Share-Based Payments (Tables)

12 Months Ended

Apr. 30, 2012

Share-Based Payments [Abstract]

Summary of the Company's stock option activity and related information

	Options			Weighted-Average Exercise Price
Outstanding at May 1, 2011		196,925		$	41.18
Exercised		(72,084	)		39.46
Outstanding and exercisable at April 30, 2012		124,841		$	42.18

Summary of company's restricted shares, deferred shares, deferred stock units, and performance units

	Restricted/Deferred Shares and Deferred Stock Units			Weighted-Average Grant Date Fair Value		Performance Units			Weighted-Average Fair Value
Outstanding at May 1, 2011		1,157,266		$	49.39		125,360		$	77.53
Granted		152,180			78.32		99,455			76.37
Converted		125,360			77.53		(125,360	)		77.53
Vested		(430,831	)		52.60		—			—
Forfeited		(12,985	)		52.91		—			—
Outstanding at April 30, 2012		990,990		$	55.95		99,455		$	76.37

Weighted-average grant date fair values of the equity awards

Year Ended April 30,	Restricted/ Deferred Shares and Deferred Stock Units		Weighted- Average Grant Date Fair Value		Performance Units		Weighted- Average Grant Date Fair Value
2012		152,180	$	78.32		99,455	$	76.37
2011		303,863		58.32		125,360		77.53
2010		504,580		44.63		190,010		57.37