Statements of Consolidated Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended								12 Months Ended
	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Statement of Stockholders' Equity [Abstract]
Cash dividends declared, per common share	$ 0.88	$ 0.88	$ 0.88	$ 0.88	$ 0.85	$ 0.85	$ 0.85	$ 0.85	$ 3.52	$ 3.40	$ 3.12