Consolidated Statement of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Cash dividends paid, per share	$ 0.66	$ 0.58	$ 0.51
Stock options exercised, shares	36,800	50,075	84,000
Additional Paid-in Capital [Member]
Stock options exercised, shares	36,800	50,075	84,000
Retained Earnings [Member]
Cash dividends paid, per share	$ 0.66	$ 0.58	$ 0.51

Number of share options (or share units) exercised during the current period.

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