CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION - UNAUDITED (Parenthetical) - $ / shares	Jan. 31, 2018	Apr. 30, 2017
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)	70,107,103	70,086,003
Treasury stock (in shares)	21,875,409	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)	13,074,567	13,095,667
Treasury stock (in shares)	3,917,574	3,917,574

Face amount or stated value per share of common stock.

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- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

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- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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No definition available.

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- Definition

Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29,30)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

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