Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Goodwill [Roll Forward]
Goodwill before impairment losses, beginning balance	$ 540,168	$ 523,504
Accumulated impairment losses, beginning balance	(32,297)	(32,297)
Goodwill, beginning balance	507,871	491,207
Acquisitions	651	252
Disposals and foreign currency changes, net	(581)	2,532
Impairments	0	0
Goodwill before impairment losses, ending balance	540,238	526,288
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 507,941	$ 493,991