Goodwill and Intangible Assets (Schedule Of Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Goodwill [Roll Forward]
Goodwill before impairment losses, beginning balance	$ 552,234	$ 540,168
Accumulated impairment losses, beginning balance	(32,297)	(32,297)
Goodwill, beginning balance	519,937	507,871
Acquisitions	1,083	651
Disposals and foreign currency changes, net	(3,101)	(581)
Impairments	0	0
Goodwill before impairment losses, ending balance	853,575	540,238
Accumulated impairment losses, ending balance	(32,297)	(32,297)
Goodwill, ending balance	821,278	$ 507,941
Wave
Goodwill [Roll Forward]
Acquisitions	$ 303,359