Stock-Based Compensation (Schedule Of Stock Options Oustanding Activity)(Details) (USD $)	12 Months Ended
	Apr. 30, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding	1,401,813
Options exercisable	1,156,809
$17.62 - $18.16 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option price per share, lower range limit	$ 17.62
Option price per share, upper range limit	$ 18.16
Options outstanding	223,334
Options outstanding remaining life	8 years 8 months 12 days
Options outstanding exercise price	$ 17.86
Options exercisable	14,998
Options exercisable exercise price	$ 18.16
$20.87- $26.85 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option price per share, lower range limit	$ 20.87
Option price per share, upper range limit	$ 26.85
Options outstanding	497,467
Options outstanding remaining life	5 years
Options outstanding exercise price	$ 24.05
Options exercisable	460,799
Options exercisable exercise price	$ 24.30
$28.97 - $34.63 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option price per share, lower range limit	$ 28.97
Option price per share, upper range limit	$ 34.63
Options outstanding	658,400
Options outstanding remaining life	3 years 4 months 24 days
Options outstanding exercise price	$ 32.39
Options exercisable	658,400
Options exercisable exercise price	$ 32.39
$38.37 - $42.17[Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option price per share, lower range limit	$ 38.37
Option price per share, upper range limit	$ 42.17
Options outstanding	22,612
Options outstanding remaining life	1 year 6 months
Options outstanding exercise price	$ 41.73
Options exercisable	22,612
Options exercisable exercise price	$ 41.73