Stock-Based Compensation (Schedule Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Oustanding number of options, Beginning Balance	851,314	1,401,813	1,624,760
Options granted	66,600	60,500	125,000
Options exercised	(508,639)	(551,485)	(251,799)
Options cancelled or expired	(11,200)	(59,514)	(96,148)
Oustanding number of options ending balance	398,075	851,314	1,401,813	1,624,760
Remaining contractual term outstanding	5 years	4 years 3 months 18 days	4 years 9 months 18 days	5 years 1 month 6 days
Remaining contractual term, granted	9 years 1 month 6 days	9 years 1 month 6 days	9 years 1 month 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Exercise price, beginning	$ 28.16	$ 27.27	$ 27.64
Exercise price, granted	29.92	36.74	17.62
Exercise price, exercised	28.05	26.61	23.35
Exercise price, cancelled or expired	32.64	30.17	31.03
Exercise price, ending	$ 28.46	$ 28.16	$ 27.27	$ 27.64
Aggregate intrinsic value outstanding, beginning balance	$ 3,121	$ 9,272	$ 0
Aggregate intrinsic value, exercised	7,209	5,156	1,868
Aggregate intrinsic value outstanding, ending balance	$ 8,851	$ 3,121	$ 9,272	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Vested and expected to vest in the future, Number of options	385,250
Vested and expected to vest in the future, Remaining contractual term	4 years 11 months
Vested and expected to vest in the future, Exercise price	$ 28.45
Vested and expected to vest in the future, Aggregate intrinsic value	$ 8,571
Exercisable, Number of options	263,541
Exercisable, Remaining contractual term	3 years 4 months
Exercisable, Exercise price	$ 28.38
Exercisable, Aggregate intrinsic value	$ 5,882