Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2013	Jul. 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	2,155	3,651
Disposals and foreign currency changes, net	(1,270)	(116)
Impairments	0	0
Goodwill before impairment losses, ending balance	467,964	463,398
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 435,667	$ 431,101