Common Shares (Details) - shares	3 Months Ended
	Jul. 31, 2022	Jul. 31, 2021	Apr. 30, 2022
Common Shares Information
Common shares authorized	300,000,000.0		300,000,000.0
Common shares outstanding	106,600,000		106,500,000
Treasury shares	39,900,000		40,000,000.0
Board Authorized Repurchased Plan
Equity, Class of Treasury Stock [Line Items]
Shares repurchased	0	0
Shares remaining for repurchase	5,800,000