Stock-Based Compensation (Schedule Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Oustanding number of options, Beginning Balance	126,633	398,075	851,314
Options granted	0	30,700	66,600
Options exercised	(71,715)	(287,975)	(508,639)
Options cancelled or expired	0	(14,167)	(11,200)
Oustanding number of options ending balance	54,918	126,633	398,075	851,314
Remaining contractual term outstanding	5 years 7 months 6 days	5 years 9 months 18 days	5 years	4 years 3 months 18 days
Remaining contractual term, granted		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	$ 35.15	$ 28.46	$ 28.16
Exercise price, granted	0.00	57.11	29.92
Exercise price, exercised	33.00	27.99	28.05
Exercise price, cancelled or expired	0.00	40.43	32.64
Exercise price, ending	$ 37.95	$ 35.15	$ 28.46	$ 28.16
Aggregate intrinsic value outstanding, beginning balance	$ 4,773	$ 8,851	$ 3,121
Aggregate intrinsic value, exercised	2,597	11,089	7,209
Aggregate intrinsic value outstanding, ending balance	$ 2,963	$ 4,773	$ 8,851	$ 3,121
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	52,283
Vested and expected to vest in the future, Remaining contractual term	5 years 6 months
Vested and expected to vest in the future, Exercise price	$ 37.76
Vested and expected to vest in the future, Aggregate intrinsic value	$ 2,830
Exercisable, Number of options	17,949
Exercisable, Remaining contractual term	1 year 4 months 24 days
Exercisable, Exercise price	$ 28.13
Exercisable, Aggregate intrinsic value	$ 1,145