Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Goodwill [Roll Forward]
Goodwill before impairment losses, beginning balance	$ 503,054	$ 474,128
Accumulated impairment losses, beginning balance	(32,297)	(32,297)
Goodwill, beginning balance	470,757	441,831
Acquisitions	19,261	27,765
Disposals and foreign currency changes, net	(1,189)	1,161
Impairments	0	0
Goodwill before impairment losses, ending balance	523,504	503,054
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 491,207	$ 470,757