ 7.79	$ 6.84
Net income per common share - assuming dilution (in dollars per share)	$ 5.83	$ 7.79	$ 6.84
Two-class method [Member]
Schedule of Earnings Per Share, Two Class Method [Line Items]
Net income	$ 631.7	$ 876.3	$ 779.5
Less: Net income allocated to participating securities	1.8	3.7	4.4
Net income allocated to common stockholders	$ 629.9	$ 872.6	$ 775.1
Weighted-average common shares outstanding (in shares)	107.9	112.0	113.4
Add: Dilutive effect of stock options (in shares)	0.0	0.0	0.0
Weighted-average common shares outstanding – assuming dilution (in shares)	107.9	112.0	113.4
Net income per common share (in dollars per share)	$ 5.84	$ 7.79	$ 6.84
Net income per common share - assuming dilution (in dollars per share)	$ 5.84	$ 7.79	$ 6.84