Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
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	7,435	1,852
Disposals and foreign currency changes, net	832	1,615
Impairments	0	0
Goodwill before impairment losses, ending balance	509,657	474,365
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 477,360	$ 442,068