CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - $ / shares	Apr. 30, 2018	Apr. 30, 2017
Shareholders' Equity
Preferred Stock, par value (in dollars per share)	$ 1	$ 1
Preferred Stock, shares authorized (in shares)	2,000,000	2,000,000
Preferred Stock, shares issued (in shares)	0	0
Class A [Member]
Shareholders' Equity
Common Stock, par value (in dollars per share)	$ 1	$ 1
Common Stock, shares authorized (in shares)	180,000,000	180,000,000
Common Stock, shares issued (in shares)	70,110,603	70,086,003
Treasury stock (in shares)	21,853,257	22,096,970
Class B [Member]
Shareholders' Equity
Common Stock, par value (in dollars per share)	$ 1	$ 1
Common Stock, shares authorized (in shares)	72,000,000	72,000,000
Common Stock, shares issued (in shares)	13,071,067	13,095,667
Treasury stock (in shares)	3,917,574	3,917,574