Stock-Based Compensation (Schedule Of Stock Option Activity)(Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Stock-Based Compensation [Abstract]
Oustanding number of options, Beginning Balance	1,624,760	1,605,356	2,105,515
Options granted	125,000	130,000	115,000
Options exercised	(251,799)	(1,200)	(27,000)
Options cancelled or expired	(96,148)	(109,396)	(588,159)
Oustanding number of options ending balance	1,401,813	1,624,760	1,605,356	2,105,515
Remaining contractual term outstanding	4 years 9 months 18 days	5 years 1 month 6 days	5 years 8 months 12 days	5 years 7 months 6 days
Remaining contractual term, granted	9 years 1 month 6 days	9 years 1 month 6 days	9 years 1 month 6 days
Exercise price, beginning	$ 27.64	$ 28.48	$ 29.03
Exercise price, granted	$ 17.62	$ 18.16	$ 20.87
Exercise price, exercised	$ 23.35	$ 14.93	$ 14.80
Exercise price, cancelled or expired	$ 31.03	$ 28.82	$ 29.58
Exercise price, ending	$ 27.27	$ 27.64	$ 28.48	$ 29.03
Aggregate intrinsic value outstanding, beginning balance	$ 0	$ 29	$ 295
Aggregate intrinsic value outstanding, ending balance	9,272	0	29	295
Aggregate intrinsic value, exercised	1,868	6	216
Vested and expected to vest in the future, Number of options	1,375,039
Vested and expected to vest in the future, Remaining contractual term	4 years 8 months 12 days
Vested and expected to vest in the future, Exercise price	$ 27.43
Vested and expected to vest in the future, Aggregate intrinsic value	8,871
Exercisable, Number of options	1,156,809
Exercisable, Remaining contractual term	4 years
Exercisable, Exercise price	$ 29.17
Exercisable, Aggregate intrinsic value	$ 5,509