Stock Split (Tables)

3 Months Ended

Jul. 31, 2012

Stock Split [Abstract]

Change in the company's outstanding shares

	Three Months Ended
	July 31
(Shares in thousands)	2011			2012
Class A (voting) Common Shares:
Balance at beginning of period		56,561			56,251
Acquisition of treasury stock		(64	)		—
Stock issued under compensation plans		—			46
Stock split (3-for-2)		—			28,149
Balance at end of period		56,497			84,446
Class B (nonvoting) Common Shares:
Balance at beginning of period		88,429			85,823
Acquisition of treasury stock		(193	)		—
Stock issued under compensation plans		54			80
Stock split (3-for-2)		—			42,951
Balance at end of period		88,290			128,854