Goodwill And Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
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	11,579	13,346
Disposals and foreign currency changes, net	(2,003)	(783)
Impairments	0	0
Goodwill before impairment losses, ending balance	537,086	515,617
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	$ 504,789	$ 483,320