Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2017	Oct. 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	961	7,435
Disposals and foreign currency changes, net	(891)	(832)
Impairments	0	0
Goodwill before impairment losses, ending balance	525,356	509,657
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 493,059	$ 477,360