Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Goodwill [Roll Forward]
Goodwill before impairment losses, beginning balance	$ 523,504	$ 503,054
Accumulated impairment losses, beginning balance	(32,297)	(32,297)
Goodwill, beginning balance	491,207	470,757
Acquisitions	252	23
Disposals and foreign currency changes, net	2,532	162
Impairments	0	0
Goodwill before impairment losses, ending balance	526,288	503,239
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 493,991	$ 470,942