Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Goodwill [Roll Forward]
Goodwill before impairment losses, beginning balance	$ 467,079	$ 459,863
Accumulated impairment losses, beginning balance	(32,297)	(32,297)
Goodwill, beginning balance	434,782	427,566
Acquisitions	9,207	6,922
Disposals and foreign currency changes, net	(1,177)	4
Impairments	0	0
Goodwill before impairment losses, ending balance	475,109	466,789
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 442,812	$ 434,492