Condensed Statements of Consolidated Shareholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Shares	Additional Capital	Retained Income	Accumulated Other Comprehensive Income (Loss)
Balance at Apr. 30, 2021	$ 8,124.8	$ 27.1	$ 5,527.6	$ 2,847.5	$ (277.4)
Balance, shares at Apr. 30, 2021		108,339,057
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	153.9			153.9
Other comprehensive income (loss)	(4.2)				(4.2)
Comprehensive Income	149.7
Purchase of treasury shares	(6.8)	$ 0.0	(6.1)	(0.7)
Purchase of treasury shares, shares		(50,203)
Stock plans	9.5	$ 0.0	9.5
Stock plans, shares		71,140
Cash dividends declared	(106.9)			(106.9)
Balance at Jul. 31, 2021	8,170.3	$ 27.1	5,531.0	2,893.8	(281.6)
Balance, shares at Jul. 31, 2021		108,359,994
Balance at Apr. 30, 2021	8,124.8	$ 27.1	5,527.6	2,847.5	(277.4)
Balance, shares at Apr. 30, 2021		108,339,057
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	429.6
Other comprehensive income (loss)	8.1
Comprehensive Income	437.7
Balance at Jan. 31, 2022	8,266.9	$ 27.1	5,553.6	2,955.5	(269.3)
Balance, shares at Jan. 31, 2022		108,462,330
Balance at Jul. 31, 2021	8,170.3	$ 27.1	5,531.0	2,893.8	(281.6)
Balance, shares at Jul. 31, 2021		108,359,994
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	206.0			206.0
Other comprehensive income (loss)	11.1				11.1
Comprehensive Income	217.1
Purchase of treasury shares	(0.7)	$ 0.0	(0.6)	(0.1)
Purchase of treasury shares, shares		(5,676)
Stock plans	6.6	$ 0.0	6.6
Stock plans, shares		8,521
Cash dividends declared	(106.9)			(106.9)
Balance at Oct. 31, 2021	8,286.4	$ 27.1	5,537.0	2,992.8	(270.5)
Balance, shares at Oct. 31, 2021		108,362,839
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	69.7			69.7
Other comprehensive income (loss)	1.2				1.2
Comprehensive Income	70.9
Purchase of treasury shares	(0.2)	$ 0.0	(0.2)	0.0
Purchase of treasury shares, shares		(1,505)
Stock plans	16.8	$ 0.0	16.8
Stock plans, shares		100,996
Cash dividends declared	(107.0)			(107.0)
Balance at Jan. 31, 2022	8,266.9	$ 27.1	5,553.6	2,955.5	(269.3)
Balance, shares at Jan. 31, 2022		108,462,330
Balance at Apr. 30, 2022	$ 8,140.1	$ 26.6	5,457.9	2,893.0	(237.4)
Balance, shares at Apr. 30, 2022	106,500,000	106,458,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 109.8			109.8
Other comprehensive income (loss)	4.0				4.0
Comprehensive Income	113.8
Purchase of treasury shares	(7.8)	$ 0.0	(6.7)	(1.1)
Purchase of treasury shares, shares		(61,693)
Stock plans	6.5	$ 0.0	6.5	0.0
Stock plans, shares		162,735
Cash dividends declared	(108.3)			(108.3)
Balance at Jul. 31, 2022	8,144.3	$ 26.6	5,457.7	2,893.4	(233.4)
Balance, shares at Jul. 31, 2022		106,559,359
Balance at Apr. 30, 2022	$ 8,140.1	$ 26.6	5,457.9	2,893.0	(237.4)
Balance, shares at Apr. 30, 2022	106,500,000	106,458,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 509.4
Other comprehensive income (loss)	0.2
Comprehensive Income	509.6
Balance at Jan. 31, 2023	$ 8,335.0	$ 26.6	5,469.4	3,076.2	(237.2)
Balance, shares at Jan. 31, 2023	106,600,000	106,634,289
Balance at Jul. 31, 2022	$ 8,144.3	$ 26.6	5,457.7	2,893.4	(233.4)
Balance, shares at Jul. 31, 2022		106,559,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	191.1			191.1
Other comprehensive income (loss)	(13.9)				(13.9)
Comprehensive Income	177.2
Purchase of treasury shares	(0.1)	$ 0.0	(0.1)	0.0
Purchase of treasury shares, shares		(580)
Stock plans	4.4	$ 0.0	4.4
Stock plans, shares		67,757
Cash dividends declared	(108.5)			(108.5)
Balance at Oct. 31, 2022	8,217.3	$ 26.6	5,462.0	2,976.0	(247.3)
Balance, shares at Oct. 31, 2022		106,626,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	208.5			208.5
Other comprehensive income (loss)	10.1				10.1
Comprehensive Income	218.6
Purchase of treasury shares	(0.1)	$ 0.0	(0.1)	0.0
Purchase of treasury shares, shares		(746)
Stock plans	7.5	$ 0.0	7.5
Stock plans, shares		8,499
Cash dividends declared	(108.3)			(108.3)
Balance at Jan. 31, 2023	$ 8,335.0	$ 26.6	$ 5,469.4	$ 3,076.2	$ (237.2)
Balance, shares at Jan. 31, 2023	106,600,000	106,634,289