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, 2019	$ 7,970.5	$ 28.9	$ 5,755.8	$ 2,367.6	$ (181.8)
Balance, shares at Apr. 30, 2019		113,742,296
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	154.6			154.6
Other comprehensive income (loss)	(34.9)				(34.9)
Comprehensive Income	119.7
Purchase of treasury shares	(2.9)	$ 0.0	(2.7)	(0.2)
Purchase of treasury shares, shares		(22,793)
Stock plans	20.5	$ 0.1	20.4
Stock plans, shares		330,289
Cash dividends declared	(100.1)			(100.1)
Other	0.0			0.0
Balance at Jul. 31, 2019	8,007.7	$ 29.0	5,773.5	2,421.9	(216.7)
Balance, shares at Jul. 31, 2019		114,049,792
Balance at Apr. 30, 2020	$ 8,190.9	$ 29.0	5,794.1	2,746.8	(379.0)
Balance, shares at Apr. 30, 2020	114,100,000	114,072,726
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 237.0			237.0
Other comprehensive income (loss)	18.1				18.1
Comprehensive Income	255.1
Purchase of treasury shares	(4.6)	$ 0.0	(5.5)	0.9
Purchase of treasury shares, shares		(42,194)
Stock plans	6.2	$ 0.0	6.2
Stock plans, shares		56,910
Cash dividends declared	(102.4)			(102.4)
Other	0.0	$ (0.5)	0.5	0.0
Balance at Jul. 31, 2020	$ 8,345.2	$ 28.5	$ 5,795.3	$ 2,882.3	$ (360.9)
Balance, shares at Jul. 31, 2020	114,100,000	114,087,442